slab with double layer of reinforcement 2

[cdous]

Reinforcement to control cracking in a spillway slab is of the order of 60cm2/m.
If the reinforcement is placed in two layers the reinforcement cover should be considered as the average cover (layer1 + layer2)/2 or that of the first (top) layer.

 

[hokie66]

Cover is to the outermost bar.

 

[cdous]

Thanks your your reply.
I was rather confused because if someone placed lets say 3 layers,I quess the sections effective depth for structural analysis would be the average depth but for cracking I quess it makes sense to consider the outmost layer.

 

[hokie66]

For bending, the effective depth is normally taken as from the extreme compression fibre to the centroid of tension reinforcement in a given direction. For restrained shrinkage crack control in a slab, all reinforcement in the section can be assumed to take direct tension. But you asked about cover, which is normally about corrosion protection for the reinforcement, and cover is simply the amount of concrete between the surface and the nearest bar.

 

[csd72]

cdous,

I suggest you do a search on concrete design as it appears you have a bit to learn. This forum is not really the place to learn the fundamentals.

1. normally you would not use more than 2 layers of reinforcement (one in each direction). this would be repeated at each face.
2. you would then use the actual depth of the reinforcement in the particular direction for strength calculations.
3. cover is as it sound, the minimum amount of concrete covering the steel i.e. the smallest distance from steel to edge of concrete.