This research focuses on evaluating the seismic properties of corrosion-damaged RC columns strengthened by bonded steel plate (BSP) and high-performance ferrocement laminate (HPFL). The mechanical properties are experimentally investigated based on various combined loading cases. A total of nine square RC columns with identical structural properties are produced, and five of them are corroded and poststrengthened with BSP and HPFL. The effects of the combined loadings, bearing capacity, failure mode, skeleton curves, hysteretic curves, ductility, stiffness degradation, energy dissipation, and plastic hinge characteristics are analyzed. In particular, a new method for calculating the skeleton curves under different failures modes is proposed and agrees well with the experimental results by comparison.

This study investigated the mechanical properties and the effects of the volume fraction for carbon fibers (CF-VF), polypropylene fibers (PPF-VF) and aramid fibers (AF-VF) with a fixed aspect ratio of 650 for the carbon fibers, 400 for the polypropylene fibers and 900 for the aramid fibers in hybrid fiber-reinforced concrete (HFRC). Furthermore, compressive, splitting tensile and flexural tensile tests were carried out to obtain the optimal total volume fraction for the three types of fibers, as well as the optimal ratio between the CF-VF, PPF-VF and AF-VF. In addition, stress–strain curves of normal concrete and HFRC were examined to explore the whole mechanical process. The results indicated the CF-VF, PPF-VF and AF-VF have a significant effect on the tensile and flexural strengths of HFRC. The HFRC with a fiber additional ratio of 25:50:25 had the best hybrid effect. Moreover, a calculation method based on the compressive strength of normal concrete and HFRC and the volume fraction is proposed to calculate the strength of HFRC in engineering as a reference. Besides, a uniaxial compression constitutive mathematical model of normal concrete and HFRC is established.

After the ground motion, a large number of columns remain intact and can be retrofitted and reused. In this paper, to explore the effects of the loading scenario, predamage level and strengthening measures on the seismic performance of reinforced concrete (RC) columns, seven predamaged specimens strengthened with high-performance ferrocement laminate (HPFL) and bond steel plate (BSP) were tested. The results show that the bearing capacity, ductility, single-cycle energy dissipation and stiffness of all the predamaged specimens can be effectively restored and improved by this strengthening method for different loading cases. This strengthening method also significantly improves the shear capacity and changes the failure modes of the predamaged strengthened specimens from those of the corresponding predamaged unstrengthened specimens. The vertical eccentricity only slightly affects the seismic behavior of the specimens, while the horizontal eccentricity significantly increases the length of the failure region and reduces the seismic behavior of the specimens, considering the bearing capacity, energy dissipation capacity, and stiffness. The effects of different predamage levels are unique.