This tool calculates the bearing, shear, and flexural capacity of a strip footing in accordance with CSA A23.3

- Definitions
- ϕ
_{c}= Resistance factor for concrete - ϕ
_{s}= Resistance factor for reinforcing steel - f
_{c}= Specified concrete strength (psi) - f
_{y}= Specified reinforcing steel yield strength (ksi) - λ = Concrete density modification factor; 1.0 for normal density concrete
- A
_{s}= Area of reinforcing steel (in^{2}) - α
_{1}= Stress modification factor for equivalent stress block - β = Cracked concrete shear factor
- d = Depth to primary reinforcing (in)
- B = Width of footing (in)
- L
_{f}= Footing length (ft) - t
_{w}= Wall thickness (in) - Cover = concrete cover to centroid of reinforcing (in)
- q
_{a}= Allowable bearing resistance for service conditions (ksf) - q
_{ult}= Ultimate bearing resistance (ksf) - q
_{s}= Service bearing demand (ksf) - q
_{u}= Factored ultimate bearing demand (ksf) - d
_{v}= Shear depth, normally taken as 0.9d (in) - Calculate soil bearing stresses
- P
_{s}= (D + L)/L_{f}= (10 + 5) / 1 = 15 kip/ft - P
_{u}= max[1.4D, 1.25D + 1.5L] / L_{f}= max[14, 20] / 1 = 20 kip/ft - q
_{s}= P_{s}/ B = 15 / (18/12) = 10 ksf --> Service bearing capacity exceeded! Revise design - q
_{u}= P_{u}/ B = 20 / (18/12) = 13.33 ksf --> Ultimate bearing capacity exceeded! Revise design

- P
- Calculate shear capacity at critical section, located 'dv' away from the face of the wall
- d = h - cover = 30 - 3 = 27 in
- d
_{v}= max[0.9d, 0.72h] = 0.9 (27) = 24.3 in - β = 0.21 if h < 14in or (B-t
_{w}< 2d_{v})). Else β = 230/(1000 + d_{v}*25.4). --> β = 0.21 - tw + dv > B --> Vu = 0 kip
- V
_{c}= ϕ_{c}λ β √f_{c}L_{f}d_{v}= (0.65) (1) (0.21) (0.852) (1) (24.3) = 33.9 kip - V
_{u}/ V_{r}= 0 / 33.9 = 0 --> okay

- Calculate the flexural capacity at the critical section, located at the face of the wall
- M
_{u}= q_{u}L_{f}(B-t_{w})^{2}/ 2 = (13.33) (1) (18 - 12)^{2}/ 2 = 240 kip-in = 20 kip-ft - M
_{r}= ϕ_{s}A_{s}f_{y}(d - a/2), where a = (ϕ_{s}A_{s}f_{y}) / (ϕ_{c}α_{1}f_{c}L_{f}) - Mr = (0.85) (5) (60) (27 - 5.449/2)
- Mr = (255) (24.276)
- Mr = 6190 kip-in = 515.85 kip-ft
- M
_{u}/ M_{r}= 20 / 515.85 = 0.04 --> okay

- M