Fig. 1 FE-model

On behalf of GEODESIGN AB, Ingenjörsdata AB has done the sizing of a foldable support for the 2.70 m PALLET BARRIER, used for temporary water damming.

The support is built up by a number of beams with C- or hat-profile made of 2.0 - 3.0 mm SSAB/DOMEX 350 Yp steel. The design is a challenge since the support shall have the necessary strength but at the same time be foldable, have a reasonably low weight and be robust in field service. The pre-processing was done by MEDINA, and the post-processing by FEMVIEW.

Supports placed with a 1 m spacing, fix an inclined ( ca. 45 °) wall/barrier consisting of a membrane (type tarpaulin) + backing (type Europallet), for damming water to a depth of 2.7 m.

The sizing, according to the design guide Plåthandboken/SSAB, considers stability (bifurcation, local buckling) of the axially loaded inclined columns, and the section bending moment (plastic collapse) of the other beams. The hinges are sized with respect to local stresses and contact pressures.

Fig. 2 Deformation and distribution of bending moment

An FE model (system ASKA) using beam elements for the structure and spring elements to represent the feathering action of ground, was used for the calculations. Various ground support layouts (roughness, stones, holes, etc) were analysed.

Data for the ground support feathering action was retrieved from a (former) separate analysis of the interaction between Aqua Barrier 1.80 m and (sandy) earth, that was modelled (system LS-DYNA) with earth as an elasto-plastic frictional material ( Drucker-Prager).

Fig. 3 Deformations in (sandy) earth under load of the Aqua Barrier 1.80 m

Keywords: beam element, stability, plastic collapse, Plåthandboken/SSAB, ASKA, ground support stiffness, LS-DYNA, sandy earth, frictional material, elasto-plastic, Drucker-Prager.