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lecture14 - Lecture14Bar Development July9,2003 CVEN444...

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    Lecture 14- Bar  Lecture 14- Bar  Development Development July 9, 2003 CVEN 444
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    Lecture Goals Lecture Goals Critical Sections Hook Development Bar Cutoff
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    Critical Sections in Flexural Members Critical Sections in Flexural Members The critical sections for development of reinforcement in flexural members are: At points of maximum stress; At points where tension bars within span are terminated or bent; At the face of the support; At points of inflection at which moment changes sign. 1. 2. 3. 4.
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    Critical Sections in Negative  Critical Sections in Negative  Moment Reinforcement Moment Reinforcement Three sections are critical for the negative moment reinforcement: Section 1 is at the face of the support, where the negative moment as well as stress are at maximum value. Two development lengths, x 1 and x 2 must be checked.
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    Critical Sections in Negative  Critical Sections in Negative  Moment Reinforcement Moment Reinforcement Section 2 is the section where part of the negative reinforcement bar can be terminated. To develop full tensile force, the bars should extend a distance x 2 before they can be terminated Once part of the bars are terminated the remaining bars develop maximum stress.
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    Critical Sections in Negative  Critical Sections in Negative  Moment Reinforcement Moment Reinforcement Section 3 is a point of inflection The bars shall extend a distance x 3 beyond section 3: x 3 must be equal to or greater than the effective depth d, 12d b or 1/16 the span, which ever is greater. At least 1/3 of the total reinforcement provided for negative moment at support shall extend a distance x 3 beyond the point of inflection.
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    Critical Sections in Positive  Critical Sections in Positive  Moment Reinforcement Moment Reinforcement Section 4 is that of maximum positive moment and maximum stresses. Two development lengths x 1 and x 2 have to be checked. The length x 1 is the development length l d specified by the ACI Code Section 12.11. The length x 2 is equal to or greater than the effective depth d, 12d b .
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    Critical Sections in Positive  Critical Sections in Positive  Moment Reinforcement Moment Reinforcement Section 5 is where part of the positive reinforcement bars may be terminated. To develop full tensile force, the bars should extend a distance x 2 . The remaining bars will have a maximum stress due to the termination of part of the bars.
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    Critical Sections in Positive  Critical Sections in Positive  Moment Reinforcement Moment Reinforcement Section 5 At the face of the support section 1, at least 1/4 of the positive moment reinforcement in continuous members shall expend along the same face of the member into the support, according to ACI 12.11.1. For simple members at least 1/3 of the reinforcement shall extend into the support
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    Critical Sections in Positive  Critical Sections in Positive  Moment Reinforcement Moment Reinforcement Section 6 is at the points of inflection limits are according to section 12.11.3 of the ACI Code.
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