Your single point of reference for all your Geotechnical Inquiries


All buildings are subjected to some degree of torsion which in turn changes the member demands from that of translation only. Torsional effects on buildings subjected to earthquakes are not found directly in structural analysis unless full three-dimensional inelastic dynamic time history analysis is conducted. Since design is often conducted using two-dimensional analysis, these effects are not directly considered. There is currently an understanding of how different parameters may influence torsion, however, the degree to which these factors influence torsion is relatively unknown. Currently there are two simple design recommendations by Beyer/Priestley and MacRae; however, these need to be verified to be used in design. To do this, earthquake ground motions are applied in one direction to single storey structures with different inplane wall strength and stiffness, rotational inertia and torsional restraint to obtain the inelastic dynamic response considering torsion. A single multistorey analysis is performed to verify the  response compared to that of the single storey. It is found that an increase in strength on an element does not increase the demand on any critical element. An increase in rotational mass or a decrease in stiffness eccentricity decrease critical wall displacement. Increasing torsional restraint reduces the critical wall displacement. Beyer/Priestley’s prediction is generally non-conservative while MacRae’s is conservative. The multistorey analysis was well approximated by the single-storey response. Both single and multistorey structures are recommended to be designed by MacRae’s method of which a design example is provided.
NZSEE Annual Technical Conference & AGM, 13-15 April 2012, Christchurch
Novare Design, Wellington
New Zealand
User Rating:
You must be registered to vote.