某预应力连续箱梁底板开裂成因分析

Analysis on Causes of Baseplate Cracking a Prestressed Continuous Box Girder

摘要:

某3跨预应力混凝土连续箱梁桥，施工过程中发现已浇筑节段底板存在较多纵向裂缝。在底板增加抗裂钢筋网片处理后，后续节段依然有开裂程度不同的裂缝出现。为分析裂缝出现的原因，为后续施工避免出现裂缝提供依据，采用理论计算与有限元模型验算相结合的方式对裂缝产生的原因进行分析验证。结果表明：箱梁底板裂缝应为早期混凝土的收缩裂纹，主要为箱梁相邻节段混凝土浇筑时间相差过大、箱梁自身的收缩受上节段箱梁混凝土的约束而引起，同时，纵向预应力的横向效应以及底板内部与表面温差的影响，又加剧了混凝土开裂现象。

Abstract:

During the construction, it is found that there are many longitudinal cracks in the baseplate of the poured segments of a three-span prestressed concrete continuous box girder bridge. After the treatment of adding the anti-crack reinforcing mesh, there are still cracks in different degrees in the subsequent segments. In order to analyze the causes of cracks and provide a basis for subsequent construction to avoid cracks, the method of theoretical calculation combined with finite element model checking is used to analyze and verify the causes of cracks. The results show that the baseplate cracks of box girder should be the shrinkage cracks of the early concrete, which are mainly caused by the excessive age difference of the concrete pouring of the adjacent segments of the box girder, and the shrinkage of the box girder being restrained by the concrete of the upper segment box girder. At the same time, the transverse effect of the longitudinal prestress and the influence of the temperature difference between the interior and the surface of the baseplate aggravate the phenomenon of concrete cracking.