Pushover analysis of reinforced concrete structures applied to blast load using different plastic hinge models

Abstract

The current work developed a modified pushover method using the Dynamic Load Factor DLF concept to give reasonable results compared to the more complex and time-consuming method (i.e., the non-linear time history method). A charge of 100 kg TNT is assumed to explode at different stand-off distances to cover the three blast design ranges of the (UFC 340-02) Code. The values of (DLF) were checked by applying them to the value of the blast load at the stand-off distances range between (10-70m). The results of the modified pushover method approached that of nonlinear time history with differences not exceeding (11.8%) and (4%) for maximum displacement and shear force, respectively. The DLF was suggested to be constant and equal (2.5) for the (high-pressure) design range and (1) for the (very-low pressure) design range. A formula was proposed for the (low-pressure) design range to simulate the descending values from (2.5) to (1). The prior plastic hinge models proposed by other researchers (Hawraa 2019 and Samer 2020) were used to explore the more realistic structural response to blast loads compared to the standard model of ASCE41-17. Both models of the plastic hinge demonstrated a Collapse Prevention (CP) performance at the (high-pressure) design range. However, the ASCE model indicated that more columns failed in this range. Considering the ASCE 41-17 and proposed approaches, the building performance at the (low-pressure) design range corresponds to the CP and Immediate Occupancy (IO) categories. Some plastic hinges were found when using the proposed plastic hinge model, but the number was nearly identical to that obtained using the ASCE method. The structure did not go beyond the elastic behavior if the proposed plastic hinge model is used in the (very low-pressure) design range. In the same design range, the structure performance lies within the (IO) category concerning the ASCE model. Generally, the suggested plastic hinge approach has been deemed sturdy due to being developed using the blast load and considered more dependable than those of ASCE41-17, which is acceptable for seismic events.