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Why does RFEM find no equilibrium for an upward load on a membrane roof curved downwards?

Answer

The downwardly curved, synclastic roof geometry is numerically stable for downward loads. Loads in the direction of the arc ultimately increase the tensile load in the membrane and thus stabilize the structure.

Loads against the arch shape of the roof reduce the tensile load in the membrane. If the tensile stress of the membrane cable approaches zero in this case, numerical difficulties result due to the sole, membrane tension resistance of the element used. In this case, the solution process reacts with a poor convergence, instability messages, or messages about a positive definite Jacobian matrix.   





Keywords

instable Jacobian membrane lifting

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RFEM Main Program
RFEM 5.xx

Main Program

Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements

Price of First License
3,540.00 USD
RFEM Tensile Membrane Structures
RF-FORM-FINDING 5.xx

Add-on Module

Form-finding of tensile membrane and cable structures

Price of First License
1,750.00 USD