217 pubblicazioni classificate nel seguente modo:

Experimental study on instrumented micropiles
EESMS 2016 - 2016 IEEE Workshop on Environmental, Energy, and Structural Monitoring Systems, Proceedings
Autore/i: Capatti, Maria Chiara; Carbonari, Sandro; Gara, Fabrizio; Roia, Davide; Dezi, Francesca
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In the present work, first steps of an extensive experimental study carried out on two vertical micropiles in alluvial silty soil are presented. One of the vertical micropiles is injected throughout valves a-manchèttes placed along the steel core of the shaft, while the other one is grouted with a unique global injection. Both of them are instrumented with several strain gauges along the shaft and an accelerometer at the head. The protection technique adopted to prevent damages on the strain gauges during micropile installation and high-pressure injections is also discussed. The main objectives of this experimental campaign are the monitoring of the modifications in the dynamic characteristics of the complex soil-micropile system due to execution techniques and construction stages, and the investigation of the dynamic response considering different kind of cyclic and dynamic loading. In particular, the effect of the high-pressure injections on the dynamic response of vertical micropiles is here investigated, by means of series of ambient vibrations and lateral impact loading tests. Experimental data of impact load tests are finally compared with results obtained from an analytical model.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240910

Dynamic structural control of the “Caffaro Viaduct” by means of vibrational measurements
Proceedings of the 2016 IEEE Workshop on Environmental, Energy and Structural Monitoring Systems (EESMS)
Autore/i: Roia, D.; Speranza, E.; Gara, Fabrizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240881

Current state of the dynamic monitoring of the "chiaravalle viaduct"
EESMS 2016 - 2016 IEEE Workshop on Environmental, Energy, and Structural Monitoring Systems, Proceedings
Autore/i: Roia, Davide; Regni, Marco; Gara, Fabrizio; Carbonari, Sandro; Dezi, Francesca
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper describes some notable aspects regarding the dynamic monitoring planned for the Chiaravalle viaduct, linking SS76 and airport of Ancona in Falconara, in Italy. The viaduct is 875 m long and consists of four r.c. kinematic chains separated by joints. The deck is constituted by three beams supported by column bent piers constituted by two circular r.c. columns founded on a continuous footing on six concrete piles. The first purpose of the dynamic monitoring is to determine the experimental natural frequencies and mode shapes of the viaduct before a scheduled seismic rehabilitation. Then, comparison of the first results with those obtained after the retrofit of foundation and piers and finally after the substitution of the deck bearing, will contribute to evaluate efficiency of the executed works. Two different inputs are used for the dynamic tests, ambient and traffic vibrations. An Operational Modal Analysis is carried out starting from the collected data, using the Enhanced Frequency Domain Decomposition technique. Different sensor configurations are used to evaluate the overall behaviour of the viaduct. The Pre Global Estimation Re-scaling method is adopted in order to merge the different parts of mode shapes relevant to each configuration. Results of dynamic tests are interpreted through a 3D Finite Element model of the viaduct. Firstly, a conventional fixed base model is considered, then a model including the Soil-Structure Interaction phenomena is developed in order to improve consistency between numerical and experimental results. The modal parameters obtained by the model including Soil-Structure Interaction are in good agreement with those estimated experimentally.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240911

A higher order finite element to analyse steel-concrete composite bridge decks
Proceedings of the 19th IABSE Congress
Autore/i: Carbonari, Sandro; Dezi, Luigino; Gara, Fabrizio; Leoni, Graziano
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper presents a novel interdependent interpolation finite element for a higher order beam model capable of capturing the shear-lag phenomenon and the overall shear deformability of composite beams. After a brief overview of the beam kinematics and of the differential solving equations, the stiffness matrix and the nodal forces to be used in a standard finite element procedure are derived in a consistent way by exploiting properties of exponential matrices ad their application in the solution of linear differential equation systems. Some comparisons with solutions obtained by using finite elements with polynomial interpolating functions demonstrate the capability of the new element.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240871

Modal Properties and Seismic Response of Existing Building Retrofitted by External Bracings with Viscous Dampers
Proceedings of ECCOMAS, European Congress on Computational Methods in Applied Sciences and Engineering
Autore/i: Gioiella, Laura; Tubaldi, E.; Gara, Fabrizio; Dall’Asta, A.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240878

An innovative seismic protection system for existing buildings: External Dissipative Towers
Proceedings of the 19th Congress of IABSE, Challenges in Design and Construction of an Innovative and Sustainable Built Environment
Autore/i: Carbonari, Sandro; Dezi, Luigino; Gara, Fabrizio; Leoni, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240884

Experimental and numerical modal analysis of a historical masonry bridge
Proceedings of the 16th Int. Brick and Block Masonry Conference - Trends, Innovations and Challenges, IB2MAC
Autore/i: Dezi, Luigino; Gara, Fabrizio; Roia, D.; Leoni, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240882

Esempio di indagini sperimentali eseguite per il controllo e la qualificazione meccanica del calcestruzzo in opera mediante la prova di estrazione (pull-out) con l'impiego di innovativo tassello post-inserito Thoro
INGENIO
Autore/i: Gara, Fabrizio; Bufarini, S.; D’Aria, V.; Foglia, M.
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240921

The Rocca Roveresca of Senigallia: seismic vulnerability of the defensive walls
Accademia Nazionale dei Lincei, XXXIII giornata dell’ambiente, Resilienza delle città d’arte, Enhancing Resilience of historic cities to earthquakes
Autore/i: Dezi, Luigino; Carbonari, Sandro; Gara, Fabrizio; Dall’Asta, Andrea; Leoni, Graziano; Zona, Alessandro
Editore: Bardi Edizioni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: With the advent of cannons in XV century, many defensive walls underwent retrofitting to improve their capac-ity to withstand shots of the new powerful weapons. New lines of walls were erected by filling the left space with rubble stone materials. The different strata are characterized by specific behaviours and by well definite discontinuity surfaces so that the assessment of seismic vulnerability of such kind of defensive walls requires the definition of tailored failure mechanisms. A study on the behavior of the walls of the Rocca Roveresca of Senigallia in Italy is presented. A linear finite element model is first developed in order to understand the dy-namic behavior of a generic portion of the wall and to detect the probable incipient failure mechanisms. A subsequent static nonlinear analysis is carried out to investigate the formation of the cracking layout and to detect the position of plastic hinges. The last analysis level is carried out by supposing the wall to behave as a set of rigid blocks constituting a kinematic chain subjected to a finite displacement field typical for the col-lapse situation by introducing the degradation of the behavior of the inner (the less consistent) stratum.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/233497

Modal properties of existing building retrofitted by external bracings with viscous dampers
Atti del XVI Convegno ANIDIS
Autore/i: Gioiella, Laura; Gara, Fabrizio; Tubaldi, Enrico; Dall'Asta, Andrea
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The paper deals with the seismic protection of existing buildings using external viscous damper systems to increase energy dissipation capacity. Dampers and bracings can be arranged in very different configurations and the possible solutions can be grouped into different categories, depending on the specific kinematic behavior. In this work, the formulation of the problem involving the coupling of the existing frame with an external damping system is presented in general terms and some issues concerning the influence of the bracing properties on the dynamic response of the coupled system are investigated. Presented results concern the so called "dissipative tower", a recent solution which exploits the rocking motion of a stiff steel truss hinged at the foundation level for the dampers activation; the influence of the external dissipative bracings on the most important modal properties of the system, such as the mode displacement profile, relevant internal action distribution and relations between damper dimensions and effective modal damping are shown. Finally the global effect on the seismic response, in terms of displacements and base shear, is presented by solving the dynamic problem with the modal decomposition method in order to investigate the contribution of the higher modes on the dynamic response.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/233584

Analytical solution for a new higher order steel-concrete composite beam model
Proceedings of ICASS2015 – Eighth International Conference on “Advances in Steel Structures”
Autore/i: Gara, Fabrizio; Carbonari, Sandro; Leoni, Graziano; Dezi, Luigino
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper presents an analytical solution of a composite beam model in which the constrained kinematics takes account of the overall shear deformability, warping of the slab cross section and of the steel beam, and partial shear interaction between slab and girder. The warping functions are obtained by considering the problem of unrestrained thin-walled members subjected to self-equilibrated elementary load schemes. The governing equations are derived from the balance condition imposed with the Virtual Work Theorem. The analytical solution of the governing differential equations is obtained exploiting exponential matrices. This method, furnishing the exact formulation of the solution without requiring any discretization of the beam, is used to determine the solution of the proposed applications according to the stiffness method, deriving the stiffness matrix and the reactions of fixed-end beams. Two case studies, i.e. a symmetric two span bridge deck subjected to a uniformly distributed load and to a point load, are presented; the comparisons with results obtained with a refined shell finite element model are very satisfactory.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/233486

Influence of connections modeling on the seismic behaviour of industrial buildings
Proceedings of COMPDYN 2015
Autore/i: Tassotti, Luca; Radi, Mohammed; Gara, Fabrizio; Ragni, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Many industrial buildings with a precast concrete structure have been designed in accordance with non-seismic provisions by considering only gravity loads or, in some other cases, in accordance with not adequate seismic detailing requirements .In particular, seismic events that occurred in the recent past have shown that the connections between the main structural elements play an important role on the dynamic and seismic behaviour of the pre-cast concrete structure. Nowadays, the more advanced technical standards require mechani-cal connections between the precast elements; however codes do not furnish exhaustive information about the design and modelling of these connections neither in the seismic vul-nerability assessment of existing buildings nor in the design of new constructions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/233472

Impedances of inclined piles: an analytical solution
Atti del 16° Convegno Nazionale – L’ingegneria sismica in Italia (ANIDIS 2015)
Autore/i: Carbonari, Sandro; Morici, Michele; Gara, Fabrizio; Dezi, Francesca; Leoni, Graziano
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The paper presents an analytical solution, based on the beam-on-dynamic Winkler foundation approach, for the evaluation of the dynamic impedances of inclined single piles. The Euler-Bernoulli beam model is adopted for the pile whereas analytical expressions available in literature for viscoelastic layers undergoing harmonic vibrations of a rigid disk are used for the soil. The system of partial differential equations, governing the coupled flexural and axial behaviour of the pile embedded in a homogenous soil layer, is solved analytically in terms of exponential matrices. By assuming non-homogeneous kinematic boundary conditions, the dynamic stiffness matrix of the soil-pile system is derived analytically. In the case of layered soils, the pile is discretized into segments within which soil properties are constant and the dynamic stiffness matrix of the system is obtained according to the direct stiffness approach assembling contributions of all segments. Expressions of the soil-foundation impedance functions are derived by the problem condensation. Comparisons of results with those obtained from rigorous boundary element formulations demonstrate that the model, characterised by a very low computational effort, is able to reproduce the dynamic compliance of the soil-pile system with a good level of accuracy.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/227951

Operational Modal Analysis on r.c. building for the evaluation of the dynamic changes due to retrofitting
Proceedings of EESMS 2015, Environmental, Energy and Structural Monitoring Systems
Autore/i: Roia, Davide; Gara, Fabrizio; Speranza, Elisa; Gioiella, Laura; Dezi, Luigino
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The paper deals with the changes of the modal parameters of a r.c frame building sited in Camerino, Italy. Operational modal analysis were performed before and after the seismic retrofitting of the building achieved with an innovative system that uses external steel towers equipped with dissipative devices. Before retrofitting, ambient vibration tests were carried out with the aim of evaluating the actual linear dynamic behavior of the building including the contribution of non-structural components (e.g. external and internal walls); modal parameters, i.e. natural frequencies and mode shapes determined by means of experimental modal analysis, allowed the calibration of a predictive f.e. model of the building which was crucial for the final design of the retrofitting system. Tests were repeated after the retrofitting works, with the main objective to verify that changes of modal parameters are in agreement with those predicted by the f.e. model. Results and comparisons between the modal parameters obtained before and after the retrofitting works demonstrate that the ambient vibration tests and the data processing techniques used allow the identification of the dynamic behavior of r.c. few-storeys buildings under operating conditions and, then, the identification of dynamic changes due to seismic retrofitting works performed with external steel “dissipative towers”. A model updating procedure is carried out to identify the value of the elastic modulus of the different materials constituting structural and non-structural elements.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/233480

