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The research work presented is aimed at the assessment of the influence of infill walls on the seismic vulnerability of existing RC buildings. In particular, the paper presents some results obtained from the analysis of recurrent building typologies, for which the structural representative models have been defined from the observation of existing building stock at the regional scale. A sensitivity analysis was performed by assuming various hypothesis about the infills’ features, and the results allowed to point out and discuss the differences regarding the structural behavior, the seismic demand and other representative output parameters.

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The work herein presented is devoted to the comparison between two design approaches leading to the same design goal, i.e. the design of structures able to develop a collapse mechanism of global type. These selected design procedures are the Performance- Based Plastic Design approach (PBPD) and the Theory of Plastic Mechanism Control (TPMC). To this scope reference is made to several MR-Frame structures designed by means of both procedures. The seismic performances of such MR-Frames have been investigated by both push-over and dynamic non-linear analyses.

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The seismic vulnerability assessment of existing and historical masonry structures is an important priority to preserve them over time. Several mechanical models available in literature are based on the limit analysis and may require a relevant computational burden. In this paper, an adaptive numerical method to analyse the seismic response of masonry vaults is presented. The approach is developed within Heyman’s safe theorem and extends the funicular curve concept to the 3D case, by searching a ‘safe’ thrust surface within a design domain. The thrust surface is obtained by means of a Genetic Algorithm applied to a refinement adaptive finite element model. This approach can be easily implemented in existing FEM codes and gives a useful tool to assess seismic vulnerability of curved masonry structures and to design selective reinforcements. It is validated against a case study of a vault available in literature. Some numerical results dealing with a cloister vault subject to static and dynamic loads are given.

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In the framework of risk assessment at national and regional scale, the analysis of collapse mechanisms induced by seismic accelerations constitutes a useful tool to understand the behaviour of masonry structures and to plane mitigation strategies and rehabilitation interventions. In this perspective, the objective of the present study is the identification of the correlations among three factors: 1) structural-typologies which characterize Italian masonry buildings, 2) possible collapse mechanisms (in-plane and out- of-plane), 3) ground accelerations. The analyses developed concern a sample of 100,000 models representing the structural typologies of ordinary masonry buildings distributed on Italian territory. They have been derived through examination of structural characteristics (dimensions of structural elements, mechanical characteristics of material, typologies of horizontal structures and roofing, presence of vaults and/ or ties or ring beams, number of floors, etc.) collected by ‘in situ’ survey of about 250,000 buildings distributed along the Italian territory. For each model, the acceleration able to induce the first collapse mechanism has been calculated, adopting simplified limit state analyses. The results have been then elaborated to set, for different vulnerability classes (assigned combining typological- structural characteristics), the probability of occurrence of each collapse mechanism varying the peak ground acceleration (PGA) is analysed.

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The introduction of high energy dissipation in base-isolated structures is often prescribed to minimize the device displacements as well as the effects of near-field earthquakes. The identification of effects on the superstructure due to the high energy dissipation is, therefore, an important aspect of the base-isolated structure design. In this study, the seismic response of base-isolated structures with Lead Rubber Bearing (LRB) devices is estimated aiming at the evaluation of the adverse effect of damping on the structural response parameters. Four base-isolated structures are considered taking into account a complete damping matrix. Their structural seismic response evaluation is first performed using nonlinear response history analysis (NRHA) by considering a bilinear device behaviour. The increase in the superstructure response parameters is detected. A structural analysis by considering an equivalent linear viscoelastic LRB behaviour was also performed. A frequency domain method through transmissibility was applied to explain the influence of isolation damping on the higher mode effects and inter-storey drift ratios. The comparison between the NRHA results and response spectrum analysis (RSA) results highlights meaningful differences between the values of some structural response parameters (displacements of the isolation system and inter-storey drift ratio). A seismic analysis of baseisolated structures with High Damping Rubber Bearing (HDRB) and supplemental linear viscous damping (VD) devices is also carried out. The results point out that the use of HDRB devices with linear viscous dampers, as compared to LRB devices, lead to a reduction of the devices displacements and to a beneficial or least detrimental effects on the superstructure response parameters in base-isolated structures.

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In this work, through analyzing the effects of large deformation, lining damage and collapses, which happen frequently in the soft rock tunnels in the Guang-Gan Expressway, the characteristics and causes of the geological disasters for the soft-rock tunnels are investigated. The results show that the large deformation and collapses occur near the vault and tunnel face. The poor mechanical properties and weak self-bearing capacity of the surrounding rock and the softening caused by the groundwater are important factors for the disasters. The lack of experience in design and construction in the meizoseismal area and the aftershocks are other important factors. The field test indicates that three benches and the reserved core soil construction method should be applied to control the stability of the broken phyllite tunnels, and the key technology should be strictly controlled during the construction. In particular, increasing the stiffness of the supporting structure and enclosingof theliningin timeare efficient methods to control the large deformation and collapses in crushing soft-rock tunnels in the meizoseismal areas.

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In order to meet the requirements of maintaining the original condition of rock faces, avoiding the heavy excavation to protect the ground environment, and reducing support cost of large-span shallow buried cavern, a new supporting method of shallow- buried caverns was proposed in this paper. Such a supporting method was successfully applied to the underground cavern project. For this project, some crisscross small tunnel sheds were embedded in the overburden layer. As a result, the interaction between the surrounding rock and supporting structure can play a significant role in the constructed supporting system, and the surrounding rock can display its self load-bearing capacity in the shallow buried cavern.

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In the last decades many strategies for seismic vulnerability mitigation of structures have been developed through analytical studies and experimental tests. Among these, energy dissipation by external devices assumes a great relevance for the relative design simplicity, even if applied to complex structures, and the effectiveness in reducing seismic demand. In particular, the use of fluid viscous dampers represents a very attractive solution because of their velocity-dependent behaviour and relatively low costs. The application on structures requires specific study under seismic excitation and a particular care of structural details. In this context the use of proper constitutive models for the dampers assumes a fundamental role. Seismic codes, as well as literature models generally provide a velocity-dependent relationship with two characteristic constants defining the shape of the force-displacement curve. In this paper an experimental campaign aimed at the determination of the damper constants in the range of low velocities is presented. A fluid viscous damper is tested with different ramp velocity functions. Results show that the assumption of velocity independence of the damper constants fails for the case of low velocity, giving rise to new issues about the limit of validity of the constitutive models generally adopted for viscous dampers.

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In the last twenty years, the field of earthquake engineering experienced a noticeable improvement. The results of experimental and theoretical researches have contributed to the development of modern technical codes, which provide innovative solutions for the structural assessment and new design approaches. Despite this large amount of improvements, several open questions are still open, and the need for large scale testing has been deeply proved and discussed. A new research facility, namely the Laboratory of Earthquake engineering and Dynamic Analysis (LEDA), has been recently completed at the University of Enna “Kore”. This research centre, funded with a grant from Italian Ministry of Education, University and Research, includes several laboratories operating in the fields of structural engineering and dynamics. The most attractive features of LEDA are the wide range of tests that can be performed and the simultaneous presence of a high capacity strong floor – reaction wall system and of two six-degrees-of-freedom shaking tables, so that the complementarity of both traditional techniques (pseudo-dynamic and dynamic tests) can be fully exploited and advanced hybrid testing method can be explored. In this paper the features of the main research facilities in LEDA are briefly presented. Furthermore, the design procedures of the reaction structure, built in order to perform large scale static and pseudo-dynamic testing, are described and discussed.

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