Dynamic fracture mechanisms and mechanical property enhancement effects in UHPFRC
Through multiple Hopkinson pressure bar tests conducted at various strain rates(47～163 s-1),this paper investigates the dynamic failure modes and mechanical property evolution of ultra-high-performance fiber-reinforced concrete(UHPFRC)under impact loading.Based on experimental results,the dynamic compressive strength en-hancement factor formula provided in the Comité Euro-International du Béton(CEB)and Federation Informationale de la Precontralnte(FIP)guidelines is revised.The test results indicate that as the strain rate increases,with the peak impact load continuously rising,the failure mode of UHPFRC transitions from localized failure at weak boundary areas to overall specimen fracture.The dynamic compressive strength,peak strain,and energy absorption capacity of UHPFRC show a positive correlation with the strain rate.Compared to ordinary concrete,the high-density structure of UHPFRC effectively transmits stress,reducing sensitivity to strain rate,and exhibits a significantly weaker dynamic enhancement effect.The paper presents a revised calculation formula for the dynamic enhancement factor of UHP-FRC,achieving a 14%improvement in accuracy compared to the formula in the CEB-FIP code.
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