International Journal of Advancements in Research & Technology, Volume 4, Issue 11, November ISSN

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1 51 PUSH OVER ANALYSIS FOR RC BUILDING WITH AND WITHOUT FLOATING COLUMNS Stella evangeline 1, Student(m.tech) D.Satish 2, M.Tech (structures) E V Raghava Rao 3, Civil engineering dept, Asst.professor, HOD of civil dept, Visakha technical campus civil engineering dept, Visakha technical campus, Visakhapatnam,,India Coastal institute of technology. -evrrao@yahoo.com. Stellaevangeline.mb@gmail.com Abstract Rc structure and Floating column structure are typical features in the modern multi-storey constructions in urban India. Such features are highly undesirable in buildings built in seismically active areas; this has been verified in numerous experiences of strong shaking during the past earthquakes like Bhuj In this study an attempt is made to reveal the effects of floating column & rc building effected with sesmic forces. For this purpose Push over analysis is adopted because this analysis will yield performance level of building for design capacity (displacement) carried out up to failure, it helps determination of collapse load and ductility capacity of the structure. To achieve this objective, three RC bare frame structures with G+4 stories will be analysed and compared the base force and displacement of RC bare frame structure for earthquake forces by varing column dimensions using SAP analysis package. Keywords floating column, rc structure, pushover analysis, earthquake forces. Many urban multistorey buildings in India today have open first storey as an unavoidable feature. This is primarily being adopted to accommodate parking or reception lobbies in the first storey. Whereas the totalseismic base shear as experienced by a building during an earthquake is dependent on its natural period, the seismic force distribution is dependent on the distribution of stiffness and mass along the height. The behavior of a building during earthquakes depends critically on its overall shape, size and geometry, in addition to how the earthquake forces are carried to the ground. 2.1 FLOATING CLOUMNS Floating column is also a vertical member, The Columns Float or move in above stories such that to provide more open space is known as Floating columns. Floating columns are implemented, specially above the base floor, so that added open space is accessible for assembly hall or parking purpose. For the study of the floating column many projects have been undertaken where the transfer of load is through the girders. Floating columns are usually adopted above the ground storey level. So that maximum space is made available in the ground floor which is essentially required in apartments, mall or other commercial buildings where parking is a major problem. But those structures cannot be demolished; rather study can be done to strengthen the structure. The stiffness of these columns can be increased by retrofitting or these may be 1. INTRODUCTION provided by bracing to decrease the lateral deformation. Many high rise buildings are planned and constructed with architectural complexities. The complexities are nothing but soft storey, floating column, heavy load, the reduction in stiffness, etc. 3. METHODLOGY In the of case structures to avoid earth quake damages, special arrangement needs to be made to increase the lateral strength and stiffness of the members. As per IS 1893 (part-1): 2002, Dynamic analysis (Linear or Non-linear) of building is carried out including the strength and stiffness effects and inelastic deformations in the members and the members designed accordingly. The lateral loads due to earthquake were calculated using Response spectrum method as per IS 1893 (part-1): CALCULATION OF SHEAR The total design lateral force or design seismic base shear (V B ) is calculated according to clause of IS 1893:2002 (IS 1893:2002 is referred to as the Code subsequently). The total Base shear

2 52 Where A h is the design horizontal seismic coefficient Here Z = Zone Factor I = Importance Factor R = Response Reduction Factor The values of Z, I, R are given in Tables 2, 6, 7 respectively in IS 1893 (part-1):2002. S a /g = Spectral acceleration coefficient. It is calculated according to Clause of the Code corresponding to the fundamental time period T a in seconds is given as follows. For a Moment Resisting Frame without infill NON-LINEAR STATIC ANALYSIS The existing building can become seismically deficient since seismic design code requirements are constantly upgraded and advancement in engineering knowledge. Further, Indian buildings built over past two decades are seismically deficient because of lack of awareness regarding seismic behaviour of structures. The widespread damage especially to RC buildings during earthquakes exposed the construction practices being adopted around the world, and generated a great demand for seismic evaluation and retrofitting of existing building stocks. In the figures below different nodes subjecting to different levels of elastic zone are represented with respective colors mentioned at the bottom of the figures. The elastic zone is categorized into three parts likely Immediate Occupancy (IO) Life safety (LS) Collapse prevention (CP) For a Moment Resisting Frame with brick infill panels Here h = Height of the Building Frame CASE 1 : RCbuilding is considered with all beams and columns of same d = Base dimension of the building at the plinth level in dimensions and in the meters, along the considered direction of the lateral load s PUSHOVER ANALYSIS Pushover analysis is a static, nonlinear procedure in which the magnitude of the lateral loads is incrementally increased, maintaining a predefined distribution pattern along the height of the building. Pushover analysis can determine the behaviour of a building, including the ultimate load and the maximum inelastic deflection. Local nonlinear effects are modelled and the structure is pushed until a collapse mechanism is developed. At each step, the base shear and the roof displacement can be plotted to generate the pushover curve with the same structural dinmension for the same structure floating cloumns are assumed and push over curves are studies and in the by incresing the size of the surroubnding columns near the Floating cloums the pushover curve is studied Floating columns are provided in the top floor and surrounding columns dimensions are increased and push over is studied and compared The frames have to be designed so as to satisfy strength checks under several load combinations. To start with, the approximate values for dead loads have to be assumed based on the usual range of geometric ratios such as span to depth ratios for beams and widths of members. The earthquake loads can also be assumed correspondingly to the plateau in the response spectrum. In the current study, the length, width and storey heights were 3.0 m. Beam = 450x230 mm Columns = 450x230 mm = 600 x 400 mm Pedestal Columns = 450x230 mm

