Abstract: According to current codes, seismic performance tests on reinforced concrete (RC) beams considering axial constraints were conducted. The axial constraints were implemented by setting floor slabs and steel strands to consider the axial restraint imposed by floor slabs and vertical members. The specimens included 9 T-shaped beams with steel strand constraints, 3 T-shaped beams without steel strand constraints, and 3 rectangular beams without steel strand constraints. The seismic performance of the specimens was recorded and analyzed, including failure process, hysteresis characteristics, bearing capacity, axial deformation and axial force development. Compared with unrestrained rectangular beams, the axial constraints imposed by floor slabs and steel strands can increase the positive bearing capacity of beams by 46%~86% and negative bearing capacity by 8%~40%. The increase in bearing capacity is positively correlated with the degree of steel strand constraint. The axial elongation of RC beams increases with the displacement angle, and the axial elongation is more obvious in large shear span ratio beams, which are dominated by bending deformation, exhibiting cumulative effects. Axial constraints limit the axial elongation of RC beams, leading to dynamic passive axial forces in the beams. As a result, the beams are not pure bending members as assumed in general structural design, but compression-bending members subjected to dynamic axial forces, with significant changes in mechanical properties.