含湿接缝的钢-UHPC组合桥面板收缩效应

Shrinkage effect of steel-UHPC composite bridge deck with wet joint

正交异性钢-超高性能混凝土(UHPC)组合桥面板中UHPC早期收缩较大,在组合桥面板界面约束下会产生较高次内力,存在开裂的风险,进而引发结构的安全和耐久性问题。为此,基于实际工程背景,对含湿接缝的组合桥面板收缩效应开展90 d的自然环境下常温养护静置监测研究,考察组合桥面板UHPC收缩及其引发的次内力发展及分布规律,探究龄期差对湿接缝区域收缩效应发展的影响特点;建立板壳实体有限元模型,通过多模型线性叠加的方法来模拟组合桥面板湿接缝浇筑前后的收缩效应。试验和有限元分析结果表明:在炎热潮湿的养护环境下,UHPC收缩发展经历了早期膨胀、初凝硬化后快速收缩、缓慢收缩以及稳定4个阶段;UHPC在浇筑后约6 h初凝硬化,以此刻应变为参照测得前72 h收缩量约为700×10^(-6),在此期间测得钢板翼缘最大压应变约为78×10^(-6);UHPC收缩在靠近桥面板边缘区域更大,靠近板中心区域更小;湿接缝处在初凝硬化后测得的收缩量比周边区域更小,湿接缝与周边连接完好,收缩引发的UHPC拉应力在湿接缝附近有增加的趋势。研究结果可为含湿接缝组合桥面收缩研究积累监测数据和分析基础。

For the orthotropic steel-ultra high performance concrete(UHPC)composite bridge deck,the early shrinkage of UHPC is relatively large.Under the constraint of the interface of the composite deck,high-order internal forces can be generated,and there is a risk of cracking,thus endangering the safety and durability of the structure.On the basis of the actual engineering background,the shrinkage effect of the composite bridge deck with wet joints was monitored for 90 d under normal temperature curing in natural environment.The development and distribution of UHPC shrinkage of composite bridge deck and the induced secondary internal force were investigated,and the influence of age difference on the development of the shrinkage effect of wet joint area was explored.The finite element model of plate and shell was established,and the shrinkage effect before and after the wet joint pouring of composite bridge deck was simulated by linear superposition of multiple models.Test and finite element analysis results showed that under hot and humid curing environment,the shrinkage development of UHPC experienced four stages:early expansion,rapid shrinkage after initial setting and hardening,slow shrinkage,and stability.The initial setting and hardening of UHPC occurred about 6 h after pouring.Taking the strain at this moment as the reference,the measured shrinkage of UHPC for the first 72 h was about 700×10^(-6),and the maximum compressive strain of the steel deck flange measured during this period was about 78×10^(-6).UHPC shrinkage was larger in the area near the edge of the bridge deck and smaller in the area near the center of the deck.The shrinkage measured at the wet joint after initial setting and hardening was smaller than that in the surrounding area.The wet joint was well connected with the surrounding area,and the UHPC tensile stress caused by shrinkage tended to increase near the wet joint.The research results can accumulate monitoring data and foundation for the study of shrinkage of composite bridge deck with wet joints.