Strip foundation design
Part 1: Geotechnical verification
Hi friends,
Today, we cover what verifications you need to do to design a strip foundation in clay.
In this e-mail, we start with the geotechnical design and next week Wednesday, we’ll cover the reinforced concrete design. So stay also tuned for that. 💯💯
You can find the in detail article here. ⬇️⬇️
The overall step-by-step process we always follow looks like this: 👇👇
Calculate characteristic loads that act on the strip foundation
Load combinations
Define properties of the clay and concrete
Geotechnical design – bearing resistance verification
Geotechnical design - Sliding resistance verification (if vertical load is excentric or horizontal load acts on foundation)
Reinforced concrete design – bending verification
Reinforced concrete design – shear verification
Geotechnical design - pad foundation
1. Calculate characteristic loads that act on the strip foundation
In order to verify the strip foundation, we need to know the exact loads that act on it
⬇️⬇️. We first calculate the loads and then do a vertical and horizontal load transfer In case you don’t know which loads act on a building check out his article: The 7 Types of Loads on Structures & Buildings.
2. Load combinations
Once the characteristic loads (snow, wind, dead, live load) on the strip are found (unit is kN/m), we need to do load combinations in order to find the design load. You can check out this article about load combinations where we explained it in detail or use our 👉 load combination generator 👈.
3. Define properties of the clay and concrete
Usually we design strip foundations for either sand, clay or a mix of the two. In general, we need the following parameters
Density of the soil
Density of water
Angle of friction for sand
Undrained shear strength for clay
4. Bearing resistance verification
The formulas for the bearing resistance are different for sand and clay.
Design bearing resistance clay (EN 1997-1 (D.1)):
Now, the design bearing resistance needs to be greater than the vertical design load that you calculate in step #2.
There are a lot of parameters in those formulas. So check our blog post to find out what they are and how to set their values (the links are in the beginning of this email).
5. Sliding resistance verification
The sliding verification only has to be done if there is a horizontal load acting on the strip foundation.
Again, the formulas for sand and clay are different.
Design sliding resistance sand (EN 1997-1 (6.3)):
Design sliding resistance clay (EN 1997-1 (6.4 + 6.5)):
I recommend reading up on it in Eurocode to get a better understanding of the formulas.
Alright, this was it for this week.
Hope to see you for part 2 - next Wednesday!
Have a great rest of the week! 🙋♂️🙋♂️
Laurin. 😎😎