Remaining capacity of deteriorated I-section structural steel members

Abstract

Abstract

Steel have many design and functional advantages as a material in the construction process and in structures in use. However, deterioration of steel e.g. due to corrosion is one of the drawbacks for steel structures. Understanding the behaviour of steel structures under corrosion and assessment of remaining load carrying capacity of existing steel structures because of this possible corrosion become an important topic. In line with this challenge, this thesis is aiming to provide analytical formulas for calculating remaining capacity of structural steel members namely column, beam and a beam-column member

In this thesis a theoretical background for structural steel members and their behaviour is presented. In addition, analytical methods of strength calculations and design of structural steel members based on EC3 is discussed in brief. The cause and effect of corrosion on steel structures and the methods of corrosion prevention in design and service phases is also described. Some previous studies on similar topics are also evaluated and summarized.

The main parameter used in this thesis for formulating the equations is the eccentricity (shift) of the elastic and plastic neutral axes caused by the unsymmetrical material loss due to corrosion. Hence a corrosion damage model of an I-section is adapted for analysis purposes, where an eccentricity is introduced about the major axis. As result, a generalized and a specific geometrical property of the corroded model are presented as a function of the magnitude of the eccentricities and other parameters. Formulas for calculating the remaining capacities are also provide based on the section properties.

Typical I-sections in this thesis are selected for demonstrating the reduction in load carrying capacities and illustrations of effective capacity versus percent (%) area loss is provided. The results show that a significant capacity reduction occur for the member with axial compressive force. For 10% area loss the results of the analytical evaluations indicate a capacity reduction of about 40% & 50% reduction of critical elastic buckling load and axial plastic compressive capacity respectively about the major axis when the eccentricity due to unsymmetrical corrosion was introduced. For the member with a pure bending moment the reduction was about 22% & 18% of the elastic and plastic moment capacity. This indicates that the eccentricity due to corrosion have a significant effect, especially for members with axial forces.