Sharif Digital Repository

Stone masonry construction is still a common practice in remote mountainous areas of many developing countries. Field investigations have shown that the traditional construction practices do not usually provide adequate seismic resistance for such buildings. This study was carried out to investigate and improve the construction of single-story stone masonry buildings in terms of safety in extreme events, economy, and ease of construction. The current construction methods were first studied through field investigations, and their deficiencies were identified. Then, improved stone masonry walls were designed that provide some confinement for the masonry by adding steel and reinforced-concrete... 

A large portion of the railway bridge stock in many countries is comprised of masonry arch bridges. During recent years, more attention has been paid to the maintenance of such structures. Rehabilitation and retrofitting methods have been proposed to enhance the performance of masonry arch bridges and extend their service life. Because a large portion of forces exerted on such structures comes from the railway track and passing trains, structural elements are added to the track to reduce the forces transmitted to bridges. One such element is the ballast mat, which, according to suppliers, has a positive impact on the structural performance of the track. This paper tries to assess the effects... 

After an earthquake, the residual stiffness and strength of structural elements are typically estimated based on a qualitative visual inspection of cracks that is prone to error. In this paper a new approach is proposed to automatically estimate the updated stiffness and strength of damaged unreinforced masonry walls by characterization of crack patterns by a mathematical index. It is shown that structural and textural fractal dimensions of a crack pattern reflect the extent of cracking and the type of cracking or crushing, i.e., whether the cracks pass through joints or whether bricks have been damaged and crushed. Using results of six quasi-static cyclic tests on unreinforced brick masonry... 

This paper describes the results of an experimental and numerical study that focused on multi-directional behavior of unreinforced masonry walls and established the requisite of the related proposed design equations. The tests were conducted following several sets of multi-directional loading combinations imposed on the top plane of the wall along with considering monotonic and cyclic quasi-static loading protocols. Various boundary conditions, representing possible wall–roof connections, were also considered for different walls to investigate the influence of rotation of the top plane of the wall on the failure modes. The results of the tests were recorded with a host of high precision data... 

Empirical drift capacity models for in-plane loaded unreinforced masonry (URM) walls are derived from results of quasi-static cyclic shear-compression tests. The experimentally determined drift capacities are, however, dependent on the applied demand, i.e., on the loading protocol that is used in the test. These loading protocols differ between test campaigns. The loading protocols applied in tests are also different from the displacement histories to which URM walls are subjected in real earthquakes. In the absence of experimental studies on the effect of loading histories on the wall response, this article presents numerical simulations of modern unreinforced clay block masonry walls that... 

This paper addresses the behavior of confined masonry walls with dominating shear failure mode in walls. For this purpose, failure modes of these walls are classified in details. For each failure mode, complete set of analytical-based relations for deriving parameters related to backbone curves is introduced. Calibrated finite element analyses are utilized as a benchmark for verification of some of the assumptions. The results of the proposed relations are compared with those of several Iranian and non-Iranian experimental data. Sensitivity analysis is performed in order to understand the effects of important behavioral characteristics of these walls. The results of this study indicate that... 

Displacement-based assessment procedures require as input reliable estimates of the deformation capacity of all structural elements. For unreinforced masonry (URM) walls, current design codes specify the in-plane deformation capacity as empirical equations of interstory drift. National codes differ with regard to the parameters that are considered in these empirical drift capacity equations, but the inhomogeneity of datasets on URM wall tests renders it difficult to validate the hypotheses with the currently available experimental data. This paper contributes to the future development of such empirical relationships by investigating the sensitivity of the drift capacity to the shear span,... 

Seismic performance of a representative single-story confined unreinforced masonry school building in Tehran, Iran is evaluated by means of incremental dynamic analyses according to FEMA P-58 framework. For this purpose, fragility curves are derived for each of the constituent walls of the building. The in-plane behavior of the walls is considered only. Both flexible and rigid diaphragm conditions are investigated. For comparison purposes, the corresponding unconfined building exactly duplicating the considered confined unreinforced masonry building is also studied. In order to analyze the effects of near-source seismic actions on the performance of masonry buildings, two separate far-field... 

This study proposes predictive equations for estimating the peak-experienced drift ratio of unreinforced masonry walls based on the visual characteristic of the damages. In this regard, a comprehensive database comprised of 190 images associated with 30 unreinforced masonry walls at different drift ratios between 0.0 and 1.1 percent is collected, and the visual features of the progressive damages are extracted. Various image processing filters are implemented to the images to quantify the cracking length and crushing areas. The filters are capable of distinguishing different crack patterns, such as joint cracking and block cracking. In the following, four scenarios are introduced based on... 

A single storey full-scale unreinforced brick masonry building with confined walls was designed based on Iranian building code and constructed on the shaking table facility of EERC of Sharif University of Technology. The model consisted of plain brick masonry walls confined with concrete tie columns and steel bond beams and had a typical jack-arch roof system. Wall panels included openings of different dimensions making it possible to investigate the effects of shape, geometry and location of openings. The model was subjected to several seismic excitations, consisting of scaled records of Bam 2003, Tabas 1978 and Elcentro 1940 earthquakes as well as a harmonic acceleration with a gradually... 

