Fragility curves for reinforced concrete frames characterised by different regularity

This paper presents a comparison between fragility curves developed for regular and non-regular reinforced frames. Three 3D reinforced concrete multi-story frames characterised by different regularity are analysed. These fragility curves are developed through the “Cloud Analysis“ procedure, which evaluates the structural response via Non-Linear Time History Analysis (NLTHA). Both maximum inter-story drift and maximum chord-rotation demand/capacity ratio are used as Engineering Demand Parameters, in which the chord-rotation capacity is calculated according to the Italian Code. To fully develop the fragility curves, both structure-independent and structure-dependent scalar intensity measures are selected among the most referred in practice and literature. This work shows the influence of regularity on the damage levels of the three buildings. Furthermore, it shows the uncertainties caused by the selection criteria for EDP thresholds, which are necessary for a correct representation of the Limit State

Assessment of the effect of seismic sequences on steel X-CBF for industrial buildings

This work concerns about the study of the effect of the seismic sequences on steel mono-storey industrial buildings equipped with X-CBFs, with the aim to evaluate a code change to adequately consider this issue. Indeed, current technical regulations (CEN, 2004; MIT, 2018) do not take into account this phenomenon, thus the structure are designed only to withstand a single main-shock, without considering the possible accumulation of damage due to the after-shocks. In this work it is instead shown how this effect has to be properly considered and evaluated. First, a mono-storey industrial building is analysed as preliminary case study. Fragility curves are built for both sequences and single main events, thus obtaining an important comparison. Then the study focuses on a single X-CBF, validated through an experimental test from literature. The calibrated system is subjected to both seismic sequences and corresponding mainshocks. Analyses are carried out also by varying brace profiles. The results show a significant influence of the seismic sequences on the increase of the ductility request of the structure. Therefore, with the aim to properly represent the effect of the sequences, it is considered necessary to require a reduction of the available behavior factor, providing a precautionary estimate. This operation wants to give a first preliminary estimate of the increase of the seismic risk only on the seismic vulnerability side of this kind of structures

Design of X-Concentric Braced Steel Frame Systems Using an Equivalent Stiffness in a Modal Elastic Analysis

In this work, a general method for the design of concentric braced steel frames (CBF) with active tension diagonal bracings, applicable to single- and multi-storey structures, is presented. The method is based on the use of an elastic modal analysis with a response spectrum, which is carried out using an appropriate modified elastic stiffness of diagonal bracings. The reliability of the proposed method is validated through the analysis of significant case studies, making a series of numerical comparisons carrying out time-history non-linear dynamic analysis

Identification of mesoscale model parameters for brick-masonry

Realistic assessment of existing masonry structures requires the use of detailed nonlinear numerical descriptions with accurate model material parameters. In this work, a novel numerical-experimental strategy for the identification of the main material parameters of a detailed nonlinear brick-masonry mesoscale model is presented. According to the proposed strategy, elastic material parameters are obtained from the results of diagonal compression tests, while a flat-jack test, purposely designed for in-situ investigations, is used to determine the material parameters governing the nonlinear behaviour. The identification procedure involves: a) the definition of a detailed finite element (FE) description for the tests; b) the development and validation of an efficient metamodel; c) the global sensitivity analysis for parameter reduction; and d) the minimisation of a functional representing the discrepancy between experimental and numerical data. The results obtained by applying the proposed strategy in laboratory tests are discussed in the paper. These results confirm the accuracy of the developed approach for material parameter identification, which can be used also in combination with in-situ tests for assessing existing structures. Practical and theoretical aspects related to the proposed flat-jack test, the experimental data to be considered in the process and the post-processing methodology are critically discussed

