长周期空间地震动下超2000m级悬索桥抗震性能研究

Seismic performance study of an over-2000-meter-class suspension bridge under long-period spatial ground motions

摘要

随着跨径超过2000m的超大跨悬索桥的建设发展，其抗震安全面临长周期地震动成分缺失与空间变异效应显著的双重挑战。本文以主跨2180m的狮子洋双层钢桁梁悬索桥为工程背景，发展了一套融合功率谱模型、空间相干函数与局部场地效应的长周期空间地震动模拟方法，并成功生成了与场地专属反应谱及相干模型兼容的非平稳空间地震动时程。研究首先验证了基于大质量法的多维多点激励分析模型的正确性。进而系统分析了长周期行波效应与空间效应对结构地震响应的影响。分析表明:与一致激励相比，长周期行波效应使纵桥向塔底弯矩、剪力及梁端位移分别增大28%、10%和53%；而全空间效应的影响更为显著，致使上述响应与一致激励相比进一步增大了36%、20%和59%。研究同时发现，当地基剪切波速大于800m/s时，行波效应的影响趋于稳定。研究表明，忽略长周期与空间效应将严重低估超2000m级悬索桥的关键响应，所提出的模拟方法与分析结论可为同类重大工程的抗震设计提供重要理论依据与技术支撑。

Abstract

With the development of super-long-span suspension bridges with spans exceeding 2000 meters, their seismic safety faces dual challenges: the lack of long-period ground motion components and significant spatial variation effects. This paper takes the Shiziyang double-deck steel truss girder suspension bridge with a main span of 2180 meters as the engineering background and develops a simulation method for long-period spatially varying ground motions that integrates power spectrum models, spatial coherence functions, and local site effects. Non-stationary spatial ground motion time histories compatible with site-specific response spectrum and coherence models were successfully generated. The study first verified the correctness of the multi-dimensional multi-support excitation analysis model based on the large mass method. Subsequently, the effects of long-period wave passage and full spatial variation on structural seismic responses were systematically analyzed. The results show that, compared with uniform excitation, long-period wave passage effects increase the longitudinal bending moment, shear force at the tower bottom, and girder end displacement by 28%, 10%, and 53%, respectively. The full spatial variation effects are even more significant, further increasing these responses by 36%, 20%, and 59% compared with the uniform excitation. Additionally, it was found that when the shear wave velocity of the foundation exceeds 800 m/s, the influence of the wave passage effect stabilizes. The findings indicate that neglecting long-period and spatial effects would seriously underestimate the key responses of super-long-span suspension bridges. The proposed simulation method and analytical conclusions can provide important theoretical basis and technical support for the seismic design of similar major engineering projects.

关键词

长周期地震动 / 空间变异性 / 地震动模拟 / 悬索桥 / 多点激励 / 抗震分析

Key words

long-period ground motion / spatial variation / ground motion simulation / suspension bridge / multiple-support excitation / seismic analysis

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基金资助

中交集团院士专项项目(YSZX-01-2025-01-B)