الفهرس 
CHAPTER (1) IntroductionOnly 14 pages are availabe for public view
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Abstract
Reinforced concrete (RC) frame buildings with unreinforced masonry (URM) infill walls are commonly built throughout the world. URM infill walls are widely used as non-structural elements, they affect both the structural and non-structural performance of RC buildings. During earthquakes, infill walls affect the response of the structure, and have either beneficial or detrimental effects. Infill walls contribute to the lateral force- resisting capacity and damping of the structure up to a certain level of ground motion. Infill walls increase the initial stiffness and ultimate strength of the structure but to the contrary, the fundamental period of the structure, ductility, and energy absorption are reduced.
URM infill walls are prone to early brittle failure, and infill wall failures may lead to the formation of a weak story, which can cause the building to collapse. Infill walls interact with the surrounding frame in such a way that column shear failure is made more likely. In addition, the unequal spatial distribution of infill walls for functional reasons can create torsion that places additional demands on columns.
Recent earthquakes that have accelerated this field’s research have resulted in a significant increase in awareness of the damage that infills during earthquakes can cause. Regarding in-plane loading, our understanding of the seismic behavior of infilled frames has substantially increased. Many experimental and numerical investigations demonstrated that the negative impact of conventional infills in frame buildings cannot be ignored, but no comprehensive design approach has yet to be developed. A few national codes included infill walls in the design, but they tended to
lack specific formulas and measurements. This is a difficult operation because standard infill modelling is fairly intricate. As a result, numerous studies sought to create policies that would enhance the performance of infilled frames.
The seismic behavior of infills under in-plane loading was thoroughly researched in the literature. RC frames’ seismic behavior is impacted by the infill wall; however, this effect is still not fully understood. The resistance, stiffness, ductility, and deformation capacity of infilled frames are altered by walls, but not significantly, according to some of researchers. According to a wide range of characteristics, including the frame/infill stiffness ratio, the masonry compression strength, slenderness, height/length ratio, etc., several failure modes are recognized for the in- plane direction. It is understood that infills have a negative impact on frame behavior, causing damage to border columns and possibly even posing a hazard to human life. The lateral load resistance and seismic performance of RC frames are greatly impacted by partial or complete collapse of the infill walls.
Several academics have conducted experimental studies to determine how well infilled frame’s function when subjected to lateral loads. Investigations have been done into the effects of factors such as panel aspect ratio, lateral load history, vertical load, and infill’s relative strength and stiffness to the frame. With minor in-plane drifts, high stiffness and strength are observed along with observable brittle behavior. Infill walls are successful in raising the base shear but lowering the displacement demand of the structure, according to studies on the dynamic parameters of RC frames with masonry filling conducted using pseudo-dynamic tests
or shaking table tests. When infills have previously suffered damage, both in-plane and out-of-plane capacities are dramatically decreased. This reduction is brought on by the infill damage brought on by the frame’s in- plane movement as well as the incomplete mortar filling of the gap between the frame and the infill or detachment from the tensioned diagonal.
After detailed literature review for past research, finite element models were conducted and verified against experimental results. It is obvious that there is a good agreement between the real case study and the results of the 2D FE models, more specifically, the factors that influenced the simulation and analysis of the results of the model were the type of elements, the mesh, the material models capacity, the nonlinear time history analysis, infill modeling, applied loads. Thus, we reached a reliable finite element model of infill and its interaction with the surrounding frame.
The research specifically addressed the issue of infill damage from in- plane loading. The primary driving forces behind the research were the increased losses and damage brought on by infill failure during earthquakes. As a result, the numerical model was created and tested against the outcomes of experiments. Further research on various setups and characteristics was conducted using the validated model.
Numerical model of 15-storeys RC frame in cases of inclusion and exclusion of infill walls was conducted. Accordingly, strength and stiffness of the structures as well as the structural response determined focusing on infill layout and irregularities in both horizontal and vertical direction using multi-modal pushover analysis to capture the effect of higher mode.