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Report No.: CCEER-10-7

Title: Stability of Bridge Column Rebar Cages during Construction

Authors: Builes-Mejia, J. C., Itani, A.

Date: November 2010

Sponsoring Agency: California Department of Transportation (Caltrans)

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

Abstract:

The lateral behavior and stability of bridge column rebar cages were investigated to reduce the potential of failure and collapse during construction. Rebar cages are temporary structures made of longitudinal and transverse reinforcing bars that are connected by tie wire connections. Recent collapses during construction exposed the vulnerabilities of these temporary structures to accidental loads that may occur at this stage. Therefore, experimental and analytical investigations were conducted to understand the lateral behavior of bridge column rebar cages. Experimental work was performed on individual components of rebar cages, such as tie wire connections and reinforcing bars, under various types of loading. Two full-scale bridge column rebar cages were subjected to incremental loading to determine the lateral behavior, identify failure modes, and calibrate the analytical models. Using the results from the experimental study, nonlinear finite element analyses were developed to determine the effect of critical parameters on the lateral behavior of column rebar cages. The investigated parameters were: tie wire connections, internal braces, column diameter, longitudinal and transverse reinforcement ratios, and column height. The results of these analyses showed that the internal braces have a significant effect on the lateral behavior and failure mode of bridge column rebar cages. Guidelines for determining the lateral stiffness and improving the bridge column rebar cage stability are proposed.

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