Continuous Reinforcement Requirements
Continuous Reinforcement Requirements
(OP)
This is an incredibly tedious question so bear with me.
I'm trying to terminate some negative moment reinforcement and AASHTO Section 5.10.8.1.2c states that At least one third of the total tension reinforcement provided for negative moment at a support shall have an embedment length beyond the point of inflection not less than the greast of the following....
The bars I'm terminating are #5's @ 6" but instead of taking them out to the inflection point, I was going to terminate them early (per the general requirements of 5.10.5.1.2a) and use the continuous temperature and shrinkage reinforcement (#4's @ 12") to meet the 1/3 requirement.
Unfortunately 1/3 of 0.62 in^2 is 0.207 in^2/ft so a #4 @ 12" violates this ever so slightly. Would any of you be OK with this? I don't feel I can justify basing it on the required steel because the code clearly states that the 1/3 is based on the total steel provided, not required.
I'm trying to terminate some negative moment reinforcement and AASHTO Section 5.10.8.1.2c states that At least one third of the total tension reinforcement provided for negative moment at a support shall have an embedment length beyond the point of inflection not less than the greast of the following....
The bars I'm terminating are #5's @ 6" but instead of taking them out to the inflection point, I was going to terminate them early (per the general requirements of 5.10.5.1.2a) and use the continuous temperature and shrinkage reinforcement (#4's @ 12") to meet the 1/3 requirement.
Unfortunately 1/3 of 0.62 in^2 is 0.207 in^2/ft so a #4 @ 12" violates this ever so slightly. Would any of you be OK with this? I don't feel I can justify basing it on the required steel because the code clearly states that the 1/3 is based on the total steel provided, not required.
RE: Continuous Reinforcement Requirements
Rod Smith, P.E., The artist formerly known as HotRod10
RE: Continuous Reinforcement Requirements
RE: Continuous Reinforcement Requirements
BTW, for your other interpretation (ie contrary to mine above), you would have to add the #4 and #5 bars and provide 1/3 of that. ie if your #4 bars can meet the 1/3 requirement then they have been 'provided' as strength reinforcement.
RE: Continuous Reinforcement Requirements
Honestly, when we do continuous beams, we never terminate any of the negative moment reinforcing. The rebar is so cheap, it's not worth the hassle for us to detail it, the rod busters to place it properly, nor for our field people to make sure they placed it properly. With all of that, there's still the potential for construction errors; it's just not worth it. We terminate some of the positive moment steel at the columns, just to cut down on the congestion between the column steel and the tension steel in the bottom of the beam/cap. Of course, with bridge substructures, the inflection points can move quite a bit with different live load patterns (truck positions).
Rod Smith, P.E., The artist formerly known as HotRod10