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The objective of this study is to present the formulation and applications of the optimization problem of steel-concrete composite alveolar beams. In addition to presenting the formulation, a comparative analysis of the predominant collapse modes is performed numerically via the finite element method. The optimization program was developed with the GUI platform available in Matlab 2016. Since this is a discrete problem, a Genetic Algorithm (GA) was used to solve the optimization model, implemented with the Matlab optimization toolbox. Numerical examples using finite elements model are presented to validate the solution and analyze its effectiveness, along with an assesment of the predominant collapse modes for a group of 12 beams. The results show that more efficient designs are obtained when optimization tools are applied.

This paper presents a study of the stability and collapse modes of a system made up of a masonry arch resting on two piers subject to its own weight. It examines both semicircular arches and three different types of pointed arches commonly found in architecture, namely low-pointed, equilateral, and lancet-pointed arches. The collapse modes characterizing each type of arch-piers systems are then compared by extending the results obtained by the authors in previous work on stand-alone masonry arches of different shapes. The mechanical behavior of these systems is examined via Durand-Claye’s method in order to follow the evolution of the stability area and determine the collapse modes of these masonry structures. The method takes into account both the bounded bending capacity of the arch cross section and the limited friction along the joints. Furthermore, the system’s safe domain is determined in terms of the limit conditions for arch thickness, pier height and friction coefficient. As expected, arch-piers systems of different shapes exhibit different behaviors at collapse in terms of minimum thickness and collapse modes.

This paper addresses the problem of characterizing the mechanical behaviour and collapse of symmetric circular and pointed masonry arches subject to their own weight. The influence on the arch’s collapse features of its shape and thickness, as well as the friction between the arch’s voussoirs, is analysed. The safety level of arches is then investigated by suitably reworking in semi-analytical form the graphical method of the stability area proposed by the renowned nineteenth century French scholar, Durand-Claye. According to Durand-Claye’s method, the arch is safe if along any given joint both the bending moment and shear force do not exceed the values determined by some given limit condition. The equilibrium conditions corresponding to all possible symmetric collapse modes are individuated. As was expected, pointed and circular arches exhibit different collapse behaviours, in terms of both collapse modes and safe domain. The limit values of arch thickness and friction coefficient are determined and the results obtained consistently compared with those published by Michon in 1857.

This paper investigates the axial crushing response of concentric expanded metal tubes under impact loading. The study is conducted by means of nonlinear finite element simulations, considering the speed of deformation and the size of the expanded metal cells. In the analysis, two tubes are placed concentrically and then axially crushed with an impact mass at various speed levels. Crushing load-displacement responses are analyzed to investigate the influence of the size of the mesh and the impact speed. The results show that specimens with the same mesh sizes increases their crushing length with increasing speed. Finally the main outcome of this investigation is to add to the state of knowledge information concerning the use of expanded metal meshes in impact attenuation devices.

This paper discusses the seismic behavior of reinforced concrete (RC) bridge structures, focusing on the shear&ndash, flexure interaction phenomena. The assessment of reinforced concrete bridges under seismic action needs the ability to model the effective non-linear response in order to identify the relevant failure modes of the structure. Existing RC bridges have been conceived according to old engineering practices and codes, lacking the implementation of capacity design principles, and therefore can exhibit premature shear failures with a reduction of available strength and ductility. In particular, recent studies have shown that the shear strength can decrease with the increase of flexural damage after the development of plastic hinges and, in some cases, this can cause unexpected shear failures in the plastic branch with a consequent reduction of ductility. The aim of the research is to implement those phenomena in a finite-element analysis. The proposed model consists of a flexure fiber element coupled with a shear and a rotational slip spring. The model has been implemented in the OpenSEES framework and calibrated against experimental data, showing a good ability to capture the overall response.

Appropriate seismic assessment of reinforced concrete bridges is an important challenge in structural engineering in consideration of the number and relevance of bridges built without applying advanced codes of practice and of the strategic role of transportation networks in modern economy. This paper focuses on some relevant aspects of the damage development and collapse modes of hollow piers, as commonly designed in the past. The following aspects have been considered: absence of confinement, inadequate shear strength, shifting of the critical section, insufficient length of lap splices. A series of experimental tests has been designed and performed; the capacity of predicting appropriate results of formulations recommended in codes of practice or proposed in recent research documents has been checked comparing experimental and analytical results.

The control of the plastic flow mechanism during axial collapse of metallic hollow cylinders is of particular interest in the present work for the absorbed energy. Hence, an experimental methodology is developed during which some different tubular structures are loaded under compressive quasi-static strain rate. These structures of various geometrical parameters η = R m / t and λ = R m / L ( R m : mean radius, L : initial length and t : thickness of tube) are made either from copper or aluminum considered as an energy dissipating system. At this point, the effects of both parameters on the mean collapse load and absorbed energy are appropriately studied. The role of η ratio, which has been largely investigated previously, is studied again. Moreover, it is found that the λ ratio has a non-negligible influence on the deformation mode for a given η . It is well known that the absorbed energy is influenced by the deformation mechanism, i.e., for the axisymmetric mode, the related absorbed energy becomes more important than that of the diamond fold mechanism for a given cylinder. Accordingly, to maximize the absorbed energy, two different structural solutions, namely fixed-ends and subdivided structure, are developed for encouraging the axisymmetric mode. It is convenient to consider the classical axial collapse situation (noted as free-ends) as a comparison reference. In this work, it is recognized that the subdivided solution is relatively the best solution. As a result, the absorbed energy increases up to 21% in comparison with the free-ends situation for copper tubes.