变截面箱梁剪应力分布规律及影响研究

Study on Distribution Law & Influence of Shear Stress of Box Girder with Variable Cross Section

利用微元体平衡关系,推导出适用性更广泛的变截面梁剪应力计算公式。通过单因素分析,研究梁高、底板厚度及腹板厚度的变化对变截面箱梁剪应力的影响。以某主跨144 m的预应力混凝土变截面连续箱梁桥为对象,分析变截面梁剪应力及其各分量的分布规律,结果表明变截面箱梁桥剪应力与主拉应力的分布方式与等截面梁有较大差异。在梁高变化剧烈时,变截面箱梁截面上的最大剪应力发生在箱梁形心轴以下区域。最后提出剪应力计算方法可真实反映变截面剪应力分布特点,提高对剪切裂缝的预测精度。

The formulas for calculating shear stress of variable cross-section beams are derived by using the balance relation of microelements.The effects of the changes of beam height,floor thickness and web thickness on the shear stress of the box girder with variable cross-section are studied by single factor analysis.Taking a prestressed concrete continuous box girder bridge with variable section of 144 m of a main span as the object,the distribution law of the shear stress and its components of a variable section girder bridge is analyzed.When the beam height changes violently,the maximum shear stress on the cross section of the box girder occurs in the area below the box girder's central axis.Finally,the calculation method of shear stress can truly reflect the characteristics of shear stress distribution of variable section and improve the prediction accuracy of shear crack.