Truss Bridge with a Concrete Deck - Gusset Plate and Truss to Bridge Connections

[burakdur]

Hi All,

I do have a Truss Bridge with a concrete deck. I've modeled the deck as shell, then the stringers and floor beams are all fiber sections. This model without Truss itself works perfect and I do get the same modal analysis results with CSI.

Then, the problem starts with adding the Truss members. I do have top and bottom chords, vertical and diagonal members and they have gusset plates almost at every connection i.e. top chord - vertical member connection, bottom chord - diagonal - vertical member connections.

Thus, the first question is how to create this rigid end zone details. If I use Truss elements, just a geomTransf with a rigid offset definition is enough to define the rigid offset due to a gusset plate? If so, I am confused as of the i and j node inputs for the offset. Additionally, in this approach, all RX, RY and RZ for all Truss nodes should be fixed, right?
ops.geomTransf('Linear',1,'-jntOffset',......)

Second problem is that the bottom chords are connected to the floor beams through a gusset plate, so, I need to connect the truss system to the floor beams. Considering this, what should be the best approach to model the Truss members and connect them to the moment resisting system? I see that in some models they use forceBeamColumn and define Moment Releases to model Truss members rather then directly Truss Elements, but it comes with more constraints definitions. Is this the best approach? In this scenario, what about the all constraints and zeroLength member definitions?

I was trying to play with this small example https://opensees.berkeley.edu/wiki/inde ... ss_Example. Herein, let's say I have a gusset plate the top joint where all truss members should have a rigid end zone. I defined three additional nodes, which are 5, 6 and 7. Then, defining rigidbar from 5 to 4, 6 to 4 and 7 to 4 did not work out. Or, defining more nodes to have a zeroLength member and then having rigidBars at the top end did not work too.

Overall, creating gusset plate details, Truss element definitions in terms of the connection details to the frame members got me confused a little bit. I just wanted to try different scenarios on a small example before I try them in a real bridge model. Can you please help me?