大跨连续梁桥横隔板裂缝统计及成因分析

Statistics and Cause Analysis on Diaphragm Cracks of Long-span Continuous Beam Bridge

以某大跨径混凝土连续梁桥为工程背景,探究其跨中横隔板裂缝成因。对跨中横隔板中已产生的裂缝进行了检测并统计。应用ABAQUS建立了单跨实体模型对多种因素影响情况进行了分析,并基于现场实测数据及规范加载温度荷载,结合裂缝检测情况分析了跨中横隔板裂缝形成的主要影响因素。结果表明:跨中横隔板混凝土在浇注后自身水化收缩过程中会产生较多的裂缝,浇注后至混凝土龄期14 d时,跨中横隔板由人洞两侧开始出现裂缝,随着龄期增加裂缝数量增多并逐渐向人洞及顶板方向扩展,至龄期14 d时已基本形成裂缝与扩展;龄期28 d时,裂缝略有扩展,总体分布与龄期14 d基本相同;跨中横隔板在3种温度加载作用下开裂情况不同,顶板温升产生的裂缝主要由人洞延伸至顶板,整体温降产生的裂缝主要位于人洞与腹板之间,整体沿竖向扩展,整体温升产生的裂缝主要位于顶板以及人洞附近;车辆偏载作用下跨中横隔板产生的局部最大拉应力为2.18 MPa,不足以促使横隔板开裂,但在和其他因素共同作用下,会使横隔板在已产生微裂缝的情况下导致裂缝扩展,扩展方向与水平方向夹角大约为45°。有限元模拟裂缝扩展趋势与实际检测情况基本一致,研究成果可为类似工程设计和施工提供参考。

Taking a long-span concrete continuous beam bridge as the engineering background,the causes of cracks in the mid-span diaphragm are explored.The cracks in the mid-span diaphragm are detected and counted.The single-span solid model is established by ABAQUS to analyze the influence of various factors.Based on the field measured data and the standard loading temperature load,the main influencing factors of the crack formation of the mid-span diaphragm are analyzed combing with the crack detection.The result shows that(1)There are many tiny cracks in-span diaphragm concrete during self-hydration shrinkage after pouring.After pouring to the concrete age of 14 d,the mid-span diaphragm begins to crack from both sides of the manhole.With the increase of age,the number of cracks increases and gradually expands to the manhole and the roof.At the age of 14 d,cracks and expansion have been basically formed.When the age is 28 d,the cracks expand slightly and the overall distribution is basically the same as that of 14 d.(2)Cracking of mid-span diaphragm is different under 3 kinds of temperature loading.Cracks caused by roof temperature rise extend from manhole to roof.The cracks caused by the overall temperature drop are mainly located between the manhole and the web,and the overall expansion is along the vertical direction.Cracks caused by overall temperature rise are mainly located near roof and manhole.(3)Local maximum tensile stress of mid-span diaphragm under partial load is 2.18 MPa,which is not enough to induce diaphragm cracking,however,under the combined action of other factors,the diaphragm will cause crack propagation in the case of micro cracks.The angle between the expansion direction and horizontal direction is about 45°.The crack propagation trend of finite element simulation is basically consistent with the actual detection.The study result can provide reference for similar engineering design and construction.