The effect of tie beams on the kinematic response and impedence functions of monopile foundations
Proceedings of the Second European Conference on Earthquake Engineering
Autore/i: Capatti, M. C.; Carbonari, Sandro; Dezi, F.; Gara, Fabrizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The paper focuses on the effect of tie beams on the kinematic response and impedance functions of monopile foundations. Considering a foundation system of a regular framed structure, constituted by monopiles connected with tie beams, a representative portion of the foundation is isolated by suitably modelling its boundary conditions, and kinematic Soil-Structure Interaction analyses are performed exploiting the numerical formulation proposed by Dezi et al. (2009) for the soil-pile system modelling. The model assumes a linear behaviour for the pile and is able to include the soil non linearity in a linear equivalent manner; this allows formulating the problem in the frequency domain where elastodynamic Green’s functions are used to account for the soil-pile interaction and for both the hysteretic and radiation damping. Tie beams are included into the formulation and the problem is solved by means of the finite element approach. A non dimensional parametric investigation is performed by varying the main geometrical and mechanical parameters affecting the whole system response. Results are presented in terms of impedance functions and kinematic response parameters, focusing on the effects of the foundation tie beams on the system response.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/212149

Seismic response of bridge piers founded on inclined pile groups
Proceedings of the Second European Conference on Earthquake Engineering
Autore/i: Morici, M.; Carbonari, Sandro; Dezi, F.; Gara, Fabrizio; Leoni, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper investigates the seismic response of bridge piers founded on inclined pile groups, evaluating effects of soil-structure interaction by considering different pile group geometries and piles inclinations. Analyses are performed by means of the direct approach taking advantage of a 3D numerical model developed by the authors for the analysis of inclined pile groups. In particular, both the superstructure and piles are modelled by means of beam elements and the soil is schematized as a visco-elastic medium constituted by independent infinite horizontal layers. The soil-pile and the pile-soil-pile interaction are captured in the frequency domain by means of elastodynamic Green’s functions that also allow including the hysteretic and radiation damping. In order to investigate kinematic stress resultants in piles and to evaluate the significance of the soil-foundation system filtering effect, kinematic interaction analyses of the soil-foundation systems are also performed by removing the superstructure mass from the models. The influence of key parameters such as the piles inclination and the group configuration on the structural behaviour (displacements and stress resultants) and on the foundation response (maximum shears and bending moments in piles) is discussed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/212150

Analisi sismica di edifici prefabbricati con connessioni deformabili
Atti del Workshop tecniche innovative per il miglioramento sismico di edifici prefabbricati
Autore/i: Tassotti, Luca; Radi, Mohamed; Gara, Fabrizio; Ragni, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Nel contesto nazionale le strutture prefabbricate monopiano risultano in larga parte concepite mediante concezioni strutturali superate dagli attuali criteri antisismici. Gli eventi sismici recenti e del passato hanno evidenziato come la loro vulnerabilità sia spesso associata alle connessioni tra elementi strutturali. Le norme attuali risultano tuttavia carenti nel fornire indicazioni in merito alla progettazione e alla modellazione delle stesse. Nella presente memoria viene presentata una procedura di modellazione delle connessioni a spinotto per la valutazione della vulnerabilità sismica degli edifici esistenti. La metodologia proposta viene applicata a due capannoni industriali esistenti. Dai risultati delle analisi dinamiche lineari e statiche non lineari condotte è emerso che una modellazione delle connessioni rigide può portare a sovrastime della domanda sismica in esse e alla variazione della risposta sismica globale dell’edificio, modificando l’esito delle verifiche di sicurezza sia globali che locali.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/234008

NONLINEAR DYNAMIC RESPONSE OF NEAR-SHORE PILES SUBJECTED TO SNAP-BACK TESTING
Proceedings of the 15th European Conf. on Earthquake Engineering and Seismology, 15ECEES
Autore/i: Francesca, Dezi; Gara, Fabrizio; Roia, Davide
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper presents the results of free vibration tests carried out on a near-shore steel pipe pile vibrodriven into soft marine clay. The tests were carried out by quickly releasing a free head pile from a deformed configuration obtained by applying a quasi-static horizontal loading by means of a hydraulic jack. Different tests were performed at increasing loading levels with the aim of investigating the dynamic soil-water-pile system interaction and investigating how the nonlinear dynamic behaviour develops as the applied load increases. The results of experimental modal analyses, based on the signals recorded by strain gauges applied along the pile, are presented in terms of natural frequencies and damping ratios of the soil-water-pile system and the variations with loading level, due to the nonlinear behaviour of the system, are discussed. The dynamic effects induced on two pipe piles vibrodriven near the loaded pile to form an L-shaped in plan configuration are also discussed on the basis of signals measured by accelerometers applied at the head of the receiver piles; in order to investigate the pile-to-pile dynamic interaction.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/225197

Risposta sismica di pile fondate su gruppi di pali inclinati
Atti delle Giornate A.I.C.A.P. 2014
Autore/i: Morici, M.; Carbonari, Sandro; Dezi, F.; Gara, Fabrizio; Leoni, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Questo lavoro indaga la risposta sismica di pile da ponte fondate su gruppi di pali inclinati tenendo conto dell’interazione terreno-struttura e considerando gruppi di pali con differente geometria e caratterizzati da pali con diversa inclinazione. Le analisi di interazione sono eseguite ricorrendo al metodo per sottostrutture ed utilizzando, per le analisi di interazione cinematica delle palificate a pali inclinati, un modello numerico 3D agli elementi finiti sviluppato dagli autori. In particolare, i pali sono modellati con elementi trave mentre il terreno è schematizzato come un mezzo visco-elastico costituito da strati orizzontali indefiniti tra loro indipendenti. L’interazione palo terreno e palo-terreno-palo è colta nel dominio delle frequenze utilizzando funzioni elastodinamiche di Green che permettono implicitamente di tenere conto anche dello smorzamento geometrico e isteretico. Le sovrastrutture hanno un comportamento lineare e sono schematizzate con elementi trave. L’approccio per sottostrutture permette di indagare separatamente gli effetti cinematici ed inerziali in fondazione, al variare della geometria della palificata, e di evidenziare il contributo dell’interazione nella definizione del moto sismico per le analisi delle sovrastrutture (moto della fondazione). I risultati delle analisi permettono di esprimere delle prime considerazioni circa l'influenza della configurazione della palificata e dell'inclinazione dei pali sul comportamento strutturale delle pile (spostamenti e caratteristiche di sollecitazione) e sulla risposta delle fondazioni (massimi tagli e momenti flettenti nei pali dovuti all'interazione cinematica e inerziale).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/212146

A higher order steel-concrete composite beam model
ENGINEERING STRUCTURES
Autore/i: Gara, Fabrizio; Carbonari, Sandro; G., Leoni; Dezi, Luigino
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents a model for the analysis of composite beams in which the constrained kinematics encompasses the overall shear deformability, warping of the slab cross section and of the steel beam and partial shear interaction between slab and girder. The warping functions are obtained by considering the problem of unrestrained thin-walled members subjected to self-equilibrated elementary load schemes. The governing equations are derived, according to the stiffness method, both in the weak and strong forms starting from the Virtual Work theorem which makes it possible to consistently obtain the resultants of stresses, the applied forces and the inertia involved in the problem. The analytical solution is obtained from the governing differential equations and the relevant boundary conditions exploiting exponential matrices. Some simple applications show the capability of the model to accurately describe both the global behaviour of composite beams, in terms of displacements and stress resultants, and local effects, in terms of normal stresses. The comparisons with results obtained with a refined shell finite element model are very satisfactory.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/212143

Seismic response of reinforced concrete frames on monopile foundations
SOIL DYNAMICS AND EARTHQUAKE ENGINEERING
Autore/i: Carbonari, Sandro; Dezi, F.; Gara, Fabrizio; Leoni, G.
Classificazione: 1 Contributo su Rivista
Abstract: The paper focuses on the effects of soil-structure interaction on the seismic response of reinforced concrete frames on monopile foundations connected by tie beams. Such systems are usually designed by considering fixed restraints at the column bases and the effects of the foundation compliance have not yet been investigated. The soil-foundation system is analysed in the frequency domain by means of a numerical model that allows obtaining the dynamic impedance functions of the system and the foundation input motion necessary for the subsequent nonlinear inertial soil-structure interaction analysis which is performed in the time domain. Tie beams with different stiffness and soil deposits characterised by three different profiles of shear wave velocity are considered. Results of incremental dynamic analyses carried out on frames with monopile foundations are compared with those obtained considering double-pile foundations and the fixed base assumption. Soil-structure interaction is found to affect considerably the response of frames on monopile foundations by increasing the structural deformation and modifying the evolution of the dissipative mechanisms. Analyses accounting for the actual soil-foundation system compliance and the foundation input motion may be crucial for a reliable prediction of the actual distribution of stresses in the superstructure and the foundation elements.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/212137

Design expressions for the effective width of composite steel-concrete members
Proceedings of the 37th IABSE Symposium
Autore/i: Gara, Fabrizio; Ranzi, Gianluca; Leoni, Graziano
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper presents a new approach for the evaluation of the effective width for the analysis of composite steel-concrete members. The proposed method is based on the use of simple expressions which enable the calculation of the effective width of the slab accounting for shear-lag effects. Its particularity relies on its ability to utilize the results of a global analysis carried out specifying the real width of the slab along the whole bridge length and to port-process these by means of a crosssectional analysis using simple design equations to define the geometry of the concrete slab. The expressions for the effective widths have been derived for different loading conditions including constant uniformly distributed loads, envelopes of transverse actions due to traffic loads, support settlements, thermal effects and shrinkage. Several applications are then presented to outline the ability of the proposed method to accurately predict the stress state in the concrete slab while accounting for shear-lag effects. These results are also compared against those obtained based on available design guidelines and calculated by means of the finite element method using line and shell elements
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/225195

Lateral impact loading and snap-back testing to estimate linear and nonlinear dynamic response of near-shore piles
Proceedings of the 20th IMEKO TC-4
Autore/i: Dezi, Francesca; Gara, Fabrizio; Roia, Davide
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper presents some results of dynamic lateral loading tests on a near-shore steel pipe pile vibrodriven into soft marine clay. Two typologies of tests are carried out on a free head pile: impact load tests and free vibration tests at different load levels. The aim of this experimentation is to investigate the dynamic soil-water-pile interaction and determine the dynamic characteristics of the whole system by means of the two different typologies of test and for different levels of the dynamic input. The obtained results show the complex dynamic behaviour of the vibrating soil-water-pile system in terms of natural frequencies and damping ratios. The values obtained from the two test typologies are compared and the variations with the level of the input force, due to the nonlinear behaviour of the system, are discussed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/225196

