墩塔焊接钢筋部品刚度计算方法及工程应用

Stiffness Calculation Method and Engineering Application for Welded Rebar Parts of Bridge Pylons and Piers

针对桥梁墩塔焊接钢筋部品变形计算难题,从揭示焊接钢筋部品整体刚度本质出发,提出了焊点三向转动刚度求解模型。考虑钢筋直径的影响,设计了105组T形焊接钢筋试件及2类加载固定装置,开展了分级加载破坏试验。在此基础上,构建了焊点三向转动刚度的力学本构模型,重点分析了模型参数的合理取值方法。研究结果表明:分析焊点三向转动刚度是计算焊接钢筋部品整体刚度的关键,其转动刚度经历一个弹性平台后快速下降;初始刚度、弹性转角和刚度退化率等焊点力学本构模型参数均符合高斯分布;初始刚度受钢筋直径的影响较大且随钢筋直径的减小而降低,弹性转角和刚度退化率基本不受钢筋直径影响;同一钢筋直径下,转向刚度Rx的初始刚度及刚度退化率最大、弹性转角最小,转向刚度Ry的弹性转角最大、初始刚度及刚度退化率最小,转向刚度Rz的初始刚度、弹性转角和刚度退化率均居中。同时,为验证所提本构模型及其参数取值的合理性,分别测试了常泰长江大桥中塔钢筋部品起吊状态下的竖向变形及支撑状态下的平面变形。结果表明:当焊点弯矩-转角本构模型参数取均值时,模拟值与实测值基本吻合良好,说明所提本构模型可较好地量化焊接钢筋部品整体刚度;当焊点弯矩-转角本构模型参数取95%保证率的值时,模拟值大于实测值,取值偏保守。研究结果有望为桥塔、墩柱等混凝土结构焊接钢筋部品设计及施工控制提供理论依据。

To calculate the deformation for the welded rebar parts of bridge pylons and piers,a three-dimensional rotational stiffness solution model of the welded joints is proposed to determine the overall stiffness of the welded rebar parts.Considering the influence of rebar diameter,105 sets of T-type welded rebar specimens and two types of test devices were designed,and graded loading failure test were performed.Accordingly,a constitutive model of the welded joint and an evaluation method for the model parameters are presented.The results show that analyzing the three-dimensional rotational stiffness of welded joints is key to obtaining the overall stiffness of the welded rebar parts.The rotational stiffness of the welded joint decreases rapidly after exceeding an elastic platform.The constitutive model parameters of the welded joints,such as the initial stiffness,elastic rotation angle,and stiffness degradation rate,conform to a Gaussian distribution.The initial stiffness is significantly affected by the rebar diameter,decreasing with a decrease in the rebar diameter.The elastic rotation angle and stiffness degradation rate are unaffected by changes to the rebar diameter.When the rebar diameter is constant,the rotational stiffness component Rx has the largest initial stiffness and stiffness degradation rate,and the smallest elastic rotation angle,of the rotational stiffness components.In the same conditions,the rotational stiffness component Ry has the largest elastic rotation angle,and the smallest initial stiffness and stiffness degradation rate of the rotational stiffness components.The initial stiffness,elastic rotation angle,and stiffness degradation rate of the rotational stiffness component Rz are between the equivalent values for the Rx and Ry rotational stiffness components.To verify the rationality of the proposed constitutive model and its parameter values,the vertical deformation in the lifting state and the plane deformation in the support state for the welded rebar parts of the middle pylon of Changtai Yangtze River Bridge were tested,respectively.The results show that when the parameters of the bending moment-rotation constitutive model of the welded joints are taken as the mean values,the simulated values are in good agreement with the measured values.The results indicate that the proposed constitutive model can better quantify the overall stiffness of the welded rebar parts.When the parameters of the bending moment-rotation constitutive model of the welded joints have a 95%guarantee rate,the simulated value is greater than the measured value,providing a conservative estimate of the value.The obtained results are expected to provide a theoretical basis for the design and construction control for the welded rebar parts of concrete structures,such as bridge pylons and piers.