Blind prediction of the seismic response of the NEESWood Capstone Building

The NEESWood Project is a multi-year US research project that involves analysis, testing, and societal risk assessment with the intent of safely increasing the height of light-frame wood buildings to six stories in regions of moderate to high seismicity. Within this project a full-scale seven-storey, 12.1 m x 18.1 m, condominium building (one storey steel frame and 6 storey wood frame construction) has been tested during July 2009 on the world’s largest earthquake shake table in Miki, Hyogo, Japan. As part of the NEESWood Project the international engineering community was invited to blind predict the inelastic seismic response of the Capstone Building. In this paper results of the blind prediction using the commercially available DRAIN 3-D structural analysis program are presented. The model for the test structure was composed of essentially rigid straight members connected to semi-rigid rotational springs in the vertical plane to represent the shear walls, while floor and roof diaphragms were assumed as rigid. The semi-rigid spring elements were incorporated into the DRAIN- 3D program using a proprietary subroutine simulating the hysteretic behaviour of wood mechanical connections. Properties of the hold-down rods were also included in the model. The required hysteretic parameters for each spring element were obtained by the data package provided by NEESWood researchers for this benchmark study. The results were then compared in terms of time-history responses, maximum base shear, maximum average displacements, interstorey drifts and hold-down tension forces experienced at each storey.