Development Length of Bars in Compression

• In the case of bars in compression, a part of the total force is transferred by bond along the embedded length, and a part is transferred by end bearing of the bar on the concrete.

• Because surrounding concrete is relatively free of cracks and because of the beneficial effect of end bearing, shorter development lengths are permissible for compression bars than for tension bars.

• Hooks are not effective in transferring compression from bars to concrete, and if present for other reasons, should be disregarded in determining required embedment length.

• The ACI code equation for basic development length in compression is

• but not less than 0.0003dbfy. Modification factors given in table should be applied but in no case is ld to be less than 8 in.

Development Length of Deformed Bars in Compression

Modification factors to be applied to ldb 

• Reinforcement in excess of that required by analysis  

• Reinforcement enclosed within spiral reinforcement not less than ¼ in. diameter and not more than 4in 
  pitch or within #4 ties spaced at not more than 4in on centers.................0.75