Training 14: A small project, chaining calculations
One interior column line of a three-story office building, from the floor load to the footing. Bays are 30 ft × 30 ft, with beams at 10 ft. Floors carry 65 psf dead and 50 psf live; the roof carries 20 psf dead and 20 psf roof live.
Calculations do not link to each other. You carry each result to the next by hand, which is one more moment to think about it. Create one project, and one calculation per step.
1. Floor beam takeoff (LD-1, Load takeoff) #
Beam, floor level, span 30 ft, tributary width 10 ft, live load reduction on. D = 0.650 kip/ft, L = 0.431 kip/ft, as in Training 12.
2. Floor beam (B-1, Steel beam) #
W18X40, 30 ft simple span, D = 0.65 and L = 0.431 kip/ft, self-weight on, deck bracing the top flange (Continuous).
| Check | Required | Available | Ratio |
|---|---|---|---|
| Flexural strength | 170.7 kip-ft | 294.0 kip-ft | 0.581 |
| Live load deflection | 0.443 in | 1 in | 0.443 |
| Total load deflection | 1.151 in | 1.5 in | 0.767 |
The factored reaction is 22.8 kips. The beam's end connections are not part of this calculation.
3. Column takeoff (LD-2, Load takeoff) #
Column, 3 floors and a roof, 900 ft² each, live load reduction on. The reduced floor live load is 22.7 psf.
| Result | Value |
|---|---|
| Dead D (point load) | 193.5 kips |
| Live L (point load) | 61.3 kips |
| Roof live Lr (point load) | 10.8 kips |
4. Column (C-1, Steel column) #
W12X65, A992, 13 ft, K = 1.0 both ways, the three point loads with no moments. Adequate: compression demand 335.7 kips under 1.2D + 1.6L + 0.5Lr, against 707.2 kips available, a ratio of 0.475. You could go lighter, and Auto-design will say how far.
5. Base plate (BP-1, Column base plate) #
Column W12X65, plate 18 × 18 × 1.25 in. on a 24 × 24 in. pier, f'c = 3,000 psi, the same three loads. Adequate: concrete bearing strength 716.0 kips at a ratio of 0.469, and plate bending of 9.14 kip-in/in against 17.58 kip-in/in, a ratio of 0.52.
6. Footing (F-1, Spread footing) #
A steel column on an 18 × 18 in. plate, with the same three loads, allowable soil pressure 3.50 ksf gross, 9 ft × 9 ft × 24 in., 11 #6 each way.
Not adequate: 3.57 ksf against 3.50 ksf, a ratio of 1.019. Make it 9.5 ft × 9.5 ft with 12 #6 each way: Adequate, 3.24 ksf and a ratio of 0.927. Then flexure along L is 282.7 kip-ft against 480.3 kip-ft, and two-way shear is 96 psi against 190 psi.
Issue the set #
In the project's menu, Calc package (PDF) gives one report of all six and All sheets (PDF) the sheets of those that have them.
What this chain leaves to you #
- The load path itself: which beam frames where, the tributary areas, the girder between the beam and the column. The girder is not in this example.
- Lateral loads, and the column moments they cause.
- Keeping the chain current. If the roof load changes, nothing updates downstream: you must revise each step.