YS-RCS-BS-07

PILE CAP DESIGN

Problem

Design a grade 45 reinforced concrete pile cap carrying 200mm x 200mm column stump. The pile cap is expect to carry 2 nos. 200mm x 200mm square pile with 250kN working load.

Solution

1. Determine the pile spacing and the dimension of pile cap.
2. Calculate the lever arm between pile centroid to the face of stump, while taking the pile eccentricity into consideration (cl.2.4.4, BS8004:1986).
3. Arrange the reinforcement in pile cap section.
4. Calculate the design bending moment using bending theory.
5. Determine the effective depth to tension reinforcement.
6. Determine whether singly reinforced section is sufficient as per cl.3.4.4.4, BS8110-1:1997. If doubly reinforced section is required, use thicker section as it is impractical to provide compression reinforcement.
7. Determine the lever arm of tension reinforcement in pile cap section using the formulation provided in cl.3.4.4.4, BS8110-1:1997.
8. Determine the area of reinforcement required based on cl.3.4.4.4, BS8110-1:1997. The area of reinforcement required should not be less than minimum requirement as stated in Table 3.25, BS8110-1:1997.
9. Determine the maximum allowable stump load by total up the factored pile working load.
10. Determine the punching shear stress at the face of stump as per cl.3.7.7.2, BS8110-1:1997.
11. Make sure the shear stress does not exceed the limit as stated in cl.3.7.7.2, BS8110-1:1997.
12. Calculate design shear force developed in pile cap section.
13. Calculate design shear stress developed in pile cap section, as per cl.3.7.7.3, BS8110-1:1997.
14. Determine concrete shear strength based on the method provided in Table 3.8, BS8110-1:1997.
15. Determine av based on Figure 3.23, BS8110-1:1997.
16. Determine the value of 2d/av, as per cl.3.4.5.8, BS8110-1:1997.
17. Calculate enhanced concrete shear strength in accordance with cl.3.4.5.8, BS8110-1:1997.
18. Check whether the concrete shear strength is adequate in resisting the design shear stress. If not, consider thicker section since shear link may not be practical.
19. Determine the binder bar required for pile cap.