Publication: Influence of repeated ground motion to in-plane rotation of asymmetric reinforced concrete building
Date
2020-06-01
Authors
Rashidi, Azida Hj.
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Abstract
The seismic response of buildings due to ground motions may considerably be affected by torsion. Studies on the inelastic torsional behaviour of a torsionally restrained asymmetric building using simplified models are on going until present. However, results from a simplified one storey eccentric model are very important because they are used for the torsional behaviour assessments and pertinent code provisions for design. These results obtained using the tradionally strength-independent stiffness wall models and considering only single earthquake loadings are debateable. Repeated earthquake load condition has never been considered. Therefore this study uses a simplified, 3-dimensional one storey strength-stiffness dependant shear wall in a parametric study on the behaviour of inelastic torsion of a asymmetric building due to repeated earthquakes. Five parameters namely centres of strength (CR) and centre of stiffness (CS), lateral uncoupled period (Ti), behaviour factors (q), and slopes (r) based on elastic and inelastic conditions due to single and repeated near fault ground motion (NFGM) and far fault ground motions (FFGM) are investigated. The slab rotation results are analyzed based on two coefficient models where ‘CR’ and ‘CS’ are the variant parameters. It is concluded that the ‘CR’, ‘Ti’ and ‘q’ have significant influence to in-plan rotation while the ‘CS’ and ‘r’ did not contribute to in-plan rotation. The higher lateral uncoupled period (Ti = 1.5s) produces greater floor rotation than the lower lateral uncoupled period (Ti = 0.3s), irrespective of single or repeated NFGM or FFGM. Generally, the floor rotation is elastic in nature except when CR is close to the centre of mass of the structure. The repeated NFGM causes the building to rotate to a twice larger rotation compared to that due to repeated FFGM. Results from regression analysis show that the in-plane rotation responds exponentially due to NFGM and linearly proportional when the FFGM is applied.