Graphical dynamic trends for earthquake incidence response of plan-asymmetric systems

A Graphical Dynamic model is derived to describe the directional earthquake response of two-ways plan-asymmetric systems, which retains the insightful educational evidence of traditional graphical static methods and the accuracy of computational methods of analysis. The dynamic directional response is expressed in terms of modal rotational kinematics about modal centers of rotation, referred to as modal torsional pivots. Seismic forces and response decomposition are handled through geometric modal torsional trends and the earthquake incidence response envelopes are described through directional modal participation radii and graphic spectrum-based "8-shaped" directional influence circles. The graphic approach provides good predictions of the maximum response and of the critical angle computed through CQC3 and other directional analysis methods

Numerical modelling of in-plane behaviour of adobe walls

Some tests for material characterization of adobe blocks and adobe masonry have been carried out in universities and laboratories around the world. However, the number of tests is quite limited in comparison with those carried out with other structural materials, such as masonry or reinforced concrete, and even those tests just refers to elastic properties. The results of adobe tests (i.e. compression strength, elasticity modulus, shear strength, etc.), as well as the results of cyclic and dynamic tests on adobe masonry components and small buildings show that the mechanical properties of adobe masonry and the seismic performance of adobe constructions highly depend on the type of soil used for the production of units and mortar. Basic properties, such as elasticity modulus, can have significant variation from one soil type to another. The state-of-the-art for the numerical modelling of unreinforced masonry point to three main approaches: macro-modelling, simplified micro-modelling and detailed micro-modelling. In all three approaches, the use of elastic and inelastic parameters is required. For adobe masonry, the lack of knowledge concerning some of the material properties makes numerical modelling more difficult. In the proposed work, the mechanical properties of the typical adobe masonry in Peru have been calibrated based on a cyclic in-plane test carried out on an adobe wall at the Catholic University of Peru (PUCP). The mechanical parameters calibration and the modelling results of the in-plane behaviour of the adobe wall are presented. Macro-modelling and simplified micro-modelling strategies are used in finite element software with an implicit solution strategy. The results of this work represent the first step for the numerical modelling of the seismic behaviour of adobe constructions

The use of continuum models for analyzing adobe structures

As it is known, the adobe structures have a high seismic vulnerability principally due to the low material strength and sometimes due to the inadequate structural configuration. One way for understanding the seismic behaviour of these structures is by experimental tests. However, those are costly and sometimes not easy to make. An alternative for this is the analysis of adobe structures by numerical tools with the possibility to make parametric studies for understanding the behaviour of different geometrical configurations. In a previous work, some adobe material parameters have been calibrated based on a cyclic in-plane test. In this paper, that work was extended to a numerical modelling of the non-linear dynamic behaviour of an adobe module experimentally tested at the Pontificia Universidad Católica del Perú. For this, a continuum model in the finite element program Abaqus/Explicit, was used to represent the adobe masonry as a homogeneous and isotropic material

Multiscale computational first order homogenization of thick shells for the analysis of out-of-plane loaded masonry walls

This work presents a multiscale method based on computational homogenization for the analysis of general heterogeneous thick shell structures, with special focus on periodic brick-masonry walls. The proposed method is designed for the analysis of shells whose micro-structure is heterogeneous in the in-plane directions, but initially homogeneous in the shell-thickness direction, a structural topology that can be found in single-leaf brick masonry walls. Under this assumption, this work proposes an efficient homogenization scheme where both the macro-scale and the micro-scale are described by the same shell theory. The proposed method is then applied to the analysis of out-of-plane loaded brick-masonry walls, and compared to experimental and micro-modeling results

A Discontinuum Finite Element Modelling Approach for Reproducing the Structural Behaviour of Masonry Walls