Ambient vibration tests on a reinforced concrete school building before and after retrofitting works with external steel "dissipative towers”
Proceedings of the IX Int. Conf. on Structural Dynamics, EURODYN
Autore/i: Roia, Davide; Gara, Fabrizio; Balducci, Alessandro; Dezi, Luigino
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The paper deals with the ambient vibration tests carried out on an existing reinforced concrete school building sited in Camerino, a small town in central Italy near the epicentre of Umbria-Marche 1996 earthquake. Tests were performed before and after the seismic retrofitting of the building achieved with of an innovative system that uses external steel dissipative towers. Before the retrofitting, ambient vibration tests were carried out with the aim of evaluating the actual linear dynamic behaviour of the building including the contribution of non-structural components (e.g. external and internal walls); modal parameters, i.e. natural frequencies and mode shapes determined by means of experimental modal analysis, allowed the calibration of a predictive f.e. model of the building which was crucial for the final design of the retrofitting system. Tests were repeated after the retrofitting works, with the main objective to verify that changes of modal parameters are in agreement with those predicted by the f.e. model. Tests were carried out by positioning low noise piezoelectric accelerometers opportunely so as to survey the rigid motion of each storey. The modal parameters were identified with two identification techniques, the Enhanced Frequency Domain Decomposition and the Covariance-driven Stochastic Subspace Identification, in order to assess whether a method is more suitable in such cases. Results and comparisons between the modal parameters obtained before and after the retrofitting works demonstrate that the ambient vibration tests and the data processing techniques used allow identifying the dynamic behaviour of r.c. few-storeys buildings under operating conditions and catching the changes due to seismic retrofitting works performed using external steel dissipative towers.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/225175

Interdependent interpolation element for shear deformable composite beams
Atti del XXIV Congresso C.T.A.
Autore/i: Carbonari, Sandro; Dezi, Luigino; Gara, Fabrizio; Leoni, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper presents a novel interdependent interpolation finite element for a higher order beam capable of capturing shear-lag phenomenon and overall shear deformability of composite beams. After a brief overview of the beam kinematics and of the differential solving equations, the stiffness matrix and the nodal forces to be applied in a standard finite element procedure are derived in a consistent way by exploiting properties of exponential matrix ad their application in the solution of linear differential equation systems. Some comparisons with solutions obtained by using finite elements with polynomial interpolating functions demonstrate the capability of the new element.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/163559

Dynamic tests on an existing r.c. school building retrofitted with external steel "dissipative towers
Proceedings of the Int. Conf. on Vibration Problem ICOVP
Autore/i: Roia, Davide; Gara, Fabrizio; Balducci, A.; Dezi, Luigino
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper deals with the dynamic tests carried out on a school building (four story reinforced concrete frame) seismically retrofitted with an innovative system that uses external steel dissipative towers. Before the retrofitting, ambient vibration tests were carried out with the aim of evaluating the actual linear dynamic of the building including the contribution of non-structural components (e.g. external and internal walls). Modal parameters determined by means of experimental tests are crucial for the final design of the retrofitting system allowing the calibration of a predicting f.e. model. Three low noise servo-accelerometers per floor were opportunely positioned at each floor to monitor its rigid motion. The modal parameters are identified with the Enhanced Frequency Domain Decomposition technique obtaining the natural frequencies, mode shapes and damping ratios. After the building retrofitting, snap-back tests at different load levels were performed in order to evaluate the dynamic characteristics of the new structural system. The load was applied in a quasi-static manner by means of two Dywidag bars 47 anchored at the last floor and connected to a steel triangular truss pulled by two hydraulic jacks; the instantaneous release was obtained by cutting a dog-bone shaped steel plate with a blowtorch. In addition to the accelerometers, displacement transducers were positioned at the base of the steel towers, close to the viscous dampers, to measure the motion of the two towers. The natural frequencies and the damping ratios of the retrofitted building are estimated from the time histories of accelerations (free decay functions) by means of the crossing time and the logarithmic decrement techniques, respectively. The adopted experimental methodology adopted has revealed to be effective for the dynamic characterization, both at very low strain and at higher strain level, of a low-rise reinforced concrete frame building in service, which is characterized by a high overall stiffness due to the contribution of the non-structural components.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/163746

Full-scale pile subjected to different lateral dynamic loadings
Proceedings of the Int. Conf. on Earthquake Geotechnical Engineering ICEGE
Autore/i: Dezi, F.; Gara, Fabrizio; Roia, Davide
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper presents some results of dynamic lateral loading tests on a near-shore steel pipe pile vibrodriven into soft marine clay. Two typologies of tests are carried out on a free head pile: impact load tests and free vibration tests at different load levels. The aim of this experimentation is to investigate the dynamic soil-water-pile system interaction and determine the dynamic characteristics of the whole system by means of two different typologies of test and for different levels of the dynamic input. The obtained results show the complex dynamic behaviour of the vibrating soil water pile system in terms of natural frequencies and damping ratios. The values obtained from the two test typologies are compared and the variations with the level of the input force, due to the nonlinear behaviour of the system, are discussed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/163744

A comparative study on the time-dependent analysis of composite beams using available modelling techniques
Applied Mechanics and Materials - Advances in Computational Mechanics
Autore/i: O., Vallati; Gara, Fabrizio; G., Ranzi; G., Leoni
Editore: Publishing Editor Wolhlbier T., USA
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper presents a comparison of available numerical structural formulations for the short- and long-term analysis of composite beams with partial shear interaction. Four methods of analysis are considered and these include the finite difference method, the finite element method, the direct stiffness method and the exact analytical model. The results btained using these formulations are compared qualitatively and their accuracy is estimated, adopting the exact analytical model as a benchmark reference with the objective of establishing the minimum spatial discretisations required to keep the error within an acceptable tolerance. These comparisons are carried out for two static configurations, i.e. simply-supported beams and propped cantilevers, from which the qualitative behaviour of these formulations in the modelling of continuous beams can also be deduced.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/175703

Slab Cracking Control in Continuous Steel-Concrete Bridge Decks
JOURNAL OF BRIDGE ENGINEERING
Autore/i: Gara, Fabrizio; Graziano, Leoni; Dezi, Luigino
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents a study on the effectiveness of various casting techniques used to control slab tensile stresses during the construction of continuous steel-concrete composite bridge decks. The main features describing the early age behavior of concrete are outlined and available modeling options are considered. A practical procedure is presented for the evaluation of the slab stress state taking place at various construction stages based on the modular ratio approach suggested by Eurocode 4. The method, which can be implemented using commercial software, requires the evaluation of suitable modular ratios and creep coefficients to estimate the time-dependent effects of the concrete slab weight and the thermal, endogenous, and drying shrinkage components. This simplified procedure is then applied to a case study to evaluate, for various casting sequences, the contributions of the concrete weight and shrinkage components to the slab early cracking. Finally, the efficiency of various casting techniques in controlling the slab tensile stresses is presented and discussed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/133462

Experimental study of near-shore pile-to-pile interaction
SOIL DYNAMICS AND EARTHQUAKE ENGINEERING
Autore/i: F., Dezi; Gara, Fabrizio; Roia, Davide
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents the results of lateral impact load field tests carried out on a system of three steel pipe piles vibro-driven into soft clay in a near-shore marine environment, with the aim of evaluating the pile-soil-pile dynamic interaction. Piles are arranged in an “L” shaped horizontal layout and are instrumented with accelerometers at their free heads. The obtained results show the complex dynamic behaviour at very small strain of the vibrating soil water piles system. The role of different type of waves in the pile to pile interaction is investigated by analyzing the results in the time and frequency domains and by means of a time-frequency analysis. The effects of the pile spacing and input direction on these interaction mechanisms are also presented. Finally, important dynamic parameters of the soil, such as the velocities of the shear waves and surface waves (Scholte waves) of the upper soil are directly estimated from the time delays between signals recorded at the pile heads.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/90264

Simplified method to analyse casting sequence of composite bridge slabs
Proceedings of the 36th IABSE Symposium
Autore/i: Dezi, Luigino; Gara, Fabrizio; Leoni, G.
Editore: IABSE-ETH Honggerberg, Zurich, Switzerland
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper presents a simplified procedure to analyse the effects of construction sequences of slabs in steel-concrete composite bridge decks. The procedure allows accounting for shrinkage and casting sequence effects. The time-dependent behaviour of the concrete is also included to capture the stress relaxation that mitigates the effects of the fast thermal shrinkage. Main features related to modelling of early-age concrete behaviour and tensile creep are discussed. The proposed simplified method is applied to evaluate the stresses in the slab of a realistic three-span composite bridge deck by considering different casting sequences. The comparison between the results obtained with the proposed method and those given by a step-by-step procedure shows the accuracy of the simplified method that can be considered a useful tool for practical applications.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/163747

Slab cracking influence in the fatigue assessment of continuous composite bridge decks
Proceedings of the 36th IABSE Symposium
Autore/i: Dezi, Luigino; M., Formica; Gara, Fabrizio; Leoni, G.
Editore: Editore IABSE-ETH Honggerberg, Zurich, Switzerland
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The paper analyzes the influence of the slab cracking in the fatigue assessment of continuous composite decks by considering the effects of slab casting sequences and the shrinkage components (thermal, endogenous and drying). A numerical procedure for the stress calculation accounting for the tension stiffening of the slab longitudinal rebars is presented. The long term effects of casting sequences and concrete shrinkage are analysed with a simplified procedure based on the application of the modular ratio method. With reference to a realistic continuous twin girder composite deck the fatigue verification of the longitudinal girders is carried out by considering three different casting modalities. The obtained results show the important role of the slab casting sequences in the stress range calculation and the remarkable influence of the slab cracking in the fatigue assessment.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/163748

Tests on two 18-years-old prestressed thin walled roof elements
ENGINEERING STRUCTURES
Autore/i: Carbonari, Sandro; Gara, Fabrizio; Roia, Davide; G., Leoni; Dezi, Luigino
Classificazione: 1 Contributo su Rivista
Abstract: The paper presents the experimental tests carried out on two prestressed thin walled V-shaped elements, used over a period of 18 years as the roof of an industrial building and removed after having exhibited marked deflections and crack patterns. The experimental program, including material characterization, impact load and ultimate static load tests, is aimed at valuating the actual load carrying capacity of the elements. The survey of the elements geometry, with special attention to imperfections, is presented; then results of the impact load test, namely the fundamental frequencies and modal shapes of free vibration, are reported. Successively, the results of static load tests up to failure are discussed. Due to the small thickness of the cross section walls, second order effects strongly interact with the global failure mechanism. The combination of dynamic impact and ultimate static load tests allowed the calibration of an accurate finite element model, accounting for both mechanical and geometrical nonlinearities, capable to predict the behaviour of the elements up to collapse and useful to design repairing and strengthening works.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/86615

Effects of soil-foundation flexibility on the performance of reinforced concrete frame structures
Proceedings of the 2nd Int. Conf. on Performance Based Design in Earthquake Geotechnical Engineering, IIPBD
Autore/i: Dezi, F.; Carbonari, Sandro; Gara, Fabrizio; Leoni, G.
Editore: Pàtron Editore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The paper focus on the effects of soil-structure interaction on the seismic response of reinforced concrete frames designed according to displacement-based approaches and founded on piles. The substructure method is adopted and 6-storeys 3-bays frames founded on 3 different two-layered soil deposits are considered. For each soil deposit two foundation typologies are adopted: mono-pile and double-pile foundations. Soil-structure interaction effects on the seismic response of the structures are evaluated both in the linear and nonlinear field by means of incremental dynamic analyses. Results, in terms of forces and displacements, are compared with those achieved from conventional fixed base analyses demonstrating that soil-structure interaction effects are more evident for moderate earthquakes, inducing early structural damages, and for soft soil deposits. For earthquakes of high intensity soil-structure interaction is less important. The mono-pile foundation, suitably designed in conjunction with stiff tie-beams, is able to guarantee an efficient degree of restraint at the base of columns, comparable with that provided by the double-pile foundation.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/74916

