基于静力修正的钢管混凝土拱桥Pushover法

Pushover method for concrete-filled steel tube arch bridges based on the static correction

钢管混凝土拱桥形式复杂、振型数量多,基于传统Pushover方法的抗震评估存在高阶振型控制点选取困难、精度难以保证等问题。为此,提出一种基于静力修正的钢管混凝土拱桥Pushover法。首先,根据动力学原理,通过确定的荷载形式并结合结构振型与位移的相关联系,建立基于整体位移的能力谱模型,然后根据不同振型动力贡献系数,提出计算振型的遴选方法;其次,引入静力修正方法对结构位移矩阵进行修正,求出原结构的位移解;最后,根据结构的刚度矩阵与恢复力的关系,构建结构内力求解模型,同时建立钢管混凝土拱评估指标系数,以评估结构的屈服状态以及稳定性。采用文献算例验证并以某钢管混凝土拱桥为例,采用提出的方法进行横向地震响应评估,将计算结果与传统方法、非线性时程方法对比。研究结果表明,由于确定了振型阈值,通过快速遴选动力贡献较大的振型,有效减少了求解的振型数量;而能力谱模型避免了传统方法选控制点的过程,结合静力修正方法,降低了高阶振型的截断误差。算例结果显示,位移计算精度整体提高20%,内力结果改善10%;在0.4g横向地震作用下,吊杆的指标系数在0.125~0.25之间,处于较安全状态,弦杆的强度指标系数均小于0.125,较安全;桥面梁指标系数在0~0.25之间,偏于安全;腹杆的强度和稳定系数有部分达到1.0,这部分杆件已经进入屈服阶段,且出现失稳,但是桥梁结构整体并没有失稳破坏,该方法可用于钢管混凝土拱桥的抗震评估。

Seismic evaluation,which is based on the traditional pushover method,suffers from the difficulty of selecting high-order vibration control points and estimating accuracy due to the complex form and a large number of modes for concrete-filled steel tube(CFST)arch bridges.Therefore,a pushover method for CFST arch bridges based on static correction was proposed.First,a capability spectrum model based on the overall displacement was established by the dynamic theory,which was combined with the correspondence between vibration mode and displacement.Meanwhile,the selection method of vibration mode was proposed based on the dynamic contribution coefficient;further,the static correction method was introduced to correct the structural displacement matrix and obtain the displacement solution of the original structure.Furthermore,the structural internal force solution model was derived based on the relationship between the stiffness matrix and the restoring force.Besides,index coefficients of the CFST arch bridge were established to determine the yield state as well as the stability.The developed stated above was employed for evaluating the examples of literature and a CFST arch bridge.As compared to the conventional method and nonlinear time history analysis method,the results indicate that due to the determination of the vibration threshold,the number of solved modes is reduced effectively through higher contribution;the capability spectrum model avoids the process of selecting control points and reduces the truncation error of higher-order vibration modes by the static correction method;further,the overall accuracy of displacement and internal force calculation are improved by 20%and 10%,respectively;during 0.4g transverse earthquake,the index coefficients of the suspender are between 0.125~0.25 and the chords are less than 0.125,which are safe relatively;indicators of the deck beam are between 0~0.25 and indicate safe;the strength and stability coefficients of the webs partially reaches 1.0,part of which are in yielding stage and instability.The bridge,however,is not destabilized,and the method can be used for the seismic evaluation of CFST arch bridges.