Abstract
The paper presents an analytical investigation of the effect of vertical ground motion on the selected 13 reinforced concrete (RC) frames with different geometric configurations. For this purpose, earthquake ground motions with various vertical-to-horizontal peak acceleration ratios are selected to which a suitable scale factor is applied to match with seismic hazards of Korea. The methodology involves the evaluation of the structural responses of RC frames subjected to the selected records by means of nonlinear time history analyses. The results from the analysis are compared with results from studies of the case of horizontal-only excitation. The effect of the vertical earthquake component on damage of RC frames is considered at both the global and the local levels. The effect of vertical ground motion on axial force, shear demand, and shear capacity of RC columns is investigated to assess failure on a local level. In particular, the shear capacity is evaluated by using both the conservative method of a design code and more realistic predictive approaches. The results of the extensive analyses indicate that vertical ground motion can significantly affect the response of RC members in terms of axial force variation and shear capacity. These results point to the conclusion that vertical ground motion needs to be included in analysis for assessment and design.
Highlights
Field observations from recent earthquakes (Northridge earthquake (1994) in USA, Hyogo-ken earthquake (1995) in Japan, Yojakarta earthquake (2006) in Indonesia, and Christchurch earthquake (2011) in New Zealand) report that the vertical component of strong ground motion causes significant damage to reinforced concrete (RC) structures
Mwafy and Elnashai [1] evaluated the effect of vertical ground motion on 12 RC buildings and indicated that an interstorey drift of the collapse limit state was frequently reached when vertical ground motion was included. e study revealed that the axial compressive force and the curvature ductility demand in columns increased by up to 45% and 58%, respectively
Hosseinzadeh [3] investigated the seismic response of a simple RC bridge pier before and after retrofitting, considering both horizontal and vertical ground motions. is analytical study indicated that the maximum axial force, bending moment, and shear force demand of the pier increased by about 30%, 10%, and 15%, respectively, due to vertical ground motion
Summary
Field observations from recent earthquakes (Northridge earthquake (1994) in USA, Hyogo-ken earthquake (1995) in Japan, Yojakarta earthquake (2006) in Indonesia, and Christchurch earthquake (2011) in New Zealand) report that the vertical component of strong ground motion causes significant damage to RC structures. Is analytical study indicated that the maximum axial force, bending moment, and shear force demand of the pier increased by about 30%, 10%, and 15%, respectively, due to vertical ground motion. It was observed that the vertical ground motion significantly affected the axial force variation and spiral strain of the second specimen, which were increased by 98% and 200%, respectively, compared with those of the first specimen. Lee et al [6] performed a combined experimental and analytical study on the effects of vertical ground motion on the shear capacity in bridge columns. In this study, three-storey RC frames with different geometric configurations are designed, and the effects of vertical ground motion on those frames are analytically investigated taking into account various verticalto-horizontal peak ground acceleration (V/H) ratios
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