原桥与加固桥的承载能力现场试验研究

In-situ experimental study on bearing capacity of original and reinforced bridge

以河南某高速公路东孟姜女河预应力混凝土板桥为工程实例,在各板底部0、L/4、L/2、3L/4和L(L为预应力板长度)处安装了数码位移传感器,采用铺石子、堆土袋和加水袋的方式在桥梁中间10 m处施加均布荷载并使桥梁接近极限状态,然后卸载并采用纵向和横向体外预应力钢铰线对其进行加固,最后堆置高速公路废弃的混凝土路缘石和沥青混凝土混合料直至桥梁破坏,记录了整个过程的裂缝和挠度发展。结果表明:原桥的荷载-挠度曲线大致可分成两段,分界点对应的荷载略大于开裂荷载;在略大于开裂荷载的恒载作用下,挠度会继续增长;当荷载接近极限承载能力时,裂缝由中间向两端发展至L/4和3L/4位置;纵向和横向体外预应力加固能够加强桥梁各板之间的横向联接,降低各板之间的挠度差异,提高桥梁的受弯能力,减小各板的挠度。

East Mengjiangnv Bridge located on one highway in Henan province was taken as an engineering example, which is composed of prestressed concrete slabs. A lot of digital displacement sensors were assembled at the key positions of 0, L/4, L/2, 3L/4 and L on all slabs, where L is slab length. Uniform loads were placed on bridge at center 10 meters length of slab by stacking cobblestones, soil bags, and water bags. When the total loads reached the ultimate bearing capacity, the uniform loads were then unloaded. The bridge was reinforced by transverse and longitudinal external steel cables, and finally other loads were placed again by stacking abandoned concrete curbstones and pitch mixtures. Deflections and width and positions of cracks were timely collected, measured and recorded in the whole process. Some important conclusions were obtained. The curves of deflections change with loads for original bridge and could be parted to two lines according to their slope ratios. The load at the demarcation point is slightly larger than crack load, and the deflection would increase at constant load which is slightly larger than crack load. When the load reaches the ultimate bearing capacity, some cracks appear at the positions of L/4 and 3L/4. The transverse and longitudinal external prestressing technique could reinforce transverse connections of slabs, increase bending resistance of bridge and decrease variance of deflections in different slabs. © 2016, Editorial Office of Journal of Building Structures. All right reserved.