Dynamic analysis of high-strength concrete frame buildings for progressive collapse

The issue of progressive collapse of two real-scale frame buildings examples (three and six stories) constructed from High-Strength Concrete (HSC with fc` =75 MPa) and Normal-Strength Concrete (NSC with fc` =32 MPa) under central column removal have been studied using numerical analysis. Initially, a finite element linear static analysis was carried out. Next, linear dynamic and non-linear dynamic analyses were conducted to account for the extreme dynamic effects that arise during central column removal. The values of Demand-Capacity Ratios are considered in each analysis. The results showed that, the analysis of progressive collapse under central column removal of three and six stories frame buildings constructed from HSC is approximately similar to that of the same structures constructed with NSC. The three stories building constructed from NSC and HSC would not be susceptible to collapse for linear statically central column removal, while the situation is reversed for both NSC and HSC six stories buildings. NSC and HSC three and six stories buildings would be susceptible to progressive collapse for linear and nonlinear dynamic central column removal. The ratio between the maximum nonlinear dynamic displacement and the maximum linear dynamic displacement for NSC and HSC three stories buildings at the column removal are 1.17 and 1.18, respectively, whereas these ratios become 1.89 and 1.86 for NSC and HSC six stories building, respectively. The internal forces at the most critical sections for NSC and HSC three story building in the case of linear dynamic analysis are larger than that of linear static analysis by about 58% and 39%, respectively, while for six story building these ratios become 82% and 80%, respectively. For the case of nonlinear dynamic analysis, these ratios for NSC and HSC three story building are larger than that of linear dynamic analysis by about 9% and 7%, respectively, while for six story building these ratios become 11 % and 8%, respectively due to activation of plastic hinges.