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This study evaluates two different types of techniques for concrete hollow-block sections reinforced with traditional steel rebars and wire meshes, and compares their structural behaviour to that of an ordinary reinforced concrete beam section. The comparisons are based on the responses both before and after they were repaired with glass fibre reinforced polymers (GFRP). The specimens were subjected to concentrated loading up to initial failure. After failure, the specimens were repaired and loaded once again until ultimate failure. It was shown that the success of the repair by GFRP depended on the mode of failure of the hollow-block concrete beams.

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The objective of this paper is to present a new method for protecting the lives of residents in catastrophic earthquake failures of unreinforced masonry buildings by introducing some safe rooms within the buildings. The main idea is that occupants can seek refuge within the safe rooms as soon as the earthquake ground motions are felt. The information obtained from the historical ground motions happened in seismic zones around the globe expresses the lack of enough safety of masonry buildings against earthquake. For this potentially important reason, an attempt has been made to create some cost-effective seismic-resistant areas in some parts of the existing masonry buildings, which are called safe rooms. The practical method for creating these areas and increasing the occupant safety of the buildings is to install some prefabricated steel frames in some of their rooms or in their halls. These frames do not carry any service loads before earthquake. However, if a near field seismic event happens and the load bearing walls of the building destroy, some parts of its floors, which are in the safe areas, will fall on the roof of the installed frames consequently, the occupants who have sheltered in the safe rooms will survive. This paper expresses the experimental and theoretical work executed on the steel structures of the safe rooms for bearing the shock and impact loads. Finally, it was concluded that both the strength and displacement capacity of the steel frames were adequate to accommodate the distortions generated by seismic loads and aftershocks properly.

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Confined masonry buildings are used in rural and urban areas of Iran. They performed almost satisfactory

during past moderate earthquakes of Iran. There is not a methodology in Iranian Seismic Code (Standard 2800-3rd

edition) to estimate their capacities quantitatively. In line with removing this constraint, an attempt is made to study

in-plane behavior of two squared confined masonry walls with and without opening by using a numerical approach.

These walls are considered based on Iranian Seismic Code requirements. Finite element 2D models of the walls are

developed and a pushover analysis is carried out. To model the non-linear behavior of the confined masonry walls, the

following criteria are used: (1) The Rankine-Hill yield criterion with low orthotropic factor to model the masonry

panel (2) The Rankine yield criterion to model reinforced concrete bond-beams and tie-columns (3) The Coulomb

friction criterion with tension cutoff mode to model the interface zone between the masonry panel and reinforced

concrete members. For this purpose, the unknown parameters are determined by testing of masonry and concrete

samples and by finite element analysis. Comparing the results show that the initial stiffness, the maximum lateral

strength and the ductility factor of walls with and without opening are different. Also, the severe compressed zones of

the masonry panels within the confining elements are found different from what are reported for the masonry panels

of infilled frames by other researchers. This study shows that a further investigation is needed for estimating capacity

of confined masonry walls with and without opening analytically and experimentally. Also where openings, with

medium size are existed, the confining elements should be added around them. These issues can be considered in the

next revisions of Iranian Seismic Code.

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Pullback test has no scrupulous theoretical establishment. It is based on the hypothesis that the response of

the structure can be related to the response of an equivalent single degree-of-freedom (SDOF) system. This implies that

the response is controlled by a single mode. In fact, the steel frame of each safe room, which is introduced within the

unreinforced masonry buildings for protecting the lives of residents in catastrophic earthquake failures, contains a

SDOF structural system. In pullback test, the steel frame carries its gravity load first, and then it will be pushed under

an incremental lateral roof displacement pattern, which is imposed to its center of mass. This paper expresses the

results of 13 pullback tests executed by the authors on the steel frames of safe rooms. The results show that pullback

test is a practical method for seismic performance evaluation of safe rooms. Also the performance of these frames

located in a collapsing three storey masonry building is presented with favorable conclusions. In fact, the results of

pullback test of the safe room located at the ground-floor level were compared with the requirements of Iranian code

for seismic resistant design and it was concluded that the steel frame had an acceptable performance against seismic

effects.

