Stirrup spacing check

[GalileoG]

There are two code requirements that I look at when spacing my stirrups and these are:

s =< 48db, column width, (and one more that I can't remember!)

AND

Maximum spacing: s =< min(600mm, 0.7dv)

What is the difference between both of these checks and why was I told that the second check should not be performed when spacing stirrups in columns? The clause does not mention that the latter check is for beams only, which is why I was left confused when I was told to ignore it when designing stirrups in columns.

Of course, upon asking the question to my supervisor, he responded "I don't have time to explain, just do it." Heh.

Clansman

 

[GalileoG]

I might as well ask in this thread: Why are minimum requirements for horizontal rebar on walls higher than the minimum requirement for the vertical spacing of rebar on walls? Just curious.

Clansman

 

[BAretired]

I think the one you forgot was 16d where d is the diameter of the vertical bars. I just looked for it in the code, but cannot find it either. I believe I recall from some long forgotten source that it has something to do with the buckling length of the vertical bars. If the column ties (not stirrups) are further apart than 16d, the main bars might buckle and fail to carry their expected load.

If you are talking about stirrups in a beam, they have to be spaced closer to avoid a shear failure resulting from a crack falling between the stirrups.

Best regards,

BA

 

[bazflexure]

THE SPECIFICATION OF MAXIMUM SPACING OF STIRRUPS OF 48dT,16DB AND b OR h whichever is smaller is only for column in ACI code(318) and max. ermitted spacing of d/2 is for beams.The above specifications are apllicable to non-seismic resistant buildings.
The limit of d/2 is secified because length of shear crack is about 'd' in beams.
Shear is not critical in columns beacuse shear strength of members increases considerably in presence of axial comressive force.

 

[DaveAtkins]

I agree, except shear CAN control in a column on occasion, and then you actually need to design the ties as stirrups (and the spacing will be less than d/2).

Horizontal reinforcement in a wall is heavier than vertical reinforcement, because a wall is much longer parallel to the horizontal bars. The bars are for crack control.

DaveAtkins