International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 6, June 2017, pp. 91 98, Article ID: IJCIET_08_06_011 Available online at http://www.iaeme.com/ijciet/issues.asp?jtype=ijciet&vtype=8&itype=6 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 IAEME Publication Scopus Indexed ANALYSIS OF MULTISTORIED BUILDING WITH AND WITHOUT FLOATING COLUMN USING ETABS Sasidhar T M.Tech Student, Structural Engineering, VIT University, Vellore, TamilNadu, India P. Sai Avinash M.Tech Student, Structural Engineering, VIT University, Vellore, TamilNadu, India N. Janardan M.Tech Student, Structural Engineering, VIT University, Vellore, TamilNadu, India ABSTRACT In the modern era of construction multi-storied building with floating column plays a major role in Urban India. These floating columns are used mainly for satisfying the space requirement in the structure and to get good architectural view of the building. In the present study, the analysis and design of multistoried building with and without floating columns was done using static analysis. A residential multistoried building consisting of G+5 has been chosen for carrying out project work. The work was carried out considering different cases of removal of columns in different positions and in different floors of the building. The equivalent static analysis is done on the mathematical 3-D model of building and results have been compared. All the work was carried out by using the software ETabs Version 9.7.4. Key words: Floating Column, ETABS, Equivalent static analysis, Magnification factor. Cite this Article: Sasidhar T, P. Sai Avinash and N. Janardan. Analysis of Multistoried Building with and Without Floating Column Using ETabs. International Journal of Civil Engineering and Technology, 8(6), 2017, pp. 91 98. http://www.iaeme.com/ijciet/issues.asp?jtype=ijciet&vtype=8&itype=6 1. INTRODUCTION In the present day construction of buildings in urban India the main problem arises in the accommodation of parking areas, reception lobbies etc. To overcome this problem floating columns came into existence and now it has become an unavoidable feature in most of the multistoried buildings. The floating column shows undesirable results during earthquake http://www.iaeme.com/ijciet/index.asp 91 editor@iaeme.com
Sasidhar T, P. Sai Avinash and N. Janardan excitation and the base shear induced is dependent on the natural period and shape of the building. As the height of the building is increased, the earthquake load acting at different floors of the building varies and these should be carried down in the shortest distance. If the load travelling has any discontinuity in its path, it will cause the reduction in the performance of the building. Due to discontinuity in the load transfer path, many buildings in Gujarat have been collapsed in Bhuj 2001 and the buildings with the vertical setbacks caused a sudden jump. The floating column are safe for the vertical loading but the lateral loads acting on the building causes overturning of the building and load travel path is also disturbed which results in the damage of the columns by buckling. This is because the strength of the lower floor is less due to removal of the columns. This project mainly focuses on the comparison of the building with and without floating columns. 1.1. Floating Column A column is supposed to be a vertical member which starts from the foundation level and transfers the load safely to the ground from the building. Floating column is a vertical member in which the lower end rests on the beam and load is transferred to the nearby column through the beam as shown in fig 1. Figure 1 Load transfer system 2. LITERATURE ON ANALYSIS OF MULTISTORIED BUILDING WITH FLOATING COLUMN USING ETABS Floating columns are used in many multistoried building to provide good architectural flexibility and more floor space index. Many researches has been carried out on these floating columns for comparison with normal building some of them are T.Raja sekhar et al (2014) computed the behavior of multistoried building with and without floating columns and its seismic behavior for different intensities using Finite Element Analysis. Srikanth.M.K et al (2014) specified about Seismic response of multistoried building with floating columns at different zones. A.P Mudada et al (2014) showed comparative seismic analysis of multistoried building with and without floating columns. Prema Nautiyal(2013) discussed about seismic response of RC framed building with floating column for different soil conditions. Sukumar Behra (2012) worked on the seismic behavior of multi storied building with floating column. http://www.iaeme.com/ijciet/index.asp 92 editor@iaeme.com
