新型装配式倒T形空心板桥受力性能

为解决现有装配式空心板桥的铰缝病害, 提出了一种新型装配式倒T形空心板桥; 进行了跨径8 m的倒T形空心板桥足尺模型试验和非线性有限元分析, 研究了车辆荷载作用下倒T形空心板桥各组成构件的应力、挠度和裂缝分布等, 得到了倒T形空心板桥的受力机理与破坏模式; 对比了倒T形空心板桥与带门式钢筋空心板桥的受力性能, 验证了倒T形空心板解决铰缝开裂问题的有效性。研究结果表明: 倒T形空心板桥的破坏过程分为弹性阶段、空心板开裂阶段、现浇结构层混凝土开裂阶段和受拉钢筋与钢板屈服阶段, 其整体受力性能良好, 极限荷载是带门式钢筋空心板桥的1.4倍; Ω形钢板上方受拉区混凝土首先达到拉应力限值3.17 MPa, 是受力薄弱部位; 由于Ω形和L形钢板的设置, 现浇结构层混凝土开裂时, 与结构层等高度的各结合面处的法向和切向黏结应力均不会超过限值2.30和0.29 MPa, 避免了结合面的黏结失效; 与带门式钢筋的空心板桥相比, 倒T形空心板构造不会减小空心板的开裂荷载, 且新旧混凝土结合面开裂在空心板开裂之后, 可从根本上解决传统空心板桥在车辆荷载作用下铰缝先于空心板开裂的问题。 

Mechanical property of new type of prefabricated inverted T-shape voided slab bridge

To solve the disease of hinged joint in the existed prefabricated voided slab bridges, a new type of prefabricated inverted T-shape voided slab bridge was presented. The full-scale model experiment and the nonlinear finite element analysis on the inverted T-shape voided slab bridge with 8 m span were conducted. The stress, deflection and crack distributions of each component of inverted T-shape voided slab bridge subjected to the vehicle load were analyzed. The force mechanism and failure mode of inverted T-shape voided slab bridge were obtained. The mechanical behaviors of inverted T-shape voided slab bridge and voided slab bridge with gate-type steel bars were compared. The effectiveness of inverted T-shape voided slab solving the problem of cracking in hinged joint was verified. Research result shows that the failure process of inverted T-shape voided slab bridge can be divided into the elastic stage, cracking stage of voided slab, cracking stage of concrete in the field-cast structure layer, and yielding stage of tensile steel bars and steel plates. The inverted T-shape voided slab bridge have a good overall mechanical property, its ultimate capacity is 1.4 times of that of voided slab bridge with gate-type steel bars. The concrete in the tensile area above the Ω-shape steel plate is a weak part, for its tensile stress firstly reaching the limit 3.17 MPa. Due to the existences of Ω-shape and L-shape steel plates, when the concrete in the field-cast structure layer cracks, the normal and tangential bonding stresses of each junction surface as high as the field-cast structure layer will not exceed their limit 2.30 and 0.29 MPa, respectively, avoiding the bonding failure on the junction surface. Comparing with the mechanical property of voided slab bridge with gate-type steel bars, the inverted T-shape voided slab structure does not reduce the cracking load of voided slab, and the junction surface between the old and new concretes cracks after the cracking of voided slab. It can fundamentally solve the problem that the hinged joint cracks before the cracking of voided slab under the vehicle load.