development length of top bars in compression

[ajk1]

For the development length and of bars in compression, why is there no increase required in the length for top bars (and for epoxy coated bars) as there is when the bars are in tension?

 

[BridgeSmith]

I suspect it has to do with bars in compression not relying on bond with the concrete to transfer force into the concrete. The top bar adjustment accounts for air bubbles getting trapped under the bars and decreasing the surface area of the bars bonded to the concrete. Similarly, the adjustment for epoxy coating accounts for the decreased bond strength to the concrete of the smooth epoxy vs. uncoated steel.

 

[Hokie93]

The absence of cracks in the compression region, along with the bars transferring a portion of their force via end bearing, both contribute to shorter development lengths for rebar in compression.