Most of the studies related to the modeling of masonry structures have by far investigated either the in-plane (IP) or the out-of-plane (OP) behavior of walls. However, seismic loads mostly impose simultaneous IP and OP demands on load-bearing or shear masonry walls. Thus, there is a need to reconsider design equations of unreinforced masonry walls by taking into account bidirectional effects. The intent of this study is to investigate the bidirectional behavior of an unreinforced masonry wall with a typical aspect ratio under different displacement-controlled loading directions making use of finite element analysis. For this purpose, the numerical procedure is first validated against the... 

Different types of macro-elements have been proposed to simulate the behavior of unreinforced masonry (URM) structures under seismic loads. In many of these, macro-elements URM walls are replaced with beam elements with different hysteretic behaviors. The effect of out-of-plane loading or change of gravity load due to the overturning moment is usually not considered in the behavior of these macro-elements. This article presents interaction curves for bidirectional loadings of unreinforced masonry walls to investigate the importance of these factors. Two parameters are systematically changed to derive the interaction curves for a wall with specific dimensions, including compressive traction... 

In this paper, a confined infill panel previously experimented under out-of-plane loading is modeled and analyzed by the dynamic explicit method (DEM). This method is shown to have a good estimation of the experimental results, and is thus adopted to investigate the out-of-plane behavior of an infill model. Based on the analytical results, the stress distribution of an infill panel prior to and after cracking, and the effect of an arching mechanism on post-cracking behavior, is studied. A semi-empirical relationship is accordingly developed for predicting the transverse resistance of masonry infills due to one-way arching action, which accounts for the effects of the boundary frame... 

Current design codes provide empirical equations for the drift capacity of unreinforced masonry (URM) walls that are based on results of quasi-static cyclic shear-compression tests. Yet different experimental campaigns have used various approaches of imposing fixed-fixed boundary conditions at the wall top which may affect the test results. This article investigates, by means of numerical simulations, the influence of experimental setups on the force and drift capacities of in-plane loaded URM walls subjected to double-fixed conditions. It is shown that controlling the shear span or the top rotation while keeping the axial force constant leads to very similar results. Controlling the axial... 

There are numerous studies on the behavior of Unreinforced Masonry (URM) walls in both in-plane (IP) and out-of-plane (OP) directions; however, few aimed at understanding the simultaneous contribution of these intrinsic responses during earthquakes. Undoubtedly, even a strong URM wall shows weakened capacity in the OP direction because of minor cracks and other damages in the IP direction, and this capacity reduction has not yet been accounted for in seismic codes. In this study, performance of three URM walls is evaluated by several numerical analyses in terms of the OP capacity reduction because of IP displacements and failure modes. Several parameters influencing the OP capacity have been... 

Unreinforced masonry (URM) buildings are rather popular around the globe due to low construction costs, even though they can be prone to substantial damage caused by even moderate earthquakes. Numerous URM buildings that have experienced damages from past earthquakes require to be upgraded or at least return to their undamaged state in order to be able to withstand future earthquakes. In many cases, reconstruction is not the best choice because of financial and time restrictions. As such, repair/retrofit is the best choice, assuring the post-earthquake serviceability. Furthermore, seismic repair/retrofit can be a cost-efficient method to avoid reconstruction complexities and expenses. In... 

This paper presents in-depth results of a proposed strut model for masonry infill walls in moment-resisting steel frames. The proposed model is based on the results of calibrated finite element analyses and hence gives realistic representation of infilled frames behavior. Comparisons are made between the results of the proposed model and other existing strut models; ASCE beam-to-beam, ASCE column-to-column and El-Dakhakhni. The results prove that considerable improvement has been made in capturing the internal forces of the frame members and force-displacement diagram of infilled frames by the new model compared to the existing models. Robustness of the proposed model is also confirmed in... 

This paper develops the seismic damage models of brick masonry veneer attached to the masonry infill without metal ties and assesses the life cycle cost of veneers subjected to earthquake excitation. Even though anchoring veneers to the backup wall has been prescribed in recent building codes, most of the existing brick veneers in seismic prone areas around the world lack the anchoring details. Besides, the damage and consequence models of masonry façades have not been presented in the FEMA-P58 database restricting detailed performance evaluation of buildings with unanchored masonry veneers. This study develops detailed finite element models to simulate various failure modes of the masonry... 

In order to evaluate the seismic behavior of confined masonry buildings, based on Iranian seismic code design, a single storey full-scale unreinforced confined brick masonry building has been constructed on the shaking table facility at the Earthquake Engineering Research Center (EERC) of Sharif University of Technology. The 4 by 4 meter model consists of four brick masonry walls confined with reinforced mortar tie-columns and steel bond beams, with a traditional jack-arch roof system. Three of the wall panels contained openings of different sizes and geometries. The model was subjected to the scaled earthquake records of Bam, Tabas and El Centro, as well as a harmonic acceleration with...