超高性能纤维增强混凝土板的受弯性能试验研究

为研究超高性能纤维增强混凝土(ultra high performance fiber-reinforced concrete, UHPFRC)板的受弯性能，进行了10块UHPFRC板的弯曲试验，研究了板的破坏形态、破坏过程、开裂弯矩、极限弯矩以及混凝土和钢筋的应变。在试验结果基础上，建立了考虑受拉区混凝土抗拉强度和应变硬化效应的UHPFRC板受弯承载力计算式。研究结果表明：UHPFRC板的弯曲破坏形态表现为一条主裂缝并伴有多条微裂缝出现，其破坏过程可分为线性变形、微裂缝发展、主裂缝发展和承载力下降四个阶段；UHPFRC板首次出现裂缝时的弯矩为极限弯矩的50%~55%；在设计板时应以变形作为控制指标，且可以少配或不配钢筋以发挥UHPFRC的材料优势；UHPFRC板在受力过程中表现出显著的应变硬化特性。给出了UHPFRC板的弯曲承载力计算式，可以反映受拉区UHPFRC的应变硬化特性。

Experimental study on bending performance of ultra high performance fiber-reinforced concrete slab

To investigate the bending performance of ultra high performance fiber-reinforced concrete (UHPFRC) slab, ten UHPFRC slabs were tested under bending load. The failure modes, failure processes, cracking moments, ultimate moments of slabs and strain of concrete and steel bars were studied. On the basis of experimental study, a calculation model of bending capacity considering the tensile strength and strain hardening effect of concrete in tensile area for UHPFRC slabs was suggested. The results show that the cracking mode of UHPFRC slabs is a combination of one main crack accompanied by many micro-cracks. The failure process can be divided into four stages: linear elastic deformation stage, micro-crack expansion stage, main crack expansion stage and bearing capacity decrease stage. The initial cracking moment of the UHPFRC slabs is 50%-55% of their ultimate bending moment. Deformation should be considered as the governing parameter in UHPFRC slab design. Steel bars can be reduced or even eliminated in UHPFRC slab to take full advantage of UHPFRC. The UHPFRC slab possesses a significant strain hardening characteristic during bending. The formulas for calculating the bending capacity of UHPFRC slab were proposed, and strain hardening of UHPFRC in tension zone can be represented in the formula.