Analysis of Natural Time Period of Moment Resisting Frame Buildings

Empirical equations of natural time period of a framed building, provided in the Indian Seismic Design Code IS 1893, are primarily as a function of the height of the building without considering the effect of number of bays, stiffness of the structure, plan area of the building etc. It is observed through relevant literatures that there is scope for further improvement in these equations since the height alone seems to be inadequate to explain the period variability. Natural period predicted by these expressions are widely used in the practice. It is therefore, very important to use realistic values of the time period of the buildings in the seismic design. This paper deals with study of effects of various other parameters of the building along with its height on the natural time period of vibration. The paper discusses about revision of the equations of time period of the design code.