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The increase in the computational capabilities in the last decade has allowed numerical models to be widely used in the analysis, leading to a higher complexity in structural engineering. This is why simple models are nowadays essential because they provide easy and accessible understanding of fundamental aspects of the structural response. Accordingly, this article aims at showing the utility and effectiveness of a simple method (i.e. the Load Path Method) in the interpretation of the behaviour of masonry buildings subjected to foundation settlements due to landslide. Models useful for understanding brick-mortar interface behaviour as well as the global one are reported. The global proposed approach is also validated by using Bi-directional Evolutionary Structural Optimization method. Moreover, drawing inspiration from a case study, the article shows that the proposed approach is useful for the diagnosis of crack patterns of masonry structures subjected to landslide movements.

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Seismic retrofit of masonry slabs in existing steel or masonry buildings has found special significance in current codes as failure of unstable jack arch slabs has been reported as a major reason for collapsing structures in Middle East deadly earthquakes. In this paper, three retrofit schemes are investigated and compared. The proposed rehabilitation techniques consist of a single X strapping, SXS, a double X strapping, DXS, and a two-way jack arch slab supported by a steel grid. Using experimental studies, advantages and disadvantages of each scheme are evaluated. In-plane stiffness and capacity of the diaphragm are adopted as the seismic performance index of each rehabilitation scheme. According to the obtained results, the jack arch slab systems designed and constructed based on proposed retrofit methods provide an appropriate alternative to other forms of flooring in seismic zones. DXS can greatly improve diaphragm performance in terms of in-plane stiffness, capacity and even energy dissipation of the diaphragm compared with the other two techniques. The second place belongs to SXS while the steel grid scheme has a minor effect on the in-plane stiffness of the diaphragm.

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The dynamic mechanical behaviour of a stone block masonry cupola composed of non-convex discrete elements is studied. This cupola is designed in innovative and modern ways and was recently constructed in southern France. The necessity for an accurate numerical study to take into account the real geometry of each non-convex block is presented. Different results, concerning the stability of the masonry structure, or its mechanical behaviour during a simulated collapsing state, are given for several sets of parameters describing the contact condition between the blocks, or the blocks and the structure foundations, under various seismic loads.

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Replacement of existing unreinforced masonry (URM) walls, commonly used as a non-structural member in apartments, with new reinforced concrete (RC) components has been used as a reliable method when remodeling is carried out. However, special care needs to be taken when URM walls are removed not to waste construction time and materials. Therefore, retrofitting existing URM walls can be deemed a better solution rather than replacing URM walls with RC ones. Using shotcrete is one of retrofitting techniques of URM walls. However, using normal shotcrete cannot improve adequate ductility and may cause brittle failure at a wall-frame or slab connection. Therefore, new materials such as engineered cementitious composite (ECC) and ultra-high performance concrete (UHPC) have emerged to resolve the problem of normal shotcrete by increasing ductility and toughness of retrofitting materials. In this study, sprayed ECC was used to increase both strength and ductility of existing URM walls. The results of two retrofitted URM walls under lateral quasi-static loading were compared to non-retrofitted one. One strengthened wall, retrofitted masonry wall (RTM)-ECC, was just sprayed and anchored to a wall base. Another strengthened wall, RTM-ECC-WM, was the same as RTM-ECC except for addition of wire mesh. The retrofitted specimens showed significant increase of strength, ductility, and energy dissipation capacity in comparison with the control one. In addition, RTM-ECC-WM indicated better strength degradation due to the load transferring effect of wire mesh than RTM-ECC.

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THIS IS THE REVISED VERSION OF THE PAPER A-10-581-3, CONSIDERED AS "MAJOR REVISION": One of the best methods to improve structural seismic behavior is to strengthen the infills by shotcreting. Most rehabilitation codes have a special part for masonry buildings and masonry infill panels. However they are completely silent for infills improved by concrete covers, probably for the lack of sufficient experimental test data. This paper focuses on the ultimate strength and modification factor of this type of infill panels, based on some experimental studies. The proposed formula of the existing codes for the equivalent width of the masonry infill panels is improved for the ultimate strength of shotcreted infill panels. It is also shown that the modification factors of the masonry and clay tile infill panels are downgraded and upgraded, respectively, if they are rehabilitated by concrete covers. The envelopes of the load-displacement behavior of the specimens are applied to calculate the modification factor, rather than the standard back bone curves. It is shown that they give more conservative values for the m-factor. Subsequently, some suggestions are proposed to estimate m-factor of shotcreted infill panels.