Corrosion of steel structures poses both financial and safety issues if not properly maintained. Even if proper maintenance techniques are followed, the cost can be substantial. In many industries, the current approach to determine the adequacy of structural components is based on visual inspection. While helpful, visual inspection alone is not enough to determine whether these structural components are acceptable from a structural standpoint.
A frame system affected by corrosion damage was analyzed for structural adequacy using SAP2000. In addition, a methodology is introduced to help define the criticality of the frame members relative to one another. Finally, two analyses are conducted assuming various element thickness losses for each member to simulate corrosion and to determine frame behavior as it undergoes various degrees of corrosion. The frame system is based upon an industrial plant. The objectives of the study were:
1. To analyze the adequacy of an existing structural frame system at an industrial chemical process plant based on its current condition.
2. Introduce an approach to help determine which structural frame members are inadequate and need to be replaced due to corrosion. A corrosion rating system relevant to steel structures was developed to compare the members. Based on this system, a higher rating indicates that a member is more critical to the overall structural stability of the frame. In general, failure of beams and columns were found to be more critical than the failure of cross bracing members.
3. Evaluate the impact of the uniform corrosion on an existing structural frame system.
4. Evaluate the impact of elevation dependent uniform corrosion on an existing frame system. For this scenario, corrosion damage was set to be most severe at the lower elevations and decrease at higher elevations. A uniform corrosion model was applied to the frame with a linear varying distribution to model this effect.