Dynamic and buckling behaviour of combined conical tanks.

摘要

During the past century, it was estimated that strong earthquakes resulted in the death of more than two million persons around the globe. In addition to human casualties, devastating economical and social losses result from these earthquakes. A large portion of these losses is directly related to the fires that usually occur at the aftermath of an earthquake. As such, water reservoirs are critical post disaster structures that should remain safe and functional during an earthquake in order to supply water needed to extinguish these fires. Elevated combined conical tanks are very common in North America as well as in the other continents. It is estimated that 10,000 of these structures exist in North America alone. They typically consist of reinforced concrete shaft that supports a steel vessel having the shape of truncated cone with a top cylindrical cap. The design of water structures in North America is governed by the specifications provided by either the American Water Work Association (AWWA) or the American Petroleum Institute (API). However, no provisions for the seismic analysis and design of combined conical tanks are specified in these codes.; Experimental and analytical studies are conducted in the thesis with the objective to lay down the basis of seismic design procedures for elevated combined conical tanks. In the experimental phases, a small-scale combined conical tank model is mounted to a shake table and is subjected to various types of base excitations. The tests are conducted while the combined conical model is empty and then after filling it with water. The dynamic characteristics of the empty and water-filled models are identified from the test results. These are used to validate a number of numerical and analytical tools; a shell model for the analysis of thin-walled curved structures, a coupled finite-boundary element model for the simulation of the vibrational response of liquid-filled conical vessels, and, a closed form solution for the prediction of the free surface sloshing motion in conical shells. The study proceeds numerically based on these validated tools.; An equivalent mechanical analogue that can be used to predict seismic forces associated with hydrodynamic pressure acting on combined conical tanks subjected to a horizontal ground excitation is developed based on these tools. The effect of rocking motion occurring at the base of the vessels is included.; Having identified the acting loads, the last part of the Thesis focuses on the buckling resistance of steel combined conical vessels under simulated seismic loads taking into account the effect of geometric imperfections.