Torsional Load Effects on Buildings Under Wind

The wind-induced torsional response is important for the design of tall buildings in terms of both serviceability and survivability. Nevertheless, current codes and standards provide very little guidance in this regard. This paper aims to provide a framework for the formulation of torsional load effects for possible inclusion in codes and standards. The formulation is based on the high frequency force balance (HFFB) technique that has generally been recognized as an effective wind tunnel technique. The major shortcoming of this technique is that it provides mode-generalized torsional loads associated with a uniform mode shape. This paper first discusses the effects of a non-uniform mode shape on the results. An example from a database derived from the HFFB measurements of a host of prismatic and a group of unconventional building configurations is presented. Based on the aerodynamic force information, a "gust loading factor" (GLF) formulation is developed for estimating the torsional response. It is envisaged that the proposed formulation will be useful for inclusion in codes and standards along the format of the along-wind response. An example is presented to illustrate the effectiveness of the proposed procedure and the significance of torsional load effects for design application.