Min reinforcement steel in foundation for self erecting crane

[TWfea]

Hi all, I have been asked to approve a raft foundation for a self erecting crane, and am running into an issue regarding the minimum steel requirement (As,min). The foundation has already been poured and is designed in accordance with the suppliers design recommendations.

The raft is 7m x 7m x 0.5m C35 concrete with a layer of A393 mesh top and bottom.

• Based on the design bending moment, the as-built steel is fine (unity check = 0.9).
• The min requirement As,min = 0,26(fctm/fyk)btd ≥ 0,001 3btd (Eurocode 2 - 9.2.1.1 - Beams) gives a value that is 1.8x greater than the specified steel.

I understand the Eurocode is for permanent structures, and this is only a temporary structure (1yr). So I was wondering

• If there were any allowances when dealing with As,min for temporary foundations
• Is the strict application of the As,min design critera for beams necessary

You feedback, insights, and expereince would be very welcome!

 

[hemiv]

I worked for a large heavy civil contractor, and we would, as a rule, take advantage of the temporary nature of our projects. We made use of ASCE 37. I am not familiar with Eurocode.

If the foundation works for the loads, and if the As min is just there for crack control, and if you can live with the cracks for the life of the structure, then it may be okay.