The Effect of P-Wave Propagation on the Seismic Behavior of Steel Pipelines

Underground structures perceived as one the most vital infrastructures,which include a variety of tunnels, subway lines,gas, oil and water pipe. Plenty of studies devoted to the investigationof the effect of wave propagation method on the seismicbehavior of steel pipelines. It should be mentioned thatanalyses have been carried out on both clayey and sandy soilwith different propagation speed in each of them. The aim ofthis research is the investigation of the effect of longitudinalp-wave propagation method on the amount of nonlinear strainsof pipeline with different way such as Pipe and Psi element or2D modelling of soil. It became evident that the amounts ofMaximum tension strain produced in the pipe have the maximumdifference, equaling 3.4 per cent. In addition, it investigatesthe effect of frequency of input motion on nonlinearstrains and the effect of frequency content in the results. &nbsp

The Effect of Three-Dimensional Earthquake P-Wave Propagational Speed on Buried Continues Straight Steel Pipelines

The analysis and design of gas and oil pipelines is of importance given the fact that they are long and go through lands. They are laid besides the faults and sometimes cross the faults. Various studies have already investigated the design process and the damages imposed on the pipelines crossing the faults. The aim of this research is studying the effect of longitudinal wave propagation method on the amount of nonlinear strains of pipeline. In addition, it investigates the effect of wave propagation speed as well as the simplified hypothesis of the same effect of the wave on the pipeline. Many researchers study on modal analyses or two-dimensional analyses. In this paper used three-dimensional modeling with propagational P-wave. It should be mentioned that analyses carried out on both clayey and sandy soil with different propagational speed in each of them. The accuracy of the proposed analyses is validated by the comparison of the proposed solution results with some existing solutions.  According to the analyses, it became obvious that in dense soil the amounts of strain are less than soft soil. This amounts to 71 per cent in a sinusoidal wave. The average of the values of the reduced strain in different type of soil could reduce the amount of strain to be considered equal to 0.592 for clayey soils, and equal to 0.61 for sandy soil

Study of Stiffness Effect of Panel Zone on Ductility of RBS Joint

Beam to column joint fractures on steel structures in Northridge earthquake produced some worries about the reliability of steel connections. Brittle fracture of bending joints indicated that ductility of construction materials doesn't ensure structure ductility, and structure geometry, loading type, and other specifications influence structure behavior. Stress (strain) concentration due to seismic moment changes may prevent distribution of plastic zone around joint, and this can be a justification for joint brittle fracture. RBS joint is one that came after Northridge earthquake, which is known as dog bone joint. In this kind of joint, by minimizing section of beam flange near support area (in which possibility of plastic joint formation is more), plastic joint is transferred from column side and joint area to inside beam and at proper interval with joint. To design this joint and achieve the goal of formation and development of plastic hinge in reduced area, many parameters must be considered. Panel zone is one of the most effective parts of a rigid steel joint. Resistance and stiffness value of panel zone has a large effect on behavior and performance of joints. This paper studies these kinds of joints and effects of changes in panel zone using cross-shaped substructure and ANSYS software. Regarding to the studies it was indicated that weak panel zone doesn't develop plastic hinge in beam, so collapses merely occurs in panel zone and joint area. In specimens with strong panel zone, because of elastic behavior of panel zone, all substructure energy is wasted in beam, so panel zone is not used efficiently