Hey everyone,
I am now creating a 2D bridge model for the following concrete bridge. It has two spans. The bridge superstructure is basically a concrete slab, with the middle fixed by a shear wall and the two supports built in the abutments.
My aim is to obtain the natural frequency for this bridge; however, I am not sure what boundary or constraints should I put on the bridge supports. Can someone help with this?
You can simulate the middle fixed by a shear wall by two hinged supports and the distance between them equals the shear wall thickness. The two supports built in the abutments may be simulated by roller support with or without friction.
Hi Hossam, Thanks a lot for your instructions. I have a few questions regarding your answer.
1, May I know why did you suggest two hinged supports with the distance between them equal to the shear wall thickness? Why couldn't I use one pin support?
2, if I simulate the abutment ends supports as rollers, wouldn't it mean I will get zero moments at ends, is it sensible?
Thanks a lot !
Why couldn't I use one pin support? to simulate fixation
is it sensible? If the bridge is rested on the abutment the joint deals as roller support with small friction
Dear Hossam, you suggestion above depends on the detailing of reinforcement of slab and abutment.
I think this is a concrete box culvert that is probably better modeled by a rigid frame analysis. The walls are as important as the slab.
I agree that it appears to be a box culvert and it should be modeled as such
This bridge system is best calculated as an integral frame construction
I prefer to model all the geometry together (external walls + internal walls + deck slab) from foundation to the top level. This will give you the real behavior. Best regards.
Yes, it is best to integrate based construction (foundation),walls and slabs into an integral construction.Cross-section of the wall can be variable.
Greetings.
It is best if you have geomechanical soil data to simulate soil over the soil response coefficient: K = computational soil stress / computational soil settlement.
Greetings.
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