Importance of ductile detailing, sketches

Ductile detailing is the arrangement of reinforcement (IS 13920) that lets RC members deform plastically in an earthquake without brittle failure.

Importance

• Allows design for a reduced seismic force ($R$ factor in IS 1893), so the building is economical.
• Dissipates energy through hinges, preventing sudden collapse and saving lives.
• Gives warning before failure through large deformation.
• Confined concrete has greater strain capacity and strength.
• Prevents brittle shear, bond and joint failures.
• Moves hinges to the beams, keeping the columns, which carry gravity load, intact.

Beam detailing

 |-2d-|------- d/2 --------|-2d-|
 ||||| |  |  |  |  |  |  | |||||   closed hoops
 =====================================  2 bars continuous
 ===  =====================  ===      top / bottom
  s<=min(d/4,8phi,100)       lap in middle half

• Closed stirrups with $135^\circ$ hooks and $10\phi$ tails; first at 50 mm; $s \le \min(d/4,\ 8\phi,\ 100)$ over $2d$; $\le d/2$ elsewhere.
• Bottom bars at the joint face $\ge$ 50% of top bars.

Column detailing

  --------------
  | ##########  |  lo = max(D, h/6, 450)
  | ##########  |  s = 75-100 mm
  |     #  #     |  normal spacing in
  |     #  #     |  mid-height
  | ##########  |  lo again
  --------------

• Hoops with $135^\circ$ hooks, tail $6\phi$; splices only in the middle half.
• Strong column - weak beam at each joint.