Modelling of Ramp on Etabs
Modelling of Ramp on Etabs
(OP)
I'm designing a five story parking structure using double T's supported on precast inverted T and L beams. I have modelled the ramps on ETABS as a membrane element with one way load distribution and have meshed it into 1x1 elements. The load it appears is transferred correctly to the supporting beams,in terms of the shear and moment values of the beam. However,there is a large amount of torsion transferred to the beams, which is inexplicable since the model should assume the support of the slab at the top center of the beam and there should thus be no torsion on the beams. I have attached the model and would greatly apprectiate any help I could get on this.






RE: Modelling of Ramp on Etabs
As a result, you will have a lot of deflection and corresponding rotation at the supports. This is a classic case of compatibility torsion. (See ACI Chapter 11).
You will have torsion in the L beams due to the way the load is placed on the ledge from the double Tee. That torsion should be designed for.
The torsion that you are getting in ETABS is not realistic. For starters, I would bump up the slab stiffness to match the stiffness of the double tees.
I am getting a lot of warnings running your model. Don't know why, did not check it. I would suggest to be careful if this is your first big model in ETABS.
RE: Modelling of Ramp on Etabs
This building is essentially a cantilever in the direction of the ramp. Consider adding a shear wall parallel to the short direction on the right side.
RE: Modelling of Ramp on Etabs
RE: Modelling of Ramp on Etabs