STANDARD ACI HOOKS

[JD2]

I AM WORKING ON A JOB NOW WHERE SEVERAL CONCRETE COLUMNS HAVE ALREADY BEEN POURED AND IT WAS DETERMINED, AFTER THE FACT, THAT HOOKS (IN THE FOOTINGS) ON DOWELS COMING OUT OF THE FOOTING INTO THE COLUMN FOR SOME OF THE BAR TYPES (#7 AND #9 BARS) DO NOT MEET THE MINIMUM BENDING RADIUS REQUIREMENTS FOR A STANDARD ACI HOOK (THE HOOK EXTENSION IS ADEQUATE). IT WAS FIRST NOTICED WHEN A HOOK ON ONE OF THE BARS WAS DISCOVERED TO HAVE A CRACK APPROXIMATELY 3/4'S THE WIDTH OF THE BAR AND APPROXIMATELY 3/16" DEEP. I KNOW THAT THE BEND RADIUS FOR THE STANDARD ACI HOOK IS DESIGNED TO MINIMIZE THE STRESS IN THE BAR DUE TO THE BENDING PROCESS AND PREVENT SPLITTING OR FAILURE OF THE BAR AT THE HOOK. I HAVE NOT GONE BACK TO DETERMINE IF THE HOOKS ARE ACTUALLY REQUIRED IN THE BARS OF THESE PARTICULAR COLUMNS TO DEVELOPE THE REQUIRED FORCES SO MY QUESTIONS AT THIS POINT ARE SOMEWHAT ACADEMIC - FOR MY INFORMATION. IF BARS TERMINATING IN HOOKS HAVE BEEN BENT AND DO NOT SHOW SIGNS OF SPLITTING OR CRACKING AT THE BEND OF THE HOOK, CAN THE HOOK STILL BE COUNTED ON AS BEING EFFECTIVE? DOES IT DEPEND ON THE ACTUAL RADIUS OF THE BEND? IS THERE ANYTHING IN THE RESEARCH LITERATURE THAT CAN BE REFERENCED? ANY INFORMATION WOULD BE GREATLY APPRECIATED.

 

[ERV]

JD2,

The specified radius is critical to the stength of the bars even if no cracks are showing, the hooks are dependent for base shear of the columns (if that was the intended design). If the bars do not conform to radius requirements then the pull out strength will be compromised.