Design parameters and material-scale damage evolution of seismic upgraded RC frames by viscoelastic haunch bracing-dampers

摘要

To improve the seismic design of reinforced concrete (RC) frame structures and upgrade existing RC frame structures that have insufficient seismic design, a new suitable seismic upgraded solution, the installation of viscoelastic haunch bracing-dampers (VHBD) to increase the seismic performance of RC frames, is proposed in this paper. For a comprehensive and systematical research about this new upgraded frames system, a comparative study on the seismic performance between 15 RC frame structure specimens by adding the VHBD with different design parameters and one common RC frame structure specimen is performed under sinusoidal dynamic loading. The specific items of seismic performance mainly include hysteresis performance, load-bearing capacity, stiffness degradation, energy dissipation capacity, and additional damping ratio, and so on. First, on the basic of this, the material-scale damage evolution of structure specimens at each stage is qualitatively analyzed. Then, six reasonable material-scale damage indexes that can describe the damage evolution of the structures precisely are proposed. Finally, a quantitative comparative analysis on the material-scale damage evolution of structure specimens in the whole process is carried out under different design parameters. The research results indicate that the upgraded scheme (reasonable design parameters of lambda and theta) proposed in this study can improve the seismic performance of RC frame structures to the appropriate level required for the design, in terms of load-bearing capacity, stiffness, energy dissipation capacity, and damping ratio. At the same time, the failure mode of the structures can be well controlled. The occurred damage at beam-column joints is reasonably transferred to the beam area, which can guarantee the seismic design requirements of "strong joints and weak components."