Finite Element Analysis of Fibre Augmented Steel Technology Pipe (FAST-Pipe™)

Abstract

The FAST-Pipe™ concept involves wrapping a conventional strength steel pipe (e.g. X70), whose thickness is selected to satisfy axial and bending load requirement, with dry fibreglass to achieve the pressure load requirement. FAST-Pipe™ offers several technical and economical advantages over high strength steel concepts. Since FAST-Pipe™ is a new technology, there is a need to develop analytical methods for its design. This paper describes the finite element analysis (FEA) models used to predict experimental response. The calibration of the FEA models for FAST-Pipe™ involved the pressure-strain history, the burst pressure, the moment curvature history and the bending strain capacity of FAST-Pipe™ subjected to a combination of internal pressure, axial force and bending. The finite element program ABAQUS was used to develop shell models capable of simulating the burst and bending behaviour of FAST-Pipe™. Several burst and bend tests performed on 48- and 12-inch pipes were used to verify and calibrate the finite element analysis models. The effects of the type of steel-fibre bond, the thickness of the wrap, the wrap elastic modulus and the steel yield criteria were studied for the bend model. In the main FEA bend models, no bond was assumed to exist between the steel liner and the wrap in the hoop direction, and the steel liner was modelled using an elastic-plastic, kinematic hardening material model with an initially shifted yield surface. The failure of both the burst and bend models was defined as the point where the wrap hoop strain reached a failure strain of about 2%. The implementation of the FEA burst model was validated based on the burst test results. The assumption of no bond in the hoop direction and full bond in other directions resulted in reasonable predictions of the bending strain capacity. The autofrettage process influenced only the initial part of the moment-curvature response of a FAST-Pipe™ by producing a stiffer response, without significantly affecting the bending strain at failure and moment capacity. The wrap elastic modulus value and the type of yield criteria used for the steel liner had no significant effect on the moment capacity reached by the FEA models.