Field Adjustment of Tapered Shims Using a Least Squares Algorithm

Buildings that are used in oil field operations at Prudhoe Bay, Alaska are built in warm water ports thousands of miles away. These buildings (modules) are fabricated on top of columns (stub columns) that have square flat plates at the bottom (stub column base plates). At Prudhoe Bay, the modules are placed at various drill sites, flow stations, and piping facilities. They are supported by large diameter metal pilings that have square flat plates (pile caps) on the top. Modules weigh up to 5,000 tons (2,300 metric tons) and may be supported by 50 pilings or more. The planes of the corresponding flat plates, the pile cap, and the stub column usually are not parallel. They are required to be parallel, however, to ensure the best bearing surface. Parallel planes are formed on site by the insertion of two identical circular tapered shims between the flat plates before the module is set in place. A program that finds the correct orientation of the tapered shims through a least squares fitting procedure is presented here.