摘要
Abstract
In recent years,it has been observed that many prestressed concrete small box girder bridges have developed numerous vertical cracks in their webs after years of operation.Furthermore,the effectiveness of maintenance and reinforcement is still not obvious.To investigate the causes of vertical cracks in the webs of small and medium-sized box girder bridges during operation,this paper examines a real-world project.The study focuses on examining the influence of longitudinal self-stress on the web of a small box girder,considering two factors:shrinkage,creep inconsistency,and the temperature gradient effect.Additionally,the paper utilizes Midas Fea software to numerically simulate the actual operating state of small box girder with different web thicknesses.It also analyzes the variation in longitudinal stress in the web under different operating years.It is found that the thickness of small box girder varies greatly along the beam height,so the effect of shrinkage,creep and temperature gradient on the non-uniform distribution of section is significant.This will cause longitudinal self-tensile stress of the web,reduce the compressive stress reserve of the web,and increase the risk of cracking.The absence of the actual thickness of the web due to fabrication or installation errors can,to some extent,enhance the compressive stress reserve of the web.Nevertheless,as the operating years increase,the tensile stress within the web will gradually increase.Furthermore,the growth rate of this tensile stress is significantly accelerated as the thickness of the web diminishes.After 5 years of operation,if the local thickness of the web is reduced by 20%,the longitudinal tensile stress of the web exceeds the concrete's standard value of tensile strength,leading to vertical cracks in the web.This finding is consistent with the actual condition of the bridge,confirming that the longitudinal self-stress of the small box girder section is a significant factor contributing to the occurrence of vertical web cracks.关键词
小箱梁/竖向裂缝/非一致性/自应力/腹板厚度Key words
small box girder/vertical crack/nonuniformity/self-stress/web thickness分类
交通工程