3 CASE 1 :- RC BUILDING WITH COLUMN,BEAMSOF SIZE 450X230MM WITHOUT FLOATING COLUMNS CASE 2 :RC BUILDING WITH COLUMN,BEAMSOF SIZE 450X230MM WITH FLOATING COLUMNS AT STILT LEVEL 53 CASE 3 :RC BUILDING WITH COLUMN,BEAMSOF SIZE 450X230 MM WITH FLOATING COLUMNS AT STILT LEVEL AND IN DIMENSION OF STILT COLUMNS 600 X 400 MM. RC BUILDING WITH COLUMN,BEAMSOF SIZE 450X230 MM WITH FLOATING COLUMNS AT TOP FLOOR AND IN DIMENSION OF SURROUNDING COLUMNS TO 600 X 400 MM

4 HINGE FORMATION PUSH OVER CURVES CASE 1: 54 CASE 1:

5 55 EVALUATION RESULTS RESULTS AND DISSCUSSIONS RESULT 1: DISPLACEMENT KN DISPLAC MENT % 1. With the increase in the stilt column dimensions the displacement varies and base force also increases. 2.Increase in 150 mm dimension in slilt-cloumns results 62 % variation in the base force With increase in the surrounding columns near floating columns. The base shear will be increased By providing floating columns at the top floor and with increase in the surrounding columns the displacement and base force decreases. 5.For existing rc buildings effected by earthquakes, and tsunami the column size and be increased by method of shorcreting REFERENCES RESULT 2: 7(COL UMN SIZE.6 X.4 ) CHANG E % DISPLACM ENT % RESULT 3: DISPLACEM ENT KN (COLU MN SIZE.45 X.23) 7(COL UMN SIZE.6 X.4 ) [1]. Srikanth.M.K, Yogeendri.R.Holebagilu, Seismic Response Of Complex Buildings With Floating Column For Zone II and Zone V, International journal of Engineering Research-Online, Vol.2., Issue.4, 2014, ISSN: [2]. Spoorthi S K, Dr. Jagadish Kori G, Effect Of Soft Story On Tall Buildings At Various Stories By Pushover Analysis, International journal of Engineering Research-Online, Vol.2., Issue.3., 2014, ISSN: [3].RizaAinul Hakim, Mohammed SohaibAlama, Samir A. Ashour, Seismic Assessment of an RC Building Using Pushover Analysis, Engineering, Technology & Applied Science Research Vol. 4, No. 3, 2014, [4]. Naga Sujani.S, Phanisha.K, MohanaRupa, Sunita Sarkar, P.Poluraju, Comparison of behavior of a multistorey building situated in zone II and zone V, using pushover analysis by Sap 2000, International Journal of Emerging Trends In Engineering And Development, Issue 2, Vol.2(March-2012), Pp [5]. SukumarBehera, Seismic Analysis Of Multistory Building With Floating Column A Thesis Of National Institute Of Technology Rourkela, (2012), Pp [6]. Amit V. Khandve. (2012), Seismic Response of RC Frame Buildings with Soft Storeys, International Journal of Engineering Research and Applications (IJERA), vol 2, Issue 3, pp [7]. Mehmet Inel, Hayri. B. Ozmen. (2008), Effect of infill walls on soft story behavior in mid-rise RC Buildings, The 14th World Conference on Earthquake Engineering, Beijing, China, pp [8]. Federal emergency management agency (FEMA 356), Nov 2000, is a report on Prestandard and commentary for the seismic rehabilitation of buildings prepared by American society of civil engineers. [9]. Ri-Hui Zhang1 and T. T. Soong, Member, ASCE Seismic Design of Viscoelastic Dampers for Structural Applications J. Struct. Eng : (COLU MN SIZE.45 X.23) DISPLACME NT DISPLACEM ENT KN