Experimental and numerical study on low-velocity lateral impact behaviors of RC, UHPFRC and UHPFRC-strengthened columns

Abstract

This paper aims to develop a strengthening method based on ultra-high performance fiber reinforced concrete (UHPFRC) to improve the performance of a column under impact loading. Impact performances of UHPFRC columns were first examined by using the drop-hammer impact test system. The impact-resistant performance of an axially-loaded UHPFRC column was experimentally confirmed to be superior to that of the conventional RC column. The importance of exerting an axial load was highlighted and addressed by comparing the experimental data of UHPFRC columns with and without axial loads. Subsequently, three different types of UHPFRC-strengthened RC columns were experimentally investigated in detail. Superior performances were observed for the strengthened column with two-end (i.e., potential plastic hinge zone) UHPFRC jackets in comparisons with the other strengthening schemes. Impact strengths could be improved when adding a UHPFRC jacket in the contact zone, but significant increases in impact forces would be induced simultaneously. The column with UHPFRC jackets in both the contact zone and the two ends was shown to be the worst configuration because shear (or punching) failure is prone to occur in the remaining RC portions. A finite element (FE) modeling method was proposed and demonstrated as being capable of reasonably predicting impact responses of UHPFRC columns and UHPFRC-strengthened columns. The findings drawn from the experimental and numerical studies can facilitate the strategic application of UHPFRC for improving the impact-resistant performance of bridge and building columns.