Symmetric Frame Subjected to Vertical Forces — Detection of “Weak” Elements

Objective: Verification of the determination of elements with forced or constricted deformation at buckling.

Initial data file:  Energy.SPR

Problem formulation: The plane frame is subjected to different vertical nodal forces. Find the “weakest” elements in terms of the loss of stability of the system as a whole for the first buckling mode.

References: Perelmuter A.V., Slivker V.I., Design Models of Structures and Possibilities of Their Analysis. — M, DMK-Press, 2007, § 9.4.

Initial data:

Р1 = 4 t, P2 = 6 t

- values of the concentrated forces.

Bar sections have the following ratios of the stiffnesses per running meter 2:4:6.

Finite element model: Design model – general type system, 9 bar elements of type 2, 10 nodes.

Design model (with the numbers of the rigidity type and loads)

 

Results in SCAD:

Values of the energy

 

Comparison of solutions:

Parameter	Theory	SCAD
Elements with the negative energy	edge columns	edge columns