A New Type Of Mild Steel Damper And Its Application In Structural Control

Earthquake is one of the most serious disasters that threaten the lives and fortunes of human beings. Energy dissipation technology is one of the new methods for earthquake resistant design of structures. Hysteretic energy dissipators possess easy-to-get materials, cheap cost and good endurance. The main objective of the thesis is to study the effectiveness of hysteretic dissipators, especially the new type of mild steel damper (MSD) developed by IEM.Main efforts has been done as follows:1. The state-of-the-art and practice in structural control is comprehensively reviewed and the principle of energy dissipation system is presented.2. The mechanism of the MSD is discussed. It is pointed out that they can add both stiffness and damping to the main structure. In order to investigate the hysteretic and fatigue behavior of the damper, several dampers with different dimensions and materials are tested through quasi-static tests. According to the testing data, the hysteretic model (Bi-linear model) is set up and the formula of characteristic parameters are presented. The fatigue model parameters are determined based, on the low cycle fatigue test of the MSD and the achievements of past study. This will provide the base for the design of MSD.3. Based on the hysteretic model of the MSD set up in the second part, the seismic response analysis program for the system incorporating MSD is compiled by employing Wilson-@ method and story drift model.4. This part is parameter studies of the energy dissipation system of both single-degree-of-freedom system and multi-degree-of-freedom system using the program developed in this thesis. The influence of ratio of MSD's initial stiffness to structural story stiffness without the device in place, ratio of yield displacement of MSD to that of structural story, the degradation coefficient of stiffness and the arrangement of the MSD in the main structure, on the suppressive effectiveness of structural vibration are analyzed based on the numerical simulation. Then the suitable range of parameters of bilinear hysteretic energy dissipators is presented.5. This part is case studies. According to the hysteretic model of the MSD and the conclusions of parameter studies, two structures including one 6-story RC frame structure, one 10-story steel frame structure is analyzed. The suppressive effectiveness of structural vibration under several strong ground motions is analyzed respectively according to the numerical simulation. A 3-story one-bay steel model structure is presented and its earthquake response with and without dampers is analyzed. The dynamic characteristics and the numerical simulation of the seismic performance of the model structure set a reference for the design of shaking table test6. It is also pointed out that through optimal design of the parameters of the MSD, different control objects can be achieved.7. In the conclusion and prospect, the main achievements of this thesis are summed up and the direction of further study is pointed out.