This is going to be the design considerations page

CM Work Area
To meet the needs of an easy clean up work area for the CM Department, a concrete slab has been proposed as one design alternative.  An article printed by the Portland Cement Association concerning industrial concrete floors on grade was used to assist in slab thickness.  All charts and calculations this article used based its information on 4,000 f’c concrete.  Since flexure is the most critical factor in concrete design, slab thickness will be calculated considering the effects of flexural stresses only. 

Design Considerations and Calculations
Vehicle loads will be considered from the following characteristics (ARTICLE page 4):

1. Maximum axle load – 10000 lbs
2. Tire contact area – Wheel load/inflation pressure = 10000*.5/110 = 45.45 in2
3. Spacing between wheels on heaviest axel – guess 3ft. = 36 in.
4. Subgrade – Subase strength – k-value = 100, for average soil
5. Flexural strength of concrete – MR = 9*sqrt(4000psi)=569
6. Safety factor – 2.0

These consideration are presented in the following design steps

• SF – 2.0
• Concrete working stress – WS= MR/SF = 569/2 = 284.5 psi
• Slab stress per 1000 lbs = WS/axel load, kips = 284.5/10 = 28.45 psi

Using Fig 3, acceptable slab thickness will be about 5.5 inches.

Steel Requirements
ACI requirements for cover are 2.5 inches for direct contact with the ground and 1.5 inches for exposed concrete.  Plus a minimum steel value needs to be determined for the slab using 60 ksi steel and 4000 f’c concrete to account for temperature and shrinkage.  The ρ value for minimum requirements is 0.0018.  So steel area required for this design is

• As = ρ*slab thickness*slab length = .0018*5.5”*12” = 0.1188 in2 (Temp/Shrink)
• As = ρ*slab thickness*slab length = .0033*5.5”*12” = 0.2178 in2 (Flexure)

Minimum spacing requirements are that steel bars are not placed more that 18” apart in either direction.  Steel spacing for various sizes of steel for the given requirement are

• Spacing – From McCormac Table A.6 = #3 @ 10 in. provides As = .13 in/ft
• Spacing – From McCormac Table A.6 = #4 @ 10 in. provides As = .24 in/ft

Minimum cover

• Sides = 2.5 inches
• Bottom = 2.5 inches
• Top = 1.5 inches

This creates a minimum thickness of 2.5” + 1.5” + .5” = 4.5”, assuming #4 bars are used.

Fence around perimeter
Fencing was also requested for this site.  Chain link fence with a gate seems to be the most appropriate choice to accommodate seclusion along with vehicle access.

Cost Estimates
Concrete
Concrete for 72’x72’x5.5” thick slab is estimated by the equation:
(72’*72’*(5.5”/12))/27= 88 cubic yards
Steel
Quantity of steel for both #3 & #4 steel bars can be estimated by the following equation:
(Length – Min Side Cover)/Bar Spacing = (72’ * 12”/’ – 2.5”*2edges) / 10” = 85.9 bars
In both directions the total amount of steel needed then is 2*85.9 = 171.8, or about 172 bars.
Fence Costs and amounts related to the installation and material costs are included in the Appendix of this report.

Utility requirements include 120-V power and a source of water.  Service exist already for the WWTP, so capital assets will have to be contacted to determine the responsible party to extend utilities to the CM construction pad.

Substances used in the construction pad will consist of degradable lime based concrete and masonry materials, therefore no extra considerations need to be made for containment and/or disposal of waste products.