Design loads Building1.4 on the dead load, 1.6 on the live load

Why an 'increased' load? (30 seconds)

• f_ser = what really sits on the slab on an ordinary day. Deflection is checked with it.
• F_d,max = the 'worst' load the slab must survive without breaking → safety factors.
• On q the coefficient is larger (1.6): a live load varies and is less predictable than the weight of the concrete itself.

The slab from the route — two lines

• g
  0.2 + 0.375 = 0.575 t/m²
• F_d,min
  1.2 · 0.575 = 0.69 t/m² 3 supports — not a special scheme
• F_d,max
  1.4 · 0.575 + 1.6 · 0.3 = 1.285 t/m²

That's it. F_d,max moves on to the moments step.

And why Fd,min? For loading patterns — 'checkerboard' — when you need the truly worst case: for the maximum positive moment in a span, load Fd,max on that span, and on the other spans alternate Fd,max and Fd,min; for the maximum negative moment over a support — Fd,max on both sides of it, and the rest alternating. The coefficient formulas on the moments page — with Fd,max on the whole slab.

In a ribbed slab: one more line — load on one rib: F_d,max · b_f = 0.844 t/m (b_f = 0.65 m — the tributary width of one rib, in metres).

4 pitfalls

• 1.4 on q and 1.6 on g. Reversed. The heavy one (1.6) — on the live load.
• Forgetting S.w inside g. The self-weight is a dead load.
• The same coefficient for all schemes. F_d,min: 1.2 · g in most schemes, 1.0 · g only in the special schemes (2 supports with a cantilever).
• f_ser in the moments step. Moments and reinforcement — always with F_d,max.