Seismic Performances of High Rise R/C Frame Structures Reinforced with High Strength Rebars

Abstract

Construction of high rise buildings as supporting infrastructures for economic growth has increased significantly in numbers in many big cities around the world. In Indonesia, most of the high-rise buildings constructed are made of reinforced concrete structures. In principles, the use of high-strength concrete, coupled with high strength rebars for high rise r/c buildings will result in more efficient and more constructible r/c constructions. However, in Indonesia, the use of high strength rebars for seismic-resistant r/c buildings is still prohibited. SNI 2847:2013 Section 21 specifies that the yield strength for reinforcing bars used in structural elements of special moment resisting frames is limited to 420 MPa. This provision is meant to limit higher shear and higher bond demand in the structural elements assigned to dissipate seismic energy. This paper presents a study on the use of high strength rebars in seismic resistant r/c buildings. In the study, 20 story buildings located in a region with high seismicity are designed. Two types of rebars are used, i.e., those with the yield strength of 550 MPa and of 690 MPa. The building structures are designed as the special moment resisting frame. The seismic performances of the buildings are then investigated by performing non-linear time history analysis. Seven pairs of scaled ground motions are used for the analysis. From this analysis, the failure mechanism of r/c buildings reinforced with 550 MPa yield strength is governed by beam mechanism, while the buildings reinforced with 690MPa yield strength rebars shows failure mechanism dominated by story mechanism. Globally, the performance levels of the buildings are within the zone of Damage Control (i.e., between immediate occupancy and life safety). Based on the findings, some recommendations are proposed for the use of high strength rebars in the design of seismic resistant high rise r/c buildings.