Abstract
Half-scaled reinforced concrete frame of two storeys and two bays with unreinforced masonry (URM) infill walls was subjected to base excitation on a shake table for seismic performance evaluation. Considering the high seismic hazard Zone IV of Pakistan, reinforcement detailing in the RC frame is provided according to special moment resisting frames (SMFRs) requirement of Building Code of Pakistan Seismic-Provisions (BCP SP-2007). The reinforced concrete frame was infilled with in-plane solid masonry walls in its interior frame, in-plane masonry walls with door and window openings in the exterior frame, out-of-plane solid masonry wall, and masonry wall with door and window openings in its interior frame. For seismic capacity qualification test, the structure was subjected to three runs of unidirectional base excitation with increasing intensity. For system identification, ambient-free vibration tests were performed at different stages of experiment. Seismic performance of brick masonry infill walls in reinforced concrete frame structures was evaluated. During the shake table test, performance of URM infill walls was satisfactory until design ground acceleration was 0.40g with a global drift of 0.23%. The test was continued till 1.24g of base acceleration. This paper presents key findings from the shake table tests, including the qualitative damage observations and quantitative force-displacement, and hysteretic response of the test specimen at different levels of excitation. Experimental results of this test will serve as a benchmark for validation of numerical and analytical models.
Highlights
Constructions such as Reinforced Concrete (RC) frame with unreinforced brick masonry (URM) are commonly observed all over the world in the seismically active regions [1, 2]
Performance of the infilled RC frame has been studied with simplified analytical models; Madan et al [8] detailed finite element analysis (FEA) [9,10,11,12] and with experiments, i.e., quasi-static, pseudodynamic, and shake table tests [13,14,15,16,17]
Limited experimental data are available on the dynamic behavior of RC frame infilled with URM since few shake table studies have been conducted on large scale [31, 32]. e typical construction of Pakistan is deficient in terms of workmanship, quality of materials, and arrangement of infill regarding the URM infill wall position and size of opening [33]; material properties of local brick masonry such as initial rate of absorption and compressive strength of the mortar are different from those normally used across the world, which results in low compressive and tensile strength and weak bond between bricks and mortar [33, 34]
Summary
Constructions such as Reinforced Concrete (RC) frame with unreinforced brick masonry (URM) are commonly observed all over the world in the seismically active regions [1, 2]. For the reason of damage evaluation of masonry infilled buildings, FEMA 306 [26] characterizes opening within infill as one of the most critical parameters affecting both the global and local seismic behaviors of structure. Limited experimental data are available on the dynamic behavior of RC frame infilled with URM since few shake table studies have been conducted on large scale [31, 32]. Experimental assessment of RC frame infilled with URM typically constructed according to local construction practices of Pakistan is unavailable on large scale having multistorey, multibays under real dynamic loading which is necessary for the calibration and verification of analytical model, providing foundation in defining new strategies of design as recommended by ACI (American Concrete Institute). E RC frame was infilled with URM walls having door and window openings at different locations according to local construction practices of Pakistan. Experimental programs, including designing, construction, and testing of the specimen as well as the qualitative and quantitative experimental results are reported in this paper. e main original aspect of this research is to explore the damage mechanism of URM infill and RC frame and its ultimate seismic resistance in terms of maximum base shear force and ultimate drift capacity of SMRFs structures infilled with URM infill walls. e results will be further utilized in developing numerical and analytical models, which will provide foundation for the development of seismic design guidelines of infilled RC frame structures
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