Experimental study of FRC-encased steel joist composite beams

An experimental study was conducted to investigate the behavior of fiber reinforced concrete (FRC)-encased steel joist composite beams under monotonic loading. This new and innovative composite system eliminates the need for shear connectors between the steel joists and surrounding concrete and the need for conventional longitudinal and transverse reinforcement, all of which are quite labor intensive. All connections in the system are steel-to-steel. Therefore, the system can be used with cast-in-place or precast construction. Ten beam specimens were tested, each consisting of open-web steel sections encased in concrete containing discrete steel fibers. In the test program, the important variables studied were the percentage of tensile steel reinforcement ratio, the shear span-to-depth ratio, and the configuration of steel elements. The test results are very encouraging. The two materials (structural steel and FRC) interact to provide better behavior than that of conventional reinforced concrete beams containing steel fibers. This new structural system appears promising.