普光气田冲沟跨越桁架的安全评价

桁架作为油气管道跨越某些障碍物时的支撑体之一,若发生破坏会威胁油气管道的安全运行,对已发生破坏的桁架设施进行安全评价十分必要。普光气田P201~P301桩某冲沟跨越因实际施工时变更设计方案、场地沉降的原因,桁架西端工字梁腹杆发生变形、管箍发生损坏。以该跨越桁架为研究对象,建立跨越结构在沉降状态下的有限元模型,运用AUTOPIPE软件对桁架变形与受力情况进行分析。结果表明:桁架的3根长弦杆是安全的;最西端横梁的轴向内力、垂直方向剪力、水平方向弯矩均远远大于东端横梁的受力与弯矩,其所受的最大相当应力超过许用应力,处于不安全状态;除最西端横梁外其他横梁均是安全的。针对西侧横梁的不安全性,建议去除桁架西侧盖梁顶与工字钢中间的支撑构件,以减少受力,并需定期对该桁架设施进行检测。

Safety evaluation on the gully crossing truss in the Puguang Gas Field

Truss is one of the supports for oil and gas pipelines crossing certain obstacles, and its damage will threaten the safe operation of oil and gas pipelines. Therefore, it is particularly necessary to carry out safety evaluation on the truss facilities that have been damaged. Due to the modification of the design scheme during construction period and the settlement of the field, the web member of the I-beam at the western end of the truss is deformed and the pipe coupling is damaged in one certain gully crossing at P201-P301 pile in the Puguang Gas Field. In this paper, the deformed crossing truss was taken as a research object to establish a finite element model for the crossing structures in the state of settlement.And its deformation and stress were analyzed by the software AUTOPIPE. It is indicated that three long chords of the truss are safe. The axial internal force, vertical shearing force and horizontal bending moment on the beam at the westernmost end are much greater than those on the beam at the eastern end, and the maximum corresponding stress applied on the beam at the westernmost end exceeds its permissible stress, so the beam at the westernmost end is in the state of unsafety.All beams except the one at the westernmost end are safe. To deal with the unsafety of the beam at the westernmost end, it is recommended to remove the support component between the capping beam top in the western side of the truss and the middle of the I-beam to reduce the stress, and to detect the truss facilities regularly.