Headed bars in simulated exterior beam–column joints of UHPFRC

Abstract

Ultra-high-performance fibre-reinforced concrete (UHPFRC) exhibits improved compressive and tensile strengths considerably superior to those of conventional concrete. While these characteristics can significantly reduce the cross-sectional area of the member, the space for accommodating development lengths of straight or hooked bars is deficient. A headed bar can be a viable option for this problem. The anchorage strengths of headed bars were evaluated by simulated exterior beam–column joint tests where the joints were cast of 120, 150 or 180 MPa UHPFRC. A headed bar with only 4db embedment length in 120 MPa UHPFRC can develop a yield strength of 600 MPa. The effects of embedment length, bar diameter and compressive strength of UHPFRC on the anchorage strength of headed bars are investigated. From a regression analysis, assuming that the anchorage strength is proportional to (fc′)α, a model for predicting the anchorage strength of headed bars in UHPFRC is developed.