组合加固足尺预应力混凝土空心板梁抗弯性能
Flexural behaviors of full-scale prestressed concrete hollow slab girders with composite strengthening

对3片足尺预应力混凝土空心板梁进行抗弯性能试验,其中1片足尺梁不进行加固, 2片分别采用钢板-混凝土组合加固和钢板-预应力混凝土组合加固,分析了试验梁主要部位的应变、滑移、裂缝分布、承载力、刚度和延性; 基于试验梁塑性破坏机理,并考虑二次受力的影响,推导了足尺试验梁的抗弯极限承载力计算公式。试验结果表明:加固后试验梁的破坏形态表现为塑性弯曲破坏, 跨中横截面变形符合平截面假定; 组合加固钢板与新混凝土之间以及加固部分与原结构之间相对滑移小于0.05 mm,因此,加固后试验梁各部分协同工作性能较好; 与未加固梁相比,钢板-混凝土组合加固试验梁抗弯极限承载力提高了1.08倍,钢板-预应力混凝土组合加固试验梁抗弯极限承载力提高了1.43倍,因此,组合加固能显著提高试验梁的极限承载力; 与未加固梁相比,2片加固试验梁的延性系数均提高了21%,当试验荷载为200 kN时,2片加固试验梁刚度分别提高了1.55、3.07倍,因此,组合加固能显著提高试验梁的刚度和延性; 与钢板-混凝土组合加固技术相比,钢板-预应力混凝土组合加固技术对试验梁在使用阶段的承载性能和刚度的提高更加明显; 2片加固试验梁抗弯极限承载力的计算值与试验值的比值分别为0.94和0.96,因此,抗弯极限承载力计算公式计算精度较高,可用于钢板-混凝土组合加固预应力混凝土空心板梁的抗弯承载性能计算与分析。
The flexural behavior experiments of three full-scale prestressed concrete hollow slab beams were carried out, including unreinforced girder, steel plate-concrete composite strengthening(SPCCS)girder, and steel plate-prestressed concrete composite strengthening(SPPCCS)girder. The strain, slip, crack distribution, bearing capacity, stiffness, and ductility at the critical position of each full-scale test girder were analyzed. According to the plastic failure characteristics of test girders, the effect of secondary loading was taken into account, and the calculation formulas of ultimate flexural capacities of full-scale test beams were proposed. Test result shows that the failure modes of strengthened girders are plastic bending failure, and the deformations of mid-span cross-sections satisfy the plane cross-section assumption. The relative slips between the strengthening steel plate and the new concrete, the strengthening part and the original structure are less than 0.05 mm, all parts of test girders after strengthening can cooperatively work. Compared with the unreinforced girder, the ultimate flexural capacity of SPCCS concrete hollow slab girder increases by 1.08 times, and the value of SPPCCS concrete hollow slab girder increases by 1.43 times. Therefore, the composite strengthening can obviously improve the ultimate bearing capacity of test girder. Compared with the unreinforced girder, the ductility coefficients of 2 strengthening test girders increase by 21%, and when test load is 200 kN, the stiffnesses increase by 1.55 times and 3.07 times, respectively. Therefore, the composite strengthening can obviously improve the stiffness and ductility of test girder. Compared with SPCCS technology, SPPCCS technology can significantly improve the bearing capacity and stiffness of test girder in the service stage. For 2 strengthening test girders, the ratios of ultimate flexural capacities computed by using the proposed simplified formulas to the experimental values are