9520233 Roeder Composite steel and concrete infrastructures and buildings are desirable for seismic design, because they economically provide both the strength and stiffness needed to assure good performance under adverse loading conditions. However, composite action requires a shear transfer between the steel and the concrete. The transfer requirements are highly variable depending upon the location of the component in the structure. Los of this transfer through slip may result in a dramatic loss of strength and stiffness with very little energy dissipation. Shear connectors may be used to transfer shear force between elements but they are costly, and engineers are motivated to minimize their use. At present, there are no guidelines or specification provisions to help them determine the best shear connector placement in US practice. This research will provide design guidelines for establishing the most economical shear connector requirements in both encased steel (SRC) and concrete filled tube (CFT) construction, while assuring good seismic performance. This project will consist of a thorough review of existing test data to determine the shear capacity that can be developed with various CFT and SRC applications. A series of experiments will be performed to fill gaps in existing knowledge and data. Studies on creep, shrinkage and the Poisson effect represent potential problems in using bond or adhesion for the shear transfer mechanism, and experiments will be performed. The experiments will establish a more complete picture of bond stress and shear transfer capacity for both CFT and SRC applications. A range of SRC and CFT prototype structures based on the Theme Structures established for this research project will be analyzed to determine the shear transfer demand necessary to assure satisfactory seismic performance. The shear transfer capabilities will be correlated to the demand to develop design guidelines and recommendati ons. This is a project supported under the year 1 program of the Civil Infrastructure Systems (CIS), solicitation NSF 94-154. ***
