Finite Element Analysis of Industrial Steel Elbows Under Strong Cyclic Loading

Abstract

Steel elbows are used in petrochemical facilities and power plants. In the case of an earthquake event, in addition to other service loads, they are subjected to strong repeated cyclic structural loading that may lead to failure due to cyclic accumulation of plastic strain or collapse. Furthermore, due to their flexibility, significant non-linearities occur and the elbow cross-section shape distorts as cyclic loading takes place resulting at an oval or flatten shape at the end of the loading sequence. Accumulation of plastic strains takes place at the most stressed parts of the elbow, associated with extensive bulging of the cross-section which is more pronounced in the presence of internal pressure. The present study is numerical, based on a finite element simulation of the elbow, and examines elbow behavior subjected to strong cyclic bending in the presence of internal pressure. The material constitutive model has a dominant effect on describing the elbow response, and this is shown through the employment of three different classical plasticity models.

Mechanical Behavior of Steel Pipe Bends: An Overview

“…More specifically, a series of experiments on pipe elbows under cyclic in-plane bending has been conducted, supported by numerical simulations. A first publication from this research effort, which included only numerical results, was reported recently (Varelis et al, 2011), followed by a series of publications that reported both full-scale tests and numerical simulations (Varelis et al 2013(Varelis et al , 2015. It is important to notice that all the available data on cyclic loading of pipe elbows refer to inplane bending loading, whereas there exist little information on test data and numerical simulations for cyclic loading under out-of-plane bending conditions.…”