结合面底部设开孔钢板的铰接空心板力学性能

针对现有铰接空心板桥的薄弱部位——铰缝, 提出一种在空心板与铰缝结合面底部设开孔钢板的空心板构造, 通过开孔钢板改变结合面裂缝开展的路径, 达到延缓空心板与铰缝结合面通缝形成的目的, 并进行了8m跨径的铰接空心板足尺模型试验。在试验和非线性有限元分析的基础上, 与结合面底部带钢筋的铰接空心板试验进行了对比。分析结果表明: 当试验荷载为100kN (1.43倍车辆荷载) 时, 空心板跨中出现横向裂缝, 空心板梁整体刚度降低, 空心板受力状态由弹性阶段进入弹塑性阶段; 在试验荷载加至300kN (4.29倍车辆荷载) 为止的整个加载过程, 未观察到空心板与铰缝结合面底部出现裂缝; 当结合面底部设门式钢筋时, 裂缝沿结合面从下向上扩展, 最终形成通缝, 然而, 当结合面底部设开孔钢板后, 铰缝沿结合面开裂至开孔钢板下方后, 裂缝的扩展需要绕过开孔钢板, 使得开孔钢板下方铰缝混凝土开裂后, 再沿开孔钢板上方结合面向上扩展, 形成通缝; 铰缝开裂荷载由结合面设置钢筋的69kN (0.99倍车辆荷载) 提高到314kN (4.49倍车辆荷载), 提高了3.50倍; 铰缝形成通缝时的荷载由结合面设置钢筋的199kN (2.84倍车辆荷载) 提高到489kN (6.99倍车辆荷载), 提高了4.51倍。可见, 在结合面底部设开孔钢板后, 铰缝裂缝开展路径发生变化, 延缓了空心板与铰缝结合面的开裂。

Mechanical property of hinged voided slab with perforated steel plates at bottom of junction surface

In view of the weakest point of hinged voided slab bridge, namely hinged joint, a kind of voided slab with perforated steel plates at the bottom of hinged joint-to-voided slab interface was put forward, the perforated steel plates were used to change the crack propagating path at the interface, so as to delay the formation of through crack at the hinged joint-to-voided slab interface, and the full-scale model experiment on 8 m-span hinged voided slab was conducted. Based on the experiment and nonlinear finite element (FE) analysis, the result was compared with the experiment result of hinged voided slab with gate-type steel bars at the bottom of interface. Analysis result shows that when the experiment load is 100 kN (1.43 times vehicle load), the lateral crack emerges in the mid-span of voided slab, the integral rigidity of voided slabdecreases, and the stress state of voided slab comes into elastoplastic stage from elastic stage. The test load is applied up to 300 kN (4.29 times vehicle load), no crack is detected at the bottom of hinged joint-to-voided slab interface during the entire loading process. For hinged voided slab with gate-type steel bars at the bottom of hinged joint-to-voided slab interface, the crack extends from the bottom to the top along the interface, and then forms a through crack. However, for the hinged joint-to-voided slab interface with perforated steel plates, after the crack propagates along the interface to the bottom of perforated steel plate, the expansion of the crack needs to bypass the perforated steel plate, so that the joint concrete below the perforated steel plate cracks, and then the crack expands upward along the junction surface above the perforated steel plate until the formation of through crack. The joint cracking load increases from 69 kN (0.99 times vehicle load) for the interface with gate-type steel bars to 314 kN (4.49 times vehicle load), and increases by 3.50 times. The through-crack-formation load increases from 199 kN (2.84 times vehicle load) for the junction surface with gate-type steel bars to 489 kN (6.99 times vehicle load), and increases by 4.51 times. It can be seen that the extension path of crack changes after the perforated steel plate is set at the bottom of junction surface, which slows down the cracking of the junction surface between the voided slab and the hinged joint.