What values do I input for the Bearing Capacities A1 and A2 soil parameters for a pad base?
2022
Tekla Structural Designer
2023
Tekla Structural Designer
2024
Tekla Structural Designer
2025
Tekla Structural Designer
2026
Tekla Structural Designer
Environment
Eurocode
Question
What values do I input for the Bearing Capacities A1 and A2 soil parameters for a pad base?Image
Answer
Principles for pad base design in Tekla Structural Designer
Some of the principles on which the current pad base design in Tekla Structural Designer is based on are as follows:- GEO combinations are only used for the bearing capacity design; - This is because EC7 2.4.7.1 (1)P states that this a ULS for “- failure or excessive deformation of the ground (…)".
- All pad base checks are performed to STR combinations.
- The designer has control over the bearing capacity resistance values – This allows you to apply the analytical, semi-empirical, presumed, etc. method.
- The bearing capacity values inserted in the isolated pad properties need to be design resistance values.
What are design resistance values?
These are the calculated values of resistance affected by the material and resistance factors from the user chosen EC7 design approach - there are three available in cl.2.4.7.3.4.This means that depending on the chosen design approach, you can come up with different values of design resistance for STR/GEO combinations to use in Tekla Structural Designer.
Example
If design approach 1 is used, there are two combinations required for pad base design:Combo 1: A1 "+" M1 "+" R1 (STR)
Combo 2: A2 "+" M2 "+" R1 (GEO)
- Set A1 is for actions – catered for in the current design
- Set M1 and M2 are soil property factors – Differ between combo 1 and 2 and need to be considered by the user where applicable when calculating bearing resistance
- Set R1 is for resistances (capacity) - needs to be considered by the user where applicable when calculating bearing resistance
So generally the design resistance values are expected to differ between STR and GEO when considering the code prescribed design approaches.
Nonetheless, this is a designers choice, and if for example a presumed bearing capacity method is used it is up to the user to choose if the pad is designed to GEO combinations as well and what would be reasonable resistance factors.