In this article, a new retrofit method that the frame column is strengthened by asymmetric increased single lateral concrete section is proposed. The new added section could be ordinary reinforced concrete, bonded prestressed concrete, or unbonded prestressed concrete. The new added section could be connected with the column through anchor rebars, or prefabricated first, then be connected to the column through high strength bolts. The low cyclic reversed load experiment has been launched on understanding the seismic performance of one unretrofit specimen and six retrofitted specimens. The experiment has considered four main factors that is loading direction, material adopted on the new added section, different orders of unification of the retrofit column, and the process of prestress applying. Based on the experiment study, the characteristics including the failure mode, hysteresis loops behavior, bearing capacity, ductility, stiffness degradation, and energy dissipation ability are demonstrated. The bearing capacity calculation method of the retrofit column under compression–bending action is established. The calculation results and the experiment results show good agreement. Some suggestions for seismic design of the retrofit column are proposed. The experimental results show that the retrofitted column has good seismic performance and good retrofit effects. The research results could be references to the practical engineering design works.

In order to study the performances of high-strength concrete beams including steel fibers and large-particle recycled aggregates, four different beams have been designed, tested experimentally and simulated numerically. As varying parameters, the replacement rates of recycled coarse aggregates and CFRP (carbon fiber reinforced polymer) sheets have been considered. The failure mode of these beams, related load deflection curves, stirrup strain and shear capacity have been determined through monotonic loading tests. The simulations have been conducted using the ABAQUS finite element software. The results show that the shear failure mode of recycled concrete beams is similar to that of ordinary concrete beams. The shear carrying capacity of high-strength concrete beams including steel fibers and large-particle recycled coarse aggregates grows with an increase in the replacement rate of recycled coarse aggregates. Reinforcement with CFRP sheets can significantly improve the beam’s shear carrying capacity and overall resistance to deformation.