Effects of Soil-Structure Interaction on the Linear and Nonlinear Seismic Behaviour of Coupled Wall-Frame Systems
Dynamic Interaction of soil and structure (DISS_12)
Autore/i: Carbonari, Sandro; Dezi, Francesca; Gara, Fabrizio; Leoni, Graziano
Editore: Aracne
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The effects of Soil-Structure Interaction (SSI) on the response of coupled wall-frame structures on pile foundations are investigated. The analysis methodology based on the substructure method is re-called focusing on the modelling of pile group foundations. The iner-tial interaction analysis is performed in the time domain by using a fi-nite element model of the superstructure and suitable Lumped Pa-rameter Models (LPMs) are implemented to reproduce the frequency-dependent compliance of the soil-foundation systems. The effects of SSI are evaluated by considering realistic case studies consisting of 6-storey 4-bay wall-frame structures founded on piles. Moderate and strong seismic actions are simulated employing real and artificial earthquakes. The superstructure is assumed to behave linearly under moderate shakings; on the other hand, the nonlinear structural behav-iour is accounted for in the case of strong earthquakes. Comparisons of the results obtained considering compliant base and fixed base models are presented by addressing the effects of SSI on the main re-sponse quantities of linear and nonlinear structures. SSI effects on displacements, inter-storey drifts and base shears are discussed and, with reference to the nonlinear structures, effects on the ductility de-mand and the evolution of dissipative mechanisms are investigated by considering earthquakes with increasing intensity.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/225215

Seismic response of reinforced concrete frames on pile foundations
Proceedings of the 18th IABSE Congress on Innovative Infrastructures – Towards Human Urbanism
Autore/i: Dezi, F.; Carbonari, Sandro; Gara, Fabrizio; Leoni, G.
Editore: IABSE-ETH Honggerberg
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The paper focus on the effects of soil-structure interaction on the seismic response of reinforced concrete frames founded on piles. The substructure method is adopted and 6-storeys 3-bays frames founded on 3 different two-layered soil deposits are considered. For each soil deposit two foundation typologies are adopted: mono-pile and double-pile foundations. Soil-structure interaction effects on the seismic nonlinear response of the structures are evaluated by means of incremental dynamic analyses. Results are compared with those achieved from fixed base analyses demonstrating that soil-structure interaction effects are more evident for moderate earthquakes, inducing early structural damages, and for soft soil deposits. The mono-pile foundation, suitably designed in conjunction with stiff tie-beams, is able to guarantee an efficient degree of restraint at the base of columns, comparable with that provided by the double-pile foundation.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/82712

Experimental tests and numerical modelling of wall sandwich panels
ENGINEERING STRUCTURES
Autore/i: Gara, Fabrizio; Ragni, Laura; Roia, Davide; Dezi, Luigino
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents the first part of an experimental investigation carried out on a construction system based on completed in situ sandwich panels with non-shear connectors, concerning the study of vertical panels used as structural walls. Compression tests with axial and eccentric loads were carried out on several full scale panel specimens with different slenderness ratios in order to study the behaviour of panels under vertical in-plane forces. Additionally, diagonal compression tests were performed on square specimens in different configurations in order to study the behaviour of panels under horizontal in-plane forces. The most significant load-displacement diagrams for increasing load are illustrated and the failure modalities are discussed. The semi-composite behaviour of the panels, guaranteed by the internal layer of polystyrene and the reinforced concrete beams at the panel ends, is highlighted. Finally, some numerical simulations are performed with non-linear finite element models and some useful design indications are given. (C) 2011 Elsevier Ltd. All rights reserved.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75125

Experimental behaviour and numerical analysis of floor sandwich panels
ENGINEERING STRUCTURES
Autore/i: Gara, Fabrizio; Ragni, Laura; Roia, Davide; Dezi, Luigino
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents the second part of an experimental investigation carried out on a construction system based on completed in-situ sandwich panels with non-shear connectors, concerning the study of floor sandwich panels. Four-point flexural tests were carried out on several full-scale panel specimens with different slenderness ratios in order to study the behaviour of panels under vertical loads. Additionally, wall-floor nodes with different connection details were tested to analyze the effective degree of the rotational restraint of different realistic nodes. Furthermore, a loading test on the floor of a full scale 3D mock-up entirely built with sandwich panels was carried out to investigate the service and ultimate behaviour of a real floor. The most significant load-displacement diagrams for increasing load are illustrated and the failure modalities are discussed. The semi-composite behaviour of the panels, guaranteed by the internal layer of polystyrene and the reinforced concrete beams at the panel ends, is highlighted. The effects of the wall-floor connection and the bi-dimensional behaviour of the floor are also evaluated. Finally, some numerical simulations are performed with non-linear finite element models and some useful design indications are given. (C) 2011 Elsevier Ltd. All rights reserved.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75126

Dynamic response of a near-shore pile to lateral impact load
SOIL DYNAMICS AND EARTHQUAKE ENGINEERING
Autore/i: Francesca, Dezi; Gara, Fabrizio; Roia, Davide
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents the results of lateral impact load field tests conducted on a near-shore steel pipe pile vibro-driven into soft marine clay. Two series of tests are carried out, the first 1 week and the second 10 weeks after the vibro-driving. The pile is instrumented with an unconventional technique for field tests in marine environment which includes an accelerometer at the pile head, strain gauges and pore pressure transducers along the pile. Instruments are properly protected from marine environment and pile driving installation method. Tests are aimed at investigating the dynamic soil-water-pile interaction and determining the dynamic characteristics of the whole system at very small strain. The obtained results show the complex dynamic behaviour of the vibrating soil-water-pile system in terms of natural frequencies, damping and mode shapes. The variation in the dynamic behaviour in time, due to reconsolidation of soil subsequent to vibro-driving is also discussed. Furthermore, the horizontal dynamic impedance function of the whole system is derived from the experimental data over a wide frequency range and compared with that obtained from a numerical soil–pile interaction model.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/69943

Il getto delle solette nei ponti composti: confronto tra varie tecniche di frazionamento
Atti del 26° Convegno nazionale “Giornate A.I.C.A.P.”
Autore/i: Gara, Fabrizio; Leoni, G.; Dezi, Luigino
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Slabs of continuous steel-concrete composite viaducts are usually constructed for segments on the unpropped steel girders. The contemporary action of restrained shrinkage and of forces due to the construction phases may lead to the concrete early cracking. This paper presents a study on the effectiveness of various casting techniques that may be used to control tensile stresses in continuous composite bridges. Numerical results obtained analysing a case study by means of a dedicated computer program, capable of taking into account effects of structural changes and of early shrinkage, are discussed. The various actions (self-weight, thermal, endogeneous and drying shrinkage) are considered separately in order to understand mechanisms that are responsible for tensile stresses and to evaluate the effectiveness of the various construction techniques considered.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63576

Field tests and numerical analysis of piles under lateral impact loading
Proceedings of the 5th Int. Conf. on Earthquake Geotechnical Engineering, 5ICEGE
Autore/i: F., Dezi; Gara, Fabrizio; Roia, Davide
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47585

L’influenza della fessurazione nella verifica a fatica dei ponti con impalcato continuo composto
Atti del XXIII Congresso C.T.A.
Autore/i: Dezi, Luigino; Formica, M.; Gara, Fabrizio; Niccolini, S.
Editore: Doppiavoce
Luogo di pubblicazione: Napoli
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63570

Simplified analysis of shrinkage and casting sequence effects in composite bridge decks
Atti del XXIII Congresso C.T.A.
Autore/i: Dezi, Luigino; Gara, Fabrizio; Leoni, G.
Editore: Doppiavoce
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT This paper presents a simplified procedure to account for shrinkage and casting sequence effects in the time-dependent analysis of steel-concrete composite continuous decks. Main features related to modelling of early-age concrete behaviour and tensile creep are discussed. The proposed simplified method is applied to evaluate the service response of a realistic three-span composite bridge deck by considering different slab casting sequences. The comparison between the obtained results and those given by the step-by-step procedures shows the accuracy of the simplified method, which can be considered a useful tool for practical applications. The numerical simulations highlight how the various casting sequences affect the development of tensile stresses in the slab.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63569

Prove in vera grandezza e analisi numeriche di pali con forzante orizzontale impulsiva
Attid dell'Incontro Annuale dei Ricercatori Italiani, IARG 2011
Autore/i: Dezi, F.; Gara, Fabrizio; Roia, Davide
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Sommario This paper presents the results of lateral impact load field tests carried out on three steel pipe piles at the tourist port of La Spezia, Italy. The piles are vibro-driven into marine soft clay, with a L-shaped plan layout, kept free at the head. Two test campaigns are carried out, the first 1 week and the second 10 weeks after vibrodriving of the piles. The dynamic behaviour of the complex soilwaterpile system at very small strain is discussed. In particular, the response of the single pile and the mutual interaction between loaded and receiver piles are presented. The variation in dynamic behaviour of the whole system in time (for the two campaigns), due to reconsolidation of the soil close to the pile subsequent to the vibrodriving, is observed. The experimental data are compared with the results obtained from a 3-D finite element models of the whole soilwaterpile system considering both a solid and a shell model for the piles and linear behaviour for the soil.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63575

Risposta sismica di telai in calcestruzzo armato fondati su pali
Atti del XIV Convegno ANIDIS
Autore/i: Carbonari, Sandro; Dezi, F.; Gara, Fabrizio; Leoni, G.
Editore: Digilabs
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT Questo lavoro presenta uno studio sugli effetti dell’interazione terreno-struttura nella risposta sismica di telai in calcestruzzo armato fondati su pali. Adottando un approccio per sottostrutture, sono stati studiati telai in calcestruzzo armato di 3 campate e 6 piani, fondati su 3 differenti depositi bistrato al di sopra di un substrato sismico. Per ciascun deposito sono state ipotizzate due tipologie di fondazione: mono-palo e bi-palo. Gli effetti dell’interazione sulla risposta delle strutture sia in campo elastico che post-elastico sono valutati per mezzo di analisi incrementali delle strutture a base deformabile. I risultati, in termini di forze e spostamenti, confrontati con quelli ottenuti da analisi convenzionali a base fissa, dimostrano che il ruolo dell’interazione terreno-struttura è più significativo per intensità sismiche moderate, che provocano il primo danneggiamento delle strutture, e per i depositi più deformabili. Per terremoti di alta intensità, l’interazione terreno-struttura gioca un ruolo minore. Il sistema mono-palo, opportunamente progettato insieme con gli elementi di collegamento, si è dimostrato capace di garantire un grado di vincolo alla base paragonabile a quello offerto dal sistema bi-palo.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63573

Indagini sperimentali su due tegoli in c.a.p. dopo 18 anni di esercizio
Atti del 26° Convegno nazionale “Giornate A.I.C.A.P.”
Autore/i: Carbonari, Sandro; Gara, Fabrizio; Roia, Davide; Leoni, G.; Dezi, Luigino
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: SOMMARIO In questo lavoro si presenta un’indagine sperimentale eseguita su due tegoli in c.a.p. con sezione a V utilizzati per circa 18 anni in copertura di un edificio industriale. I tegoli presentano quadri deformativi e fessurativi che hanno suggerito l’esecuzione di prove di carico statico spinte fino a rottura. Le prove sono state precedute dalla caratterizzazione dinamica dei tegoli con forzante impulsiva che ha permesso di determinare le frequenze proprie e i modi di vibrare. Per la caratterizzazione del calcestruzzo sono state eseguite prove a compressione su provini cubici e cilindrici ricavati da carote prelevate dai tegoli. I risultati sperimentali sono stati interpretati con un modello numerico non lineare agli elementi finiti che ha permesso di formulare alcune prime osservazioni sulla sensibilità del tegolo alle non linearità geometriche e meccaniche.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63577

Field tests of vibro-driven piles under lateral impact loading
Atti del XIV Convegno ANIDIS
Autore/i: Dezi, F.; Gara, Fabrizio; Roia, Davide
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT This paper presents lateral impact load tests carried out on three steel pipe piles vibro-driven into marine soft clay at the tourist port “Mirabello” in La Spezia. Piles are displaced with a L-shape plane layout and kept free at the head. The instrumentation system of piles, unconventional for field test in marine environment, includes accelerometers, strain gauges and pore pressure gauges, with the relevant chemical and mechanical protections. The impact load tests were carried out in two different campaigns, the first 1 week and the second 10 weeks after the pile vibro-driving. Some of the results collected are presented, i.e. time histories of strains and accelerations. The response of the single pile and the dynamic behaviour of the pile group, at very small strain, are investigated: the dynamic behaviour of soil-water-pile system is discussed in terms of natural frequencies, damping and mode shapes; the pile-soil-pile interaction is studied by analyzing the different types of wave propagating from loaded pile to the receivers and estimating the shear wave velocity. Furthermore, the variation in time (for the two experimental campaigns) due to the re-consolidation of the soil close to the pile subsequent to the vibro-driving is observed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63574

