Dynamic Analysis of Tall Building Using Reduced-Order Continuum Model

Abstract

On Oct. 17, 1989, a tall, steel-framed, San Francisco office building with 47 above-grade stories was excited by the Loma Prieta earthquake. The building response was recorded by accelerometers maintained by the California Division of Mines and Geology Strong Motion Instrumentation Program. From the records, important characteristics of the building response can be identified. In this paper, a computationally efficient, approximate dynamic analysis of the building using a reduced-order continuum model is conducted. By making use of the repetitive nature of the lattice framing system, finite-element models generated using continuum methodology have significantly fewer degrees of freedom than models generated using classical discrete finite-element techniques. These reduced-order models can therefore lead to significant savings in the computational effort and cost typically associated with dynamic analyses of large structures. The vibrational characteristics of the continuum model, as well as the results of the dynamic analysis, are compared to the building's recorded response. The continuum model is accurate in capturing the dominant periods of vibration as well as the time-history response and shows promise as a tool for preliminary design of large lattice structures.