Date of Award

2006

Degree Type

Thesis

Degree Name

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Dr. F.M. Bartlett

Second Advisor

Dr. H.P. Hong

Abstract

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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