某预应力混凝土连续梁桥受损评估与加固

Damage Assessment and Strengthening of a Prestressed Concrete Continuous Beam Bridge

某桥为(34+40+34)m预应力混凝土连续箱梁桥,受上层高架钢结构滑落撞击,2跨部分翼缘板严重开裂。为研究该桥损伤情况及受损后结构的安全性,采用MIDAS Civil有限元软件建立受损箱梁有限元模型,评估主梁截面特性,计算受损前后主梁的应力和挠度;采用ANSYS软件进行桥梁撞击仿真分析。结果表明:单侧翼缘板受损使主梁截面面积削弱7.7%,使主梁截面抗弯刚度减小6.6%;受损前后主梁应力和位移变化较小,受损后满足规范要求,但应力储备很小;在撞击荷载作用下,翼缘板和腹板交界处顶板开裂,与实际情况基本吻合。根据检测及评估结果,采取将第二、第三跨防撞护栏切除60m,受损主梁翼缘板从悬臂根部整体切除,将原后浇调平层凿除后重新浇筑等加固措施。该桥加固后的动静载试验结果表明,主梁的加固部分能很好地与保留的主梁共同受力,主梁的整体性能有较大的提高。

Due to the accidental attack of the fallen steel structures from the upper viaduct,part of the flanges in the two spans of a bridge which is a prestressed concrete continuous box beam bridge with span arrangement of （34＋40＋34）m,severely cracked.To study the damage condition of the structure and the safety of the structure after damage,the MIDAS Civil software was used to establish the finite element model of the damaged box beams,to assess the cross section property of the main beam and calculate the stress and deflection of the main beam before and after the damaging event.The ANSYS software was used to conduct simulation analysis of the collision event of the bridge.The results of the analysis indicate that the damage of the single-side flange makes the area of the main beam cross section reduced by 7.7%,and the anti-bending stiffness of the main beam cross section reduced by 6.6%.The stress and displacement of the main beams before and after the damage exhibited slight changes,and the main beam still meets the code requirements,but with very small stress margin.Under the action of impact loads,the top slabs at the junction of the flanges and the webs cracked,which is basically compliant with the actual condition.According to the inspection and evaluating results,a series of strengthening measures were taken,including cutting off 60 mlong balustrades in the second and third spans,and removing the main beam flanges damaged from the root,and recasting the leveling layer after the original postcast one was chiseled off.The dynamic and static tests after the strengthening demonstrate that the part of the main beam strengthened bears loads in coordination with the remained part,and the global performance of the main beam has been greatly improved.