Behavior of steel beams subjected to alternating inelastic strains
Ozier, Lynn Davis
Vann, W. P.
Master of Science
This thesis reports an experimental study of the load deflection behavior and fialure characterisitcs of cantilevered rolled steel beams which undergo alternating inelastic strains. The beams are clamped into a rigid fixture to avoid connection problems, and are loaded cyclically between equal positive and negative values of end deflection which are of a magnitude such that fracture occurs at a relatively low number of cycles. The boundary conditions for twist and for lateral deflection are approximately "fixed-pinned". The development of flange, web, and lateral buckling is observed along with the effects of this buckling on the load capacity and the development of failure. The experimental parameters studied are the values of the flange width-to-thickness ratio, b/t (9.97 and 16.0); the web depth-to-thickness ratio, d/w (16.0and34.7); the length ratio, L/ry (30 and 60); and the magnitude of the end deflection at which each beam is cycled. It is found that, in general, after two or three cycles of loading the load-deflection hysteresis loops become smaller, due to a decrease in the peak cyclic loads and to a reduction in stiffness. These losses in load capacity and stiffness are related to the development of the different types of buckling.