This paper defines an innovative approach for modelling masonry walls when the structural behaviour of new or existing buildings, subjected to vertical and lateral load, has to be evaluated. Such an approach aims to provide a calculation tool that allows to model the non-linear behaviour of masonry structures with a reduced numerical effort, but, nonetheless, without jeopardizing the accuracy of obtained results. The proposed model is a typical D-FEM (Discontinuum Finite Element Model) that, differently by the most common methodologies, is composed by deformable blocks separated by interface elements arranged along pre-established surfaces of potential cracks. To this aim, the 'Combined Cracking-Shearing-Crushing' model, proposed by Lourenco for the FEM analysis with the so called simplified micro-models, is used. Some experimental tests taken by litterature are described. Such tests are used as reference for setting up a non-linear model with the 'simplified micro-modelling' approach, which considers the presence of blocks, of the same geometry of the stone units, separated by interface elements. Once that this modelling approach is validated, it is used to obtain the nonlinear response of 65 masonry panels which differ in terms of geometry, vertical loads, as well as in terms of the most significant mechanical parameters. The obtained responses for the 65 panels are taken into account for the calibration of the here proposed model. In detail, a proper variation of the coefficients contributing to the 'Combined Cracking-Shearing-Crushing' formulation is implemented through a trial and error procedure, which ends when a satisfying comparison between the results provided by the two different methods of modelling is achieved; this for taking into consideration the constraints imposed on the development of cracking surfaces. The outcomes obtained with the here proposed modelling approach are then elaborated in order to develop suitable closed form equations, which provide the necessary coefficients that have to be used for implementing the modified 'Combined Cracking-Shearing-Crushing' when a generic masonry panel has to be modelled

Seismic analysis of Fujian Hakka Tulous

The overall earthquake response of Hakka Tulous, traditional earth constructions of the Fujian Province (China) and listed among the UNESCO World Heritage buildings, is investigated. Non-linear static analysis (pushover) with the equivalent frame approach is used. Although some rough approximations are assumed, this approach is well suited to model complex masonry structures, like Tulous. In fact, nonlinear analysis implemented by finite elements or by discrete elements would involve complex models hard to converge and needing long computational time. After carrying out seismic analysis of a Tulou prototype, its failure modes and overall seismic response were evaluated. The Tulou has shown to have good earthquake resistance with respect to the maximum seismic action that can be expected in the Fujian Province

Equivalent Frame Method Combining Flexural and Shear Responses of Masonry Buildings

This work presents the results of quasi-static non-linear analyses of two masonry buildings using, for the discretization of walls, a macro-element that combines the bending and the in-plane shear responses. The macro-element uses the force-based beam- column element equipped with cross sections discretized in fibers, where the behavior of each fiber is described by uniaxial constitutive models. To describe the shear response of the structural element, the macro-element embeds a shear hinge at mid-span, with a phenomenological non-linear constitutive model calibrated on experimental data. The analyzed buildings are two tangibles examples of un-reinforced and reinforced masonry of the Italian Heritage. The un-reinforced masonry building is a strategic building monitored by the O.S.S., partially damaged by the seismic events in Center Italy in 2016. The reinforced masonry building, a three-storey residential structure, is subject of evaluations carried out in the ReLuis RINTC project, designed as per D.M. 2018

A development cooperation Erasmus Mundus partnership for capacity building in earthquake mitigation science and higher education

Successful practices have shown that a community’s capacity to manage and reduce its seismic risk relies on capitalization on policies, on technology and research results. An important role is played by education, than contribute to strengthening technical curricula of future practitioners and researchers through university and higher education programs. EUNICE is a European Commission funded higher education partnership for international development cooperation with the objective to build capacity of individuals who will operate at institutions located in seismic prone Asian Countries. The project involves five European Universities, eight Asian universities and four associations and NGOs active in advanced research on seismic mitigation, disaster risk management and international development. The project consists of a comprehensive mobility scheme open to nationals from Afghanistan, Bangladesh, China, Nepal, Pakistan, Thailand, Bhutan, India, Indonesia, Malaysia, Maldives, North Korea, Philippines, and Sri Lanka who plan to enroll in school or conduct research at one of five European partner universities in Italy, Greece and Portugal. During the 2010-14 time span a total number of 104 mobilities are being involved in scientific activities at the undergraduate, masters, PhD, postdoctoral and academic-staff exchange levels. Researchers, future policymakers and practitioners build up their curricula over a range of disciplines in the fields of earthquake engineering, seismology, disaster risk management and urban planning

Experimental and numerical investigations on the seismic behavior of bridge piers with vertical unbonded prestressing strands

