Rocking seismic excitations effect on inelastic response of reinforced concrete building with soft-story

Abstract

Well-known problem with seismic design codes is that it does not take into account the rotational earthquake components. Only Eurocode 8, in Part 6, offers response spectra of rotational accelerations for the seismic design of slender and tall structures such as towers, masts, and chimneys. However other structures such as high-rise buildings or buildings with soft-story could be influenced by the rocking seismic components. Recording rotational ground motions can only be considered in its infancy. One approach to solve this problem involves the use of computed rotational accelerograms. The effect of rotational components on the structural response is still insufficiently explored. This paper investigate the influence of the rocking seismic components on the structural response of reinforced concrete structures with soft-story. Two types of rotational ground motions are used: recorded and computed accelerograms. Under combined translational and rotational accelerograms, the results are collected in terms of themaximum of inter-story drifts, story displacements, and internal forces. Nonlinear time history analysis shows clearly that the contribution of the rocking seismic components can be significant in structural response such as displacement (up to 60%), inter-story drift (up to 32%), and axial force (up to 8%). The existence of soft-story in the structure can amplify this contribution up to 25% compared to a structure without soft-story. Therefore, the effects of horizontal rotational components should not be ignored by the seismic codes and require further investigations.

Keywords

• rocking component
• earthquake engineering
• rotational accelerograms
• inelastic structural response