a b s t r a c tIn codes the drift capacity of unreinforced masonry (URM) walls is often estimated as a function of the failure mode and the aspect ratio. The empirical relationships are based on results from quasi-static cyclic tests on single URM walls, which were tested simulating either fixed-fixed or cantilever boundary conditions. In real structures, the stiffness and strength of slabs and spandrels define the boundary conditions of the walls and therefore the moment, shear force and axial force imposed on a wall during an earthquake. Depending on the exact configuration of wall, slab and spandrel, the boundary conditions can vary significantly.In order to investigate the influence of these boundary conditions on the force-deformation behaviour of URM walls, six quasi-static cyclic tests were performed. Different boundary conditions were simulated by varying the axial load ratio and the ratio of top and bottom moment applied to the wall. This article presents the test results and discusses the influence of the boundary conditions on the failure mechanism and the drift capacity of the walls. In addition, the results from 64 quasi-static tests on URM walls of different heights and masonry types are evaluated. These tests confirm the influence of the boundary conditions on the drift capacity. Moreover, they show that a strong size effect is present which leads to smaller drift capacities with increasing wall height. For this reason, an empirical drift capacity equation is proposed which accounts for the moment profile, the axial load ratio and the size effect.
Previous test data on unreinforced masonry walls focused on the global response of the wall. A new dataset on six wall tests, which is publically available, allows linking global to local deformations of masonry walls, which can be useful for advancing performance-based design and assessment methods for unreinforced masonry buildings. This data paper presents the results of a test series on six identical unreinforced masonry walls that were constructed using hollow clay brick units and standard cement-based mortar.The test units were subjected to quasi-static cycles of increasing drift demands and the tests differed with regard to the applied axial load and the moment restraint applied at the top of the walls. The walls were tested up to failure.Throughout the loading the deformations of the walls were recorded using a digital photogrammetric measurement system tracking the movement of 312 points per test unit.
This paper presents the results of a series of shake-table tests on a half-scale, four-storey building with reinforced concrete and unreinforced masonry walls. Due to the lack of reference tests, the seismic behaviour of such mixed structures is poorly understood. The test unit was subjected to several runs of increasing intensity yielding performance states between minor damage and near collapse. Before the test, the expected peak table accelerations leading to different limit states were estimated using the capacity spectrum method, and the predicted values corresponded rather well to actual sustained accelerations. Next to these analyses, the paper describes the test unit, instrumentation and input motion, and comments on the response of the mixed structure in terms of damage evolution and global response quantities, such as force-displacement response and drift and acceleration profiles. The raw and post-processed data sets are made publically available, and all relevant information with regard to data organisation and post-processing procedure is described in an appendix to this paper. The test serves therefore as a benchmark for the validation of numerical models of such mixed structures. The project aims at providing a foundation for the development of seismic design and assessment methods of mixed structures, which are currently not covered by structural codes, including Eurocode 8.
SUMMARYThis article presents a new mechanical model for the non-linear force-displacement response of unreinforced masonry (URM) walls developing a flexural rocking mode including their displacement capacity. The model is based on the plane-section hypothesis and a constitutive law for the masonry with zero tensile strength and linear elastic behaviour in compression. It is assumed that only the compressed part of the wall contributes to the stiffness of the wall and therefore the model accounts for a softening of the response due the reduction of the effective area. Stress conditions for limit states are proposed that characterise the flexural failure. The new model allows therefore linking local performance levels to global displacement capacities. The limit states criteria describe the behaviour of modern URM walls with cement mortar of normal thickness and clay bricks. The model is validated through comparison of local and global engineering demand parameters with experimental results. It provides good prediction of the effective stiffness, the force capacity and the displacement capacity of URM walls at different limit states.
When testing multi-storey structures, most testing facilities require the testing of a reduced-scale model. A literature review on tests of scaled masonry structural components revealed that scaling of masonry was rather challenging and often significant differences in stiffness, strength and failure mechanisms between the different sized masonry were reported. This paper addresses the scaling of hollow clay brick masonry with fully mortared head and bed joints. We investigate different choices of scaling brick units and mortar joints. Based on the results of an extensive test programme including standard material tests and quasi-static cyclic tests on masonry walls subjected to horizontal and axial loads, we formulate recommendations for the production of a half-scale model of unreinforced masonry structures. The experimental results show a good match between full-scale and half-scale masonry. We discuss the differences in material properties that remained and compare the force-displacement hystereses obtained for the wall tests.
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