Development of a new pipe element for static and dynamic analysis of nonlinear problems

Abstract

This study presents a new straight pipe element that enables the efficient computation of large, three-dimensional deformations in pipes with circular cross-sections. Existing pipe elements have difficulties in applications including three-dimensional large deformations. To overcome these diffculties, the new element (called RC pipe element in this work), which supports rigid-body and constant-strain modes, is modeled using curvilinear shell coordinates and sinusoidal interpolation functions. This new element captures all stresses except the normal stress across the shell thickness (i.e. small thickness is assumed). Euler parameters are used to describe rotational rigid-body modes and are incorporated into the element's vector of degrees of freedom. Under general loading (axial, transverse, bending and torsion), the element allows large ovalization of its cross section and large, three-dimensional angular changes in the orientation of its reference axis. The formulation used to derive the element incorporates the nonlinear coupling between torsional and bending deformations. Results of the static analysis are presented for the stresses and deformations produced by combined bending and torsional loads. A comparison of these results to corresponding quantities generated by ABAQUS using a large number of 24 degree-of-freedom shell elements indicates excellent agreement and significant gains in computational efficiency because of a reduction in number of degrees of freedom. Results are also presented for the behaviour of the element in the presence of large rotational motion with internal pressure.