Analysis of Multistoried Building with and Without Floating Column Using ETabs 3. OBJECTIVE OF PROJECT To check the behavior of multistory building with and without Floating column. To provide more open space in ground floor for parking and reception lobbies. Proper design and detailing of transfer girder for different load combinations. 4. METHODOLOGY 4.1. Modeling of the Building In this project, building selected is G+5 multistoried building in the zone II region. Static analysis was carried out. The building was analyzed in the normal condition with all the columns are present. The building is divided into 6 cases depending on the position of removal of columns in the different regions. The results that are obtained in all the cases are compared with the normal building. 4.2. Normal Building without floating Columns Figure 2 Normal building in 3-D view Fig 2 shows the 3D view of normal building obtained in the ETabs software and Table 1 shows different specifications of the normal building. Table 1 Specifications of normal building Parameters Normal building Soil Type Medium Soil Seismic Zone II Height of the Building 19.2m Floor Height 3.2m Thickness of slab 150mm Beam Dimensions Column dimensions Grade of Concrete 230mmX300mm 350mmX450mm M30 http://www.iaeme.com/ijciet/index.asp 93 editor@iaeme.com
Sasidhar T, P. Sai Avinash and N. Janardan 4.3. Different cases considered based on positioning and removal of columns in the building Normal Building: Case 3: Removing only 4 columns alternatively in the 2 nd floor Case 1: Removing the 8 columns in the 2 nd floor Case 4: Removing only 4 columns alternatively in the 4 th floor Case 2:Removing the 8 columns in the 4 th floor Case 5: Removing only 6 columns alternatively in the Ground floor Figure 3 Plan of different cases of column positioning http://www.iaeme.com/ijciet/index.asp 94 editor@iaeme.com
Analysis of Multistoried Building with and Without Floating Column Using ETabs 4.4. Loads and Load Combinations for Analysis Dead Load: As per code IS 875 Part I the calculated dead load is 17 kn/m Live Load: As per code provisions IS 875 Part II for the Residential building Live Load acting on it is taken as 3 kn/m Earth Quake Load: Static method of analysis is done by using IS1893 The base shear acting on different storey height from top is i) 113kN ii) 79kN iii) 50kN iv) 28.2kN v) 12.5kN vi) 1.75kN Table 2 Load combinations considered in the analysis Combination 1 Combination 2 Combination 3 1.5D.L+1.5L.L 1.5D.L+1.5E.L 1.2D.L+1.2E.L +1.2L.L 5. RESULTS AND DISCUSSION The Present study is to compare the results of the building with and without floating columns and finding out the optimum position of the floating column for the desired results among all the cases considered. The parameters used for comparison are displacements, bending moment, shear force and area of reinforce-ment. 5.1. Max Moment Occurred in all the Cases From the Fig 4 as shown below it was observed that maximum moment for normal building is 162.05 kn-m in storey 2, maximum moment occurred among all the cases is 463.71kN-m in case I occurred in 2 nd storey..among all the cases considered,maximum moment obtained in different cases are shown in the Table 2. 500 Moment in kn-m 400 300 200 100 0 1 2 3 4 5 6 No of Stories Normal Building case1 case 2 case 3 case 4 case 5 Figure 4 No. of floors Vs Max moment graph 5.2. Max Shear Occurred in all the Cases From the Fig.5, it was observed that maximum shear for normal building is 174.08 kn in storey 2,and maximum shear occurred among all the cases is 365.6kN in case I occurred in 2 nd storey.among all the cases considered,maximum shear obtained in different cases are shown in the Table 2. http://www.iaeme.com/ijciet/index.asp 95 editor@iaeme.com
