Seismosoft | Earthquake Engineering Solutions

Dear everyone,

I'm assessing the performance of eccentrically braced frames with short links using pushover.
Since shear yielding cannot be captured by default, I used 0-length link elements (with bi-linear kinematic in the F3 direction with initial shear stiffness, yield shear force and post yield stiffness). But the problem comes when the shear force in the link elements reaches the "ultimate capacity".

The link elements are defined using BL_KIN => No failure
So I defined performance criteria for the element in between the springs. But using performance criteria for the element between the links (with <80% residual strength) immediately gives fbd_Ite error once ultimate capacity is reached.

The problem is, the structure is having both MRF bay and an EBF bay so the structure is actually stable even if the EBF link fails completely (the diaphragm effect of slab modeled as constraint should hold the pieces together). But the analysis stops when I give a lower residual strength to the link element (which is in between the 2 linear springs).

Deactivating the shear link elements (and the springs) when load factor reaches the value corresponding to ultimate shear capacity also results in the same error.

I believe there is some issue in equilibrium but I'm unable to understand why.

Link to the model: https://www.dropbox.com/s/n2onkbgwnpi38 ... t.spf?dl=0

Any help would be extremely appreciated. Thanks !

Warm Regards,
Aravind.

When failure occurs (i.e. a performance criterion has been achieved) and the strength is dropped (especially, when it is dropped by an impressive 80%), the tforces+moments sustained by the failed element have to be redistributed to the rest of the structure. This redistribution has to be passed through the link elements that have also failed and their capacity to redistribute the forces is limited.

Also note that you are applying forces at the left of the structure, whereas you are controlling the displacement of a node at the right side of the structure. After the failure of the beams you are pushing the left half of the structure, but you are controlling the right half, while the applied forces cannot pass through.

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