IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 _______________________________________________________________________________________ Volume: 03 Issue: 07 | Jul-2014, Available @ http://www.ijret.org 265 SEISMIC EVELUTION OF RC SPACE FRAME WITH RECTANGULAR AND EQUIVALENT SQUARE COLUMN BY PUSHOVER ANALYSIS Ami A. Shah 1 , B. A. Shah 2 1 PG student, Applied Mechanics & Structural Engineering Department, Faculty of Technology & Engineering, The M. S. University of Baroda, Vadodara, Gujarat, India 2 Associate Professor, Applied Mechanics & Structural Engineering Department, Faculty of Technology & Engineering, The M. S. University of Baroda, Vadodara, Gujarat, India Abstract The present study is carried out to compare the seismic performance of RC frame structures of G+15 storey which consisting of rectangular shaped column as against equivalent square shaped column. The building is having 4.5m x 4.5m panels in both directions forming an overall plan dimension of 31.5m x 13.5m. All the beams are considered as 300 mm x 600 mm in size and columns with of 3 m height in each floor. In the above model all the rectangular shaped columns are oriented with longer side in global Y direction and shorter side parallel to global X direction. The M25 grade of concrete and Fe 415 grade of steel is considered for design. Pushover analysis is carried out, using commercially available software ETABS and behavior of RC frames is studied. One more factor which is studied in the current models is the material consumption variation for keeping the building in Immediate Occupancy stage. Also the comparison of normal RC frame and immediate occupancy level RC frame for both shaped columns is carried out. Quantity of concrete and quantity of steel is calculated for all the models and the overall structural cost is evaluated. Comparison for all the models in terms of quantity of materials and structural cost is also reported. It is concluded that the square cross section of columns perform better as compared to rectangular cross section of columns. Keywords: Performance point, Pushover analysis, RC space frame --------------------------------------------------------------------***------------------------------------------------------------------ 1. INTRODUCTION Recent earthquake in which many concrete structures have been severely damaged or collapsed have indicated the need for evaluating the seismic adequacy of existing buildings. About 60% of land area of India is susceptible to damaging levels of seismic hazard. We can’t avoid future earthquakes, but preparedness and safe building construction practices can certainly reduce the extent of damage and loss. To have a reliable estimate of a structures, sophisticated analysis tools are necessary. Nonlinear dynamic analysis is the most accurate method available for the analysis of structures subjected to earthquake excitation. Non-linear static (Pushover) analysis is also an attractive choice because of its simplicity and ability to identify component and system- level deformation demands with accuracy comparable to dynamic analysis. By conducting pushover analysis, we can predict the weak zones in the structures and then we will decide whether the particular part is required to be retrofitted or rehabilitated according to the requirement. Conventional limit-state design is typically a two-level design approach having concern for the service-operational and ultimate-strength limit states for a building. Performance-based design can be viewed as a multi-level design approach that additionally has explicit concern for the performance of the building at intermediate limit states related to such issues as occupancy and life-safety standards. With the emergence of the performance based approach to design, there is a need to develop corresponding analysis tools. Nonlinear static (Pushover) analysis is often an attractive choice in this regard because of its simplicity and ability to identify component and system level deformation demands with accuracy comparable to dynamic analysis. In the present work, a series of pushover analysis is carried out by using ETABS V9.7.4. Software. The analysis is carried out on the RC space frame for G+15 storey buildings as per ATC-40 for the models having rectangular column and equivalent square columns with 31.5m x 13.5 m overall plan of building. In both the models, optimization of column sizes are done on the basis of percentage of steel not exceeding 4 percentage, as per IS 456:2000. A comparison of the influence of the shape of the column on the seismic response of a building is presented here. The scope of the present study is limited to the analysis of buildings with rectangular columns oriented in one direction only. 2. PUSHOVER ANALYSIS Pushover analysis is an analysis method in which the structure is subjected to monotonically increasing lateral force with an invariant height-wise distribution until a target displacement is reached. Pushover analysis consists of a series of sequential elastic analysis, superimposed to approximate a force-displacement curve of the overall structure. A two or three dimensional model which includes bilinear or trilinear load-deformation diagrams of all lateral force resisting elements are first created and gravity loads are applied initially. A predefined lateral load pattern which is distributed along the building height is then applied. The lateral forces are increased until some members yield. The