随机时空地震载荷下长输埋地压力管道的响应分析

Response analysis of long-distance buried pressure pipelines under seismic loads based on the stochastic space–time coupling

传统长输管道的抗震研究仅考虑随时间变化的一致地震激励,而客观上长输管道遭受的地震载荷是随时间和空间同时变化的四维时空激励。为此,从统计学的角度将其作为随机过程和随机场进行研究,考虑场地类型的影响,基于随机过程的随机地震功率谱模型——Clough-Penzien模型的正交展开和随机场的半理论半经验模型,建立了适合于实际工程的随机时空地震载荷的数学模型,进行多点激励下的管道响应分析,结合von-Mises第四强度理论进行埋地压力管道的应力分析,并以某长输埋地压力管道为例,进行了数值模拟与分析。研究结果表明:(1)对于长输管道而言,非一致地震激励下的响应大于一致激励下响应的影响;(2)四维时空地震场域的耦合响应可以基于地震数据和模型处理后再进行分析;(3)地震作用下长输管道的响应具有随机时空的特性。结论认为:长输埋地压力管道在遭受地震载荷时,科学合理的分析设计方式需要同时考虑时空效应的影响;所建立的随机时空地震载荷模型,对于长输管道抗震设计具有重要的参考价值。

Seismic research on long-distance buried pressure pipelines has become an important issue in current pipeline safety assessment.The seismic load is objectively a four-dimensional space–time excitation that changes with time and space.From a statistical point of view,it can be used as a time-varying stochastic process and a stochastic field with spatial variation.This paper proposes a concept of stochastic space–time for the time-varying characteristics of seismic loads and the time-delay effect of spatial variation.Considering the influence of site types,based on the stochastic deployment of the Clough–Penzien model of stochastic ground motion spectrum model and a kind of a semi-theory and semi-empirical model of stochastic field,a mathematical model of stochastic space–time seismic loads suitable for practical engineering was established.According to the dynamic equation of uniform excitation,the response analysis of long-distance buried pressure pipelines under multi-point excitation was carried out,and the stress analysis was made based on the von-Mises’s fourth strength theory.In a case study,such numerical simulation and analysis were carried out and the following findings were achieved.(1)As for long-distance pipelines,response from the non-uniform excitation has a greater impact than that from the uniform excitation.(2)The coupling response from the four-dimensional space–time excitation should be re-analyzed based upon seismic data after being modeled.(3)The response of pipelines under seismic loads is featured by random time and space.In conclusion,the time-varying characteristics of the loads and the motion correlation at any point of the ground motion site should be both considered in a reasonable analysis and design method,and the proposed model is of great significance to the design and research of long-distance pipelines under seismic loads.