In the performance-based seismic bridge design, piers are expected to undergo large inelastic deformations during severe earthquakes, which in turn can result in large residual drift and concrete crack in the bridge piers. In this paper, longitudinal unbonded prestressing strands are used to minimize residual drift and residual concrete crack width in reinforced concrete (RC) bridge piers. Seven pier specimens were designed and tested quasi-statically and the numerical simulations were carried out. The effectiveness of using vertical unbonded prestressing strands to mitigate the residual drift and concrete crack width of RC bridge piers are examined and discussed in detail. It is found that the residual drift and residual concrete crack width of the piers can be reduced significantly by using the prestressing strands. Moreover, the strands can increase the lateral strength of the piers while have little influence on the ductility capacity of the piers. The hysteretic curves, residual drifts and strand stress of the piers predicted by the numerical model agree well with the testing data and can be used to assess the cyclic behavior of the piers

RINTC-E: Towards seismic risk assessment of existing residential reinforced concrete buildings in Italy

The RINTC research project (RINTC Workgroup, 2018), financed by the Italian Department of Civil Protection, is aimed at evaluating the seismic risk of buildings conforming to the Italian building code. Within the framework of this project, the attention has been recently focused on existing buildings, too. In this study, case-study structures, representative of the existing residential reinforced concrete (RC) building stock in Italy, are analyzed. These structures are three-storey buildings with compact rectangular plan, and they have been defined through a simulated design process, in order to represent two types of buildings, namely designed for gravity loads only during 1970s (gravity load designed, GLD) or for moderate seismic loads during 1990s (seismic load designed, SLD). GLD buildings are assumed to be located in three different sites, namely Milan, Naples and Catania, in increasing order of seismic hazard. SLD buildings are assumed to be located in L'Aquila. The assumed design typologies are consistent with the seismic classification of the sites at the assumed ages of construction. The presence of typical nonstructural masonry infill walls (uniformly distributed in plan as external enclosure walls) is taken into account, assuming three configurations along height, namely “bare” (without infills), uniformly infilled and “pilotis” (without infills at the bottom storey) buildings. Two (not code-based) Limit States are investigated, namely Usability-Preventing Damage, corresponding to an interruption of the building use, and Collapse. RC elements are modelled with a lumped plasticity approach, through an empirical-based macromodel. The possible occurrence of shear failures in columns is taken into account through a preliminary classification of the expected failure mode (flexure- or shear-controlled, in the latter case prior to or following flexural yielding) and, if needed, a modification of the backbone of the nonlinear moment-chord rotation response, through empirical models providing the expected deformation capacity at shear and axial failure, the latter meant as the (initiation of) loss of axial-load-carrying-capacity. The nonlinear response of beam-column joints is modelled, too, with a “scissors model” based on concentrated springs representing the nonlinear response of the joint panel, at the intersection of beams' and columns' centerlines, through a preliminary evaluation of the expected failure mode (i.e. prior to or following yielding of adjacent beam/column elements). Materials properties are provided by literature studies, consistent with the age of construction of the buildings. The in-plane response of infills is modelled, taking into account the presence of openings, too. Modeling should be considered as simplified and, from some points of view, still preliminary, since advances are foreseen within the project in order to capture further failure modes that can occur in structural and nonstructural elements of older, nonductile RC buildings. Nonlinear static analyses, allowing to identify the (top) displacement capacity at the investigated Limit States, are carried out. Multiple stripe nonlinear time history bi-directional analyses of the three-dimensional structural models are carried out in order to evaluate the demand, for ten stripes - each corresponding to a return period ranging from 10 to 105 years - and for twenty couples of records for each stripe. Records were selected, within the activities of the research project, based on a Probabilistic Seismic Hazard Analysis at the sites of interest for the selected return periods. Results are illustrated, highlighting the role of a - although obsolete - seismic design in the response of the buildings and in their capacity, more specifically in terms of displacement capacity at Collapse, but also in terms of demand estimated from multiple stripe analyses. Finally, demand-to-capacity ratios at the investigated Limit States are analyzed, which allow, within the scope of the project, the assessment of the seismic risk of the case study structures