Synergistic use of ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) and carbon fiber‐reinforced polymer (CFRP) for improving the impact resistance of concrete‐filled steel tubes

Concrete‐filled steel tubes (CFSTs) have received growing attention, owing to their rapid construction, reduced labor requirement, and reasonable material cost. While in service, the CFSTs can be subjected to unexpected impact loads, originating from vehicle and vessel collision, as well as water‐ and wind‐borne debris impact. Such extreme loading events often cause a partial or complete failure of conventional CFSTs, risking the safety and performance of the entire structural systems that rely on them. To address this issue, the current study explores how two advanced composite materials, including ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) and carbon fiber‐reinforced polymer (CFRP), can be utilized to provide superior mechanical properties and minimize the vulnerability of CFSTs to impact loads. The composite materials under consideration are appropriate for both new and existing structures, in which normal‐strength concrete can be replaced with UHPFRC, while CFRP sheets can further strengthen the CFSTs. For obtaining in‐depth insights, a computational framework validated with the experimental tests was developed in the current study. Using a set of representative impact scenarios, various response measures, such as internal forces and deflections, as well as the energy absorbed by the CFSTs, were recorded during impact simulations. The investigations were then further extended to capture the influence of the main design parameters related to concrete, CFRP, and steel tube. From the conducted investigations, an energy absorption index was introduced, as a measure to evaluate the performance of CFSTs under impact loads.