Research On The Seismic Responses And Design Method Of Damage-Controllable Structures

Earthquake is a natural disaster which usually cause significant economic losses and societal impacts. During the last decades, scientists of seismology and earthquake engineering have developed new theories and technologies to reduce such losses, thus promoted the progress of seismic design methods. Nowadays, the Code for Seismic Design of Buildings in China employ a "three level fortification criterion, TWO stage design method’, which uses force design and displacement check to ensure the structure dose not suffer any damage during a small earthquake and does not collapse during a large earthquake. However, it does not provide a design method to address the reparability of structure after which suffer a medium earthquake.It is obvious that reparability is essential to some lifeline infrastructures like telecommunications facility, transportation system, etc. these structures required to maintain its main function or able to be repaired as quickly as possible after earthquake. However, most research indicates that traditional reinforced concrete (RC) structures are unable to achieve good reparability, thus new damage-controllable structures are proposed in this study, which referred as structures whose damage will not excessively developed during earthquake and can be restored afterwards at reasonable technical and economic conditions.This dissertation aims to study the seismic responses of damage-controllable structures. Firstly, several indices to evaluate the reparability of damage-controllable structures are proposed and an evaluation framework is established. Secondly, numerous time history analysis (THA) are carried out to study the seismic responses of single degree of freedom (SDF) and multi degree of freedom (MDF) system. The relationship between post-yield stiffness, system ductility and residual displacement are studied and a fitting equation to calculating the residual displacement is proposed. Finally, a design method which is promoted from the current’three level fortification criterion, TWO stage design method’to a newly improved’three level fortification criterion, THREE stage design method’is established. The details are as follows.The relationship between the structures’reparability and damage-controllable structure are described in this study. A generalized evaluation framework of damage controllable structures, which includes both technical and economic indices are proposed. The corresponding index limits are also provided. The technical indices provide performance evaluation and the economic index provides relationships between investment and loss, repair and reconstruction, which are useful in both pre-earthquake design and post-earthquake repair decision making process. Furthermore, an extensive literature survey, summarize, and evaluate existing implementation of damage controllable structure.Based on the proposed evaluation framework, an extensive literature survey on residual displacement are conducted. The results show that, although different results are concluded due to the differences of analysis model and methods, it is commonly recognized that post-yield stiffness is a key factor which influences the residual displacement. It is obvious that by improving post-yield stiffness even for a little bit, the residual displacement of system will drop drastically. This paper research the influence mechanism of post-yield stiffness to residual displacement. The results show that by improving post-yield stiffness, it will influence the yield pattern of system and make the yield duration of system in both sides closer, thus making the residual displacement smaller.Based on the former research, extensive THAs on both SDF and MDF systems are carried out to study their maximum inelastic displacement and residual displacements. The analysis results show that post-yield stiffness, system period and site conditions are three factors that mostly influence the residual displacement. For MDF system, the influence of P-Delta effects cannot be neglected since it will drastically increase the residual displacement. The non-linear fitting method is also used and residual displacement spectrums are proposed which can be used as a design tool.Considering that THA methods are commonly used in modern design, especially in high-rise buildings and long-span structures, also the THA results of SDF and MDF system show large discreteness, it is necessary to study the earthquake selection process of THA method. The correlations between 18 earthquake intensity indices and maximum and residual displacement are analyzed in this study. The results show that the earthquake index can be categorized into acceleration type, velocity type and displacement type. It is also concluded that maximum velocity, rather than maximum acceleration shows better results when it is considering both maximum and residual displacements.Based on the former research on the reparability and residual displacement of damage-controllable structures. This paper proposed the newly improved’three level fortification criterion, THREE stage design method’, which includes both maximum inelastic displacement and residual displacement as checking criterions. A design example is also given to prove that the new methods can be easily conducted by using the residual displacement spectrum proposed in this study. The design example also prove the importance of reparability check and it is hard for traditional RC structures to achieve good reparability.In conclusion, this paper does some innovative works include establishing the quantitative evaluating system for damage-controllable structures, discovering the influence mechanism of post-yield stiffness to residual displacement, conducting extensive research on the residual displacement and proposing related calculating spectrums, providing an earthquake input selection method for THA of both maximum and residual displacement, and finally, establishing a design methods for damage-controllable structures.