Effect of severe corrosion on cyclic ductility of steel

Although some past experimental studies indicate that the monotonic structural ductility of steel is not detrimentally affected by severe corrosion, no study has investigated whether such severely rusted members can reliably exhibit the stable cyclic ductile behavior necessary for seismic survival. To generate preliminary data, a few rusted pieces taken from an existing steel bridge have been subjected to numerous cycles of alternating plasticity in flexure. Specimens had up to a 60% loss of cross-sectional area because of corrosion. This limited test program revealed that, although stable hysteretic behavior comparable with that of unrusted specimen is possible, premature failure under alternating plasticity can typically develop (in spite of satisfactory ductile behavior under monotonic loading). Irregularities along the severely rusted surface apparently act as crack initiators and precipitate crack propagation throughout the section.