Offset Bent Longitudinal Reinforcement in Columns and its Requirements

Offset bent longitudinal reinforcement is that the bending of vertical reinforcement bars of a column (larger column) at a specific construction so as to bring the bars inside the limit of a column on top of (smaller column), as illustrated in Fig. 1, A.

The maximum slope of the bent bars ought to be one in half-dozen. further to it, it’s needed to supply additional ties for the realm getting ready to the bent bars to counter the forces generated thanks to bar bending.

If the face of the column higher than is offset at 75mm or additional from the face of the column below, then offset bent isn’t thought of however rather splice of column bars by separate dowels is employed, Fig. 1, B.

Requirements of Offset Bent Longitudinal Reinforcement in Columns 

  • The maximum slope of the inclined portion of associate degree offset bent bar with the axis of column shall not exceed one in half-dozen, ACI 318-14.
  • Portions of the bar higher than associate degreed below an offset bent shall be parallel to the axis of the column, ACI 318-14.
  • Additional lateral ties, spirals or a part of the ground construction square measure samples of horizontal support that square measure placed the purpose of} the point of bend to counter the crosswise force generated thanks to the modification of direction at the bend.
  • Horizontal support provided shall be designed to resist one.5 times the horizontal part of the computed force within the inclined portion of the offset bars.
  • Lateral ties or spirals, if used, shall be placed less than a hundred and fifty metric linear unit off from the points of a bend.
  • Offset bent bars shall be bent before placement within the forms
  • When the offset between column faces exceeds seventy five metric linear unit, the vertical bars within the column below shall be terminated at the ground block, and splice of column bars by dowels could also be necessary.
  • Dowels might also be necessary once the inserting of a part of the structure is delayed, and conjointly between numerous units of structures (such as footings and columns).
  • Dowels bar size and grade ought to have constant size and grade because the bars joined, and may be of sufficient length to splice with the most bars.
  • Similar to bent offset, once column bars square measure spliced, extra ties shall be provided at and close to the ends of spliced bars, to supply confinement to the extremely stressed concrete within the regions of the bar ends.
Fig. 1: Offset Bent (A), Splicing Bars Using Seperate Dowels (B)

Fig. 1: Offset Bent (A), Splicing Bars Using Separate Dowels (B)

Sections of Columns Above ( Smaller Column)
Fig. 2: Sections of Columns Above ( Smaller Column)
Sections of Column Below (Larger Column)
Fig. 3: Sections of Column Below (Larger Column)
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