Sasidhar T, P. Sai Avinash and N. Janardan Shear in kn 400 350 300 250 200 150 100 50 0 1 2 3 4 5 6 Normal Building case1 case 2 case 3 case 4 case 5 No of Stories Figure 5 No. Of Floor Vs Max shear graph 5.3. Joint Displacement for different Floors From the Fig.6 as shown below it was observed that maximum displacement for normal building is 35mm in storey 6,and maximum displacement occurred among all the cases is 37.5mm in case 1.Among all the cases considered,maximum storey displacement obtained in different cases are shown in the Table 2. Storey Displacement, mm 40 35 30 25 20 15 10 5 0 1 2 3 4 5 6 Normal Building case1 case 2 case 3 case 4 case 5 No of Stories Figure 6 No. Of Floor Vs Storey displacement graph 5.4. Maximum Values of Moment, Shear and Storey Displacement From Table 2 it was observed that all the maximum values of moment, shear and storey displacement was occurred in case 1 because of removal of columns in 2 nd floor. http://www.iaeme.com/ijciet/index.asp 96 editor@iaeme.com
Analysis of Multistoried Building with and Without Floating Column Using ETabs Table 3 Values of Maximum Moment, shear and Storey displacement Storey Normal Building Case I Case II Case III Case IV Case V Max Moment (kn-m) 162.05 (Storey2) 463.74 (Storey2) 406.3 (Storey5) 381.11 (Storey3) 328.41 (Storey5) 420.88 (Storey1) Max Shear (kn) 174.8 (Storey2) 365.6 (Storey3) 350.9 (Storey5) 324.6 (Storey3) 284.4 (Storey5) 329.5 (Storey2) Storey Displacement 35 37.5 36.7 36.7 36.3 36.2 5.5. Area of Reinforcement Required From Table 3 area of steel reinforcement required for whole building in normal case is 7284905 mm 2 and maximum reinforcement is required in the building among all the cases is 11881475 mm 2 in case IV and minimum is 660599 mm 2 in case V. Table 4 Area of reinforcement required Type of Building Total Ast Required for whole Building in square mm Normal Building 7284905 Case I 11962541 Case II 9491283 Case III 10352693 Case IV 11881475 Case V 6640599 6. COMPARISON OF ANALYSIS RESULTS From the above results all the readings are all cases are compared to the Normal Building and the observations are as follows: 1. The moment in the case 1 has increased maximum value in the 2 nd floor when compared to the Normal Building and all other cases. 2. The Shear force has also increased to a maximum extent in the same storey and the case 1 itself when compared to the all other cases and Normal Building. 3. The Shear Requirement is higher in case 1 when compared to all other cases and it becomes uneconomical. 4. In the design of Transfer Girder has given the 1.2mX0.85m dimension and Steel bars of 25 no s of 25 mm diameter at bottom and 22 no s of 25 mm diameter at top when compared to the Normal building in the same point it is safe for 0.23mX0.3m and reinforcement of 6 bars of 16mm dia at bottom and 2 bars of 16mm diameter at top. http://www.iaeme.com/ijciet/index.asp 97 editor@iaeme.com
Sasidhar T, P. Sai Avinash and N. Janardan 7. CONCLUSIONS Based on the test results, the following conclusions were made: Use of floating columns results in the increase in the bending moment, shear and Steel requirement. These floating columns are not suitable in the seismic zones in which load travel path will be disturbed due to earth quake and building may be damaged. The optimum position to provide floating column is the at 2 nd floor alternatively so that moment, shear and steel requirement of the whole building can be minimized. Hence provision of floating column is advantageous in providing good floor space index but risky and vulnerability of the building increases. REFERENCES [1] Hardik Bhensdadia and Siddharth Shah Pushover Analysis of RC Frame structure with Floating column and soft story in different earthquake zones, International Journal of Research in Engineering and Technology, vol 2,Issue 4,ISSN 2321-7308. [2] Prerna Nautiyal, Saleem Akhtar and Geeta Batham Seismic Response Evaluation of RC frame building with Floating Column considering different Soil Condition", International Journal of Current Engineering and Technology, vol 4,2014,ISSN 2347 5161 [3] A.P.Mundada and S.G.Sawdatkar Comparative Seismic Analysis of Multistory Building with and without Floating Column, International Journal of Current Engineering and Technology,vol 4,No 5,2014. [4] Srikanth.M and Yogeendra.R Seismic Response of complex buildings with Floating column for zone ii and zone v, International journal of Engineering and Research Online, vol 2, issue 4, 2014. [5] M. Rajesh Reddy, Dr. N. Srujana and N. Lingeshwaran, Effect of Base Isolation in Multistoried Reinforced Concrete Building. International Journal of Civil Engineering and Technology, 8(3), 2017, pp. 878 887. [6] Dr. S. B. Shinde and N.B. Raut, Effect of Change in Thicknesses and Height in Shear Wall on Deflection of Multistoried Buildings. International Journal of Civil Engineering and Technology, 7(6), 2016, pp.587 591. http://www.iaeme.com/ijciet/index.asp 98 editor@iaeme.com