不同轴偏转对中、下承式拱桥吊杆承载能力的影响

Influence of rotation along different axis at ends on bearing capacity of hangers of half-through or through arch bridges

在温度作用下,中、下承式拱桥的桥面板和拱肋会在纵桥向产生不同程度的变形,这将导致吊杆尤其是长度相对较短的吊杆发生不同轴偏转。不同轴偏转可能导致吊杆内部钢绞线断裂,并进一步引起吊杆的突然断裂。通过理论推导和有限元分析研究了不同轴偏转对吊杆的不利影响,当吊杆产生不同轴偏转时,下锚固端将产生较为明显的弯曲应力且吊杆的承载能力会被削弱。以105 m主跨的下承式拱桥为例,吊杆下锚固端的弯曲应力最大可达容许应力的56.5%。基于上述结论,对组成吊杆的钢绞线进行了有限元分析和相关试验,研究其在不同轴偏转下的力学性能。结果表明,随着不同轴偏转程度的加重,钢绞线的轴向破断力明显降低,进而导致吊杆承载能力不断削弱。结合上述研究结果对相关规范中吊杆承载能力的校核方法进行了修正,并提出使用无缝桥面板结构可以降低不同轴偏转对中、下承式拱桥吊杆的不利影响。

Bridge decks and arch ribs of through arch bridges will produce different deformation along the longi-tudinal direction of the bridge due to the effect of temperature.Hangers,especially short hangers,will rotate a-long different axis at ends.This probably makes steel strands in hangers fracture suddenly and further failure of hangers.Therefore,theoretical derivation and finite element analysis were conducted in this paper to analyze the adverse influence of rotation along different axis at ends of hangers.It is found that the bearing capacity of hang-ers will decrease and the extra bending stress will exist in the lower anchorage zone when hangers rotate along different axis at ends.The maximum bending stress of hangers could reach 56.5%of the allowable stress in a through arch bridge with a span of 105 m.Furthermore,the mechanical property of steel strands is studied by the finite element analysis and tests.The results show that the breaking force of steel strands rotating along dif-ferent axis at ends could decrease significantly compared with that of straight steel strands and lead to the de-crease of bearing capacity of hangers.Finally,a promoted method to assess the bearing capacity of hangers of half-through or through arch bridges for rotation along different axis at ends is proposed.Jointless bridge decks are suggested to mitigate the adverse influence of rotation along different axis at ends on hangers.