Developed 90 deg Corner Bars 1

[eit09]

Are there any tables or articles on inside concrete cover for 90 deg corner bars to be assumed fully developed? Normally the grade beams I come across are a min of 24" wide so this is not normally a concern for me. I have been recently asked about sufficient cover for a #5 corner bar (I was told a min of 7" for #4 & #5 bars is required). From the outside of the corner bar to the outer edge of concrete there is a clear cover of about 2.5". From the inside of the corner bar to the inside edge of concrete there is about 6". Though I do not need the full capacity of the 90 deg corner bars I am interested on where to look for information on the insides cover requirements for 90 deg corner bars if there is any.

 

[TXStructural]

In general the force in the bar along the development length, hooked or not, is axial, and the action of deformed bar on the concrete is wedging. Your grade beams will have ties/stirrups confining the longitudinal bars which restrain this action. At the intersection of members, the cover near the hook will be restrained by the intersecting cover, and the hook will be away from the face of the concrete.

I do not believe there is an issue, as long as code-required minimums are maintained. Keep in mind that you cannot carry an inside bar to the inside face of an intersecting member, because you will compromise the cover.

See the CRSI Detailing Corner in Sept 2009 Concrete International Vol 31 Issue 9. Copies of the Detailing Corner series are available from your CRSI Region Manager (Find them at

http://crsi.org)

http://concreteinternational.com/pa...nth=1&searchday=1&searchyear=2010&ID=51663119

John Turner CSP PE
CRSI Greater Southwestern Regional Manager

 

[hokie66]

This issue was discussed at length in the following thread.

thread507-228698

Most of the commonly used details have limited efficiency for opening corners because they do not reinforce against diagonal cracking in the corner.

The reference in the thread to the work by Nilsson is where you want to look for a thorough treatment of corner reinforcement.