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An Equation to Estimate Maximum Normal Strain of Buried Steel Pipes at Bend Area Under Propagating Waves in Sands

The possible vulnerability of pipelines under propagating waves especially at bend area emphasizes the need of studying in this context. In the presented studies in this field the beam and beam-shell hybrid models were usually used but in this study a continuum model is examined. For this purpose, the bent pipe is modeled by shell elements and suitable boundary conditions are considered to simulate the infinite length of the pipe away from the bend. The soil around the pipe is modeled by 3D elements obeying the Mohr-Coulomb rule of behavior. Also, equivalent boundary conditions are used at the boundaries of the soil domain where it is truncated. By varying the properties of the pipe-soil model, it is investigated under seven different ground motions and the maximum axial strain is calculated at the bend area. Effects of different parameters including incidence angle of seismic waves, bend angle, pipe diameter to wall thickness ratio, and physical properties of soil are investigated. Using the results of analysis and regression, an equation is proposed for estimating the maximum normal strain of buried pipes at the bend area with good accuracy.