Eight rectangular partially encased steel beams (R-PEB), four T-shaped partially encased steel beams (T-PEB) and eight rectangular fully encased steel beams (R-FEB) were fabricated and tested under cyclic loading to study their performance. The ductility performance of two types of beam-to-column connection, including strengthened type and weakened type, for steel shape were studied. In addition, the effect of interface force transfer devices, such as shear connector, mid-span stiffener and plastic hinge zone stiffener in developing flexural strength and ductility of the beams was also investigated. It was found that: (1) All the specimens possessed fairly high flexural ductility and were found adequate for structures in high seismic zones; (2) the plastic hinge zone stiffeners performed well to develop the flexural strength and on enhancing the ductility of specimens with strengthened beam-to-column connection. And for R-PEB with strengthened beam-to-column connection, the plastic hinge zone stiffeners have potential to replace shear connectors; (3) both strengthened and weakened beam-to-column connections can be implemented in partially and fully encased steel beam. Specimens with strengthened beam-to-column connection demonstrated higher flexural strength, ductility and energy dissipation compared to that with weakened beam-to-column connection; (4) the tapering of the flange of the weakened beam-to-column connection lead to earlier and severer concrete damage, lower flexural strength, and lower ductility to the beams.

Eight rectangular partially encased steel beams (R-PEB), four T-shaped partially encased steel beams (T-PEB) and eight rectangular fully encased steel beams (R-FEB) were fabricated and tested under cyclic loading to study their performance. The ductility performance of two types of beam-to-column connection, including strengthened type and weakened type, for steel shape were studied. In addition, the effect of interface force transfer devices, such as shear connector, mid-span stiffener and plastic hinge zone stiffener in developing flexural strength and ductility of the beams was also investigated. It was found that: (1) All the specimens possessed fairly high flexural ductility and were found adequate for structures in high seismic zones; (2) the plastic hinge zone stiffeners performed well to develop the flexural strength and on enhancing the ductility of specimens with strengthened beam-to-column connection. And for R-PEB with strengthened beam-to-column connection, the plastic hinge zone stiffeners have potential to replace shear connectors; (3) both strengthened and weakened beam-to-column connections can be implemented in partially and fully encased steel beam. Specimens with strengthened beam-to-column connection demonstrated higher flexural strength, ductility and energy dissipation compared to that with weakened beam-to-column connection; (4) the tapering of the flange of the weakened beam-to-column connection lead to earlier and severer concrete damage, lower flexural strength, and lower ductility to the beams.

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