特殊支承连续箱梁弯扭性能分析

Analysis on Bending-torsional Behavior of Specially Supported Continuous Box Girders

根据力法原理,建立了分析斜支承两跨连续箱梁挠曲扭转力学性能的力法方程。分别按自由扭转和约束扭转理论计算了一斜支承两跨连续箱梁的内力和变形,并用Ansys软件对内力计算做了验证。引入正应力修正系数λ来反映双力矩对正应力的影响。为了研究斜交角变化对正应力修正系数的影响,计算了不同斜交角对应的五个控制截面上各计算点的正应力修正系数。计算表明:两种方法计算的弯矩与Ansys软件计算的结果吻合;当斜交角小于45°时,两种方法计算的各控制截面的内力、变形相差均不超过5%,所以斜支承两跨连续箱梁的弯矩、扭矩、挠度和扭转角可直接按自由扭转计算,不考虑翘曲变形的影响;斜交角的变化对同一截面各点的正应力修正系数的影响很小,因此当斜交角小于45°时,可先按自由扭转理论计算正应力,然后乘以相应的修正系数。

A basic equation of force method for analyzing flexural-torsional mechanical properties of skewly supported two-span continuous box girders was established considering the principle of force-method.The internal forces and deflections of a skewly supported two-span continuous box girders were calculated by applying free torsion and restrained torsion theory respectively.The calculated internal forces were examined by Ansys software.Normal-stress correction coefficientλwas introduced to reflect the influence of bi-moment on normal stress.The normal-stress correction coefficient corresponding to different skew angles of each calculation point in five governing cross sections was computed to study the influence of variation of skew angle on it.It is shown that the bending moment calculated by using the present two methods is in good agreement with the result calculated by Ansys software.At less than 45°of the skew angle,the difference of internal forces and that of deflections of each governing cross sections calculated by using present two methods is less than 5%,so that the bending moment,torque,deflection and torsional angle of skewly supported two-span continuous box girders can be calculated by applying free torsion theory without considering the influence of warping deformation.The variation of skew angle has very little effect on the normal-stress correction coefficient of each point in the same cross section.Therefore,when the skew angle is less than 45°,the normal stress can be calculated by applying the free torsion theory first,before being multiplied by the corresponding correction factor.