This will include the self-weight of the slabs and ribs. Characteristic superimposed loads due to screed, tiles etc. should be included.
Typical Loading Assumptions:
• Floor Finishes (Tiles + Screeding): 1.5 kN/m2
• Ceiling and Services: 0.5 kN/m2
• Dry Partition/Gypsum Walling: 1.0 kN/m2
• 115mm Brick Partition Walling: 2.5 kN/m2
• 230mm Brick Partition Walling: 5.0 kN/m2
The live load might not be given in calculations. Use the necessary code of practice; SAN10160: Part 2 (TABLE 1) South African Loading Code
The ultimate design load is calculated from: @ULS, n = 1.2 Dead load + 1.6 Live load
Before proceeding with calculations of moments, it is imperative to list down all known design data: strength of concrete, strength of steel used, assumed diameter of main steel, cover. Effective depth shall be calculated.
The bending moment at mid-span shall be calculated using formulae or using coefficients in SANS10160.
Once M is calculated, then the following parameters need to be calculated:
K, z = 0.95d (maximum), As and As min
At mid-span, Service stress fs need to be calculated. M/bd2, Modification ratio, Basic l/d shall be known, Permissible l/d calculated and Actual l/d calculated. For deflection criteria to be satisfied, the permissible l/d ratio shall be greater than the actual l/d ratio.
Maximum shear from the support center-line shall be determined and the shear stress calculated using: Shear stress = V/(bxd) < 5Mpa or formula 8sqrt (fcu) 100As/bd. From table 6 (SANS 10100-01) vc shall be determined.
Minimum steel shall be provided in the topping = 0.13%bh\