公路桥装配式桥墩承插式连接的桩基承台研究

Study of Socket Connection Between Modular Piers and Pile Caps for Highway Bridge

针对公路桥装配式桥墩采用的承插式连接,为降低承台底板厚度,减少承台混凝土用量,以湖北省监利至江陵高速公路东延段项目的装配式桥墩试验段(承台总厚1.5 m,预制管墩承插深度为1.0 m,承台底板厚度仅0.5 m)为背景进行研究。首先根据规范计算承台底板的最小厚度,采用MIDAS FEA软件建立桥墩-承台-桩基础有限元模型,分析承台的应力和破坏点;然后基于分析进行承台配筋设计;最后通过混凝土裂缝模型对配筋设计进行校核,并通过缩尺模型试验验证配筋设计的可靠性。结果表明:承插式连接桩基承台设置U形抗冲切钢筋后,承台底板未发生局部的冲切破坏;U形抗冲切钢筋可以有效地改善承台受力,可使承台底板厚度从规范计算需要的最小厚度0.963 m降至0.5 m,承台底板厚度降幅达48%,承台混凝土总用量降低约25%。

Socket Connection has been implemented for modular piers in highway bridges.To reduce the thickness of the base slab of pile cap and cut down the concrete volume,the modular pier trial section of east extension project of the Jianli-Jiangling Expressway in Hubei Province was taken as the background project for the study.The pile cap is 1.5 m in depth,and the precast pier extends 1 m into the pile cap,leaving the base slab of the pile cap with a thickness of mere 0.5 m.First,the minimum thickness of the base slab of pile cap was calculated as per the codes.Then,the software MIDAS FEA was used to build the finite element model of the pier-pile cap-pile foundation,to analyze the stresses in the pile cap and the damage locations,and based on which the reinforcement in the pile cap was designed.The model to test concrete cracks was established to verify the reinforcement design,and scale-down model test was carried out to examine the reliability of the reinforcement design.The results indicate that when the U-shaped shear reinforcement was installed in the pile cap with socket connection,no local shearing damage was observed in the base slab of the pile cap.U-shaped shear reinforcement can effectively improve the load bearing condition of the pile cap,and allow the minimum thickness of base slab of the pile cap to reduce from 0.963 m to 0.5 m,with a reduction rate of 48%.And the total concrete amount for the pile caps was cut down by about 25%.