DOUBLY REINFORCE BEAM
DOUBLY REINFORCE BEAM
(OP)
Is there a limit for a doubly reinforce beam design?
Especially for the limit of rho?
Especially for the limit of rho?
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RE: DOUBLY REINFORCE BEAM
I haven't seen a limit on the amount of compression reinforcement provided the tension only As (total As - compressive As) is below the 0.75rho balanced limit.
You also have to ensure the compression bars yield.
RE: DOUBLY REINFORCE BEAM
Appendix B contains information on reinforcement limits in terms of steel ratios for those interested in using the historic provisions. See B.10.3.
RE: DOUBLY REINFORCE BEAM
RE: DOUBLY REINFORCE BEAM
RE: DOUBLY REINFORCE BEAM
Can you correct me if I am wrong please?
My understanding is that the compression steel MUST yield. If it doesn't then you making an incorrect assumption in the beam calcs. If the compression steel doesn't yield then the steel - steel couple can't be (d-d')As'fy because the compression steel will not have reached fy.
RE: DOUBLY REINFORCE BEAM
RE: DOUBLY REINFORCE BEAM
RE: DOUBLY REINFORCE BEAM
RE: DOUBLY REINFORCE BEAM
RE: DOUBLY REINFORCE BEAM
RE: DOUBLY REINFORCE BEAM
RE: DOUBLY REINFORCE BEAM
0.85fc*b*Beta1*c^2 +87c -fy*As*c -87d' = 0
RE: DOUBLY REINFORCE BEAM
Another follow-up question i would ask, in a seismic provision, is it allow to design a beam resisting earthquake for doubly reinforced? According to ACI 318-02, seismic provision that the limit of rho is 0.025, can i still use compression bars to increase my tensile strenth of beam? Or do i making my beam brittle if i put to much of rebars or increased tensile rebars?
RE: DOUBLY REINFORCE BEAM
Adding compression reinforcing without adding additional tensile reinforcing will not increase the moment capacity of the beam by much. Adding compression reinforcing will make the beam more ductile. The compression reinforcing causes the N.A. to shift towards the top of the beam causing the strain in the tension steel to increase leading to a more ductile section.
RE: DOUBLY REINFORCE BEAM