All beams behaved "elastically" up to first
cracking. The load-deflection characteristics were straight lines and were similar
for all beams since the concrete strengths and the beam cross-sections were similar,
and the effect of different amounts of steel was small so far as the apparent stiffnesses
of' the beams were concerned.
The behavior of the beams from first cracking up to the ultimate load depended
on whether the beams were under-reinforced or over-reinforced.