自锚式梁下斜张简支桥梁破坏模式试验与数值研究

为研究自锚式梁下斜张简支桥梁的破坏模式和机理,进行了10m跨径简支试验梁的荷载试验与三维有限元精细化模拟分析,并对斜张索截面面积、撑杆高跨比及主梁的截面形式等参数对破坏模式的影响进行了分析.结果表明,试验梁破坏模式为梁下斜张索屈服断裂.主梁进入塑性后其抗弯刚度降低,结构的卸载效率值提升,使得斜张索索力随外荷载的增长斜率增大,主梁荷载弯矩随外荷载的增长斜率减小,而主梁的抵抗弯矩提升较快,从而产生了上述破坏模式.参数分析表明,增大索截面面积和降低撑杆高跨比将使得结构发生主梁先压溃而斜张索未屈服的另外一种破坏模式.主梁长细比较大的板梁结构的破坏模式与模型试件相同,所能承受的最大跨中荷载略低于试验梁,其材料成本低于工字型梁结构.

Experimental and Numerical Study on Failure Modes of Under Deck Cable Stayed Simply Supported Bridges

In order to analyze the failure mechanisms, an under deck cable stayed simply supported model bridge with a span of 10m is tested under the action of increasing mid span load. The failure mechanisms are analyzed by means of both load test and ANSYS finite element analysis. A parameter analysis is performed aiming at the area of cable section, depth span ratio of strut and section form of the deck. The results show that the failure mode of the model is caused by the fact that the cables break before the deck collapses. According to finite element analysis, when the concrete of the deck enters the plastic state, the flexural rigidity of the deck decreases and the structure efficiency increases. Since the growth rate of the tensioning force of the cables increases under the increasing mid span load, the growth rate of the resistance moment in the deck increases and the growth rate of the load moment decreases. Therefore, the failure mode occurs. The results show that the deck collapses before the cables break by increasing the area of cable section and decreasing the depth span ratio of strut. The failure mode of the structure with slab deck with a higher slenderness ratio is the same as that of the model, but the maximum mid span load of structure with slab deck is slightly lower than that of the model and its material costs are also lower than that of the model.