Zach Moussa
Structural
- Oct 21, 2023
- 3
A new AC Unit will be put on a roof in my company and it's constituted of two units with the following specifications
Air supply Unit weight = 1.2 ton will be situated on a concrete footing above the concrete slab as show in the picture
Condensing Unit weight = 0.585 ton will be situated on a concrete footing above the concrete slab as show in the picture
So my design approach was this... Calculate total loads of concrete + unit for each unit and divide it by the total area of the concrete footing
concrete footing height = 0.5 meters
for the Air supply Unit + concrete weight = (1.2) + ( 2.03 (concrete area) * 0.5 (H concrete height) * 2.3 (RFT concrete density) = 3.53 ton
let's divide it by total Area = 3.53 / (3.07*1.75) = 0.66 ton/m2
for the condensing Unit + concrete weight = (0.585) + ( 1.51 (concrete area) * 0.5 (H concrete height) * 2.3 (RFT concrete density) = 2.32 ton
let's divide it by total Area = 2.32 / (2.55*1.3) = 0.7 ton/m2
...
For the sake of simplicity I assume that both of them exert an Extra 700kg/m2 load on the concrete roof...
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Now to check for if the slab can withstand the load or not I redesign the slab with an Extra Dead load of 700kg/m2 repeated over the whole area of each slab
taking into consideration the both slabs have these specification :
-Slab thickness = 0.2 m
-Top reinforcement = mesh of rebar size 10mm every 15 cm ( 6.77 rebar/m both directions)
-Bottom reinforcement = mesh of rebar size 14mm every 15 cm ( 6.77 rebar/m both directions)
--------------
So Is this a logical approach or am I missing something?
one of my greatest concern is that I assume that the loads will be evenly distributed over the whole area of the footing and not as a line load underneath the beams of the footing
Air supply Unit weight = 1.2 ton will be situated on a concrete footing above the concrete slab as show in the picture
Condensing Unit weight = 0.585 ton will be situated on a concrete footing above the concrete slab as show in the picture
So my design approach was this... Calculate total loads of concrete + unit for each unit and divide it by the total area of the concrete footing
concrete footing height = 0.5 meters
for the Air supply Unit + concrete weight = (1.2) + ( 2.03 (concrete area) * 0.5 (H concrete height) * 2.3 (RFT concrete density) = 3.53 ton
let's divide it by total Area = 3.53 / (3.07*1.75) = 0.66 ton/m2
for the condensing Unit + concrete weight = (0.585) + ( 1.51 (concrete area) * 0.5 (H concrete height) * 2.3 (RFT concrete density) = 2.32 ton
let's divide it by total Area = 2.32 / (2.55*1.3) = 0.7 ton/m2
...
For the sake of simplicity I assume that both of them exert an Extra 700kg/m2 load on the concrete roof...
--------------
Now to check for if the slab can withstand the load or not I redesign the slab with an Extra Dead load of 700kg/m2 repeated over the whole area of each slab
taking into consideration the both slabs have these specification :
-Slab thickness = 0.2 m
-Top reinforcement = mesh of rebar size 10mm every 15 cm ( 6.77 rebar/m both directions)
-Bottom reinforcement = mesh of rebar size 14mm every 15 cm ( 6.77 rebar/m both directions)
--------------
So Is this a logical approach or am I missing something?
one of my greatest concern is that I assume that the loads will be evenly distributed over the whole area of the footing and not as a line load underneath the beams of the footing
