A Comprehensive Study on the Influence of Strength and Stiffness eccentricities to the On-plan Rotation of Asymmetric Structure
All buildings are subjected to some degree of torsion which in turn changes the member torsional 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 on how different factors may influence torsion, however, the degree to which these factors influence torsion is relatively unknown. Slab rotation effect is considered a major response parameter to represent the severity of the torsional response of eccentric systems; hence, it is considered in this study. The centre of strength (CR) and centre of stiffness (CS) are the two main factors under considerations. A comprehensive analysis on eighty different CR and CS conditions are applied to a three-dimensional, asymmetric building and their influences to slab rotation are observed. The CR/CS conditions are applied by varying strength eccentricities (er) and stiffness eccentricities (es) using two condition models. Then, earthquake ground motions are applied in z-direction under elastic and inelastic conditions. The results interpreted using a simple approach shows important slab rotation behaviour that forms interesting findings from this study. The slab rotation demand is found
to reduce as strength eccentricity moves away from the Centre of Mass (CoM) but is independent of the stiffness eccentricity. The study also confirms finding of previous works which states that stiffness eccentricity plays a minor role when assessing the torsional behaviour of a ductile systems. Results from inelastic analysis shows slab rotation demand increases as strength eccentricity is closer to the CoM but it remains constant for elastic analysis.
Crisafulli, F. Reboredo, A. and Torrisi, G. "Consideration of torsional effects in the displacement control of ductile buildings". Proceeding of 13th World Conference on Earthquake Engineering, Vancouver,B.C., Canada, August 1-6, 2004, Paper No.111
Miranda, B., MacRae, G. A. and Beyer, K. “Torsional Considerations in Building Seismic Design”. Proceedings of Conference of the New Zealand Society for Earthquake Engineering, 2012. Paper No.055
Priestley M.J.N., Calvi G.M., Kowalsky M.J., (2007) Displacement-Based Seismic Design of Structures, IUSS Press, 2007. ISBN: 88-6198-000-6, 120-125,328-353.
Roy, R.,(2016) “Seismic Behaviour of Horizontally Irregular Structures: Current Wisdomand Challenges Ahead”. Applied Mechanics. November 2016 Vol.68 / 060802-1 - 060802-17
Standards New Zealand (2004), NZS1170.5:2004 - Structural Design Actions Part 5: Earthquake actions
Georgoussis, G.K., “Yield displacement profiles of asymmetric structures for optimum torsional response”. Structural Engineering and Mechanics, Vol.45, No.2 (2013) pp 233-257
Myslimaj, B., Tso W.K., (2002). A Strength Distribution Criterion for Minimizing Torsional Response of Asymmetric Wall-Type Systems. Earthquake Engineering and Structural Dynamics, Vol. 31, 99-120.
Stefano, M. and Pintucchi, B., (2010) Predicting torsion-induced lateral displacements for pushover analysis: Influence of torsional system characteristics, Earthq Eng Struct Dyn, 39: 1369–1394
Beyer, K., Dazio, A., Priestley, M. J. L., (2008) “Seismic design of torsionally eccentric buildings with U-shaped RC walls”. Research Report No. ROSE-2008/0X , ROSE School, Pavia, Italy
Sommer, A.  “Torsion und Duktilitätsbedarf bei Hochbauten unter Erdbebeneinwirkung (Torsion and ductility demand of buildings subjected to seismic loading),” Ph.D.thesis, Zürich, Switzerland
Castillo, R.  “Seimic design of asymmetric ductile systems,” Ph.D. thesis, Christchurch, New Zealand.
Suhaila, M.N.  “Effect of Strength and Stiffness Distributions on the displacement demands of asymmetric reinforced concrete buildings,” Ph.D. thesis, Universiti Teknologi Mara, Penang, Malaysia
Carr, A. (2008). 3D Ruaumoko: inelastic three-dimensional dynamic analysis program. Department of Civil Engineering, University of Canterbury, Christchurch.
Kyrkos, M.T. and Anagnostopoulos, S.A. (2012). Assessment of earthquake resistant design of eccentric, braced frame, steel buildings and proposal for possible improvements. 15th World Conference of Earthquake Engineering, LISBOA 2012.
- There are currently no refbacks.