预应力活性粉末混凝土箱梁抗弯性能试验
Experiment on Flexural Behaviors of Prestressed Reactive Powder Concrete Box Girders

为研究预应力活性粉末混凝土(RPC)箱梁的正截面受力性能，进行了2片预应力RPC箱梁的抗弯性能试验，研究了RPC箱梁的受力变形特征以及顶板横向预应力对其抗弯性能的影响。结果表明：预应力RPC箱梁具有良好的变形能力，其极限变形可超过跨径的1/50；RPC箱梁正常使用阶段的裂缝宽度和短期刚度可参照《纤维混凝土结构技术规程》（CECS 38:2004）的相应公式计算，其中的钢纤维影响系数可分别取为0.4和0.2；RPC箱梁顶板内的横向预应力对截面抗弯承载力的影响较小，但会使受压区混凝土的应变分布更加均匀，从而减弱箱梁顶板受压的剪力滞效应并增加构件的延性；试验中对顶板内施加2.95 MPa的横向预压应力（仅为RPC棱柱体抗压强度94 MPa的3.1%）后，可使箱梁受压翼缘的有效分布宽度增加约10%，构件延性指标增加约3%。试验结果验证了提出的预应力RPC箱梁正截面抗裂和抗弯承载力的计算公式。
In order to study the mechanical behavior of prestressed reactive powder concrete (RPC) box girders, the flexural behavior tests of two prestressed RPC box girders were carried out. The force characteristic of RPC box girders and the influence of transverse prestressing force to its flexural performance were studied. The results show that the prestressed RPC box girders display a good deformation capacity, with a maximal deflection of 1/50 of its span. The crack width and the short？？time stiffness of the RPC box girders can be calculated according to the formula in ？？Technical Specification for Fiber Reinforced Concrete Structures？？ (CECS 38:2004), with a coefficient of 0.4 and 0.2 considering influence from steel fiber, respectively. The transverse prestressing force in the top plate of RPC box girders has little influence on the flexural bearing capacity, but the force can make a more uniform strain distribution of the compressive concrete so as to reduce the shear？？lag effect and increase the ductility of the specimen. By applying a transverse prestressing force of 2.95 MPa (only 3.1% of the RPC prism compressive strength of 94 MPa) at the top plate, the effective distribution width of box girder increases by 10%, and ductility index of specimen increases by 3%. The calculated formula to evaluate the cracking moment and the ultimate moment of a prestressed RPC box girders is proposed and verified by the experimental results