Partial Interaction Analysis With Shear-lag Effects of Composite Bridges: A Finite Element Implementation For Design Applications
ADVANCED STEEL CONSTRUCTION
Autore/i: Gara, Fabrizio; G., Ranzi; G., Leoni
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents a numerical model for the analysis of composite steel-concrete beams with partial interaction to account for the deformability of the shear connection. The proposed approach is capable of capturing the structural response produced by shear-lag effects and by the time-dependent behaviour of the concrete. The versatility of the FE formulation is demonstrated for a wide range of realistic bridge arrangements, e.g. from twin-deck girders to cable-stayed bridges. The accuracy of the approach is validated against the results obtained from more refined models generated with shell elements using commercial finite element software. For each bridge typology considered, both deformations and stresses are calculated to provide greater insight into the structural performance. Particular attention is placed on the determination of the effective width to be used for design purposes and on the stress distribution induced in the concrete component, together with their variation with time due to creep and shrinkage.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75128

Simplified method of analysis accounting for shear-lag effects in composite bridge decks
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH
Autore/i: Gara, Fabrizio; Ranzi, G.; Leoni, G.
Classificazione: 1 Contributo su Rivista
Abstract: This paper proposes a simplified method of analysis for the design of twin-girder and single-box steel-concrete composite bridge decks. Its main advantages rely on (i) the use of the real width of the slab for the whole bridge length when performing the global analysis, i.e. without modifying the deck geometry based on the effective width method, and (ii) its ability to evaluate the normal longitudinal stress distribution on the slab by means of a cross-sectional analysis considering the internal actions obtained from the global analysis. In the latter cross-sectional analysis the properties of the concrete component are based on an effective width calculated using new analytical expressions presented in this paper. The proposed approach is capable of handling different loading conditions, such as constant uniformly distributed loads, envelopes of transverse actions due to traffic loads, support settlements and concrete shrinkage. These analytical expressions have been obtained based on the results of an extensive parametric study carried out by means of the finite element formulation described in the first part of the paper. The accuracy of the proposed approach is validated for a typical four-span bridge with constant cross-section throughout its length against the results obtained based on the finite element method. Finally, a realistic case study of a bridge with varying cross-section is considered to show the robustness of the proposed methodology. (C) 2011 Elsevier Ltd. All rights reserved.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75127

Effective width of steel-concrete composite decks
Nota Tecnica di Dipartimento n. 26, Department of Architecture, Construction and Structures, Università Politecnica delle Marche, Italy.
Autore/i: Gara, Fabrizio; A., Mozzoni; Dezi, Luigino
Luogo di pubblicazione: Ancona
Classificazione: 5 Altro
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/74890

Caratterizzazione sperimentale di un sistema costruttivo a pannelli sandwich: pannelli parete
Atti del 18° Congresso C.T.E.
Autore/i: Gara, Fabrizio; Ragni, Laura; Roia, Davide; Dezi, Luigino
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: SUMMARY This paper presents the first part of the experimental campaign carried out on the constructive system ”Concrewall”, consisting of sandwich panels by Schnell House. The tests are conducted at the Material and Structural Testing Laboratory of the “Università Politecnica delle Marche”. In particular, Single Composite Panels (PCSP) used as vertical structural wall are tested. Compression tests, with axial and eccentric loads, and diagonal compressive tests are carried out in order to study the behaviour of panels under vertical and horizontal forces. The main results of the experimental campaign and some numerical analyses are illustrated.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63579

Full-scale lateral impact load test of a 3-pile group
Proceedings of the 14th European Conf. on Earthquake Engineering, 14ECEE
Autore/i: F., Dezi; Gara, Fabrizio; Roia, Davide; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/48462

Caratterizzazione sperimentale di un sistema costruttivo a pannelli sandwich: pannelli solaio
Atti del 18° Congresso C.T.E.
Autore/i: Gara, Fabrizio; Ragni, Laura; Roia, Davide; Dezi, Luigino
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: SUMMARY This paper presents the second part of the experimental campaign carried out on the constructive system ”Concrewall”, consisting of sandwich panels by Schnell House. The tests are conducted at the Material and Structural Testing Laboratory of the “Università Politecnica delle Marche”. In particular, Single Composite Panels (PCSP) used as roof panels are tested. Flexural tests are carried out on the panels in order to study the behaviour under vertical loads. Additionally, to investigate the behaviour of the connection between roof and wall panels cyclic tests are performed on two typical connection systems. Finally, a load test of a square roof of a real-scale 3-D mock-up is carried out to evaluate the behaviour of a real roof taking into account both the effects of the roof-wall connection and the roof bi-dimensional behaviour. The main results of the experimental campaign and some numerical analyses are illustrated in the paper.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63578

Short- and Long-term Analytical Solutions for Composite Beams with Partial Interaction and Shear-lag Effects
INTERNATIONAL JOURNAL OF STEEL STRUCTURES
Autore/i: Gara, Fabrizio; G., Ranzi; G., Leoni
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents an analytical model for the short- and long-term analysis of composite steel-concrete beams with partial shear interaction and accounting for shear-lag effects. The material properties of the concrete have been assumed to be time-dependent and have been modelled by means of the algebraic methods while the remaining materials forming the cross-section have been supposed to behave in a linear-elastic manner. The global balance condition of the problem has been obtained by means of the principle of virtual work and, integrating this by parts, the governing system of differential equations and corresponding boundary conditions have been determined. Analytical expressions for both short- and long-term solutions have been derived and, to outline their ease of use, a number of case studies relevant for bridge applications have been proposed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75129

A finite element formulation to account for shear-lag effects in composite bridges with complex structural arrangements
Proceedings of the 10th International Conf. on Computational Structures Technology
Autore/i: M., Mursi; Gara, Fabrizio; G., Ranzi; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/175902

Seismic response of a coupled wall-frame structure considering soil-pile-structure interaction
Proceedings of the 14th European Conf. on Earthquake Engineering, 14ECEE
Autore/i: F., Dezi; Carbonari, Sandro; Gara, Fabrizio; G., Leoni
Editore: MAEE
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/48463

Soil-pile-structure interaction in the seismic response of coupled wall-frame structures
Atti del XIII Convegno ANIDIS - Bologna, Italy
Autore/i: Carbonari, Sandro; Dezi, F.; Gara, Fabrizio; Leoni, G.
Editore: IMREADY
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT The aim of this paper is to study the effects of soil-structure interaction on the seismic response of coupled wall-frame structures on pile foundations considering the non-linear behaviour of the superstructure. According to the substructure method, the kinematic interaction analysis is performed by means of a numerical procedure obtaining the dynamic impedance functions and the foundation input motion both necessary to perform inertial interaction analysis. A suitable lumped parameter model is defined to reproduce in the time domain the frequency-dependent impedances of the soil-foundation system. The vertical, horizontal and rotational components of the soil-foundation impedance functions, as well as the roto-translational coupling one, are taken into account. The non-linear inertial interaction analysis is performed by using a finite element model of the superstructure. With reference to a 6-storey 4-bay wall-frame structure, designed according to the Displacement-Based Design and founded on a soft soil deposit, comparisons are made between the compliance base and the fixed base models. The effects of the soil-structure interaction, in terms of structural displacements, base shear, ductility demand and evolution of dissipative mechanisms, are evaluated.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63581

Campagna sperimentale sul sistema costruttivo a pannelli sandwich “concrewall”
Nota Tecnica di Dipartimento n. 19, Department of Architecture, Construction and Structures, Università Politecnica delle Marche, Italy
Autore/i: Dezi, Luigino; Gara, Fabrizio; R., Giacchetti; Ragni, Laura; Roia, Davide
Luogo di pubblicazione: Ancona
Classificazione: 5 Altro
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/74888

Analytical design equations for the calculation of the effective width for the analysis of composite steel-concrete bridge decks
Proceedings of the 5th International Symposium on Steel Structures, ISSS 2009
Autore/i: Gara, Fabrizio; G., Ranzi; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper proposes new analytical expressions for the determination of effective widths for the analysis of twin-girder steel-concrete composite bridge decks. The main advantage of the proposed approach relies on its ability to evaluate the normal longitudinal stress distribution on the slab by means of a cross sectional analysis carried out using the internal actions calculated by means of a global analysis specifying the real width of the slab along the whole bridge length. The proposed expressions are shown to be able to handle different loading conditions which include constant uniformly distributed loads, envelopes of transverse actions due to traffic loads, support settlements and concrete shrinkage. Comparisons with the methodology recommended by design guidelines are carried to highlight the ease of use and effectiveness of the proposed method considering realistic continuous twin-girder composite bridge decks.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47718

Shear lag effects in composite bridges with complex static scheme
Proceedings of the Int. Conf. on Computational Design in Engineering, CODE2009
Autore/i: M., Mursi; Gara, Fabrizio; G., Ranzi; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT: This paper deals with the implementation of a beam finite element, suitable for the analysis of steel-concrete composite decks affected by the shear-lag in the slab, in a program for the analysis of bridges with complex static scheme, such as arch bridges, bow-string bridges and cable stayed bridges. The advantage of this formulation relies on its ability to account for stress concentrations which can arise in the slab due to the application of longitudinal forces as in the case of anchorage of prestressing cables or stays, and in the case of differential non-mechanical deformations. An application to a realistic arch bridge is presented in order to show the potentiality of the method.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47720

Sperimentazione in vera grandezza per lo studio dell'interazione dinamica palo-terreno-palo: porto turistico Mirabello, La Spezia
Atti dell'Incontro Annuale dei Ricercatori Italiani, IARG 2009 - Roma, Italy
Autore/i: Dezi, F.; Gara, Fabrizio; Roia, Davide; Dall’Aglio, F.; Piacentini, L.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Sommario In questo lavoro si presenta una vasta campagna di prove su pali in vera grandezza realizzata nell’ambito del progetto del porto turistico Mirabello a La Spezia. I pali sono tubi in acciaio, non vincolati in testa, vibro-infissi in terreni limo-sabbiosi saturi. Il campo prova è formato da un gruppo di tre pali disposti in pianta secondo uno schema ad “L” e strumentati con estensimetri, accelerometri e trasduttori di pressione. Si sono eseguite tre tipologie di prove dinamiche con forzante orizzontale in testa al palo, caratterizzate da diversi sistemi di eccitazione: prove a segnale impulsivo, a segnale armonico a frequenza costante e armonico a frequenza variabile. Durante le diverse prove si sono acquisite le storie delle deformazioni lungo un palo e delle accelerazioni in testa a tutti i pali. La metodologia di monitoraggio dei pali e la tecnica di messa in opera degli strumenti si sono dimostrate efficaci nonostante l’aggressività dell’ambiente marino e la criticità della fase di vibro-infissione. L’obiettivo è studiare il complesso fenomeno dell’interazione dinamica palo-terreno-palo, sia nel caso di pali singoli che di pali in gruppo. I risultati sperimentali verranno poi confrontati con i risultati di analisi numeriche avanzate e di metodi semplificati.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63580

