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Re: Min. Steel in Concrete Column

[Subject Prev][Subject Next][Thread Prev][Thread Next] Lao,
Based on ACI349, to control surface cracking in beam, wall or structural slab sections having a thickness of 48 in. or greater the minimum reinforcement is obtained from
As=ft.A/fs, where ft and fs are the concrete tensile strength and 0.6fy, respectively, and A is the area of tensile concrete. If the surface is not exposed then minimum tension bars could be at least one third greater than required by the analysis.
Also, according to this code there is no minimum reinforcement requirement for members having a thickness of 72in. or more which are constructed by the practice recommended by ACI Committee 207.
Unfortunately, I have not found anything specifically on columns to allow less minimum reinforcement than the famous 1% especially in seismic regions. However, I suppose this requirement is more appropriate for normal size columns and  it will really be up to the designer's judgment to decide whether to use less reinforcement based on the level of actual stresses in the compression member and its role in the function of vertical and lateral load resisting system of the structure under consideration.

Mehdi Khabbazan PhD, CEng

"Lao, Larry" wrote: