By carrying out experiments on eight brick masonry walls with pilasters reinforced by glass fiber reinforced polymer (GFRP), a seismic shear capacity of brick masonry wall structures is studied in detail. First, the interaction coefficient of the pilaster y, modified coefficient dgfi statistic coefficient b and effective participation coefficient V are determined. Then, based on failure model of brick masonry walls and truss model of fiber reinforced polymer (FRP), the formulae of seismic shear capacity of brick masonry wall with pilaster reinforced by FRP are established, which have an excellent coincidence with the experimental results obtained from the test; Finally, the simplified design formula of seismic shear capacity of brick masonry wall reinforced by FRP has been proposed in this paper. The design formula can be used for further study or for design reference in brick masonry structures.

An experimental research program was undertaken to ascertain the compressive and shear strength enhancement of masonry wall panels using steel strips. The study includes eight wall panels, four each for compressive and shear strength evaluation. In each group of four walls, one wall was un-strengthened, the second was single sided coarse steel mesh, the third was double sided coarse steel mesh and the fourth one was single sided fine steel mesh with closely spaced horizontal strips. Separate testing arrangements were made for compressive and shear strength determination. During compression testing only vertical load was applied and for shear strength determination, lateral load with vertical pre-compression was applied.During the test observations were recorded covering all important parameters like stressstra in, vertical load-deflection, lateral load-deflection and behavior of steel strips under vertical and lateral loading. Load carrying mechanisms were observed, varying from the initial, un-cracked state, to the final, fully cracked state. The results demonstrate that a significant increase in compressive and shear strength can be achieved by anchoring steel strips to the surface of masonry walls. It is concluded on the basis of experimental work that the technique / approach is viable for rehabilitation of old deteriorating buildings and strengthening of unreinforced masonry structures in seismic zones.

An attempt has been made in this study to correlate compressive strength, shear strength, and wall stiffness for clay burnt bricks with frog mark and machine-made bricks without frog mark. In this experimental study, 8 prisms and 8 unreinforced masonry (URM) walls (254 mm) with a size of 1524 mm X 914 mm were constructed with two different types of bricks, i.e., clay burnt brick with frog mark and machine-made brick without frog mark. Two types of mortar thicknesses 13 mm and 19 mm were used in the test specimens. The prism specimens were tested under axial compression load normal to the bed joints and the wall specimens were tested under horizontal incremental cyclic loading along with the constant axial compressive load. Lateral loading was applied using a loading control pattern. The specimens were tested under cyclic loading conditions displacing them laterally, along the axis of the walls and their load-deformation behavior was measured by dial gauges. It is observed that with increasing mortar thickness prism, ultimate strength increases 18.0% for clay burnt brick and with increasing mortar thickness prism, ultimate strength increases 1.3% for machine-made brick. On the other hand, with increasing the mortar thickness, ultimate shear strength decreases 9.6% for clay burnt brick with frog mark and with increasing mortar thickness ultimate, shear strength decreases 8.0% for machine-made bricks without frog mark. In clay burnt brick shear strength is 12.5% more than machine-made brick. With increasing the mortar thickness, ductility decreases 22.0% for clay burnt brick and 20.0% for machine-made bricks. Based on the findings, it is stated that clay burnt brick is preferable to machine manufactured brick. This study will aid in the comprehension of the behavior of both types of bricks used in masonry construction, given that masonry is a common building material.

Unreinforced masonry (URM) buildings are widely used in Iran and if their details do not conform to applicable standard, they maybe vulnerable to earthquake. One of the conventional techniques used in retrofitting of existing URM buildings consists of using reinforced concrete (RC) overlay. In this method concrete with a thickness of 3 to 5 cm is sprayed onto the surface of a masonry wall over a mesh of reinforcing bars.In this paper, effect of RC overlay on nonlinear in-plane behavior of confined masonry wall is studied by FEM using 2-D analytical program WCOMD, developed in Tokyo University. In this program, average constitutive models of reinforced concrete and masonry elements are used. In addition, to model cracks constant smeared crack method is used.In this paper, the reinforced masonry wall is modeled using masonry and RC elements as well as interface elements to model sliding between masonry and RC elements. Interface elements characteristic are defined based on nonlinear shear behavior of shear bars. Then, results of the numerical model are verified against available experimental results. After verification, a parametric study is carried out on confined masonry walls and the effects of compressive strength of confinement and size of openings on behavior of walls are studied.

Unreinforced masonry buildings are among the most popular types of construction in Iran. In these buildings, walls are used to resist both lateral and gravity loads. Since brittle materials are used in the construction of these walls, they, typically, are not ductile and, when load exceeds capacity, they suddenly lose their load carrying capacity.After an earthquake, different kinds of damage are introduced to buildings which fall into the following categories; members with permanent deformation or members with cracks. Rehabilitation is the best way for enhancing the behavior of the cracked members. It is possible to rehabilitate cracked members using different approaches so that they regain their strength. This is important from two aspects: 1-There are a lot of cracked members in a structure after an earthquake 2- Because of the loss of lateral strength in the case of cracks in a load carrying member, the structure is vulnerable to future quakes. In this research, a design for the one sided rehabilitation of damaged masonry walls, using of one undamaged masonry wall and one damaged, but rehabilitated, wall, with a scale of 0.5 under cyclic load, has been investigated. Results show that this design strategy has restored most of the load carrying capacity of the wall.

In accordance with some codes of practice for seismic resistant design of buildings (e.g. Iranian Standard No. 2800 - 3rd edition), bond-beams and tie-columns must be used in all load carrying walls of unreinforced masonry buildings. Building integrity and behavior of structural components such as walls can be improved by anchoring the floors and roof to the walls and by confining the walls. Capacity curves of such load carrying walls in seismic prone areas of Iran should be determined. For this purpose, two identical specimens of confined masonry walls have been made and experimental work on them have been carried out under static monotonic lateral loading. After gathering the experimental data, the same wall has been modeled by finite element analysis. In the model, the masonry panel has been assumed to be continuum and studied by multisurface plasticity Rankine-Hill model with low orthotropic factor. Since the reinforced concrete (RC) bond-beams and tie-columns may be cracked, the Rankine yield surface is used in their modeling. Sliding, cracking, and gap opening at the interface between the masonry panel and the surrounding bond-beams and tie-columns has been modeled too. Based on the experimental and numerical results, the obtained crack pattern and capacity curves are compared and good agreement is found.

An effective approach for strengthening masonry building is to apply shotcrete  reinforced with mesh on the surface of the wall. It is not possible to assess behaviour of coated walls solely using analytical approaches based on simple equations of theory of elasticity without the use of numerical methods. Unreinforcced masonry wall is modeled in this study using the finite element software "ANSYS" to assess the behavior of walls strengthened with reinforced jacket. The accuracy of the models is ensured by calibrating the model against results from laboratory tests. Then the calibrated model is generalized to model the strengthen wall and finally, the analytical results obtained from masonry walls and strengthen walls and strengthed walls are compared and evaluated.

To understand the seismic damage characteristics of bottom frame-wall buildings and to study their seismic performance, the seismic damage outcomes of bottom frame-wall structures in Du jiang weir by the Wen chuan earthquake on May 12, 2008, China were field observed and studied. The assesment of the seismic damage to the bottom frame-wall masonry in Du jiang weir urban showed that the damage to the type of structure system was serious and including damage to the bottom frame, the bottom storey, the transition storey, the bottom node and the rear longitudinal wall, combining with the failure characteristics, the failure reasons and mechanism were analyzed and the corresponding treatment measurements are given. However, a substantial number of bottom frame seismic wall masonry structures (BFSWMSs) after 2000 are basically undamaged. The field inspections team sampled 2178 buildings of the urban ensemble observation. A considerable number of buildings seismic fortified have shown excellent seismic performance in Wenchuan earthquake, which sufficient illustrates the significant role of seismic fortification factors in structural design. Through, the investigation and analysis of its empirical seismic damage, the main measures to improve its seismic performance of construction structure. The above analysis results can provide a reference for seismic design and the revision of seismic intensity scales.

In this article, an unreinforced masonry wall under in-plane load was numerically modeled using the ABAQUS software. In order to model the material of masonry, concrete material in the material library of ABAQUS software was used. The concrete damaged plasticity method in the ABAQUS software is a model that was meticulously studied in this research. Initially the governing factors influencing the behavior of this model were introduced, and then the cases provided for this purpose were separately investigated. To this end, an unreinforced masonry wall (100 × 990 × 1000 mm) which has been placed under the in-plane load in the lab, and its laboratory results are available was modeled in the ABAQUS software and after defining the required specifications, the effect of various parameters such as stress cracking, dilation angle, strain cracking, viscosity, and etc. was investigated. For modeling the wall, macro method, which is one of the modeling methods of masonry materials was used. After calibration of the numerical model with the laboratory results, the effect of all of the available parameters in the concrete damaged plasticity model was investigated, and their effect was shown in the load-displacement diagram as well as the contour stress. A meticulous parametric investigation would give a better understanding of the way of functioning of these parameters in the modeling. In addition, it offers a better understanding for the users to use appropriate parameters in the modeling.