Diaphragm action

[Nonlinearer]

I am working on a housing scheme which consists of 2 story small buildings which are all repetitive. The scheme is to use precast planks(may be hollowcore or solid)resting on load bearing wall panels (External are sandwich panels). To speed up the work, client is suggesting to remove/minimize the wet work on site specially the screed or topping on precast slab panels. We need topping for diaphragm action in design. Although, we are not in a seismic zone, but for Code's minimum notional loads and/or wind we need screed to horizontally transfer the loads.

The question is can we get rid of screed/topping on precast slab panels on site?. Is there any alternative way (probably with steel light members integrated with precast panels to get the diaphragm action?

IR

 

[ash060]

Hollowcore can be used as a diaphragm untopped. For example, untopped double tees are used as a diaphragm in parking garages all the time.

Usually the amin thing to be concerned with is the shear stress in the keyways. PCI has several items available regarding the design of untopped precast as a diaphragm.

 

[JAE]

Precasters can add embedded steel plate connectors between the planks to take the shear along the joint.

However, with most prestressed elements you have camber - sometimes significant - and the topping allows you to have a flat surface.

Not sure I'd want to provide a cambered floor to a client. Maybe for a roof.

 

[DST148]

Like ash060 mentioned, hollowcore planks can be used as a diaphragm even without any topping. For most low-cost housing applications, grouting of the joints between the planks is adequate to take care of diaphragm shears. In some cases we provide #4 U-bar grouted into pockets(along the longitudinal joints between the planks) at 2'-0" to 4'-0" 0.c.