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 4d(b) 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 (f(c)')(alpha) a model for predicting the anchorage strength of headed bars in UHPFRC is developed.