大跨高墩连续刚构桥内力状态及其对地震反应的影响

为研究实际施工过程和混凝土收缩徐变对连续刚构桥成桥内力状态的影响以及不同内力状态下主桥的地震反应差异，以某大跨高墩连续刚构桥为背景，建立了MIDAS/Civil施工阶段分析模型，并讨论了各施工因素对主桥内力状态的影响; 基于等效荷载法提出了适用于连续刚构桥的内力等效荷载计算方法，通过将主桥内力进行分解，以若干简单的内力等效荷载分别进行等效，再利用叠加原理求和，得到符合实际情况的等效内力状态; 采用OpenSees建立了全桥非线性动力分析模型，并施加不同内力状态所对应的内力等效荷载，使其处于对应的等效内力状态; 选取40组典型速度脉冲型近断层地震动记录为输入，开展了不同内力状态下全桥非线性动力时程分析。分析结果表明：若忽略主桥预应力作用，将高估主梁最大弯矩约2.8倍，高估主墩墩顶和墩底最大弯矩分别约3.5、2.0倍，且弯矩方向皆与实际情况相反，故预应力作用对连续刚构桥内力状态的影响不可忽视; 墩梁固结附近主梁等效内力峰值与目标内力峰值的最大误差在5%以内; 近断层地震动作用下，主墩侧移角、曲率延性系数和塑性铰区钢筋最大应变都随混凝土收缩徐变的增加呈逐渐减小的趋势，沿纵桥向则更为明显; 提出的内力等效荷载计算方法可为高烈度区连续刚构桥抗震设计和性能评估提供参考。

Internal force state of long-span continuous rigid-frame bridge with high-rise piers and its effect on seismic response

An analysis model was established to study the effects of actual construction process and concrete shrinkage and creep on the internal force state of continuous rigid-frame bridge to determine the differences in seismic responses of the main bridge under different internal force states. The model was established taking a long-span continuous rigid-frame bridge with high-rise pier as the background, through MIDAS/Civil, and the effects of each construction factor on the internal force state of the main bridge were discussed. Based on the equivalent load method, the calculation formulas of internal force equivalent loads were proposed for continuous rigid-frame bridges. The internal forces of the main bridge were decomposed. Several simple internal force equivalent loads were used for equivalence, followed by the summation using the superposition principle to obtain the equivalent internal force state corresponding to the actual situation. The nonlinear dynamic analysis model of the completed bridge was established through the OpenSees, and the internal force equivalent loads corresponding to different internal force states were applied to enable the positioning of the corresponding equivalent internal force states. Forty groups of typical near-fault ground motion records with velocity pulse effect were selected as the input. The nonlinear dynamic time-history analysis of the completed bridge was carried out under different internal force states. Analysis results show that with the prestress of the main bridge ignored, the maximum bending moment of the main girder is overestimated by about 2.8 times, and the maximum bending moments of the top and bottom of the main pier are overestimated by about 3.5 and 2.0 times, respectively, with the bending moment in reverse direction to the actual situation. Therefore, the influence of prestress on the internal force state of continuous rigid-frame bridge cannot be ignored. The maximum error between the peak value of the equivalent internal force of the main girder and that of the target internal force near the pier-beam consolidation is less than 5%. Under the action of near-fault ground motions, the drift angle of main pier, curvature ductility factor, and maximum strain of reinforcement in plastic hinge area all display decreasing trends with the increase of concrete shrinkage and creep, especially detectable along the longitudinal direction of the bridge. The proposed calculation method of equivalent internal force loads can provide a reference for the seismic design and performance evaluation of continuous rigid-frame bridges in high intensity areas. 4 tabs, 12 figs, 30 refs.