Comparative Study of Response of Five Storey Moment Resisting Reinforced Concrete Frame Building With and Without Columns in Gridlines

Abstract—In the last decades the problem of structural regularity has been analyzed in a large number of papers, which pointed out the negative effects of the lack of regularity on the elastic and inelastic seismic response of structures and suggested design approaches able to limit the risks connected to it. Nearly all the seismic codes include general definitions of structural regularity and provisions aiming at limiting negative effects of irregularity.
In other hand, the perfect regularity in the building sometimes impossible due to the requirements and as well as particularly in countries like Nepal, most of the times, the shape of the land depicts the shape of the building. Therefore, in this paper, authors try to capture the seismic response due to the irregularity caused by the layout of columns not in perfect grid line. For this regular 5 storey building with 16numbers of column was first analyzed by using equivalent lateral load method . Later on, four different cases of irregularity caused by columns not in grid line were studied. The first case has 2 number of columns (12.5%) in offgrid, the second has 4 number of columns(25%) in offgrid all are in y-direction, the third case has 4 number of columns(25%) 2 in each direction are offgriid, the fourth case has 6 nubers of columns(37.50%) in offgrid. All the four cases then analysed and compared the modal and seismic responses.
Time Period of building increases when building is irregular due to the stiffness of building decrease when the columns are in offgrid. We can’t say that building is irregular by just look at it even 37.50% column in offgrid doesn’t affect the regularity of the building but it affect response of building towards seismic load and increase the demand of structural elements.
Keywords—Plan Irregularity, Column layout, offgrid, Torsional irregularity


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