Effectiveness of reinforcing methods in enhancing the lateral impact performance of geopolymer concrete column reinforced with BFRP bars

Abstract

To achieve more sustainable and durable structures, geopolymer concrete (GPC) structures reinforced with non-corrosive basalt fiber-reinforced polymer (BFRP) bars have been proposed to replace conventional steel reinforced ordinary Portland cement concrete (OPC) structures. The performances of GPC structures reinforced with BFRP bars under static loading conditions have been studied and engineering structures might be subjected to impact loading during their service life, which can cause severe damage to the structures. Therefore, it is important to also investigate the impact-resistant performance of structures. The impact-resistant response of BFRP-GPC columns under lateral impact loading has been recently investigated, and different response characteristics were observed from those of steel-OPC columns due to the different material properties. To enhance the impact resistance capacity, this study investigates the effectiveness of various reinforcing methods of BFRP-GPC columns. One BFRP-GPC column from our previous study was used as the reference column, and four BFRP-GPC columns were cast and tested by using a pendulum impact testing rig in this study. The four columns were respectively reinforced or strengthened with four different methods (i.e., increasing the longitudinal reinforcement ratio to enhance the flexural strength of the column, increasing the stirrup ratio to enhance the shear strength of the column, adding steel fibers to increase the tensile strength of GPC material, and wrapping the column with BFRP sheet). The columns under lateral impact loading were compared and analysed with respect to the failure mode, failure progress, impact force, and midheight deflection. It was found that increasing the longitudinal reinforcement ratio and using the external BFRP sheet wrapping led to better improvement in the impact resistance of the column. In addition, numerical simulations were carried out to investigate the response mechanism of the BFRP-GPC column, and a simplified model was proposed to predict the maximum shear force distribution of the column under impact for design analysis.