键齿倾斜类型对节段拼装箱梁力学性能的影响

Effect of Web Key Tooth Inclination on Mechanical Properties of a Segmental Assembled Box Girder

为了明确腹板键齿类型对节段梁力学性能的影响规律,揭示不同键齿倾斜类型节段箱梁破坏机理和破坏模式,开展了2组不同键齿类型(垂直键齿、水平键齿)节段式箱梁在不同荷载作用方式(纯弯作用、弯剪作用)下的力学性能试验,分析了梁体变形、裂缝萌生与扩展形态、体外预应力束的预应力增量以及主梁应力与裂缝宽度变化规律;建立了有限元数值分析模型,详细分析接缝局部不同角度键齿应力状态。研究结果表明:节段梁接缝开裂前,混凝土应力应变、梁体变形和预应力筋应力与荷载呈线性关系;接缝开裂后混凝土应力应变、梁体变形均与荷载呈非线性关系。纯弯荷载作用下,2种键齿梁的破坏形态相同,均为纯弯段接缝的开裂,破坏模式相同,主裂缝位置不同,垂直键齿梁破坏时的主裂缝靠近跨中位置,而水平键齿梁更靠近加载位置;弯剪荷载作用下,破坏模式为近加载点接缝弯剪破坏;2种荷载作用下,接缝顶面混凝土均压溃破坏,腹板键齿均受剪切破碎。键齿类型和荷载作用对节段梁的破坏模式影响显著,垂直键齿梁的承载能力和刚度优于水平键齿梁。键齿类型以及加载方式对预应力筋应力增量影响较小,体内束预应力增量大于体外束应力增量。建立的数值分析模型与试验结果吻合较好,可以有效分析节段梁键齿应力分布状态,揭示了节段箱梁受力破坏机理。基于既有规范和试验结果,提出了抗弯承载能力计算公式,计算值与试验值吻合良好,验证了所提出计算公式的有效性。

This study explored the effect of web key tooth inclination on the mechanical characteristics of a segmental box girder and elucidated the corresponding damage mechanism and damage mode.Two sets of tests on segmental box girders with different types of key teeth(vertical and horizontal)were conducted under different loading modes(pure bending and bending shear)to analyze the resulting deformation,crack emergence,crack expansion patterns,change in tendon prestress,girder stress,and crack width change law.A finite element numerical analysis model was subsequently established to analyze the stress state of each key tooth according to the inclination of the joint in detail.The results show that prior to joint cracking,the concrete stress-strain relationship,the girder deformation and prestressing tendon stress are linearly related to the load and the concrete stress-strain relationship and beam deformation are both nonlinear to the load after joint cracking.Under pure bending load,both types of girders exhibit joint cracking damage in the pure bending section with different main crack locations:the primary crack in the vertical key-tooth girder is close to the mid-span position whereas that in the horizontal key-tooth girder is closer to the loading position.Under bending-shear load,the joint cracking damage is near the loading point.Under both loads,the concrete at the top of the joint is crushed and the web key teeth are broken in shear.The type of key tooth and load effect both have a significant influence on the damage pattern of the segmental girders,with the vertical key tooth providing a superior load-carrying capacity and flexural stiffness compared to the horizontal key tooth.The loading method and type of key tooth have a negligible impact on the change in prestressing tendon stress;the internal tendons consistently exhibit a higher stress increase than the external tendons.The numerical analysis model established in this study is in agreement with the test results and can effectively analyze the stress distribution state of the key tooth to reveal the stress damage mechanism of the segmental box beam.Finally,this study presents an equation for calculating the flexural load capacity based on the current code and test data.The accuracy of this equation is confirmed as its results agree well with the test values.