TPT May 2010

A rticle

In this paper the buckling and post-buckling behaviour of stiffened pipeline is experimentally and theoretically investigated under hydrostatic pressure. These ring stiffeners were used as buckling arrestors which cause the buckling capacity to be increased. The geometric imperfection of specimens is carefully measured and applied on FEM models but residual stresses are disregarded. The obtained results are discussed and compared. Also, the effect of stiffener section as well as the rings spacing are evaluated. Experimental set-up and procedure All specimens were manufactured in three small and equal length parts, and then ring stiffeners added to specimens. All junctions between these three parts of specimens (circumferential and longitudinal directions) and specimens-rings junctions were performed with soldering. Hydrostatic pressure on pipeline was modelled

with a vacuum pump on specimens which absorbing the air in specimens under loading. Measuring the strains, displacements and internal pressure of specimens were performed by strain-gauges, transducers and monometer respectively which were set up on specimens. For exactly modelling the conditions of specimens on FEM software, all specimens’ geometric imperfections were measured and circumferentially and longitudinally meshed (figures 1 and 2). FEM analysis All specimens that were tested had both material and geometric nonlinearity models created. This study was performed by using the nonlinear finite element program LUSAS. All models were meshed to 48 parts circumferentially and 96 parts longitudinally (figure 4), by using 4-noded quadrilateral shell elements (figure 5). The properties of steel were applied according to the result of steel tension tests that are shown in figure 3. Material properties and boundary conditions of models exactly corresponded to experimental conditions.

Figure 1 : Strain gauges and transducers set-up

Figure 3 : Strain-stress curve of material

Figure 2 : Set-up of experiments

Figure 4 : FEM meshing type

Figure 5 : Type of using element

106

M ay 2010

www.read-tpt.com

›