体外预应力RPC箱梁受弯加载试验研究

Experimental research on the externally prestressed reactive powder concrete box beam under bending loads

进行体外预应力RPC箱梁模型两点对称受弯加载试验,研究了荷载-挠度曲线、截面应变、裂缝分布和破坏模式等问题,并对模型梁跨中正截面抗弯承载力进行了计算分析.结果表明,模型梁属于整体受弯破坏,采用预制节段拼装的施工方法是可行的;模型梁中混凝土对开裂弯矩的贡献明显大于同类普通混凝土梁,开裂时跨中受拉区边缘RPC应变约为普通混凝土的4～6倍;采用体外预应力提高了模型梁的开裂弯矩和增加了其延性,模型梁开裂弯矩为极限弯矩的55％;开裂时梁的跨中挠度仅为跨中极限挠度的20％;体外预应力RPC箱梁进行正截面承载力计算时应考虑RPC的受拉作用,并且可参照本文算法进行设计计算.

Experiment on an externally prestressed reactive powder concrete （RPC） box beam subjec- ted to symmetrical concentrically loads has been carried out. The load -deflection relationship, strain distribution, crack patterns and failure modes of the beam have been measured. The mid -span nor- mal section bearing capacities of the beam have been analyzed. The results demonstrated that the beam appears characteristic of bending failure; the method of precast segmental construction is feasible to this kind of beam. The concrete in the tested beam contributes more to the cracking moment than that of normal concrete beam; the strain on the bottom fiber of the prestressed RPC beam is about four to six times larger than that of conventional concrete while the beam cracks. The cracking moment and ductility of the beam are improved by the externally prestressed tendons. Its cracking moment is about 55 % of the ultimate capacity of the beam; and its mid - span deflection when the first crack appears is about 20% of the ultimate value. The tensile property of RPC should be taken into account in the process of calculating mid - span normal section bearing capacities of the externally prestressed RPC box beam. The design method in the paper may be used for this kind of beam.