MECHANICAL ENERGY DIFFERENCES BETWEEN WALKING AND RUNNING AT DIFFERENT VELOCITIES ON TREADMILL

INTRODUCTION: Cavanagh (1990) described a variation from 170 to 1700 W in power output for the same movement (running at 3.6 m/s) calculated by six different authors. These differences occurred mainly due to different procedures for energy calculation and generated data that are not comparable. The purpose of this investigation was to describe, analyze, and compare the mechanical energy curves (total, internal and external energies) for six subjects while walking and running on treadmill, by using the same procedure for energy calculation. METHODS: Six male subjects were filmed with two video-cameras (Sony-50Hz) while walking at 1.5 m/s and running at 3.0 and 4.0 m/s on a treadmill. After a manual digitizing process, a 3D analysis was performed from the kinematics. The analysis was based on a 13 segment model. Positions of segmental centers of gravity, segmental weights, and moments of inertia were estimated on the basis of tables devised by Dempster (1955) as revised by Winter (1979). The components of mechanical energy were calculated at each instant of time, using the equations described by Zatsiorsky et al. (1987). RESULTS AND DISCUSSION: In relation to the differences between walking and running, the following observations were made: a) in walking the greatest contribution to the total change derived from the internal energy, while in running it derives from the external energy; b) the internal and external energy were in phase in walking, and in opposition in running. Comparing the variations in the two velocities of running, the following conclusions were drawn: a) the average value of the absolute total energy at 3.0 m/s was 1237.9 J and at 4.0 m/s 1544.2 J; b) there was a linear correlation (r = 0.84) between the change in velocity and the change in total energy; b) with the increase in velocity, the average increase in the total contribution of the change in internal energy was about 72% and of the external energy 36%; c) there was no change in the contribution of the potential energy to the change in external energy; d) the increase in the internal energy was chiefly dependent on the increase in the kinetic energy. CONCLUSION: Although the results related to the shape of the curves for mechanical energy for walking and running are already a matter of consensus in the field of biomechanics, it would appear that the numerical results are still open to broad discussion

A STUDY OF THE MECHANICAL ENERGY DIFFERENCES BETWEEN TREADMILL AND OVERGROUND WALKING

The aim of this paper was to analyze the components of the mechanical energy of the body considering the differences between treadmill and overground walking. One subject was filmed while walking at 1.5 m/s on treadmill and overground. The results show that the patterns of the curves are very similar, but the change in the total energy, both in the upper as in the lower extremity were greater on overground (23.20J and 17.47J respectively for overground and treadmill and for the upper extremity 4.91J and 2.56J). The potential energy change of the trunk was also greater on overground (overground 45.97J; treadmill 24.88J). These findings, showing a lower measured mechanical cost on treadmill address the problem whether the treadmill can be used as a valid simulator for overground walking

Survey on non-linear cyclic responses of Unreinforced Masonry buildings by means of commercial finite-element codes

This work presents a comparison about the nonlinear cyclic response of unreinforced masonry structures obtained by using commercial calculation codes and on the base of the type of modeling approaches currently available. In particular, several elastoplastic modeling methodologies are considered, representative of a good part of the state of the art for this type of construction: mechanical-based concentrated plasticity macro-element (Tremuri), macro-element with diffuse fiber-based plasticity for flexure and concentrated springs for shear (SeismoStruct) and macro-element with phenomenological-based concentrated plasticity (NextFEM Designer). The purpose of the present research is to evaluate the ability of the different codes to represent the proper hysteretic response of masonry structures. To this aim, several experimental tests from literature are analyzed and compared; two different masonry panels, characterized by different resistant mechanisms, and an entire perforated wall have been studied through nonlinear cyclic static analyses. The reported comparison, mainly focused on the numerical cyclic behaviour exhibited by each computer program, is conducted on the basis of the path of the cycles obtained and on the amount of dissipated energy

Introdução à biomecânica do esporte considerações sobre métodos de investigação

Através de análise da literatura específica, discute-se o domínio da área de atuação da Biomecânica do Esporte, a interdisciplinaridade de Ciências Esportivas para a investigação do movimento e padronização conceituai, quanto à composição, classificação e metas na investigação. Quanto aos métodos de medidas, discutem-se os principais processos e suas características, visando a complexa investigação para a análise do movimento esportiv

Advancements in Design, Analysis, and Retrofitting of Structures Exposed to Blast

The objective of this special issue is to provide an overview on the current trends and recent advancements in terms of design, analysis, experimental testing, and retrofitting of structural systems and assemblies exposed to exceptional loads such as explosions