Publication

Abstract : Reinforced concrete (RC) moment frame buildings up to five storeys tall constitute over 95% of the RC building stock. In such buildings, the construction cost is economised by adopting the same formwork in the construction of all beams in all storeys and similarly of all columns in all storeys. It is needs to be clarified if such design option (with columns in all storeys proportioned to be of the same size and beams in all storeys to be of the same size) is beneficial or detrimental to good seismic resistance. This paper examines the seismic behaviour of such buildings, using Nonlinear Static Analyses (NSA) and Incremental Dynamic Analyses (IDA). Alongside three other design options also are examined (with column size different in all storeys even though beam size is same, beam size different in all storeys even though column size is same, and all column and beam sizes are different in all storeys). For each design option, analytical expressions are provided for proportioning the stiffness of members for improved seismic performance of buildings up to 5 storeys; this is compared with the traditional design option with no guidance on proportioning stiffness and strength of members of such buildings. The seismic performances are compared of buildings proportioned using the suggested expressions based on the results of NSA and IDA. The best design option is the one with varying beam and column sizes along the five storeys; the other design options are ranked in the order of their seismic performance.