体外预应力植筋复合加固空心板梁抗弯性能试验

Experiment of Bending Performance of Hollow Slab Beam Strengthened by Planting Bars and External Prestressing

针对旧桥板梁存在挠度较大、裂缝较多等问题,对旧桥进行提载加固。为研究植筋及体外预应力加固法对损伤板梁的加固效果,分别对没有铺装层的裸梁、铺装层破损旧梁、铺装层植筋加固旧梁、铺装层植筋及体外预应力复合加固梁进行了抗弯性能对比试验,并对加固梁的挠度计算进行分析。试验结果表明:公路I级荷载作用下,只有经过体外预应力植筋复合加固梁的最大裂缝宽度满足规范耐久性要求,其梁体截面应变表现出良好的弹性性质;铺装层能够显著提高梁体抗弯刚度,植筋加固后铺装层与梁的连接良好,与整体浇注的梁体相似,截面边缘混凝土的最大应变显著减小,抗裂性能显著提高。对加固梁挠度的计算表明:体外预应力梁的挠度计算应该考虑二次效应的影响;铺装层植筋加固梁的挠度计算中应考虑全截面受力。

For the large deflection and too many cracks of the slab beams, an old bridge＇s load bearing capacity is improved. In order to inspect the strengthening effect of planting bar and external prestressing method on the defective slab beams, the comparative experiments among 4 beams are carried out, the first one without pavement, the second one with damaged pavement, the third one reinforced by planting bars, and the forth one reinforced by planting bars and external prestressing. The reinforced beam＇s deflection calculation method is analysed. The test result shows that （ l ） under the level I highway load, only the forth beam＇s maximum crack width can conform to the durability requirements of the specification, and the beam＇s strain figure of section shows the good flexibility; （2） the pavement can remarkably enhance the flexural rigidity of the beam, especially when reinforced by planting bars, the pavement is bonded with the beam, the two parts work like a whole one, whose edge concrete＇s maximum strain is effectively reduced and the anti- cracking property is obviously enhanced. The deflection calculation of the reinforced beam shows that （ 1 ） the quadratic effect should be considered in the deflection calculation of external prestressed beam; （2） the total height should be adopted in the deflection calculation about the planting bar strengthened beams.