Nonbuilding and Special Structures
The food industry utilizes large cookers that might be used to perform various tasks, such as container sterilization, food cooking, food cooling... etc. Typically, these cookers are in the form of large, slender steel tanks that are partially filled with liquids or food containers. These tanks can be installed in horizontal or vertical configuration and are supported at discrete limited locations. Several large industrial food cookers are presented in this article, including the following cookers.
A five (5) foot diameter rotary cooker is comprised of a long cylindrical metal tank with various stiffeners, and supported horizontally on three (3) saddles. Several non-structural components, such as tubes and valves, are attached to the tank. The tank is about 60 to 80 ft long, and is typically operated half full of liquid. Food containers enter the tanks from on end, and exit from the other end fully cooked. This rotary cooker is installed in a seismic active area and hence, seismic upgrades were required. Because of its operation, the cooker will need to be free of restraints, which is in conflict with the seismic requirements.
The second industrial cooker is a steel tower that rises 52 ft above ground level. The footprint of the cooker is almost square and measures about 8 feet. The skin of the cooker is made of thin steel plates, about ¼” or less, reinforced with vertical and horizontal stiffeners. For maintenance purposes, large holes were required to be cut at the bottom of the vertical cooker at the most stressed location under vertical and lateral loads. These included seismic and wind lateral load.
This article will discuss the analysis and design challenges associated with developing structural retrofit solutions that ensure safe operations of these giant cookers.