Performance of reinforced concrete columns with steel-belted tires as transverse reinforcement.

摘要

The majority of column failures observed during recent earthquakes were attributed to poor column behaviour caused by lack of inelastic deformability. The deformability of reinforced concrete columns can be improved through the confinement of potential plastic hinge regions by properly designed transverse reinforcement. The conventional reinforcement used for confinement consists of closely spaced perimeter hoops, overlapping hoops, cross-ties and circular spirals. One possible alternative for column confinement is to use steel-belted tires. Scrap automotive tires may provide an environmentally friendly alternative to conventional transverse reinforcement in circular concrete columns, especially for bridge and parking structures.;The effectiveness of steel-belted tires as transverse column reinforcement was investigated experimentally by testing six full size circular concrete columns encased in either 550 mm or 700 mm diameter tires. Columns were tested under constant axial compression and incrementally increasing lateral deformation reversals. The results indicate that reinforced concrete columns, cast in steel-belted radial tires perform favorably well into the inelastic range of deformations, exhibiting drift capacities of 4% to 8%, providing superior concrete confinement. The results also indicate that the concrete between the longitudinal reinforcement and tires are able to restrain the compression bars against buckling. The results further indicate that column flexural capacity can be computed through conventional plane-section analysis when appropriate concrete models are incorporated, accounting for concrete confinement and the presence of rubber sidewalls between the layers of compression concrete. Moment-curvature relationships generated by such analysis can be used to construct the variation of curvatures along the column height. The curvature variation can be used to compute force-deformation relationships under monotonically increasing loads. These relationships are shown to provide very good agreement with experimentally recorded hysteretic relationships, further verifying the applicability of conventional techniques to tire-confined columns.;The experimental results provided invaluable information on the contribution of steel-belted radial tries to shear resistance while also providing knowledge on shear capacity of concrete enchased in tires. It is shown that the General Design Method for shear, specified in CSA A23.3-2004, can be employed to compute column shear capacity with a limit of 0.4% on transverse steel strains in tire rubber. A design approach is developed for reinforced concrete columns transversely reinforced with steel-belted tires. Design for flexure and shear under earthquake loads are illustrated.;Steel-belted radial tires contain sufficiently high percentage of high-grade embedded steel that can be effective in confining column concrete. Tires can be assembled on top of each other, clamped by longitudinal reinforcement inserted through their sidewalls, and function as stay-in-place formwork. The same assembly can confine the compression concrete and provide shear resistance while also protecting the column against corrosion and chemical attacks. They also provide energy absorption under impact loads.