Finite element formulation for the analysis of composite bridges with complex static schemes
Proceedings of the Australia-Japan Workshop on Steel and Composite Structures
Autore/i: G., Ranzi; Gara, Fabrizio; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Synopsis: This paper presents a new approach for the evaluation of the effective width for the analysis of composite steel-concrete members. The proposed method is based on the use of simple expressions which enable the calculation of the effective width of the slab accounting for shear-lag effects. Its particularity relies on its ability to utilize the results of a global analysis carried out specifying the real width of the slab along the whole bridge length and to port-process these by means of a cross sectional analysis using simple design equations to define the geometry of the concrete slab. The expressions for the effective widths have been derived for different loading conditions including constant uniformly distributed loads, envelopes of transverse actions due to traffic loads, support settlements, thermal effects and shrinkage. Several applications are then presented to outline the ability of the proposed method to accurately predict the stress state in the concrete slab while accounting for shear-lag effects. These results are also compared against those obtained based on available design guidelines and calculated by means of the finite element method using line and shell elements.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47719

Design expressions for the effective width of composite steel-concrete members
Proceedings of the 24 Biennial Conf. of the Concrete Institute of Australia, Concrete solutions 09
Autore/i: G., Ranzi; Z., Vrcelj; Gara, Fabrizio; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Synopsis: This paper presents a new approach for the evaluation of the effective width for the analysis of composite steel-concrete members. The proposed method is based on the use of simple expressions which enable the calculation of the effective width of the slab accounting for shear-lag effects. Its particularity relies on its ability to utilize the results of a global analysis carried out specifying the real width of the slab along the whole bridge length and to port-process these by means of a cross sectional analysis using simple design equations to define the geometry of the concrete slab. The expressions for the effective widths have been derived for different loading conditions including constant uniformly distributed loads, envelopes of transverse actions due to traffic loads, support settlements, thermal effects and shrinkage. Several applications are then presented to outline the ability of the proposed method to accurately predict the stress state in the concrete slab while accounting for shear-lag effects. These results are also compared against those obtained based on available design guidelines and calculated by means of the finite element method using line and shell elements.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/48460

Analysis of the shear lag effect in cable stayed bridges by means of deck finite elements
Proceedings of the 6th Int. Conf. on Advances in Steel Structures, ICASS ’09
Autore/i: Gara, Fabrizio; G., Ranzi; G., Leoni
Editore: The Hong Kong Institute of Steel Construction, Hong Kong
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT This paper presents the derivation of a finite element formulation for the analysis of composite decks accounting for partial interaction theory and shear-lag effects. The particularity of the proposed element, referred to as the deck finite element, relies on its ability to capture the structural response of cable stayed bridges, while preserving the ease of use of a typical line element. For these particular bridges, stress concentrations are induced in the slab by the application of concentrated forces due to the anchorage of stays. The ease of use of the proposed deck finite element is outlined considering a case study for which the calculated results have been compared against those obtained using a more refined model implemented using shell elements in a commercial finite element software.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47584

Early-age shrinkage and slab casting sequences in a long steel-concrete composite viaduct
Proceedings of the 6th Int. Conf. on Advances in Steel Structures, ICASS ’09
Autore/i: Gara, Fabrizio; G., Leoni; Dezi, Luigino
Editore: The Hong Kong Institute of Steel Construction, Hong Kong
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT This paper presents a study on the effectiveness of different casting sequences to control the cracking tendency in a long continuous steel-concrete composite viaduct. The main features of the early-age behaviour of concretes are addressed and the relative modelling options are discussed. Then, the application on a real viaduct with 12 spans of different length is presented considering a continuous and two fractionated sequences of casting. The importance in the selection of the casting sequence and of the segment length is discussed. The thermal shrinkage and the weight of new segments confirmed to be the main cause of the slab premature cracking. The enhanced tensile creep may reduce stresses which remain below the concrete tensile strength even in the long term.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52651

A beam finite element including shear lag effect for the time-dependent analysis of steel-concrete composite decks
ENGINEERING STRUCTURES
Autore/i: Gara, Fabrizio; G., Leoni; Dezi, Luigino
Classificazione: 1 Contributo su Rivista
Abstract: The paper presents a beam finite element for the long-term analysis of steel-concrete composite decks taking into account the shear lag in the slab and the partial shear interaction at the slab-girder interface. Using the displacement approach, beam kinematics is developed from the Newmark model for composite beams with partial shear connection: warping of the slab cross section is caught with the product of an established function which describes the warping shape, and an intensity function that measures the warping magnitude along the beam axis. Time-dependent behaviour is considered through an integral-type viscoelastic creep law for the concrete. The numerical solution is obtained by means of the finite element method and a step-by-step procedure for evolution in time. A refined, locking free, 13-dof beam finite element is derived considering second and third order hermitian polynomials in order to ensure consistent interpolation of the displacements. The convergence test results and comparisons with the experimental results of composite beams subjected to sustained loads demonstrate the precision of the proposed method. Further applications to realistic cases show the accuracy of the proposed element and its ability to describe the elastic and the time-dependent behaviour of bridge composite decks. (C) 2009 Elsevier Ltd. All rights reserved.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75130

Effects of soil-pile-structure interaction on the non-linear seismic response of coupled wall-frame systems
Proceedings of the 14th World Conference on Earthquake Engineering, WCEE 2008
Autore/i: Carbonari, Sandro; Dezi, F.; Gara, Fabrizio; Leoni, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT The aim of this paper is to study the effects of Soil-Structure Interaction (SSI) on the seismic responseof coupledwall-frame structures on pile foundations considering the non-linear behaviour of the superstructure. According to the substructure method, the kinematic interaction analysis is performed by means of a numerical procedure obtaining the dynamic impedance functions and the foundation input motion both necessary to perform inertialinteraction analysis. A suitable Lumped Parameter Model (LPM) is defined to reproduce in the time domain the frequency-dependent impedances. The vertical, horizontal and rotational components of the soil-foundation impedance functions, as well as the roto-translational coupling one, are taken into account. The non-linearinertial interaction analysis is performed by using a finite element model of the superstructure. With reference to a 6-storey 4-bay wall-frame structure, designed according to the Displacement-Based Design and founded on a soft soil deposit, comparisons are made between the compliance base and the fixed base models. The effects of the soil-structure interaction, in terms of structural displacements, base shear, ductility demand and evolution of dissipative mechanisms, are evaluated.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47717

Early-age shrinkage and slab casting sequences in a long steel-concrete composite viaduct
Atti del VII Workshop Italiano sulle Strutture Composte
Autore/i: Dezi, Luigino; Gara, Fabrizio; Leoni, G.
Editore: Aesse Stampa
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63582

Analysis of the Shear Lag Effect in Composite Bridges with Complex Static Schemes by means of a Deck Finite Element
INTERNATIONAL JOURNAL OF STEEL STRUCTURES
Autore/i: Gara, Fabrizio; G., Ranzi; G., Leoni
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents the derivation of a finite element formulation for the analysis of composite decks accounting for partial interaction theory and shear-lag effects. The particularity of the proposed element, referred to as the deck finite element, relies on its ability to capture the structural response of complex static schemes, such as those specified for arch, bow-string and cable stayed bridges, while preserving the ease of use of a typical line element. For these particular bridge Solutions, stress concentrations may be induced in the slab by the application of concentrated forces, i.e. due to the anchorage of prestressing cables or stays, or due to the presence of web members in arch bridges. The ease Of use of the proposed deck finite element is Outlined considering two case Studies for which the calculated results have been compared against those obtained using a more refined model implemented using shell elements in a commercial finite element software.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75131

Closure to "Effective slab width in prestressed twin-girder composite decks" by Luigino Dezi, Fabrizio Gara, and Graziano Leoni
JOURNAL OF STRUCTURAL ENGINEERING
Autore/i: Dezi, Luigino; Gara, Fabrizio; G., Leoni
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75132

Analysis of the shear-lag effect in composite bridges with complex static scheme by means of beam elements
Proceedings of the 3rd Int. Conf. on Structural Engineering, Mechanics and Computation, SEMC 2007
Autore/i: Dezi, Luigino; Gara, Fabrizio; Leoni, G.; Ranzi, G.
Editore: Millpress, Rotterdam, The Netherlands
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT: This paper deals with the implementation of a beam finite element, suitable for the analysis of steel-concrete composite decks affected by the shear-lag in the slab, in a program for the analysis of bridges with complex static scheme, such as arch bridges, bow-string bridges and cable stayed bridges. The deck model and the relevant beam finite element are adapted in the three-dimensional space on the basis of a model previously proposed by the authors. The problems of the spatial orientation of the element and the connectivity with traditional beam and truss finite elements are discussed. A special constraint is introduced to solve the illconditioned problem due to the zero torsional stiffness and the zero flexural stiffness on the co-ordinate plane parallel to the slab. Finally, an application to a realistic arch-latticed bridge is presented in order to show the potentiality of the method.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47714

Shear deformable steel-concrete composite beam model
Atti del XXI Congresso C.T.A.
Autore/i: Carbonari, Sandro; Dezi, Luigino; Gara, Fabrizio; Leoni, G.
Editore: Dario Flaccovio Editore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Atti del XXI Congresso C.T.A. - Catania, Italy
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63584

A steel-concrete composite beam accounting for shear deformability of the components
Proceedings of the 3rd Int. Conf. on Structural Engineering, Mechanics and Computation, SEMC 2007
Autore/i: Dezi, Luigino; Gara, Fabrizio; G., Leoni
Editore: Millpress, Rotterdam, The Netherlands
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT: This paper presents a model for the analysis of composite beams, taking into account the overall shear deformability, warping of the slab cross section and of the steel beam and partial shear interaction between the slab and the girder. A suitable restrained displacement field is introduced by considering the longitudinal displacements given by the product of known warping functions modulated by unknown functions variable along the beam axis. The warping functions are obtained by considering the problem of unrestrained thin-walled members subjected to self-equilibrated elementary load schemes. The governing equations are derived, according to the stiffness method, both in the weak and strong forms starting from the VirtualWork Theorem which makes it possible to consistently obtain the resultants of the stresses, the applied forces and the inertia involved in the problem. Some simple applications show the capability of the model to describe displacements and stresses.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50849

A shear deformable steel-concrete composite beam model
Proceedings of the 6th Int. Conf. on Steel & Aluminium Structures, ICSAS'07
Autore/i: Dezi, Luigino; Gara, Fabrizio; G., Leoni
Editore: Oxford Brookes University. Oxford, UK
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abstract This paper presents a model for the analysis of composite beams, taking into account the overall shear deformability, warping of the slab cross section and of the steel beam and partial shear interaction between the slab and the girder. A suitable restrained displacement field is introduced by considering the longitudinal displacements given by the product of known shapes modulated by unknown functions variable along the beam axis. The warping functions are obtained by considering the problem of unrestrained thin-walled members subjected to self-equilibrated elementary load schemes. The governing equations are derived, according to the stiffness method, both in the weak and strong forms starting from the Virtual Work Theorem which makes it possible to consistently obtain the resultants of the stresses, the applied forces and the inertia involved in the problem. Some simple applications show the capacity of the model to describe displacements and stresses.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52591

Assemblaggio ripetitivo di elementi prefabbricati in c.a.: un metodo semplificato per l’analisi viscoelastica
Atti del 24° Convegno nazionale “Giornate A.I.C.A.P.” - Salerno, Italy
Autore/i: Dezi, Luigino; Gara, Fabrizio; Leoni, G.; Zito, L.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: SOMMARIO In questo lavoro si propone un metodo per l’analisi semplificata di strutture costruite per assemblaggio ripetitivo di elementi prefabbricati in calcestruzzo. Dopo aver richiamato la formulazione analitica del problema viscoelastico di strutture eterogenee, si riportano i risultati di un’analisi parametrica in cui si sono studiati gli effetti sia dei parametri temporali che definiscono le sequenze costruttive sia dei parametri che influenzano la reologia del calcestruzzo. Sulla base dei risultati numerici, si propongono coefficienti che, scalando le classiche funzioni di cambiamento di schema statico, permettono di valutare le storie delle reazioni dei vincoli posticipati a partire dalle reazioni ottenute per una struttura omogenea senza cambiamento di schema statico.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63583

