When is shoring required for a 2nd floor steel beam? 4

[oengineer]

I am replacing a beam shown on construction documents. I am exchanging a beam size of W27 x 217 to W30 x 173 for a second floor. What would determine if shoring is need to place the replacement beam? The steel has not been erected yet for the building. Comments/Suggestion are appreciated.

 

[oengineer]

The floor slab is a composite slab. I have been told that the deflection in the beam will determine if shoring is necessary.

 

[msquared48]

Just before it fails.

Mike McCann, PE, SE (WA, HI)

 

[canwesteng]

How do you plan on removing a beam from a composite slab?

 

[oengineer]

@canwesteng

The structure of the building has not been constructed yet, just the foundation. This is for an RFP.

 

[canwesteng]

What are you shoring then, the sky?

 

[EZBuilding]

Shoring may be required if the self weight of the concrete topping of the composite beam would provide deflections which are detrimental to the serviceability of the building or if the beam can not support the weight of the concrete and construction live loads during concrete placement. Note that the strength and stiffness of a composite beam is only achieved once the concrete has cured, the intermediary condition could control some design parameters.

 

[oengineer]

@canwesteng

I am new to the building industry, so please bear with me. I have been told that our department designs beams for the wet concrete of the composite deck, so beam camber is not required. This also eliminates the need for beam shoring.

 

[msquared48]

Seems to me that without shoring you would need camber to decrease the volume of concrete and level the floor system out under dead load. Then you would only see composite live load deflection.

Mike McCann, PE, SE (WA, HI)

 

[Aesur]

Typically composite beams are designed for both pre and post composite action. The pre-composite deflections and stresses determine if shoring is needed. The pre-composite design typically includes construction live load and construction dead load (without finishes, ceiling, etc..), whereas the post-composite design includes all loading. If the beam is overstressed or over deflected for the pre-composite case then you would potentially need shoring and or bracing.

 

[oengineer]

@Aesur & EZBuilding

Thank you for your clarification.

@everyone

Thank you for your comments.