Pad Foundation Design
Part 2: Reinforced Concrete Verification
Hi friends, 👋👋
As promised last week, are we continuing with part 2 of the pad foundation design guide in this mail.
Last week we showed how to verify that the soil doesn’t fail/collapse due to loading.
Today, we’ll have a closer look at how to design the concrete and reinforcement.
You can find the in detail calculation here. ⬇️⬇️
Today, we’ll look at step #6 and #7 of the step-by-step process. 👇👇
Calculate characteristic loads that act on pad foundation
Load combinations
Define properties of the sand/clay and concrete
Geotechnical design – bearing resistance verification
Geotechnical design - Sliding resistance verification (if vertical load is excentric)
Reinforced concrete design – bending verification
Reinforced concrete design – shear verification
Reinforced Concrete Design Of A Pad Foundation
Bending verification
The point load is transferred to the foundation base with a strut and tie model.
Watch out here: The following strut and tie model can only be used when there is only a vertical load and no horizontal load and moment.
Due to this strut and tie model, it can be said that the soil stress = load x soil base area.
This soil pressure creates a bending moment in the cantilevering part of the pad.
Due to this bending moment the reinforcement of the bottom surface of the pad foundation is calculated like a RC beam.
This reinforcement calculation results in reinforcement which looks like in the following pictures.
Shear verification
The shear verification is like for beams. We first check if shear reinforcement is required following EN 1992-1-1 6.2.2.
If it is required, then we calculate the shear reinforcement according to EN 1992-1-1 6.2.3.
You can check out the step-by-step process with all the calculation steps in the blog posts.
The required shear reinforcement (stirrups) is then distributed along the pad foundation in both directions. 👇👇
Conclusion
Once you have done a pad foundation design, it’s relatively easy to do the next one.
But first times are always challenging because you don’t know which verifications you have to do.
AND it’s also very difficult to find a guide that covers both - the geotechnical and reinforced concrete design.
To be honest, I have looked for quite some time ⌚⏱️ and didn’t find one.
So hopefully my 2 guides will help you out when you have to design a pad foundation. 👍😃
Alright, that was it for this week.
I’ll see you next Wednesday for another structural design guide.
Cheers,
Laurin. ✌️✌️