苏家坡石拱桥病害原因分析及套拱加固

Deterioration Cause Analysis and Strengthening of Sujiapo Stone Arch Bridge with Covered Arch

苏家坡石拱桥跨径30m，检查发现该桥存在多处病害。采用有限元法分析加固前石拱桥受力性能，确定病害主要原因为u形桥台背面回填不密实及车辆超载，提出采用钢筋混凝土套拱的方法进行加固，将该桥荷载等级提高到公路－Ⅰ级。运用有限元法分析套拱厚度、混凝土强度、套拱和主拱圈的粘结强度对套拱加固效果的影响，以确定具体套拱加固方案。加固后对实桥进行静载测试，比较加固前、后的受力性能。结果表明，拱下套拱加固能够有效提高桥梁整体刚度和使用性能，具有较好的加固效果；在公路－Ⅰ级荷载作用下较经济合理的加固厚度为40～50cm，混凝土强度等级为C30～C40。

The span length of the Sujiapo Stone Arch Bridge is 30 m and it was found from regular inspection that the deteriorations existed here and there in the bridge.The mechanical behavior of the bridge before it was strengthened was analyzed by the finite element method and the analysis determined that the major causes leading to the deteriorations could be attributed to the incompact backfill behind the U-shape abutments and the excessive vehicle load on the bridge.A method for strengthening the bridge with reinforced concrete covered arch was proposed for the purpose of improving the load grade of the bridge to the Highway—Load Grade I.The finite element method was again used to analyze the influence of the thickness,concrete strength of the covered arch and also the binding strength between the covered arch and the original main arch ring on the effect of the strengthening so that the specific scheme for the strengthening could be finalized.After the bridge was strengthened,the static load tests were made for the bridge and the mechanical behavior of the bridge before and after it was strengthened was compared.The results of the comparison show that the strengthening with the covered arch under the original arch ring can effectively increase the global rigidity and service performance of the bridge and the effect of the strengthening is sound.Under the condition of the Highway—Load Grade I,the rather economic and rational thickness of the covered arch is 40~50 cm and the strength of the concrete is C30~C40.