混凝土斜拉桥箱梁强受扭损伤试验研究

Experimental Investigation of Strong Torsion Damage to Box Girder of a Concrete Cable-Stayed Bridge

某大跨斜拉桥主梁采用预应力混凝土箱梁,在施工过程中因火灾烧断主梁一侧9根斜拉索导致主梁强受扭损伤。为研究主梁强受扭损伤后的受力性能,设计制作相似比为1∶4的节段模型进行强受扭损伤模拟试验,并采用有限元程序Abaqus对模型梁的受扭损伤过程进行模拟分析,研究断索后主梁的强受扭损伤状态,评估主梁损伤后的抗扭承载力及索力恢复后的弯曲性能。结果表明:模型梁强受扭损伤后的裂缝宽度、间距和角度与实桥高度相似,与有限元计算的损伤状态也一致;模型梁实测扭转变形与计算扭转变形及实桥控制截面扭转变形吻合较好;实桥断索时主梁所受最大扭矩荷载约为其抗扭承载力的75%;索力恢复后,主梁的抗弯刚度有所下降,但对体系刚度影响有限,可加固修复。

T he m ain girder of a long span cable-stayed bridge is the prestressed concrete boxgirder. In the construction of the b ridg e, 9 stay cables on the one side of the girder w ere burnt andbroken in a fire and the breaking of the cables caused the girder to suffer the strong torsion dam age.To investigate the mechanical behavior of the girder after the torsion dam age, the sectionalmodel beam of a sim ilarity ratio of 1 ： 4 w as designed and fabricated and the sim ulation tests of thedam age w ere carried out. T he torsion dam age process of the beam w as also sim ulated and analyzed,using the finite elem ent program A BA Q U S. T he torsion dam age state of the girder after thebreaking of the cables w as studied and the torsion bearing capacity of the girder after the damageand the flexural behavior of the structure after the recovery of the stay cable forces w as evaluated.T he results yield that the w id th , spacing and angles of the cracks in the model beam after thestrong torsion dam age are highly sim ilar to those of the actual bridge and are in good agreem entw ith the torsion dam age state of the finite elem ent calculation. T he m easured torsion deform ationof the beam is in agreem ent w ith the calculated torsion deform ation and w ith the torsion deform ationin the control section of the actual bridge. T he m axim um torque load subjected by the maingirder of the bridge at the breaking of the cables accounts for about 75 % of the torsion bearing ca-pacity of the girder. A fter the recovery of the cable forces, the bending stiffness of the girder decreasesto some ex ten t, but the influence of the decreasing on the system stiffness is lim ited andthe girder can be reinforced by repairing.