多点地震动和波浪力激励下海床-桩-墩-桥的地震弹塑性:原理、方法、程序与智能建模作者: 柳国环,练继建,等 |
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2015年6月
摘要:跨海大跨桥梁体系在地震作用下的弹塑性数值模拟涉及四个问题:(1)海床(地基)-桩-墩-桥建立整体模型的合理性便捷性;(2)地下地基位置多点地震动反演途径的有效性;(3)波浪力和水动附加质量;(4)无限域地基被有限域地基代替后,粘弹性人工透射边界及其多源性。首先,阐述并指出了有无粘弹性人工透射边界下,土-结构体系地震差动输入模型的激励输入模式的本质区别;然后,提出了一种有效的地基位置具有空间变异性的地震差动反演途径,并据此成功开发了可视化程序MEMS_c(Multiple Earthquake Motions Simulation_c);进而,根据小尺度结构的波浪力及其频谱特性,开发了波浪力可视化计算程序WFS(Wave Force Simulation);最后,提出了弹性人工边界条件-地基-桩-墩-结构一体化的智能快速建模途径,并开发了可视化建模工具Foudation V2013.6,给出了图解说明。本文内容具有理论基础和实用性,为后续直接服务于工程提供了具体准备。 关键词:跨海大桥;弹塑性;多点地震动;波浪力;水动附加质量;MEMS_c;粘弹性人工边界 中图分类号: 文献标识码:A 文章编号: Abstract: Numerical studies on seismic response of long-span bridge pier-pile-soil system relate with the following several aspects : the reasonability and convenience of finite element model for long-span bridge pier-pile-soil system, validity of approach for multi-point earthquake motions at underground locations, wave force and effect of hydrodynamic pressures-induced added mass; and multi-source visco-elastic artificial boundary conditions. Firstly, the essential difference between the system long-span bridge pier-pile-soil system with and without artificial boundary conditions is expounded and pointed out. Then, a feasible and effect path for the inversion of earthquake motions, accounting for spatial variability, at under-ground location from ground surface is given and proposed, and the corresponding visible program called MEMS_c (Multiple Earthquake Motions Simulation_c) is further developed successfully. Further, a visual program named WFS (Wave Force Simulation) is developed and illustrated based on wave force and its spectral characteristics for small-scale structures. At last, in order to improve the efficiency and flexibility of preprocessor, a quick workflow for establishing numerical modeling is presented and the visual modeling tool Foundation 2013.6 is developed. The content in this paper involve theory and practicability, and can be directly applied to the follow-up engineering. Key words:long-span bridge; elasto-plasticity; spatially earthquake motion; wave force; hydrodynamic pressures-induced added mass; MEMS_c; visco-elastic artificial boundary conditions 引言
计算方法确定的前提下,数值模拟结果的可靠性直接取决于激励与模型的合理性。跨海大跨桥在地震作用下的反应包括如下问题:(1)地震差动,(2)地震引发的波浪力与水动附加质量;(3)人工透射边界。本文针对这一问题,给出了如图1所示的计算地基-桩-墩-桥体系在差动输入下地震反应的分析框架,具体包括四方面工作:(1)人工透射边界土-结构体系地震差动输入模型的激励输入模式;(2)地基位置地震差动反演的有效途径;(3)波浪力计算与程序;(4)建立地基-桩-墩-桥有限元模型的合理性与高效性。
首先,通过理论方法表现波浪力、水动附加质量以及边界条件各种因素,指出有无粘弹性透射边界结构体系的区别及原因。然后,提出了一种地基位置的地震差动反演途径,并开发了MEMS_c (Multiple Earthquake Motions Simulation_c)。其次,跨海大跨桥梁的地震反应问题除考虑地基、桩、桥墩、桥体外还要考虑接触单元以及粘弹性人工边界条件各种因素。若直接通过ABAQUS的GUI(Guide User Interaction)方式同时实现上述若干因素较为困难;相反,SAP前处理十分方便,且设计单位一般会提供所需SAP上部结构模型。为此,提出了“弹性人工边界条件-地基-桩-墩-结构一体化”的快速建模途径,开发了包括人工边界条件多土层地基建模可视化工具Foundation V2013,可通过界面直接调用SAP内部API函数实现建模;地基模型建立好后,使其与已有的上部结构SAP模型合并;随后,采用已成功开发的SAP2ABAQUS接口程序直接将模型生成ABAQUS模型文件。最后,根据随机波理论和波浪力计算理论[1],将P-M谱和莫里森方程结合,从找到与频率相关的波高,提出一套不同于以往模拟波浪力时程的有效新途径。进而,基于此开发了可视化波浪力程序WFS(Wave Force Simulation)。 本文内容按照结构系统理论公式、地下位置多点地震动模拟途径以及有限元模型建模途径与可视化程序开发依次进行,旨在立足实用和便捷性并为后续工程计算做准备。 结论 本文涉及到理论、方法和程序几方面内容,简要总结如下: (2)提出了地下地基位置地震差动的模拟途径,进而编制开发了可视化程MEMS_c,并通过计算说明了其合理性。 (3)提出了弹性人工边界条件-地基-桩-墩-结构一体化的智能快速建模思想,进而开发了可视化建模工具Foudation,并给出图解说明,旨在前处理的快速性和准确性准且便于与上部SAP模型合并。 (4)开发了波浪力的程序WFS(Wave Force Simulation),给出界面操作和后处理使用说明。WFS核心程序的特点是:将莫里森方程与P-M波高频谱相结合,发挥各自优点并弥补不足,从而形成了一种模拟浪力的简单有效新途径。 本文内容具有理论和实用性,可为后续实际工程(实现考虑波浪力的地震差动作用下海床-桩-墩-桥体系的工程分析)提供准备性工作。 t-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman";mso-ansi-language:EN-US;mso-fareast-language: ZH-CN;mso-bidi-language:AR-SA;layout-grid-mode:line'>桩-墩-结构一体化的智能快速建模途径,并开发了可视化建模工具Foudation V2013.6,给出了图解说明。本文内容具有理论基础和实用性,为后续直接服务于工程提供了具体准备。参考 文献(References): [1] 李玉成, 滕斌. 波浪对海上建筑物的作用[M]. 北京: 海洋出版社, 1993. 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