Integrated Buildings & Structures

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90 degrees hook at the bottom of Column for structures assigned to SDC D, E, or F

  • 1.  90 degrees hook at the bottom of Column for structures assigned to SDC D, E, or F

    Posted 10-10-2021 09:53 AM
    Hi, I am not so familiar with earth quake design. I have one thing to discuss.

    In the ACI 318, Clause "18.13.2.3 Columns designed assuming fixed-end conditions at the foundation shall comply with 18.13.2.2 and, if hooks are required, longitudinal reinforcement resisting flexure shall have 90-degree hooks near the bottom of the foundation with the free end of the bars oriented toward the center of the column." Is there any specific justification or reason that we need to bend the hook inward to the column?


    Thank you and regards,


    Hendi

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    Hendi Hendi Aff.M.ASCE
    Field Design Manager
    Bogor
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  • 2.  RE: 90 degrees hook at the bottom of Column for structures assigned to SDC D, E, or F

    Posted 10-11-2021 10:53 AM
    The commentary discusses this. It states that research and testing have been performed to show that flexural members terminating in a footing, slab, or beam (a T-joint) should have their hooks turned inward toward the axis of the member for the joint to be able to resist the flexure in the member forming the stem of the T.  My initial guess was that this would provide better confinement.  However, note that Section R18.8.5.1 states, "The requirement for the hook to project into the joint is to improve development of a diagonal compression strut across the joint. The requirement applies to beam and column bars terminated at a joint with a standard hook." That is not specifically for foundations, but it would make sense that the same thought process applies.

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    Daniel Hernandez P.E., S.E., M.ASCE
    S-E-A
    Rolling Meadows IL
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