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Seismic behavior of square high-strength concrete columns
Abstract
One application of high strength concrete (concrete with compressive strength exceeding 10,000 psi) has been in the columns of buildings. In recent years there has been concern over the ductility of HSC columns used in buildings subjected to seismic forces. Economic considerations demand that most buildings (except essential facilities) located in high seismic areas be provided with a resistance considerably smaller than that required by seismic forces that result during a major seismic event. In such cases, to prevent "complete" collapse of the building, reliance is made on the available ductility of the building members which in turn depends on the type of collapse mechanism which develops. The usual seismic resistant design of reinforced ductile frame buildings provides a relative condition of a strong column-weak beam at any junction. The intent is to encourage hinging in the beams to absorb the extreme displacements forced on the frame by seismic forces. The possibility of column hinging and the continuing evidence of damage in columns during earthquakes have prompted research to insure sufficient curvature ductility in building columns. A combined experimental and analytical investigation was conducted to study the ductility of square HSC columns subjected to loads simulating earthquake effects. Specifically, the following issues were addressed: (1) Determine the effect of concrete compressive strength, axial load, amount, spacing, and yield strength of transverse reinforcement on the ductility of square HSC columns. (2) Compare the ductility of square columns designed based on the present code using normal strength concrete and HSC. (3) Assess the adequacy of present code requirements for seismic design of square HSC columns. (4) Assess the flexural capacity of square HSC columns subjected to axial load and moment. Nine specimens with square cross-sections were tested. Each complete column had a cross-section of 12" x 12" and height of 8', representing a 2/3-scale model of an 18" x 18" prototype column. From results obtained, the ductility of HSC columns is evaluated and detailing criteria for transverse reinforcement is presented. A major conclusion which could have serious safety implications is that ACI-318-89 procedures overestimate the flexural capacity of HSC columns. An alternative to more adequately predict the flexural capacity of HSC columns under combined axial and bending moment is presented.
Subject Area
Civil engineering
Recommended Citation
Kuska, Sharon Suzanne Baum, "Seismic behavior of square high-strength concrete columns" (1993). ETD collection for University of Nebraska-Lincoln. AAI9333974.
https://digitalcommons.unl.edu/dissertations/AAI9333974