Structural optimization to mitigate natural hazards using stiffness decoupler.

摘要

The concept of decoupling the lateral stiffness of the structure from the strength of the column system, developed at Kansas State University and for which a patent is pending, is presented and used in the optimal structural design. This new base isolation system, called "the stiffness decoupler", helps in reducing the design earthquake response to the level of that due to design wind loads. The device can control the dynamic behavior of a structure while providing the desirable load carrying strength, damping strength, and natural period. It provides the correct flexibility, ductility, and stiffness which are necessary to optimize the required functions of the structure. It uses friction as the main source of energy dissipation. The device also includes additional multilevel safety elements to provide an even higher level of security in the event of an unusually strong earthquake.; A computer program was developed to analyze, design and optimize a three-dimensional reinforced-concrete building subject to a user-supplied ground motion. A four-story multibay structure was subjected numerically to the 1940 El Centro (N00W) earthquake and the results are presented to illustrate the effectiveness of the isolation system. A building so designed was subjected to other accelerograms to determine the sensitivity of the design. A reduced model was employed to optimize the structural performance. The use of the stiffness decoupler is shown to reduce floor accelerations and interstory drifts. The sensitivity analysis demonstrates the ability of the structure to handle very large earthquakes, even with much uncertainty about the magnitude of the earthquake. Results from an experiment consisting of a building on stiffness decouplers and a regular building also provide evidence of superior performance of the base isolation system.