SEISMIC RESISTIVITY AND RETROFITTING OF RC FRAME BUILDINGS

Generally, in open ground storey buildings, unreinforced brick masonry infill’s are present in all floors except the ground storey. This leads to severe stiffness and strength irregularity and even sometimes leads to torsion irregularity. Buildings with these irregularities has consistently shown poor performance during past earthquakes like 1999 Turkey, 1999 Taiwan and 2001 Bhuj, 2003 Algeria earthquakes and many others. In India, most of the existing as well as new infill RC frame buildings has been designed and are being designed without considering strength and stiffness of Infill’s (bare frame modeling). Due to inclusion of infill’s behavior and failure modes of buildings changes. This leads to serious concern about seismic safety of existing buildings. In the present study, various strengthening techniques for open ground storey will be discussed. This techniques can be broadly categorized in two groups: 1) Strengthening of existing members, 2) Addition of new members. Reinforced Concrete jacketing and Steel jacketing. There are two popular methods; Addition of shear wall Addition of friction dampers. Addition of new shear wall can efficiently be used for buildings with only local interventions.Addition of friction damper is attractive and easy to construct but needs sophisticated method for proper fixation with existing frames. In this study SAP2000 is used to analyze the buildings models. Keywords:-Geo-Polymer, Metakaolin, Ambient curing

STUDY ON PUSHOVER ANALYSIS OF RC FRAMES WITH VERTICAL IRREGULARITY

The aim of the study is to compare and evaluate structural response obtained from nonlinear static analysis that is Pushover analysis procedures recommended in ATC 40. Three-dimensional low-rise moments resisting RC buildings with vertical irregularity are investigated. Two types of vertical irregularities, that is, mass and stiffness, as specified in the IS 1893- 2002 are considered in this study. In order to determine nonlinear behavior of the buildings under lateral loads, the base shear-roof displacement relationships i.e. capacity curves are obtained by Pushover analysis. The effects of mass irregularity (MI) and stiffness irregularity (KI) were investigated and discussed in terms of the height-wise distribution of story drift, storey shear, Storey Displacements. The performance point and structural performance level of mass and stiffness irregularities were determined using Pushover analysis. The mass irregular buildings were observed to experience larger storey shear whereas stiffness irregular buildings experienced lesser storey shear force than regular counterpart. The storey shear is increased by 25% at fifth floor for mass irregular structure compared to regular counterpart, whereas the stiffness irregular building experience lesser storey shear. Storey drifts were maximum for the stiffness irregular buildings; the drifts were increased by 94% than regular building. The storey displacements were decreased for mass irregular structures at the floor of irregularity, but the storey displacements were increased at bottom storey. The displacements at bottom storey were increased by 40%. The storey displacement for stiffness irregular buildings is increased by 97% compared to regular structure. The capacity curve of regular building is found less than mass irregular buildings, but the capacity curves of regular building is more than stiffness irregular buildings. The structural performance level of mass irregular building was found under “collapse” level, where as the structural performance level of stiffness irregular structure was under “Life of Safety “level