Alessandro Zona

Non-linear analysis of composite beams by a displacement approach

The non-linear analysis of composite steel–concrete beams by the finite elements method permits obtaining useful information on collapse modalities but the convergence of the solution must be carefully controlled. Using the displacement formulation of the finite elements technique, the authors illustrate some aspects related to the convergence of the method by comparing solutions deriving from finite elements with 8, 10 and 16DOF. Some pathologies of the 8DOF element are posed in evidence. 2002 Civil-Comp Ltd. and Elsevier Science Ltd. All rights reserved.

Three-field mixed formulation for the non-linear analysis of composite beams with deformable shear connection

A three-field mixed finite element is proposed for the non-linear analysis of composite beam with deformable shear connection. The formulation considers the non-linear behaviour of materials and shear connectors. The established mixed element is compared to the locking-free displacement element from which it derives and to a refined locking-free displacement element previously tested by the authors. In order to evaluate the way to better improve the solution in the non-linear range (three-field mixed formulation or refined displacement formulation), numerical applications are performed using, as working example, a steel-concrete cantilever, representing a difficult test for composite beam elements.

Finite element response sensitivity analysis of continuous steel-concrete composite girders

The behavior of steel-concrete composite beams is strongly influenced by the type of shear connection between the steel beam and the concrete slab. For accurate analytical predictions, the structural model must account for the interlayer slip between these two components. This paper focuses on a procedure for response sensitivity analysis using state-of-the-art finite elements for composite beams with deformable shear connection. Monotonic and cyclic loading cases are considered. Realistic cyclic uniaxial constitutive laws are adopted for the steel and concrete materials as well as for the shear connection. The finite element response sensitivity analysis is performed according to the Direct Differentiation Method (DDM); its analytical derivation and computer implementation are validated through Forward Finite Difference (FFD) analysis. Sensitivity analysis results are used to gain insight into the effect and relative importance of the various material parameters in regards to the nonlinear monotonic and cyclic response of continuous composite beams, which are commonly used in bridge construction.

Probabilistic nonlinear response analysis of steel-concrete composite beams

This paper employs a methodology for probabilistic response analysis based on the first-order second moment (FOSM) method in conjunction with response sensitivity computation through the direct differentiation method (DDM), to study the variability of the structural response of steel-concrete composite (SCC) beams. This methodology is applied to compute the first-order and second-order statistical moments of the response of two actual structural systems for which experimental data are available. The results of the DDM-based FOSM method are compared with the experimental measurements and with the results of the computationally more expensive Monte Carlo-Simulation (MCS) method. Different modeling hypotheses for the material parameter uncertainty are considered. The DDM-based FOSM method agrees very well with the MCS results for low-to-moderate levels of response nonlinearity under low-to-moderate material parameter uncertainty and up to high level of response nonlinearity under low material parameter uncertainty. The DDM-based FOSM method is shown to correctly describe the effects of random spatial variability of material parameters.

A probabilistic three-dimensional finite element study on simply-supported composite floor beams

Composite steel-concrete beams are commonly used as flooring in buildings. The composite action between slab and steel joist is typically provided by shear connectors welded to the top of the steel joist and embedded in the concrete. This paper investigates the effects of material uncertainties on the numerically simulated structural response of simply-supported beam tests reported in the literature by means of Monte Carlo simulation (MCS). The numerical analyses are performed using a three-dimensional finite element model developed using the commercial software ABAQUS and capable of predicting the response of composite steel-concrete members as well as the influence of the shear connectors without having to rely on shear connection load-slip curves obtained from push-out tests. All materials are assumed to behave in a non-linear fashion. Contact regions between the concrete and steel elements are simulated using surface-to-surface and embedment techniques. The statistical information on the structural response obtained from MCS using different realisation sizes is compared and discussed. For the particular case studies considered in this paper it can be concluded that even a reduced number of realisations can already provide meaningful statistical representations of the structural response of the considered composite floor beams.

