Date of Award


Degree Type


Degree Name

Master of Engineering Science


Civil and Environmental Engineering


Dr. F.M. Bartlett

Second Advisor

Dr. H.P. Hong


Steel bridges designed before the mid-1950s may be deficient according to current design code requirements and thereby require strengthening. This thesis explores the responses of W-shaped compression members, such as existing columns, bents, bracing or truss members, reinforced at the flanges by new steel cover plates. The primary research objectives are: (1) to model the behaviour, accounting for residual and locked-in dead load stresses, different yield strengths of the original W-shape and new flange cover plates, initial out-of-straightness and end eccentricity; and (2) to develop a rationally based practical design method for the compressive resistance of a built-up hybrid compression member. The research reported in this thesis first develops the mechanics for the resistance of built-up hybrid steel compression members from principles of equilibrium, compatibility, and force-deformation relationships. Based on these mechanics, the Refined Numerical Analysis Model is developed and implemented in a computer program to approximate column capacities and validated by comparison to column design curves in the Canadian Highway Bridge Design Code. A parametric study is presented to determine the sensitivity of compressive resistance to the magnitude of residual stresses, locked-in dead load stresses, yield strength of the W-shape and end eccentricity. An optimal simplified design method for practical design usage is identified from four candidate procedures.



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