![]() Negative-moment reinforcement in continuous, restrained, or cantilever members should be developed in or through the supporting member. Development for Negative-Moment Reinforcement (9.53) for reinforcing bars that terminate beyond the center of simple supports with a standard hook, or terminate with a mechanical anchorage equivalent to a standard hook. The value of Mn /Vu can be increased by 30% when the ends of the reinforcement are confined by a compressive reaction. Positive-moment tension reinforcement at simple supports and at points of inflection should be limited to a diameter such that the development length, in computed for Æ’y with Eqs. ![]() Reinforcement should not be terminated in a tension zone unless one of the following conditions is satisfied:ĭevelopment for Positive-Moment ReinforcementĪ minimum of one-third the required positive-moment reinforcement for simple beams should extend along the same face of the member into the support, and in beams, for a distance of not less than 6 in.Ī minimum of one-fourth the required positive-moment reinforcement for continuous members should extend along the same face of the member into the support, and in beams, for a distance of at least 6 in.įor lateral-load-resisting members, the positive-moment reinforcement to be extended into the support in accordance with the preceding two requirements should be able to develop between the face of the support and the end of the bars the yield strength Æ’y of the bars. This requirement, however, does not apply at supports of simple spans and at the free end of cantilevers.Ĭontinuing reinforcement should extend at least the development length Ld beyond the point where terminated or bent reinforcement is no longer required to resist tension. Reinforcement should extend a distance of d of 12db, whichever is larger, beyond the point where the steel is no longer required to resist tensile stress, where d is the effective depth of the member and db is the nominal diameter of the reinforcement. Development for All Flexural Reinforcement In addition, these requirements help minimize any loss of shear capacity or ductility resulting from flexural cracks that tend to open early whenever reinforcement is terminated in a tension zone. The following requirements of the ACI 318 Building Code for the development of reinforcement were proposed to help provide for shifts in the location of maximum moment and for peak stresses that exist in regions of tension in the remaining bars wherever adjacent bars are cut off or bent. The critical sections for development of reinforcement in flexural members are located at the points of maximum stress and where the reinforcement terminates or is bent. Hooks can be used to assist in the development of tension bars only. The calculated tension or compression force in each reinforcing bar at any section must be developed on each side of that section by a development length Ld, or by end anchorage, or both. The ACI 318 Building Code requirements therefore reflect the significance of average bond resistance over a length of bar or wire sufficient to develop its strength (development length). Despite assumptions made in the past to the contrary, bond stress between concrete and reinforcing bars is not uniform over a given length, not directly related to the perimeter of the bars, not equal in tension and compression, and may be affected by lateral confinement. Steel reinforcement must be bonded to the concrete sufficiently so that the steel will yield before it is freed from the concrete. just some general knowledge (which I have discovered isn't so general!). So I wasn't fishing for "free engineering". The closer I can get to a "correct" design and call-out the least amount of time and effort it'll take the experts to change. My question here is for my own education, the work I've done is already out the door (where I used the 30x dia.s). ![]() And I'm sure you'll agree it's easier to change something that is existing rather then start something from scratch. I take my best shot at it, BUT I point out to my bosses that my work needs to be checked by someone that KNOWS WHAT THEY ARE DOING!!!. ![]() material procurement, estimating, Xerox machine repair, AND civil and structural design. I now work for a small engineering firm where I'm pressed to cover other bases. BUT I'm better then a "monkey see monkey do draftsman". Now I'm the first one to point out I am not expert in these other disciplines!. During that time I've had to "bump" up against other disciplines and got to get a "feel" for what they do and how. To explain, my discipline is process piping. ![]()
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