Design and Experimental Analysis of an Externally Prestressed Steel and Concrete Footbridge Equipped with Vibration Mitigation Devices

AbstractA 142-m, three-span continuous footbridge over the Esino River (Italy) is considered as a case study to illustrate a number of challenging aspects in its static and dynamic design. The adoption of an optimized steel deck with a variable cross section together with the use of external prestressing tendons in the central span allows a substantial reduction of structural weights. The resulting footbridge requires a proper model for the assessment of its behavior up to the ultimate limit state as well as attention to vibration control under pedestrian loading at the service limit state. The former issue is addressed through the use of a specifically developed material and geometric nonlinear finite-element formulation. Regarding vibration control, an original combination of two different systems is used, i.e., high damping rubber (HDR) stripes and tuned mass dampers (TMDs). The HDR stripes, applied between the steel deck and the concrete floor, increase the overall damping of the footbridge, whereas t...

An integrated Survey Experience for Assessing the Seismic Vulnerability of Senigallia’s Fortress (Italy): Documentation for Conservation and FEM Modeling

The paper presents the results of research carried out by an interdisciplinary team at the SAD in Ascoli Piceno in collaboration with MiBACT to verify the seismic safety of national museums. The object of study was the Rocca Roveresca Fortress complex in Senigallia (Marche, Italy), a unique example of a small 14th-century fortress shaped by a series of successive modifications. It currently houses a national museum. An integrated survey based on the acquisition of 3D laser-scanner data and endoscopic investigation was necessary to outline the traces of the stratifications and therefore to obtain different high- and low-poly 3D models useful for different purposes. The main objective was to propose an ideal workflow in developing 3D models that are useful for finite element method (FEM) analysis to detect hidden vulnerabilities in the fortress by evaluating the behaviour of several substructures in the walls.

Assessment of seismic vulnerability of historical defensive walls

Abstract. This paper presents a study on the behaviour of the walls of the Rocca Roveresca of Senigallia in Italy built in the XIV century on the ruins of a former Roman defensive struc-ture. This is a peculiar example of a small fortress that had undergone in the XV century im-portant modifications of the plant in order to enhance its defensive performances. A linear finite element model is first developed in order to understand the dynamic behaviour of a ge-neric portion of the wall and to detect the probable incipient failure mechanisms. A subse-quent static nonlinear analysis is carried out, with the same finite element model, to investigate the formation of the cracking layout and to detect the position of plastic hinges. The last analysis level is carried out with a tailored macro-element constituted by three bod-ies, namely the two external curtains and the inner fill for which a degradation of the behav-iour is considered. The results obtained demonstrates the efficiency of the wall against earthquakes characterized by return times typical for ultimate limit states. Same issues that deserve further investigation are highlighted.

Modelling Uncertainties of Italian Code-Conforming Structures for the Purpose of Seismic Response Analysis

ABSTRACT This paper describes the multivariate statistical model of the structure-related modelling uncertainty, developed with reference to reinforced concrete, masonry, steel, and seismically isolated buildings, within the framework of the RINTC project. The model describes the variability of material properties as well as the uncertainty associated with the adopted response models. Specific aspects of each structural typology are also discussed, with a focus on the statistical dependence of the random variables in the model. Finally, the paper describes also the efficient sampling procedure adopted. Effect of model uncertainty on response for each typology are discussed in the corresponding papers within this special issue dedicated to the RINTC project.

Modeling and Seismic Response Analysis of Italian Code-Conforming Single-Storey Steel Buildings

ABSTRACT This article describes the structural design, nonlinear modeling, and seismic analysis of prototype single-storey non-residential steel buildings made of moment-resisting portal frames in the transverse direction and concentric braces in the longitudinal direction. Various design parameters (building geometry, seismic hazard, foundation soil category) and different modeling assumptions (bare frame model, model including cladding elements, ground motions including vertical accelerations, and modeling uncertainties) were considered to investigate their effects on the simulated seismic performance.