c) Why this foundation repair doesn’t meet this section of code
Going back to Concrete Press Piles Foundation Repair: Building Code non-compliance Part 1 of our series, we saw that the concrete press pile foundation repair system consists of cylinders of concrete pushed one-by-one into the ground on top of each other. Some foundation repair companies put a cable through the middle and stressed it in an attempt to make the entire foundation pile act as one piece.
Assuming everything is installed perfectly straight, the concrete press pile foundation repair system simply cannot resist moments, the most basic of the loads applied to the foundation. The reason is moment resistance requires a rigid object, part of this object would have a tensile stress and the other part a compression stress, equal forces opposite to each other. This is fundamental to any structural cross section. Any object that resists a moment must have at equal internal resultant tensile and compressive force. If you push one of these cylinders sideway as to mimic a lateral force creating a moment, the cylinder would simply topple because the foundation repair method utilized doesn’t resist moments. Again, doesn’t meet the code and doesn’t meet simple and basic structural engineering principles. It just doesn’t work. (And yes, you will have moments even without lateral forces because of accidental eccentricity of the vertical loads; accidental eccentricity can be visualized by stacking several toy blocks on top of each other, eventually the tower will fall because of the eccentricity).
Now, for those foundation repair methods which include a cable through the middle of the cylinders, let’s give them the benefit of the doubt and say that the cable provides the required tensile force which equalizes the compressive force on the other half of the cylinders. However, when it comes to shear forces, the cable provides close to zero resistance to shear. So, even the better variance of this type of foundation repair system still doesn’t work or meet the code. And since buckling and deflections are so very much dependent on the structural pieces ability to resist moments and shears, then by default this foundation repair system also doesn’t handle buckling and deflections.
d) Conclusion: Don’t use Concrete Press Piles Foundation Repair
We saw in this chapter that basic structural engineering principles are not satisfied with this type of foundation repair system. It only takes one small line in the building code for something to be considered as non compliant and so far we have gone through several paragraphs of the code and this concrete press pile foundation repair system has yet to meet a single line. In this chapter in particular, we have seen that even if there was no code at all, the engineering principles, the laws of engineering, are not satisfied with this foundation repair system. Again, it just doesn’t work. Use at your own risk.