Set buckling / design data
set_member_designSet the design (code-check) data that lives on a MemberSet — buckling restraints, buckling lengths, LTB length, effective-length factors — plus the per-member chi override.
THESE FIELDS CHANGE NOTHING IN THE STATICS. Displacements, reactions and member forces come back bit-identical; the values only feed the EN 1993-1-1 unity-check evaluator. If the model has no Ec3Steel unity check and a matching load combination you will see no effect at all anywhere in the results, so add one with add_unity_check first.
A MemberSet is one physical beam: the ordered chain of collinear FE members that make it up. Design lengths resolve per axis with this precedence: explicit buckling_length_* > effective_length_factor_* > buckling_restraints spacing > member length. WATCH THE TWO BASELINES — an explicit length and a restraint spacing are measured along the WHOLE chain, but effective_length_factor_y/z multiplies the length of the INDIVIDUAL FE member. Verified on a 6 m column split into 4 x 1.5 m members: buckling_length = 6.0 reproduces the default exactly, buckling_length = 12.0 quarters N_cr, but effective_length_factor = 2.0 gives L_cr = 3.0 m (2 x 1.5 m), not 12 m.
buckling_restraints are named by the member LOCAL axis they hold (restrains_local_y / restrains_local_z / restrains_torsion), not strong/weak — which one is strong depends on the section orientation and rotation_angle. A restraint's node_id must actually lie on one of the set's own members or the whole model fails validation.
chi is a per-MEMBER override of the EN 1993-1-1 flexural-buckling reduction factor. It replaces the section-curve chi for BOTH flexural axes (the slenderness stays physical) and is written onto every member of the targeted sets; pass "clear" to remove it.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| chi | No | EN 1993-1-1 reduction factor override in (0,1], written onto every member of the set. | |
| model | No | Stringified FERS model JSON | |
| model_ref | No | Handle from stash_model, used INSTEAD of `model`. Avoids sending the whole document on every step; the tool returns the same handle back. | |
| ltb_length | No | Lateral-torsional buckling length. | |
| classification | No | Alternative selector: exact match on the set's classification. | |
| member_set_ids | Yes | JSON array of member-set ids, or "all". Give this or `classification`. | |
| buckling_length_t | No | Torsional buckling length. | |
| buckling_length_y | No | L_cr about local y, in model length units, measured along the whole member chain. | |
| buckling_length_z | No | L_cr about local z. | |
| set_classification | No | Rename the set's classification. | |
| buckling_restraints | No | [{"node_id":3,"restrains_local_y":true,"restrains_local_z":true,"restrains_torsion":true}]. Replaces the set's list; nodes must lie on the set's own members. [] clears them. | |
| effective_length_factor_y | No | K about y — multiplies the INDIVIDUAL element's length, not the chain's. | |
| effective_length_factor_z | No | K about z, same caveat. |