slab design of noncomposite girder

[Nayan67]

Hello everyone,
I am currently designing a non-composite steel box girder. Since the system is non-composite, I assumed that the entire bending moment would be resisted by the steel girder alone. During the slab design, I did not consider any longitudinal bending stress in the deck slab and provided only nominal reinforcement. My understanding was that, in the absence of shear connectors, there is no stress transfer between the deck slab and the girder. While there may be local stress in the slab, the overall stress is resisted by the box girder alone. Therefore, the slab does not need to resist longitudinal bending stresses, except for providing nominal reinforcement to address temperature, shrinkage, or other local effects. However, the reviewer has asked that I design the slab for longitudinal bending moments as well. Would anyone be able to recommend a good reference or guideline that discusses slab design for non-composite steel girders?

 

[jhnblgr]

This really doesn’t add up, regardless of composite or non composite the concrete deck design remains the same, the only difference is composite counts the effective width changing the neutral axis of the girder. The deck in one way regardless unless you designed for two way but that would make no sense. I would say one of you has a communication error or fundamental understanding.

 

[Nayan67]

This really doesn’t add up, regardless of composite or non composite the concrete deck design remains the same, the only difference is composite counts the effective width changing the neutral axis of the girder. The deck in one way regardless unless you designed for two way but that would make no sense. I would say one of you has a communication error or fundamental understanding.

Thank you for the response.
I have no issues estimating the transverse bending moment using the AASHTO method. My concern lies in the longitudinal direction. While I understand that in a non-composite system, the steel box girder resists the entire global bending moment (e.g., 10,000 kNm), I’m uncertain about the longitudinal forces that the deck slab should be designed for.
I recognize that the slab must be designed for longitudinal stresses, but determining the appropriate magnitude of these forces is challenging. Modeling the non-composite slab with allowance for slip between the girder and slab could provide an estimate, but this approach seems overly complex.





Could you advise on a practical method to determine the longitudinal forces for the slab design in a non-composite system?

 

[jhnblgr]

The deck can’t span longitudinal hence why the steel girders. The load path is deck to superstructure to substructure. Only if you have a slab by itself spanning the long way would it do what you are asking.

 

[KootK]

Could you advise on a practical method to determine the longitudinal forces for the slab design in a non-composite system?

Unless you can somehow quantify the amount of shear slip that you can expect to take place, I would think that you would have to do something like this:

1) Estimate the tension strain at the top of the box girder assuming non-composite behavior.

2) Apportion your rebar in the slab for crack control given the amount of tension strain calculated in [1].