Seismic Evaluation of Reinforced Concrete Frames in the Harsh Environment Using Pushover Analysis

Abstract

The main objective of this paper is to evaluate the seismic response of buildings of typical reinforced concrete frames when concrete starts to deteriorate gradually and to make a comparison between the base shear and the displacement at different stages of earthquake loading. Typical 5, 15, 20 and 30-storey reinforced concrete frames have been designed for seismicity according to the recently adopted seismic code in Abu Dhabi, ACI 318-08/IBC 2009 code. A pushover analysis has been performed to these four buildings by using SAP 2000. Twenty-four models have been created (6 models for each building) by decreasing the concrete strength gradually from 4000 psi (281 kg/cm 2) to 1500 psi (105 kg/cm 2). This is to simulate the effect of harsh environment on the strength of concrete in existing buildings.

Seismic Evaluation of Reinforced Concrete Frames in the Harsh Environment Using Pushover Analysis

“…For 15-storey building, it was noticed that the base shear decreases when the concrete strength decreases and the displacement at point "D" is increasing whenever the concrete strength is decreasing for all different cases, i.e.,4000 psi, 3500 psi, 3000 psi, 2500 psi, 2000 psi and 1500 psi. Also it was noticed that the failure occurred at the 4th and 5th floors for all cases except for 1500 psi the failure was at the 3rd, 4th and 5th floors, more details can be found in reference [6].…”

“…For the 5-storey building, model it was noticed that the plastic hinges start to occur in the beams in earlier steps and none of the plastic hinges occur in the columns. But in the 15, 20 and 30-storey buildings plastic hinges start to occur in the beams in earlier steps and at the columns in later steps, which satisfied the weak beam-strong column criteria, more details can be found in reference [6].…”

“…Also it was noticed that the failure occurred at the 7th and 8th floors for 4000 psi, 3500 psi and 3000 psi, whereas failure occurred at 4th, 5th, 6th and 7th for 2500 psi and 2000 psi. But at 1500 psi failure occurred at the 1st, 2nd, 3rd, 4th, 5th and 6th floors, more details can be found in reference [6].…”

“…6. Comparison between the reduction in concrete strength and the percentage of base shear of Collapse Prevention (CP) point reduction is summarized in Table 9-12, and Figure 13, more details can be found in reference [6]. Table 9.…”