Performance of Partially Encased Composite Beams Under Static and Cyclic Bending

This paper reports an experimental study on structural performance of partially encased composite (PEC) beams under monotonic and cyclic loadings. A total of nine specimens are tested, covering various link details, beam lengths, and loading schemes. The test results show that the specimens generally fail by fracture of the beam flange accompanied by local flange buckling and damages to the links and concrete. The plastic moment capacity of the composite section is exceeded for all the test specimens. The influences of link spacing and link types on the moment capacity are limited. Compared with the case of pure bending, higher moment capacities can be achieved when the specimens are under combined bending-shear action with a moderate shear span ratio of 3.0. For the specimens with a reduced shear span ratio of 1.5, the factors affecting the peak load are more complex, involving concrete damage, local flange buckling, and shear buckling of the beam web. For stiffness, Eurocode 4 is shown to provide reasonable, but overestimated predictions for the initial stiffness of the specimens, revealing the potential different flexural behaviour between the PEC columns and PEC beams. The specimens also showed good ductility under both monotonic and cyclic loadings, and the cross section classification recommended by Eurocode 4 tends to be conservative. The specimens under cyclic loading show very good energy dissipation capacities with equivalent viscous damping up to 49%.