隧道地震响应中的人工边界和地震动输入方法研究

Study on artificial boundary and ground motion input method in tunnel seismic response

动力人工边界及地震动输入方法是影响地下结构动力响应结果精度和可靠性的关键问题。为了对比常见人工边界的计算精度和实用性,提高结构地震响应数值模拟的计算效率,结合ABAQUS有限元软件的二次开发功能,采用Python语言编写了粘弹性边界、无限元边界、自由度绑定边界及竖向约束边界等常见动力人工边界的自动施加及地震动输入程序。在此基础上,结合自由场模型、隧道地震响应数值解和解析解,验证波动输入法和振动输入法及各人工边界模型的有效性,进一步探讨振动输入法与波动输入法的差异性。结果表明:采用等效节点力的波动输入时,基于各动力人工边界的计算结果均与远置边界及解析解基本重合,具有良好的计算精度,也说明所开发的人工边界及地震动输入程序的有效性。采用位移、速度或加速度时程的振动输入时,只适于远置边界或等位移边界。与其他人工边界相比,自由度绑定边界施加方便快捷,对2种地震动输入方法均适用。此外,地震动输入方式对结构地震响应存在明显影响,绝大多数地下结构的场地条件宜采用波动输入法。

Dynamic artificial boundary and ground motion input method are the key problems affecting the accuracy and reliability of dynamic response results of underground structures.In order to compare the calculation accuracy and practicability of common artificial boundaries and improve the calculation efficiency of numerical simulation of structural seismic response,combined with the secondary development function of ABAQUS finite element software,the automatic application and ground motion input programs of common dynamic artificial boundaries such as viscoelastic boundary,infinite element boundary,freedom binding boundary and vertical constraint boundary are written in Python language.On this basis,combined with the free-field model,numerical and analytical solutions of tunnel seismic response,the effectiveness of wave input method,vibration input method and each artificial boundary model is verified.The difference between vibration input method and wave input method is further discussed.The results show that when the wave input of equivalent nodal force is adopted,the calculation results based on each dynamic artificial boundary basically coincide with the remote boundary and analytical solution,and have good calculation accuracy.It also shows that the developed artificial boundary and ground motion input program is effective.When the vibration input of displacement,velocity or acceleration time history is adopted,it is only suitable for remote boundary or equal displacement boundary.Compared with other artificial boundaries,the application of freedom binding boundary is convenient and fast,and it is applicable to both ground motion input methods.In addition,the input mode of ground motion has a significant impact on the seismic response of structures.The site conditions of most underground structures should adopt the wave input method.