How to model FRP layer under the beam

[fakharifar.mostafa]

Hi
I'm studying the effects of application of FRP layers under the beams in the joint area. The length of FRP layers are 500 mm under each beam in the joint area. Beams are 500x500 mm. I carefully read the manual and found a solution in the FAQ part mentioned as "Q. How can I model a RC rectangular member retrofitted with longitudinally-oriented steel or FRP layers placed on the two opposite sides of the section?" It was pretty practical, and I used an I section, which its top flange's thickness and width are equal to 0.000000000001 (very small value representing they're not for real), its web height is qual to 500 mm (corresponding to the height of RC beam) and its web thickness also equal to 0.00000000001 and eventually bottom flange width is equal to 500 mm (corresponding to the beam's width) and its thichness 3mm (corresponding to the FRP layer thickness).
For material behavior I applied frp_tl and in element conectivity I connected this new retrofitting element to the same nodes to which the existing element is connected to.
After pushover analysis on my RC frame with retrofitted joints there's no difference between the results in comparison with the original frame without FRP layers.
Is there anything left that I might've ignored? I have carefully read the manual.
Much of thank and appreciation for your help.

[seismosoft]

Hi,

We will obviously need to see the model, in order to be able to comment on the behaviour you have observed.

You may also perhaps explore the possibility of adding a 'truss' element defined between two nodes that are 250 mm below the beam nodes, introducing then rigid link constraints between these nodes.

Seismosoft Support