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.