Bracing of Precast Concrete building during construction

[Pungineer]

I have a question regarding precast construction with CIP diaphragm & shearwalls. The job i'm working on has precast elements, beams, columns, Double-tee's...which will be erected before the CIP shearwall & diaphragm are poured. What is the lateral system during the erection process? The columns are braced during erection, however the braces are removed once the base of the column is grouted & beams are erected. I make sure to check the columns & walls for temporary wind load after erection and size the braces and deadman appropriately, but I'm lost on the building as a whole. BTW this job is in California (high seismic).

Anyone have experience with this?

Thanks,

 

[birneys]

Typically, as an EOR, I have a note that indicates the contractor is responsible for all temporary bracing until the building is complete (including diaphragms, shear walls, etc.). Often your liability insurance doesn't cover construction bracing or shoring. If your precast erector is PCI-certified, they should have plenty of experience in bracing the structure until all the CIP elements are in place. If I'm the EOR, I am staying out of any and all conversations about bracing and shoring during construction.

 

[DCBII]

The PCI handbook outlines that responsibility for stability during erection should be clearly understood. Somebody needs to provide erection drawings. You need to discuss this with your client and decide who will take on that scope of work. Generally, the general contractor will hire an erector for the precast components. I think the erector should bear this responsibility, since they have the experience and know the sequence in which it will be erected. They may not want to erect it the way you think they do. The erector will typically hire their own engineer to provide erection drawings.

 

[PROFR]

Generally speaking, the precast column is to be braced at the level of the floor diaphragm until that floor is completely done. In fact, erection sequence should be part of the column design itself. It is not right to construct the lateral load resisting system after the precast building is erected. Something does not seem correct here.

 

[KootK]

If your proposed sequence of construction is the way that it will be, then I'd imagine that you'd want something like temporary cable bracing as is done in steel erection. A precast double TT deck is pretty heavy and can exert some significant P-delta instability demand.