continuous top bar in one way slabs

[ticas]

who designs one way slabs with continuous top bar instead of at support only?

 

[BAretired]

I give up. Who?

BA

 

[ticas]

i mean additional continuous top bar in addition to top bars at support.

I saw specification with this. Maybe for added stability? How common is this?

 

[amec2004]

For crack control and shrinkage

anchor bolt design per ACI 318-11 crane beam design

http://www.civilbay.com

 

[JacksPanic]

How short are the spans? If it is short enough the positive moment might not develop, hence the need for top rebar. Also, might be for crack control.

 

[slickdeals]

I have seen some engineers do it. For example, you need #5@12" at the support and each span is say 15', they will run #5@24" x 25' long bars which overlap at the supports.

 

[rapt]

Some designers using simplified factor methods for calculation of deflections think that providing compression reinforcement at midspan will reduce long term deflections. ACI and AS formulae suggest this.

But they are misleading as this reinforcement is normally not in compression in thin slabs so its effect if often insignificant if the proper calculations are done. Tests on thin slabs confirm this. For deeper members such as beams, as long as they are heavily reinforced in tension, the logic is correct, biut not for thin slabs.