Project 2

Question- Model of a membrane roof with cables. The modeling, form-finding and create the cutting patterns to the structure.

Ans=

Aim:-

To model a Bat shaped Tensile membrane in RFEM and to perform form-finding & Cutting pattern analysis with design.

Step-1: Create a new project with enabling 'Form finding' & 'Cutting pattern' options.

Step-2: Create nodes for the membrane modeling

Step-3: Draw lines connecting the nodes

Step-4: Assign cable steel members to the line

Step-5: Select the nodes and assign hinged support

Step-6: Assign surfaces for the closed cable boundaries. And create new material for Tensile membrane with orthotropic elastic 2D type.

Step-7: In the form finding box, keep standard prestress option. Provide 1 kN/m force for both warp & weft direction.

Step-8: Select all the surfaces and go to 'Tools > Cutting pattern from cells' option and select it.

Step-9: Create new 2 Load cases for selfweight and imposed load on tensile membranes.

Step-10: Create Design combination with 'Limit state of serviceability' type

consider the following factors for the cases (1 x Selfweight + 1 x imposed load)

Step-11: Start 'RF-LIMITS' module from Data drop-down list. Choose result combination for the design limit check. Provide axial force ranges for all the surfaces both in Nx and Ny directions.

Step-12: Select the membranes and provide 0.5 kN/sq.m imposed load (negative Z direction)

Step-13: Generate mesh with maximum 1 meter triangle meshing

Step-14: Select 'calculate all' and the following points in the membrane

Deflection

Cable axial force

Warp force in Membrane

Weft Axial force in membrane

Design Limit check for the membrane

Step-15: Provide compensation 1% in warp direction and 3% in weft direction

Step-16: provide Allowance 0.1 meter for welding lines & 0.2 meter for boundary lines. Select 'Calculate'

Check the cutting pattern of the membranes and slices.

Result:-

As given above, a Bat shaped tensile membrane is modelled and form-finding, cutting pattern & design checks are performed using RFEM software.