Dynamic Modification and Damage Propagation of a Two-Storey Full-Scale Masonry Building

The progressive change of modal characteristics due to accumulated damage on an unreinforced masonry (URM) building is investigated. The stone URM building, submitted to five consecutive shakings, has been experimentally studied on the shaking table of EUCENTRE laboratory (Pavia, Italy). The dynamic characteristics of the test specimen are analytically estimated using frequency and state-space modal identification from ambient vibration stationary tests carried out before the strong motion transient tests at various levels of damage. A singular value (SV) decomposition of the cross-correlation matrix of the acceleration response in the frequency domain is applied to determine the modal characteristics. In the time domain, the subspace state-space system identification is performed. Modal characteristics evolve from the initial linear state up to the ultimate collapse state in correlation with accumulated damage. Modal frequencies shorten with increasing intensity, whereas modal damping ratios are enhanced. Modal shapes also change with increasing level of accumulated damage. Comparing the evolution of modal characteristics, it is concluded that modal damping ratio shift can be better correlated with the system's actual performance giving a better representation of damage than that of natural frequency shift ratio or the modes difference

Evaluation of infill strut properties based on in-plane cyclic tests

U nelinearnoj analizi AB okvira sa zidanom ispunom jednostavni se zamjenjujući tlačni štap često primjenjuje za modeliranje ispune, posebice u slučaju opsežnih numeričkih proračuna. Stoga je pažljiv odabir odgovarajućih svojstava tlačnog štapa od iznimne važnosti za vjerodostojni prikaz odziva zgrade. U ovom je radu predložen i primijenjen postupak određivanja svojstava tlačnog štapa za prikaz zidane ispune temeljem interpretacije rezultata cikličkih, statičkih ispitivanja u ravnini na uzorcima jednoetažnih, jednorasponskih armiranobetonskih okvira s ispunom i bez nje.In the nonlinear analysis of masonry infilled RC frame structures, simple strut models are often adopted to represent the masonry infill, particularly in the case of extensive parametric numerical studies. Therefore, a careful definition of the corresponding strut properties is of exceptional significance for achieving a realistic building response. A method for evaluation of masonry infill strut properties is proposed and applied in this paper, based on the interpretation of results obtained by cyclic in-plane testing of single-storey, single-bay bare and infilled RC frame specimens

Numerical modelling of the behavior os ties under tension in brick veneer walls

Com o objetivo de avaliar o comportamento da ligação de paredes de tijolo face à vista a paredes de alvenaria de enchimento, foi definida uma campanha de ensaios para a caracterização do comportamento de diferentes tipos de ligadores sujeitos a diferentes configurações de carga (ações monotónicas e cíclicas de tração). Adicionalmente, com o objetivo de compreender em detalhe os fatores que afetam o comportamento da ligação parede de tijolo face à vista e parede de tijolo de enchimento através de ligadores metálicos, procedeu-se à calibração de um modelo numérico com base nos resultados experimentais obtidos nos ensaios de tração. Neste trabalho pretende-se apresentar os resultados da calibração do modelo numérico e de uma análise paramétrica para avaliação dos parâmetros mecânicos que mais influenciam o comportamento da ligação a ações de tração.Aiming at assessing the mechanical behavior of the connection of brick veneer walls to the backing system (brick infill walls), an experimental campaign was defined for the experimental characterization of the behavior of distinct types of ties subjected to distinct loading configurations, namely monotonic and cyclic tension and compression loading. Additionally, with the goal of completing the experimental results and achieve a better insight on the main parameters influencing the connection, a numerical model was built and validated based on monotonic tension experimental tests. In this work, it is intended to show the results of the numerical model calibration and analyze the results of a sensitivity analyses on the influence of the mechanical properties on the tensile behavior of the tie

