Arctic Engineering: Structural Evaluation on the North Slope of Alaska

Performing structural repair work on the North Slope of Alaska presents obvious logistical and environmental challenges. Geotechnical concerns must also be considered given the nature of permafrost and the effects of varying subsurface soil conditions. Many structures on the oil fields of the North Slope are comprised of large modules housing various types of industrial equipment. The equipment often generates significant amounts of heat resulting in design temperature differentials of up to 200 degrees Fahrenheit between the inside of the module and the outside artic air. This temperature differential along with several other factors result in unique deterioration mechanisms throughout the buildings. Before implementing repairs to address structural deficiencies, identifying the root cause of the damage is of critical importance. This paper is targeted at structural design and inspection professionals and will focus on the assessment of a specific module located on the North Slope with a deteriorated roof system. An on-site field investigation was initially performed to confirm as-built drawings and identify areas of corrosion and damage that could result in a reduction of structural capacity. During the site investigation, multiple buckled diagonal braces were noted throughout the structure’s braced frames, leaving it vulnerable to design level wind and seismic events. The forensic efforts undertaken to identify the root cause of the bracing failures, the evaluation performed to assess the criticality of the damage, and the repairs designed to restore structural integrity will be discussed. Ultimately, through the detailed site investigation and data evaluation, the root cause of the damage was identified and an appropriate repair strategy is currently in process to mitigate potential instabilities resulting from the failed lateral bracing members.