TPT May 2010

106

2010

›

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 3

Strain-stress curve of material

Figure 4

FEM meshing type

Figure 5

Type of using element

Figure 1

Strain gauges and transducers set-up

Figure 2

Set-up of experiments