Implementation of a beam element including shear-lag in the analysis of bridges with complex static scheme
Proceedings of the 6th Int. Conf. on Steel & Aluminium Structures, ICSAS'07
Autore/i: Gara, Fabrizio; G., Leoni; G., Ranzi
Editore: Oxford Brookes University. Oxford, UK
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abstract This paper deals with the implementation of a beam finite element, suitable for the analysis of steel-concrete composite decks affected by the shear-lag in the slab, in a program for the analysis of bridges with complex static scheme, such as arch bridges, bow-string bridges and cable stayed bridges. The deck model and the relevant beam finite element are adapted in the three-dimensional space on the basis of a model previously proposed by the authors. The problems of the spatial orientation of the element and the connectivity with traditional beam and truss finite elements are discussed. A special constraint is introduced to solve the ill-conditioned problem due to the zero torsional stiffness and the zero flexural stiffness on the co-ordinate plane parallel to the slab. Finally, an application to a realistic arch-latticed bridge is presented in order to show the potentiality of the method.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47770

Load-consistent effective width for the analysis of composite steel-concrete bridge decks
5th International Conference on Advances in Steel Structures, ICASS 2007; Singapore; Singapore; 5 December 2007 through 7 December 2007; Code 88969
Autore/i: Carbonari, Sandro; Dezi, Luigino; Gara, Fabrizio; G., Leoni
Editore: Research Publishing Services, Singapore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abstract This paper proposes new effective widths for the analysis of twin-girder steel-concrete composite bridge decks. The method permits evaluating the normal longitudinal stress on the slab by means of a cross sectional analysis starting from the results of the structural analysis performed by considering the nominal width of the slab. The effects of a single load layout, support settlements and concrete shrinkage, as well as the maximum effects obtained by considering the envelopes of bending moments, for example due to traffic load, can be caught. Comparisons with other methods performed on realistic continuous twin-girder composite bridge decks demonstrate the simplicity and effectiveness of the method proposed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/53536

Analytical and numerical model for the time-dependent behaviour of composite steel-concrete members with longitudinal and transverse partial interaction
Proceedings of the 5th Int. Conf. on Advances in Steel Structures, ICASS 2007
Autore/i: G., Ranzi; Z., Vrcelj; Gara, Fabrizio; G., Leoni
Editore: Research Publishing Services, Singapore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abstract This paper presents an analytical and numerical formulation for the short- and long-term analysis of composite beams with longitudinal and vertical partial interaction in which the interface connection deforms both longitudinally, i.e. along the beam length, and vertically, i.e. transverse to the connection interface. The concrete behaviour is time-dependent and its stress-strain relationship is described by means of the integral-type creep law while the steel of the joist, the reinforcement and the shear connection are assumed to behave in a linearelastic fashion. The theoretical model is derived from the principle of virtual work. Due to the complexity of the problem, a numerical solution is then proposed. This solution requires the use of two discretisations, one in the time domain and one along the member axis. For the former one, the integral-type creep law describing the concrete behaviour is approximated based on the step-by-step procedure applying the trapezoidal rule while the spatial approximation is achieved by means of the finite element method. In this sense, a 14dof finite element is derived based on the weak form of the problem.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47715

Load-consistent effective widths for composite steel-concrete decks
Proceedings of the 3rd Int. Conf. on Steel & Composite Structures, ICSCS'07
Autore/i: Dezi, Luigino; Gara, Fabrizio; G., Leoni
Editore: Taylor & Francis, Leiden, The Netherlands
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT: This paper proposes new effective widths for the analysis of twin-girder and single-box girder steel-concrete composite bridge decks. The method proposed catches the effects of a single load layout, as well as the maximum effects obtained by considering the envelopes of bending moments, support settlements and shrinkage effects. The method permits evaluating the normal longitudinal stress on the slab by means of a cross sectional analysis starting from the results of the structural analysis performed by considering the geometric width of the slab. Various comparisons between the slab stresses of a realistic continuous twin-girder composite bridge deck calculated by means of the method proposed, a refined shell finite element model, are shown demonstrating the simplicity and effectiveness of the method.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52091

Slab cracking during composite bridge construction: effectiveness of fractionated castings in controlling the phenomenon
Proceedings of the 7th Int. Conf. on Short and Medium Span Bridges, ICSMSB'06
Autore/i: Dezi, Luigino; Gara, Fabrizio; G., Leoni; G., Ranzi
Editore: The Canadian Society for Civil Engineering, Montréal, Québec, Canada H3Z 1N1
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abstract This paper presents a study on the effectiveness of the different casting sequences to control the cracking in continuous composite bridges. After a brief description of the numerical procedure adopted in the analyses, the results obtained for different span lengths are reported. In particular, the results obtained by means of continuous slab casting from one end of the bridge to the other are compared with those given by optimised sequential castings and the enhanced ability of the latter to control the cracking tendency during construction has been highlighted.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52582

La fessurazione della soletta durante le fasi costruttive dei ponti composti: efficacia del frazionamento dei getti
Atti del 16° Congresso C.T.E. - Parma, Italy
Autore/i: Dezi, Luigino; Gara, Fabrizio; Leoni, G.; Ranzi, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: SUMMARY This paper presents a study on the effectiveness of different casting sequences to control the cracking in continuous composite bridges. In the first part of the paper, an overview on the modeling aspects of termal shrinkage and tensile creep of the concrete is reported, and a numerical procedure for the structural analysis is described. In the second part, the results of analyses performed on study cases of continuous composite bridge decks are shown. The results obtained by means of continuous slab casting from one end of the bridge to the other are compared with those given by optimised sequential castings and the enhanced ability of the latter to control the cracking tendency during construction has been highlighted.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63586

Un metodo semplificato per l’analisi viscoelastica di strutture in calcestruzzo armato costruite per assemblaggio ripetitivo di elementi prefabbricati
Atti del 16° Congresso C.T.E. - Parma, Italy
Autore/i: Dezi, Luigino; Gara, Fabrizio; Leoni, G.; Zito, L.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: SUMMARY This paper presents a general analytical formulation of the variable static scheme problem valid in the cases of rigid or deformable restraints. Both external loads and non-mechanical imposed strains, such as shrinkage, are considered during the construction phases. Subsequently, structures built sequentially from repetitive parts are studied. Some results of a wide parametric analysis are shown and a straightforward method for regular design, which permits evaluating the long-term restraint reactions starting from the values obtained by a normal elastic analysis, is proposed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63585

Some considerations on the long-term partial interaction behaviour of composite steel-concrete beams using displacement based finite elements
Professor Jean-Marie Aribert Retirement Symposium
Autore/i: G., Ranzi; Z., Vrcelj; Gara, Fabrizio; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abstract This paper presents some of the modelling techniques available in the literature to describe the long-term behaviour of composite steel-concrete beams with partial shear interaction. In particular, the attention is placed on displacement-based formulations. These consist of the finite difference method, the finite element method, the direct stiffness method and analytical solutions. These are derived by means of the principle of virtual work. The finite element method relies on the weak form of the problem while the remaining ones are derived from its strong form. The time-dependent behaviour of the concrete is modelled by means of the Age-adjusted Effective Modulus Method, while the other materials at the cross-section are assumed to be linear-elastic. The main difference between the modelling technique considered is that, while the finite difference method and the finite element method require discretisations in both spatial and time domains to complete a time analysis, the direct stiffness method and the analytical solutions require only the time discretisation. The ability of the proposed formulations to describe the time-dependent behaviour is then discussed using the solutions in closed form as a benchmark. Two different finite elements have been considered and the occurrence of curvature locking problems has been discussed. The comparisons have been carried out for three structural systems, i.e. for simply supported beams, propped cantilevers and fixed ended beams, subjected to a uniformly distributed load and to time effects. For each case, the minimum spatial discretisations required to keep the error within an acceptable tolerance has been identified.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/48455

Longitudinal and transverse partial interaction analysis of composite beams accounting for time effects and shear-lag effects
19th Australasian Conference on the Mechanics of Structures and Materials, ACMSM’06
Autore/i: P., Ansourian; G., Ranzi; Gara, Fabrizio; G., Leoni
Editore: Taylor & Francis
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT: This paper presents a novel analytical formulation for the analysis of composite beams with longitudinal and vertical partial interaction which accounts for time and shear-lag effects. The particularity of this model relies on the ability of the interface connection to deform both longitudinally and vertically, i.e. transverse to the connection interface. All materials are assumed to be linear-elastic except for the concrete, whose time-dependent behaviour, is modeled by means of a step-by-step procedure. The theoretical model is derived using both the principle of virtual work and, relying on the weak form of the problem, the finite ele-ment method. Their ability to accurately depict the partial interaction behaviour is then discussed using simple structural systems. Curvature locking problems, which have been observed in the finite element simulations, are discussed and their origins are demonstrated analytically.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/48459

Displacement-based formulations for the partial interaction of composite beams accounting for time effects
Proceedings of the 2nd International fib Congress, fib'06
Autore/i: P., Ansourian; G., Ranzi; Gara, Fabrizio; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: INTRODUCTION This paper presents a comparative study of available displacement-based modelling techniques for the analysis of steel-concrete composite beams with partial shear interaction, which include the finite difference method, the finite element method, the direct stiffness method and the exact analytical model. Both shortand long-term analyses have been considered in order to provide an indication of how these affect the accuracy of the predictions. For the implementation of the finite difference method and of the finite element method, discretisations in both space and time domains are required, while only the time discretisation needs to be specified for the direct stiffness method and the exact analytical solutions. The time-dependent behaviour of the concrete has been modelled by means of the age-adjusted effective modulus method (AEMM) while the remaining materials at the cross-section have been assumed to behave in a linear-elastic manner. The results obtained using these formulations are qualitatively compared and their accuracy is estimated adopting the exact analytical model as a benchmark reference with the objective of establishing the minimum spatial discretisations required to keep the error within an acceptable tolerance. These comparisons are carried out for simply-supported beams, propped cantilevers and fixed-ended beams, from which the behaviour of these formulations in the modelling of continuous beams can also be deduced.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/48454

Effective slab width in composite decks: new formulas for different loading conditions
Proceedings of the 7th Int. Conf. on Short and Medium Span Bridges, ICSMSB'06
Autore/i: Dezi, Luigino; Gara, Fabrizio; G., Leoni
Editore: The Canadian Society for Civil Engineering, Montréal, Québec, Canada H3Z 1N1
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abstract This paper proposes new effective widths for the analysis of twin-girder and single-box girder steel-concrete composite bridge decks. Thanks to an analytical model proposed by the same authors, a broad parametrical analysis is performed showing the dependency of the effective width on the type of loading in addition to the slab width-to-length ratio. The method proposed catches the effects of a single load layout, as well as the maximum effects obtained by considering the envelopes of bending moments, support settlements and shrinkage effects. Various comparisons between the slab stresses of a realistic continuous twin-girder composite bridge deck calculated by means of the method proposed, the EC4-2 method, and a refined shell finite element model, are shown demonstrating the simplicity and effectiveness of the method.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51442

Time analysis of composite beams with partial interaction using available modelling techniques: A comparative study
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH
Autore/i: Gara, Fabrizio; G., Ranzi; G., Leoni
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents a comparison of available numerical structural formulations for the short- and long-term analysis of composite beams with partial shear interaction. The finite difference method, the finite element method, the direct stiffness method and the exact analytical model have been considered, and both the instantaneous analysis and the time analysis based on the age-adjusted effective modulus method (AEMM) have been carried out. For modelling based on the first two of these formulations, a spatial discretisation and a discretisation in the time domain are required, while only the time discretisation needs to be specified for the direct stiffness method. The results obtained using these formulations are compared qualitatively and their accuracy is estimated, adopting the exact analytical model as a benchmark reference with the objective of establishing the minimum spatial discretisations required to keep the error within an acceptable tolerance. These comparisons are carried out for simply supported beams, propped cantilevers and fixed ended beams, from which the qualitative behaviour of these formulations in the modelling of continuous beams can also be deduced. (c) 2005 Elsevier Ltd. All rights reserved.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75134

