Comparative analyses of a multi-storey frame and wall using the current and draft loadings codes

The two draft loadings codes, DZ 4203-86 and 89, introduced major changes in both the response spectra used for seismic design and the methods of analysis. In this paper a wall and a frame, which have been proportioned to provide the seismic lateral load resistance for a 24 storey structure, are analysed by the methods given in these codes to highlight the differences. To simplify the comparison torsional effects have been omitted. The technique of finding a set of lateral loads, by taking the differences of the combined modal storey shears and using these to find the design structural actions, is shown to be inappropriate for structures analysed for the response spectra given in the draft loadings code (DZ 4203, 86 or 89), if the second or higher modes make a significant contribution to the combined modal storey shears.