| Abstract: | This paper develops an optimized procedure for the design of torsionally unbalanced structures subjected to earthquake loading, considering both the serviceability and the ultimate limit states. An optimal design eccentricity expression, in the form of design charts, and an optimal overstrength factor equation, are proposed. Results show that the recommended design procedure can result in nearly equal performance of both the rigid edge and the flexible edge elements. For a wide combination of primary system parameters, the responses of both edge elements are consistently lower than, or in the neighbourhood of, the response of the corresponding torsionally balanced reference model. The proposed procedure retains simplicity and can be easily implemented (with certain limitations) in design practice. It also has the added advantages of requiring the structure to be analysed only once for each limit state in each principal direction (as opposed to twice, in existing code torsional provisions), and results in a significantly lower overstrength factor, compared with the overstrength factors corresponding to the torsional provisions of seismic codes in the United States and Canada. The proposed procedure is also applicable to torsionally unbalanced structures with and without transverse resisting elements. © 1997 John Wiley & Sons, Ltd. |
