Limit Loads for Pipe Elbows With Internal Pressure Under In-Plane Closing Bending Moments

Abstract

The purpose of this study is to determine limit loads for pipe elbows subjected to in-plane bending moments that tend to close the elbow (i.e., decrease its radius of curvature), and the influence of internal pressure on the value of the limit load. Load-deflection curves were obtained, and from these curves plastic collapse or instability loads at various values of internal pressure were determined. This was done for different pipe bend factors (h = Rt/r2) using the nonlinear finite element analysis code (ABAQUS) with its special elbow element. The limit load was found to increase and then decrease with increasing pressure for all the elbow geometries studied.

Validation on large scale tests of a new hardening–softening law for the Barcelona plastic damage model

“…Under extreme loading conditions, such as the high repeated incursions in the nonlinear zone that the imposed displacement in this case causes, elbows exhibit two different failure modes. These are either significant cross-sectional ovalization or local buckling, as reported by the experimental work described in Sobel and Newman [23], [24], Dhalla [25] and Greenstreet [26], Tan et al [27], Shalaby and Younan [28] and Suzuki and Nasu [29] for monotonic bending moments and Yahiaoui et al [30], Slagis [31] and Fujiwaka et al [32] for cyclic loading, and from the work of Karamanos et al [33], [34], Pappa et al [35], Varelis et al [36], [37].…”

Some recent developments on integrity assessment of pipes and elbows. Part I: Theoretical investigations

“…This Table 3 Comparison of closing m 0 = M 0 /4R 2 tr y for p = 0.0 h Spence and Findlay (Eqs. (1) and (2) Elbow factor(h) = 0.4132 Touboul et al (1989), Instability Present (Eq.10), Closing collapse Shalaby & Younan (1998a),Closing collapse Present (Eq.11), Opening collapse Shalaby & Younan (1998b),Opening collapse is expected since Eq. (9) of Touboul et al (1989) is for instability moment and the present Eqs.…”

Determination of collapse loads in pipe bends with ovality and variable wall thickness under internal pressure and in-plane opening moment

“…For thin-walled bends, the ovalization is more prominent and hence the application of internal pressure increases the collapse load due to its stiffening effect which is due to the resistance offered by internal pressure against ovalization [27]. The stiffening effect increases for up to a particular pressure, above which the collapse load decreases as the stiffening effect decreases and it is because of the hoop stress induced by the high pressure [28]. For considerably thick pipe, the ovalization and stiffening effects are not much realized and hence the collapse load may or may not increase, depending upon the geometric parameters considered, as the internal pressure is increased.…”