Seismosoft | Earthquake Engineering Solutions

Dear SeismoStruct Support Team,

I am a structural engineer currently studying building performance under seismic loading. I would appreciate the clarification on the following two technical aspects:

1. Shear Inelasticity
When an element has undergone shear hinging that exceeds the limit defined according to design codes, the element essentially softens and its stiffness is significantly reduced.

Question: How does SeismoStruct handle element loss/failure during the analysis particularly shear degradation? Does the element still exist numerically with a very low stiffness, allowing shear forces to be redistributed to other redundant elements in the structure?

2. Torsional Stresses at U-shaped RC Walls
I noticed that an efficient way of modelling RC walls to account for inelasticity is to use inelastic frame force-based elements (infrmFB), where the node is located at the centre of the wall. When modelling a U-shaped wall using this approach, rigid links are automatically generated to connect the centres of the three wall panels.

Question: Does SeismoStruct capture the stresses that are transferred at the wall corners through this modelling strategy, or is it necessary to explicitly assign nodes at the corners for SeismoStruct to capture these effects accurately?

Appreciate your time addressing these questions. Thank you.

1. In the fiber frame models of SeismoStruct, shear deformations are not explicitly modelled, which is a typical features of fiber-based modelling. On the contrary, SeismoStruct's plastic hinge frame model can model shear deformations through appropriate selection of the parameters of the member hysteretic loops. In both cases however, shear failures can be captured through code-based checks and performance criteria that can be automatically defined and calculated. The the effect of such failures can also be modelled (through a residual strength strength or even the complete removal of the element).
2. SeismoStruct does not directly transfer stresses between elements. The user has to define rigid links to connect the sides of the U-shaped walls. Note that the Building Modeler facility adopts this strategy is all the models that are created by it.
Seismosoft Support