In-plane shear behaviour of stone masonry piers: A numerical study

Post-earthquake investigations have shown that if out-of-plane mechanisms are prevented, the seismic performance of a masonry building depends mainly on the in- plane capacity of spandrels beams and especially piers. For this reason, several investigations were done in the past to characterize the in-plane behaviour of masonry walls. A large majority of these studies consist of experimental programmes, testing the lateral response of piers. Nevertheless, very few studies focused on carrying out numerical studies and their potential was disregarded. A numerical investigation to study the in-plane behaviour of masonry piers was carried out, based on an experimental campaign performed on stone masonry piers. The experimental programme included masonry piers with two slenderness ratios subjected to two distinct levels of axial compression. Finite element models were built on the advanced software, DIANA, and according to the experimental setup test of each wall, with the aim of simulating the experimental tests. Afterwards, the non-linear numerical simulations were compared against the in-plane cyclic test results. The calibration and validation of the numerical models according to the experimental results was conducted. The results of the non-linear analyses carried out on the validated models are presented and discussed. Good agreement between experimental and numerical results was achieved both considering the force- displacement behaviour and failure mechanisms. The numerical strategy can be seen as a complementary way to study masonry piers, particularly useful for further parametrical studies.The first author acknowledges the financial support from the Portuguese Science Foundation (Fundação de Ciência e Tecnologia, FCT) through grant SFRH/BD/71599/2010

Modelling of the in-plane behaviour of stone masonry panels

Stone masonrywalls are the most relevant structural element in the seismic response of a masonry building. Once the out-of-plane mechanism are adequately prevented, the seismic response of a building depends on the in-plane strength capacity of its walls. This paper presents a discussion on the in-plane behaviour of masonry panels with different slenderness ratios and distinct levels of compression load, subjected to shear loading, using advanced numerical simulations. The numerical study is based on an experimental campaign performed at the University of Pavia on stone masonry piers. The calibrated models were also used to carry out parametric analysis varying the geometric wall configuration and the pre-compression level. Distinct walls subjected to different stress levelswere assessed and the influence of these parameters on the in-plane behaviour is discussed.The second author would like to express her gratitude to the National Foundation for Science and Technology (FCT) for the PhD grant SFRH/BD/71599/2010. This work was supported by FCT, within ISISE, project UID/ECI/04029/2013

Masonry Italian code-conforming buildings. Part 1: case studies and design methods

Several architectural configurations of unreinforced masonry residential buildings are designed according to the different methods proposed in the Italian code: rules for the so-called simple masonry buildings, linear and nonlinear static analyses. Always complying with code requirements, for each building-site combination, the design was made, as much as possible, without an excessive margin of safety. The different design methods provided buildings with very different levels of safety, being linear static analysis largely overconservative with respect to the nonlinear static approach. These buildings were then analyzed in the companion pape

Performance of masonry buildings and churches in the 22 february 2011 christchurch earthquake

As part of the „Project Masonry‟ Recovery Project funded by the New Zealand Natural Hazards Research Platform, commencing in March 2011, an international team of researchers was deployed to document and interpret the observed earthquake damage to masonry buildings and to churches as a result of the 22nd February 2011 Christchurch earthquake. The study focused on investigating commonly encountered failure patterns and collapse mechanisms. A brief summary of activities undertaken is presented, detailing the observations that were made on the performance of and the deficiencies that contributed to the damage to approximately 650 inspected unreinforced clay brick masonry (URM) buildings, to 90 unreinforced stone masonry buildings, to 342 reinforced concrete masonry (RCM) buildings, to 112 churches in the Canterbury region, and to just under 1100 residential dwellings having external masonry veneer cladding. In addition, details are provided of retrofit techniques that were implemented within relevant Christchurch URM buildings prior to the 22nd February earthquake and brief suggestions are provided regarding appropriate seismic retrofit and remediation techniques for stone masonry buildings.The authors acknowledge the financial support for Project Masonry from the New Zealand Natural Hazards Research Platform. The testing of adhesive anchors was undertaken in conjunction with the RAPID grant CMMI-1138614 from the US National Science Foundation. The investigation of the performance of residential brick veneers was financially supported by Brickworks Building Products Australia