Structural behavior of ultra-high performance (fiber-reinforced) concrete compression struts subjected to transverse tension and cracking

Abstract

Struts and stress fields with transverse tension and cracks parallel to the direction of compression lead to a reduction of compressive strength in reinforced concrete structures. Biaxial tests on fine-grained ultra-high performance concrete (UHPC) and ultra-high performance fiber-reinforced concrete (UHPFRC) panels additionally reinforced with steel bars show that this reduction in compressive strength is already pronounced even with small transverse tensile strain and crack widths, but stabilizes for larger tensile strain. A reduction could also be observed with regard to compressive stiffness of the struts, which behave quasi-linear under compressive loading. Basically, the UHPFRC panels show less reduction in strength and stiffness than the UHPC panels. Compared with the results obtained from the tests on normal-strength reinforced concrete panels and fiber-reinforced concrete panels, the reduction of compressive strength is only little larger for UHP(FR)C. Based on the test results, a proposal for modeling the stress–strain behavior of UHP(FR)C in compression–tension stress state is provided.