摘要
近年来,桥梁养护工程中发现部分预应力混凝土小箱梁桥在通车多年后,腹板出现了大量竖向裂缝,且经过维修加固处理后效果仍不明显。为探究运营过程中小箱梁腹板竖向裂缝的形成原因,以实际工程为例,重点从收缩、徐变非一致性和温度梯度效应两方面探究了梁截面纵向自应力对小箱梁腹板的影响,并利用Midas Fea软件对不同腹板厚度的小箱梁实际运营状态进行数值模拟,分析了在不同运营年限下腹板纵向应力的变化规律。研究发现,由于小箱梁截面厚度沿梁高变化较大,因此收缩、徐变以及温度梯度效应等对截面的非一致分布影响显著,均会引起腹板的纵向自拉应力,使腹板的压应力储备降低,增加开裂风险;由于制作或安装误差等原因导致的腹板实际厚度不足在一定程度上有利于增大腹板纵向压应力的储备,但随着运营年限的增加,腹板拉应力也会逐渐增大,且增长幅度随腹板厚度的削减明显增大;当腹板局部厚度削减20%时,待运营5年后,其腹板纵向拉应力已超过混凝土抗拉强度标准值,导致腹板出现竖向裂缝,这也与桥梁实际情况基本一致,验证了小箱梁截面纵向自应力是导致腹板竖向裂缝的重要原因之一。
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.
作者
胡根生
沈凯祺
王晓微
王星驰
乔杰
HU Gensheng;SHEN Kaiqi;WANG Xiaowei;WANG Xingchi;QIAO Jie(Zhejiang Communications Investment Expressway Operation Management Co.,Ltd.,Hangzhou 310020,China;Zhejiang Communications Construction Group Co.,Ltd.,Design Institute Branch,Hangzhou 310051,China)
出处
《结构工程师》
2025年第3期62-69,共8页
Structural Engineers
关键词
小箱梁
竖向裂缝
非一致性
自应力
腹板厚度
small box girder
vertical crack
nonuniformity
self-stress
web thickness
