Investigation on bolt tension of flanged pipe joint subjected to bending

Abstract

Analysis of a flanged pipe joint subjected to bending and determination of maximum bolt tension is a rather difficult task due to absence of a rational method of analysis. Conventionally, in absence of specific guideline or code provisions, a method analogous to beam flexure is adopted to determine bolt tension. It is assumed that bolt force (tension or compression) is linearly proportional to the distance from the neutral axis. But this method may not always give the accurate result since the assumptions made are not practically valid. In this research, an investigation has been made to find out the effect of various parameters relating to flanged pipe joint connection, so that a guideline can be developed to determine the bolt tension. To carry out the investigation, a flanged pipe joint subjected to bending has been modeled using finite element method, which also includes contact simulation. In this analysis, shell element has been used for the modeling of pipe and flange, nonlinear spring contact element to model flange-flange contact and linear spring element is used to model bolt shanks. Here nonlinear finite element method has been used considering material nonlinearity only. The pipe joint has been subjected to yield moment and under this moment the maximum bolt tension has been evaluated. Based on overall study, an attempt has been made to present a guideline to find out bolt tension that is structurally effective for a flanged pipe joint. The whole process is carried out for various parameters within certain range. It has been found that some parameters like flange thickness, flange width and diameter of bolt have significant effect on effective bolt tension. Based on the results of the finite element analysis, an empirical equation has been developed to determine the maximum bolt tension. It also has been shown that the suggested empirical equation is useful in structural analysis for calculating the effective bolt tension with acceptable accuracy when the flanged pipe joint is subjected to bending.