Effective slab width in prestressed twin-girder composite decks
JOURNAL OF STRUCTURAL ENGINEERING
Autore/i: Dezi, Luigino; Gara, Fabrizio; G., Leoni
Classificazione: 1 Contributo su Rivista
Abstract: The paper shows the shear-lag effect in slabs of twin-girder steel-concrete composite decks due to the main prestressing techniques such as support settlements, bonded cables inside the concrete slab, and external slipping tendons. The analysis is performed by means of a beam model taking into account the loss of planarity for the slab cross section, the flexibility of the shear connection, and the time-dependent behavior of the concrete. A linear elastic behavior is considered for the steel beams and shear connection while viscoelastic behavior is assumed for the concrete slab. A parametrical analysis is carried out on realistic bridge decks for each kind of prestressing technique, by varying the span length and the girder spacing. The distribution of longitudinal normal stresses in the slab is shown for each prestressing technique and the effective slab widths are then evaluated and compared with those suggested by ENV 1994-2 for different span lengths and for different spacing of the beams.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75135

Displacement-based formulations for composite beams with longitudinal slip and vertical uplift
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING
Autore/i: Gara, Fabrizio; G., Ranzi; G., Leoni
Classificazione: 1 Contributo su Rivista
Abstract: This paper describes three novel displacement-based formulations for the analysis of composite beams with a flexible connection which is capable of deforming along the longitudinal axis of the member as well as vertically, i.e. transverse to the interface connection. For completeness, the analytical model which forms the basis of the proposed modelling technique is presented in both its weak and strong forms. The three novel finite element formulations are derived and tested using different structural systems; their nodal freedoms include the vertical and axial displacements as well as the rotations at each element end of both layers. Curvature locking problems are observed to occur for one of these elements and the origin of this behaviour is demonstrated analytically. Two applications are then proposed adopting a bi-linear constitutive relationship for the vertical interface connection to, reflect the more realistic case in which, already in the linear-elastic range of the materials forming the cross-section and of the longitudinal interface connection, two vertical connection stiffnesses are required, i.e. one to model the event of separation between the layers and one when one bears against the other one. Copyright (c) 2005 John Wiley & Sons, Ltd.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75138

Construction sequence modelling of continuous steel-concrete composite bridge decks
STEEL AND COMPOSITE STRUCTURES
Autore/i: Dezi, Luigino; Gara, Fabrizio; G., Leoni
Classificazione: 1 Contributo su Rivista
Abstract: This paper proposes a model for the analysis of the construction sequences of steel-concrete composite decks in which the slab is cast-in-situ for segments. The model accounts for early age shrinkage, such as thermal and endogenous shrinkage, drying shrinkage, tensile creep effects and the complex sequences of loading due to pouring of the different slab segments. The evolution of the structure is caught by suitably defining the constitutive relationships of the concrete and the steel reinforcements. The numerical solution is obtained by means of a step-by-step procedure and the finite element method. The proposed model is then applied to a composite deck in order to show its potential.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75137

General method of analysis for composite beams with longitudinal and transverse partial interaction
COMPUTERS & STRUCTURES
Autore/i: G., Ranzi; Gara, Fabrizio; P., Ansourian
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents an analytical formulation for the analysis of two-layered composite beams with longitudinal and vertical partial interaction. The particularity of this model is its ability to incorporate an interface connection deforming both longitudinally, i.e., along the beam length, and vertically, i.e., transverse to the connection interface, which is modelled by means of a uniformly distributed spring. The novel formulation is based on the principle of virtual work expressed in terms of the displacement field consisting of the vertical and axial displacements of the two layers; for completeness, the proposed model is presented in both its weak and strong forms. The partial interaction problem is then solved by means of the finite element method. A parametric study is presented to investigate the effects of different combinations of longitudinal and transverse connection rigidities on the overall structural response. For the purpose of these simulations, a bi-linear constitutive model has been specified for the transverse interface connection to reflect the more realistic case in which two different responses are observed in the transverse interaction, one in which one layer is bearing against the other one, one when the two layers are separating. An iterative procedure has been proposed to obtain the convergence to the final solution. (c) 2006 Elsevier Ltd. All rights reserved.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75133

Analysis of composite beams with partial shear interaction using available modelling techniques: A comparative study
COMPUTERS & STRUCTURES
Autore/i: G., Ranzi; Gara, Fabrizio; G., Leoni; M. A., Bradford
Classificazione: 1 Contributo su Rivista
Abstract: This paper presents a comparison of available numerical structural analysis formulations for composite beams with partial shear interaction, which include the finite difference method, the finite element method, the direct stiffness method and the exact analytical model, and these formulations are briefly presented. The first two of these formulations lead to a numerical solution that requires a spatial discretisation to be implemented, while the direct stiffness method does not require this discretisation. Using the solution of the exact analytical model as a benchmark reference, the accuracy of the three numerical techniques is tested for the cases of a simply supported beam and a propped cantilever, and a qualitative comparison is carried out to highlight the adequacy and characteristics of these numerical formulations. For the two structural systems considered, the minimum spatial discretisations that need to be adopted to keep the error within an acceptable tolerance are provided for each of the formulations. (c) 2006 Elsevier Ltd. All rights reserved.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/75136

Partial interaction analysis of composite beams accounting for time effects: evaluation of displacement-based formulations
Proceedings of the 8th Int. Conf. on Steel-Concrete Composite and Hybrid Structures, ASCCS’06
Autore/i: Ranzi, G.; Ansourian, P.; Gara, F.; Leoni, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abstract: This paper discusses the ability of available displacement-based formulations to depict the structural response of composite steel-concrete beams with partial interaction accounting for time effects, such as creep and shrinkage. These include the exact analytical solution, the direct stiffness method, the finite element method and the finite difference method; while the former two require only a time discretisation to perform a time analysis, the latter two need to discretise the structural system in both time and spatial domain. The time-dependent behaviour of the concrete is modeled by means of the age-adjusted effective modulus method (AEMM) while the remaining materials at the cross-section are assumed to behave in a linear-elastic fashion. The results obtained based on the modeling techniques considered are benchmarked against those calculated using the solutions available in closed form.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/48456

A generic modelling of composite beams with longitudinal and vertical partial interaction
4th Int. Conf. on Advances in Steel Structures, ICASS'05
Autore/i: G., Ranzi; P., Ansourian; Gara, Fabrizio; G., Leoni; Dezi, Luigino
Editore: Elsevier B.V., Amsterdam, The Netherlands
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT This paper presents a novel analytical formulation for the analysis of composite beams with longitudinal and vertical partial interaction in which the interface connection deforms both longitudinally, i.e. along the beam length, and vertically, i.e. transverse to the connection interface. The theoretical model is derived from the principle of virtual work, using the displacement method. Based on the weak form of the problem, a novel finite element is proposed and applied for the analysis of a propped cantilever subjected to a point load applied to the lower layer at mid-span. In this application, the vertical interface connection is modelled by means of a bi-linear constitutive relationship to reflect the more realistic case in which the vertical connection stiffness is several orders of magnitude greater when the layers are in contact, compared with the case of layers’ separation. An iterative procedure has been proposed to obtain convergence to the final solution.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52160

A beam finite element for the shear-lag analysis of steel-concrete composite decks
Proceedings of the 4th Int. Conf. on Advances in Steel Structures, ICASS ’05
Autore/i: Dezi, Luigino; Gara, Fabrizio; G., Leoni
Editore: Elsevier B.V., Amsterdam, The Netherlands
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT The paper presents a beam model for the analysis of composite decks taking into account the warping of the slab cross section and the partial shear interaction between the slab and the girders. Slab shear-lag is taken into account by means of the product of a known function, describing the shape of the slab crosssection warping, and an intensity function measuring the magnitude of warping along the beam axis. The numerical solution is obtained by means of the finite element method with a new 13-dof beam element. The results of a number of applications of the proposed model to a realistic bridge deck are compared with those obtained by means of shell finite elements, showing the accuracy of the proposed element.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/58902

Time-dependent analysis of composite beams with partial shear interaction: a comparative study using available modelling techniques
Australian Structural Engineering Conference, ASEC’05
Autore/i: G., Ranzi; Gara, Fabrizio; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Introduction The aim of this paper is to compare the performance of available displacement-based numerical formulations for the long-term analysis of composite beams with partial shear interaction. In particular, the finite difference method, the finite element method, the direct stiffness method and the exact analytical model have been considered. Using the former two numerical formulations a time analysis requires both a spatial discretisation and a time discretisation to be specified while the latter two modelling techniques need only the time discretisation to be implemented. These comparisons have been carried out adopting the exact analytical model as a benchmark reference with the objective of establishing the minimum spatial discretisations required to keep the error within an acceptable tolerance. For this purpose, simply supported beams, propped cantilevers and fixed ended beams have been analysed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47769

A beam finite element including shear-lag effect for the long term analysis of steel-concrete composite decks
Atti del XX Congresso C.T.A.
Autore/i: Dezi, Luigino; Gara, Fabrizio; Leoni, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT The paper presents a beam finite element for the long-term analysis of composite decks taking into account the warping of the slab cross section and the partial shear interaction between the slab and the girders. Slab shear-lag is taken into account by means of the product of a known function, describing the shape of the slab cross section warping, and an intensity function measuring the magnitude of warping along the beam axis. Time-dependent behaviour is considered by means of an integral-type visco-elastic creep law for the concrete. The numerical solution is obtained by means of the finite element method with a 13-dof beam element and a step-by-step procedure for the evolution in time. The results of some applications show the accuracy and the capability of the proposed element.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63587

Displacement-based formulations for composite beams with longitudinal slip and vertical uplift
Research Report n. R837, Department of Civil Engineering, University of Sydney
Autore/i: G., Ranzi; P., Ansourian; Gara, Fabrizio; G., Leoni; Dezi, Luigino
Luogo di pubblicazione: Sydney
Classificazione: 5 Altro
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/74882

Partial interaction analysis of composite beams by means of the finite difference method, the finite element method, the direct stiffness method and the analytical solution: a comparative study
7th Int. Conf. on Computational Structures Technology, CST’04
Autore/i: G., Ranzi; M. A., Bradford; Gara, Fabrizio; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abstract This paper presents a comparison among available structural analysis formulations for composite beams with partial shear interaction. In the comparison all material are assumed to behave in a linear-elastic fashion. The formulations considered are the finite difference method, the finite element method, the direct stiffness method and the exact analytical model. The former two require a spatial discretisation to be specified along the beam length, while the latter two do not require any discretisation. Using the solution of the exact analytical model as a reference the accuracy of the three formulations has been tested for the cases of a simply supported beam and of a propped cantilever subjected to a uniformly distributed load. The comparison is carried out at various level of shear connection stiffness.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/47768

Construction Sequence Modelling of Continuous Steel-Concrete Composite Decks
2nd Int. Conf. on Steel and Composite Structures, ICSCS’04
Autore/i: Dezi, Luigino; Gara, Fabrizio; G., Leoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTRACT This paper proposes a model for the analysis of the construction sequences of steel-concrete composite decks in which the slab is cast-in-situ for segments. The model accounts for early age shrinkage, such as thermal and endogenous shrinkage, drying shrinkage, tensile creep effects and the complex sequences of loading due to pouring of the different slab segments. The evolution of the structure is caught by suitably defining the constitutive relationships of the concrete and the steel reinforcements. The numerical solution is obtained by means of a step-bystep procedure and the finite element method. The proposed model is then applied to a composite deck in order to show its potential.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52562