#br#大比例预应力UHPC-T形梁抗弯性能试验研究

为研究预应力UHPC梁的力学性能及结构设计方法，进行了一片大尺寸T梁的弯曲试验，获得了试验梁从加载到破坏全过程的主要结果。利用现有研究成果，考虑UHPC材料的受拉性能影响，给出了修正的受拉应力-应变关系曲线，建议了极限状态下截面应力应变分布模式，由此改进了开裂荷载和极限承载能力的计算方法，并获得了相应结果。分析结果很好地预测了试验梁的荷载-位移曲线及极限承载力大小；基于平截面假定，考虑UHPC材料的非线性性能，编制了UHPC梁全过程非线性分析程序，理论分析和程序计算的结果与试验结果吻合良好。以此为基础，进而分析了预应力配筋率及张拉应力大小，以及高跨比对结构抗弯承载能力的影响规律，为UHPC梁的应用提供参考。结果表明：预应力UHPC梁具有良好的延性和变形性能，其开裂弯矩可按我国桥规公式计算，并宜考虑UHPC的受拉塑性；UHPC的受拉性能对其抗弯承载能力有贡献、但不大；适当增加预应力筋面积，可充分利用UHPC的超高抗压强度，并能有效提高UHPC梁的开裂弯矩、极限承载能力大小。

Experimental study on flexural behavior of large-scale prestressed UHPC T-shaped beam

To study the mechanical property and structure design method of the ultra-high performance concrete (UHPC), a large-scale prestressed T-shaped beam was tested and intermediate and final behaviors, such as cracking loads, flexural stiffness and moment capacity, were obtained. The calculation method for the cracking loads and ultimate bending moment was improved by considering the tensile constitutive relationship and the adjustment of the tensile softening of UHPC. Furthermore, the nonlinear analysis based on the structural parameters, including reinforcement ratio, tension force and depth-span ratio, was conducted. The predicted results based on the calculation program agree well with the tested ones. It is concluded that the prestressed UHPC beam possesses good ductility and deformation capacity. The calculation of the cracking moment for prestressed UHPC beam can refer to the JTG D62-2004 Code. The tensile behavior contributes little to the ultimate bending capacity. The flexural behavior, especially the ultimate bending capacity, can be effectively improved by increasing the area of tendon to take full advantage of the ultra-high compressive strength of UHPC.