slickdeals
Structural
- Apr 8, 2006
- 2,268
Folks,
I have a situation where canopy uplift pressures are of the order of -125 psf. This is for a canopy on the entrance of a big box retail.
The canopy pressures have been calculated based on ASCE 7-05 (using a open building with obstructed wind flow) Figure 6-19A.
There are no available NOA's (Miami-Dade County) for light weight insulating concrete on metal deck for these pressures. As a result, the contractor wants to replace the LWIC with 2" of structural concrete (for which NOA's exist).
My design approach is the following:
1. Design the concrete slab on metal deck for uplift, by providing top reinforcing in the 2" concrete slab. I am assuming a "d" = (distance from top of concrete to CG of metal deck). Follow ACI procedure for calculating As.
2. Since the slab will be subject to uplift, there will be positive moment at the supports. I intend to use the deck as reinforcing for this case (1.5 VL deck). There are no studs at the support. Only puddle welds, which have been calculated for the net uplift.
3. Use the SDI Method (for no studs) and calculate the phi*Mno = phi * Sc * Fy. Compare the capacity against the positive moment.
Does the above sound reasonable?
I have a situation where canopy uplift pressures are of the order of -125 psf. This is for a canopy on the entrance of a big box retail.
The canopy pressures have been calculated based on ASCE 7-05 (using a open building with obstructed wind flow) Figure 6-19A.
There are no available NOA's (Miami-Dade County) for light weight insulating concrete on metal deck for these pressures. As a result, the contractor wants to replace the LWIC with 2" of structural concrete (for which NOA's exist).
My design approach is the following:
1. Design the concrete slab on metal deck for uplift, by providing top reinforcing in the 2" concrete slab. I am assuming a "d" = (distance from top of concrete to CG of metal deck). Follow ACI procedure for calculating As.
2. Since the slab will be subject to uplift, there will be positive moment at the supports. I intend to use the deck as reinforcing for this case (1.5 VL deck). There are no studs at the support. Only puddle welds, which have been calculated for the net uplift.
3. Use the SDI Method (for no studs) and calculate the phi*Mno = phi * Sc * Fy. Compare the capacity against the positive moment.
Does the above sound reasonable?