scope:

ABSTRACT

To investigate the effect of the yield stress on the local buckling of tubular columns fabricated by cold-rolling and welding, tests were conducted on five specimens made of ASTM A-36 steel (nominal yield stress 250 MPa (36 ksi)) and on one made of ASTM A-514 steel (nominal yield stress 700 MPa (100 ksi)). The wall thickness varied from 6.55 to 9.73 mm (0.2 6 to 0.38 in.) and the diameter-to-thickness ratio (D/t) from 59 to 233. The slenderness ratio (L/r) was less than 9 to preclude the effect of overall column buckling.

The ultimate stress was limited by the formation of local buckles in four of the specimens. In the remaining two, stresses were reached slightly above those at which buckling was observed. The buckling stresses ranged from 0.829 to 1.069 of the static yield stress and generally decreased with an increase in D/t ratio.

The initial geometric imperfections and the longitudinal welding residual stresses appeared to have no influence on either the location or the pattern of the local buckles. In the post-buckling range the specimens were able to maintain capacities of 12 to 23% of their buckling strength.

The test results were compared using several design parameters and equations. Current American design equations were all found to be conservative. An equation was proposed to predict the local buckling strength of cylindrical tubular columns fabricated from steels with a static yield stress of 250 MPa (36 ksi) to 700 MPa (100 ksi).