International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 02 | Feb -2017
p-ISSN: 2395-0072
www.irjet.net
Comparative Parametric Study of Seismic Behaviour of RC Framed Building With & Without Floating Column In Different Configuration Shreyans Kumar Jain1, Prof. Nidhi Gupta2 1PG
Student in Structural Engineering, Department of Civil Engineering, RKDF-IST, Bhopal (M.P.), India 2 Head of the Department of Civil Engineering, RKDF-IST, Bhopal (M.P.), India
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Abstract - With the increasing demand for residential
this feature is very common in high rise buildings. Most of the time, architect demands for the aesthetic view of the building, in such cases also many of the columns are terminated at certain floors and floating columns are introduced and hence such buildings are planned and constructed with architectural complexities. This discontinuation of columns introduces vertical irregularities in the structure and elongates the load transfer path which may prove to be detrimental, especially, in seismic conditions, if not taken care properly. So when irregular features such as above are included in buildings, a considerably higher level of engineering effort is required in the structural planning and design. Therefore, where provision of floating column is necessary, special care should be given to the transfer girders and columns below the transfer girders. These beams and columns should have sufficient strength to receive the load from floating column and convey it to the lower level.
and commercial space, people preferring vertical system i.e. high rise buildings. And for large uninterrupted space required for the movement of people or vehicles concept of floating columns is often used. The load transfer takes place from horizontal members to vertical members and finally transferred to foundation level, hence, there should be a clear load path available for the load to reach the foundation level. But Floating columns are discontinued at its lower level and rest on a horizontal member, usually beams. This discontinuity of columns at any floor changes the load path and transfers load of the floating column through horizontal beams supporting it. This altered path causes large vertical earthquake forces due to overturning effect. Therefore, where floating columns are provided, special care should be given to the transfer girders and column below the floating column. In the present work, variation in seismic behaviour due to presence of floating columns is studied. Also the effect of configuration of floating column is noted. For the purpose three different models of G+20 RC framed building are prepared and analysed using STAAD.Pro V8i software by Equivalent Static Method and a comparative study based on parameters such as axial force, shear, moment, base shear and displacement has been done. The study reveals that floating columns should be avoided in severe seismic zones and if not avoidable then corner columns should not be floated as the magnitude of design parameters are more severe in such configuration.
2. OBJECTIVE OF THE PRESENT STUDY The main objective of the present work is to study the effect of presence of floating columns in different configurations on seismic response of a G+20 RC Framed building under the provisions of different IS codes and with the help of STAAD.Pro software. Parameters to be compared are Column & Beam Forces, Average Displacement and Storey Drift.
Key Words: Floating Column, STAAD.Pro V8i, Equivalent Static Method, Average Storey Displacement, Storey Drift, Base Shear.
3. METHODOLOGY To achieve the objective, three Models of a G+20 RC framed building which differs in configuration of floating columns, introduced above ground floor, are prepared & analysed using STAAD.Pro V8i and results are compared. All the models are assumed to be situated in Seismic Zone IV.
1. INTRODUCTION Floating Column is a column which does not reaches to foundation level and hence also does not transfer the load carried by it to the ground. It rests on a beam which acts as a transfer girder and transfers the loads to other column(s) on which the beam rests. The floating column in this way discontinued at that beam level. This is done due to may be architectural design or site situation. A primary objective of doing this is to create an interrupted space below the columns which can be utilised as banquet halls, conference rooms, reception lobbies, show rooms or parking areas, etc. Now-a-days,
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3.1 Modelling All the three models are 18mx18m in plan, with 6 bays of 3m each in both ways. 21 floors (G+20) of height 3m each (total 63m height above GL) are considered with foundations at level -3m on medium soil. Sizes of beams and columns are kept same for all the models. One
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