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Report No.: CCEER-02-7

Title: A Performance-Based Design Method for Confinement in Circular Columns

Authors: Jessen Mortensen and M. Saiid Saiidi

Date: November 2002

Sponsoring Agency: Nevada Department of Transportation (NDOT))

Performing Organization:
Department of Civil Engineering/258
University of Nevada, Reno
Reno, NV 89557

Abstract:

In recent years, performance-based design (PBD) has become an attractive option for engineers because of the flexibility it offers. It gives designers and owners the ability to choose certain performance levels for their structures. However, there is currently no widely accepted measure of performance. Several parameters have been studied, including curvature and displacement ductility, concrete and steel strains, and drift ratio. Curvature ductility, a measure of flexural deformations in the plastic hinge region, was used in this study. The objective was to develop a design method for confinement steel in spiral reinforced circular columns and to evaluate the method based on the results of shake table testing of large-scale columns.

A simple, non-iterative PBD method was developed that was based on curvature ductility. Two specimens were constructed for shake table testing at the University of Nevada. Each specimen was a quarter scale model of a flexure dominated 4 ft. (1.219 m) spiral reinforced circular bridge column. One column was designed by the current California Department of Transportation (Caltrans) guidelines and the other by the proposed performance-based design method. The analysis included the study leading to the development of the design method, a comparison of the proposed method with other available methods, and an analysis of the test models. It was found that the proposed method was a reliable tool to design spiral steel to provide for a target curvature ductility.

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