不均匀温度场下钢管混凝土拱桥管内混凝土脱空分析

Analysis of Debonding Between Steel Tube and Core Concrete in Concrete-Filled Steel Tubular Arch Under Uneven Temperature Field

为了解不均匀温度场作用下钢管混凝土拱桥管内混凝土脱空原因,依托高原山区某跨径430 m的钢管混凝土拱桥,进行强辐射、大温差联合作用下拱肋拱顶节段足尺模型试验,分析模型温度场分布,并对该不均匀温度场作用下管内混凝土脱空机理进行研究。结果表明:钢管混凝土拱桥水化阶段和运营阶段径向温度场可简化为多段式折线变化规律。14:00时刻,水化阶段温度沿竖直径向(从向阳侧至背阳侧)先减小后升高再减小,在距向阳侧界面D/8~3D/8处(D为钢管内径)存在一个大温差面,运营阶段温度沿竖直径向(从向阳侧至背阳侧)呈先减小后不变再增加的非对称分布规律,从钢管混凝土界面至距其D/8处温度变化大。混凝土水化阶段和运营阶段管内混凝土脱空机理为:在温度场作用下钢管混凝土界面最大纵向应力差分别高达82.6 MPa和61.95 MPa,最大界面径向拉应力分别为0.8 MPa和2.06 MPa,均超过钢管和混凝土间的粘结强度。

An existing concrete-filled steel tubular arch(CFST)bridge in the mountainous area that has a main span of 430 m is used as a case to study the causes of debonding between the steel tube and core concrete in the CFST arch.The full-scale model of the arch-crown segment was prepared to test the effects of uneven temperature field on the debonding under the joint action of strong solar radiation and large temperature difference.The temperature field distribution in the model was analyzed and the debonding mechanism under uneven temperature field was studied.The results demonstrate that a radial temperature field during hydration and operation stages can be simplified as a multi-segment polyline.At 14:00,the temperature at hydration stage showed sign of from decreasing through increasing to decreasing along vertical diameter(from upsun to downsun),and there was a surface of large temperature difference near the D/8-3 D/8 upsun interface.Whereas at operation stage,the temperature showed asymmetrical distribution of from decreasing through keeping constant to increasing(from upsun to downsun),and the great temperature difference occurred in the range from steel tube and concrete interface to the interface distancing D/8 to it.The debonding mechanism at hydration and operation stages can be explained as:under the action of temperature field,the maximum longitudinal stress difference in the steel tube and concrete interface can reach up to 82.6 MPa(hydration stage)and 61.95 MPa(operation stage),maximum interface radial tensile stress are 0.8 MPa(hydration stage)and 2.06 MPa(operation stage),respectively,all surpassing the bond strength between steel tube and core concrete.