基于静力模型修正的装配式T梁桥荷载横向分布计算

Calculation of Transverse Load Distribution of Prefabricated T-beam Bridge Based on Static Model Updating

为了准确计算装配式T梁桥发生损伤情况下的荷载横向分布状况,并准确评估桥梁损伤情况,在铰接板(梁)法的基础上,提出了一种基于模型修正理论的桥梁荷载横向分布计算方法。首先建立了一个同时考虑主梁和铰缝损伤的简化模型。以主梁刚度K_(k)和铰缝刚度K_(q)作为待修正参数,定义相应的刚度折减系数η_(k)和η_(q),再以结构静力响应构造目标函数,并通过L-M法和G-N法相结合的方法对目标函数进行优化,得到桥梁损伤状况下的刚度折减系数。根据修正后的刚度参数,计算出考虑主梁和铰缝损伤的荷载横向分布系数。以一座在役15 a的装配式T梁桥为算例验证了所提出方法的准确性。算例以出现破损的3片主梁和2道铰缝的刚度为修正参数,以主梁计算挠度与实测挠度的残差为目标函数,通过不断修正损伤模型刚度参数来反映桥梁构件的实际服役状态。计算结果表明:此方法能够快捷地识别出结构损伤对主梁和铰缝刚度的影响程度;模型修正后的主梁挠度及荷载横向分布计算值均与实测值吻合良好,而在模型未修正前的计算值与实测值差异较大;本研究方法能够较好地适用于装配式铰接T梁桥及板桥损伤后的刚度参数识别和荷载横向分布计算,而初始未考虑损伤的计算模型已经不再适用于该类桥的荷载效应计算。

In order to accurately calculate the transverse load distribution of prefabricated T-beam bridge with damage,and to accurately evaluate the damage situation of the bridge,a method for calculating the transverse load distribution is proposed on the basis of the hinge-connected slab/beam method and the model updating theory.First,a simplified model considering the effect of damages in beams and hinge-joint is established.Taking the bending stiffness of the main beam K_(k) and the stiffness of hinge joints K_(q) as the parameters to be updated,the corresponding stiffness reduction coefficientsη_(k) andη_(q) are defined.Moreover,the objective function based on the structure static response is established,which is optimized by the combination of Levenberg-Marquardt algorithm and Gauss-Newton algorithm to obtain the stiffness reduction coefficients of the damaged bridge.The load transverse distribution coefficient considering the damage of beams and hinge joints is acquired according to the updated stiffness parameters.A case study on a prefabricated T-beam bridge in service for 15 years is conducted for verification of the proposed method.The stiffnesses of 3 beams and 2 hinge joints with damage are adopted as the updating parameters,and the residual between the calculated deflection and the measured deflection of the main beam is taken as the objective functions,the actual service state of the bridge components can be reflected by continuously modifying the stiffness parameters of damage model.The calculation result indicates that(1)with the proposed method,the influence of structural damage on the stiffnesses of main beam and hinge joint can be quickly identified;(2)the calculated deflection and load transverse distribution of main beam after model modification are in good agreement with the measured values,while the calculated values before model modification are quite different from the measured values;(3)the proposed method is suitable for identification of stiffness parameters and calculation of the transvers load distribution on the damaged prefabricated hinge-connected T-beam bridges and slab bridges,while the calculation model without considering damages is no longer suitable for calculating the load effect of this kind of bridge.