The safe storage of natural resources, such as liquefied natural gas or propane, is essential to the public and companies that distribute... Show moreThe safe storage of natural resources, such as liquefied natural gas or propane, is essential to the public and companies that distribute these resources. Large diameter, double walled cylindrical storage tanks are the typical structure used to store these natural resources. One of the design factors that commonly govern the structural integrity of the tank is the design seismic response spectra. A component of the tank that is not given much consideration in the industry codes is the suspended insulated deck. The purpose of the deck is to provide a layer of insulation just above the liquid level of the product. This helps control the release of gases that boil off from the product. Despite this deck being made of thin plate material, this can be a considerable mass on large diameter tanks once the insulation and deck stiffeners are accounted for. The supports for the deck are typically one-half inch or sixteen millimeter square rods, which do not provide much lateral resistance. The concern this thesis investigates is what occurs to the suspended deck during an earthquake. By treating the outermost ring of rods as a moment frame, the summation of each rod’s lateral stiffness provides the total deck stiffness and natural period of the structure as a single-degree-of-freedom system. It is determined the standard design is likely to collide with other vital components of the tank under certain seismic events. In order to prevent the deck from potentially damaging these components, the conservative route is to increase the stiffness of the deck until the displacements are within an allowable range. viii This is done by installing a tank specific number of braced frames around the outer perimeter of the deck. The above procedure is a simple method to ensure there are no unexpected collisions between tank components. More time consuming methods, such as finite element analysis may show that the standard design can sufficiently withstand any collisions. However, the ability to provide a quick, easy solution with minimal added construction materials is a considerable advantage when ensuring the safety of the storage tank. M.S. in Civil Engineering, December 2012 Show less
