International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 05 | May -2017
p-ISSN: 2395-0072
www.irjet.net
MITIGATION TECHNIQUES FOR SEISMIC PROTECTION OF RC BUILDINGS WITH OPEN GROUND STOREY Pradnya V. Sambary1, Shilpa P. Kewate2 1PG
Student, Civil Engineering Department, Saraswati College of Engineering, Kharghar, Maharashtra, India 2Associate Professor, Civil Engineering Department, Saraswati College of Engineering, Kharghar, Maharashtra, India ------------------------------------------------------------------------***------------------------------------------------------------------
Abstract - Construction of buildings with open ground
storey is being practiced on a large scale in many countries around the world and also in developing countries such as India to facilitate the increasing need to provide parking space due to increasing population and unavailability and high costs of land in urban areas. Open Ground Storey (OGS) buildings are those type of buildings in which the ground storey is left open without the provision of infill walls in between the columns of the ground storey and infilled in all the upper stories thus introducing stiffness irregularity in the building making them vulnerable to earthquakes especially when located in higher seismic zones. It was observed that most of the buildings damaged during the past earthquakes like the Bhuj earthquake of 2001, were due to presence of open ground storey. Hence strengthening of buildings with such irregularity is the need of the hour inorder to avoid their poor performance during earthquakes in future and thus saving human lives. In this study, seismic analysis of G+15 RC building with open ground storey, located in seismic zone IV is carried out using response spectrum analysis in ETABS software. The infill walls are modeled as equivalent diagonal struts. Various mitigation techniques such as provision of stiffer columns in the open ground store, providing shear walls throughout the building height and shifting of soft storey to higher levels are studied by analyzing four different models in ETABS software. Various seismic responses such as storey stiffness, lateral displacement, storey drifts and column forces of the open ground storey are evaluated and a comparative study is done on all four models to understand the most feasible mitigation technique. Key Words: Open ground storey, ETABS software, equivalent diagonal strut, response spectrum analysis, shear walls, mitigation techniques, infills etc.
1. INTRODUCTION
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Fig -1: Damage to OGS building during Bhuj earthquake
2. DESCRIPTION OF MODELS
Open ground storey building commonly known as soft storey building is an unavoidable feature in the modern multistorey building as they provide the needed space for parking of vehicles, reception lobbies etc. Also most of the malls built nowadays are of open ground storey type. There is significant advantage of these category of buildings functionally but from seismic performance point of view such buildings are considered to have increased vulnerability. It was observed from the past earthquakes © 2017, IRJET
such as during 1999 Taiwan, 1999 Turkey, 2001 Bhuj and 2003 Algeria earthquakes that most of the damage was to the open ground storey buildings. Damages included snapping of lateral ties, crushing of core concrete, buckling of longitudinal bars etc. The Indian Seismic Code IS: 1893 (Part-1)-2002 defines soft storey as the one in which lateral stiffness is less than 70% of that in the storey above or less 80% of the average lateral stiffness of the three stories above. Presence of infill walls in the entire upper storey except for the ground storey makes the upper stories much stiffer than the open ground storey introducing stiffness irregularity (vertical irregularity) in the building. Thus, the upper stories move almost together as a single block, and most of the horizontal displacement of the building occurs in the soft ground storey itself as a result of which the buildings sway back and forth like the inverted pendulum during earthquake shaking, and hence columns and the beams in the ground storey are severely stressed. Due to presence of infill walls in the upper stories, the lateral stiffness of the frame increases by three to four times.
Impact Factor value: 5.181
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The different models which are analyzed are as described below: Model 1 (M1) – Building with open ground storey Model 2 (M2) – Building with provision of stiffer columns (850x850 mm) in the open ground storey Model 3 (M3) - Open ground storey building with shear wall throughout ISO 9001:2008 Certified Journal
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