Structural Seismic Energy Response Analysis And Its Application Research On Super-high Mega-frame Structure

The current seismic analysis and design of structure based on strength and displacement can not consider the cumulative damage caused by strong earthquake impact, while energy analysis method can overcome this shortcoming, and it is a seismic analysis method with the great research and application value. Although this method has received a lot of research and advancement since its proposal in 1950s, there are still many problems to be solved. On the way of proposition on energy-based seismic design method, much research should be concerned on energy characteristic of earthquake acceleration record, structural seismic energy response and its relation to structural damage. In this paper, with the support of National Natural Science Foundation major research project "super high-rise mega-frame structure and energy of seismic response analysis of research", studies were carried out with the main line of seismic energy, research aspects including structural seismic energy response characteristics and distribution of seismic energy, relationship between structural component's hysteretic energy and its damage extent, and especially on seismic energy distribution on regular multi-or-high-rise RC structures. A 201m super-high reinforced concrete mega-frame structure was designed based on current domestic seismic design codes. Seismic energy response method was applied on it to study its seismic energy distribution, damage development and distribution. The following conclusions and research results can be reached.(1) It was proposed to study structural seismic energy response based on component-based energy response. Component-based energy response unbalanced character was proposed, and structural component was classified into 3 types of energy dissipation, energy transferring and energy absorbing. These definitions were realized on a shear-layered model, and statistic analysis on the unbalanced energy response primarily confirmed the existence of component's energy related characteristics.(2) For a structure in elastic state, some research was carried out. The seismic modal energy response spectrum method was fully proposed, and structural floor (or component) energy response can be calculated with the given uncoupled modal energy response method under some reasonable simplification, thus an expression for structural seismic energy distribution was given.(3) Methods were given related to equivalent skeleton curve formation from hysteretic data of structural test. It is conceived to code hysteretic procedures with a method called'moving skeleton curve', during which problem of turning point determination was effectively solved. This coding method can treat three major characteristics of stiffness degradation, strength reduction and slip characteristics, and it was proven to be effective.(4) For evaluation of energy extent of earthquake input record, effective energy-release related indices were defined and evaluated. A structural generalized damage index was conceived which can take full account of the importance of a structural component, and a damage distribution evaluation index was initially given. Much research was carried out on structural component's hysteretic energy response with some general laws were discovered, and method to achieve the plastic energy part from hysteretic energy was conceived.(5) It was suggested to evaluate structural seismic energy distribution from component type to type. For beam's seismic energy distribution in a moment-resisting RC frame structure, a parabolic distribution was proposed, and for multi-level or high-rise structures seismic energy distribution of frame-column or shear-wall was not sound (even unacceptable) as centralization of seismic energy happened in the bottom of the structure. It was suggested to improve seismic energy and damage distribution in way of coordination on the contradiction pair of structural component's energy dissipation and energy transferring.(6) Based on current domestic seismic design codes a 201m super-high reinforced concrete mega-frame structure was designed. Dynamic analysis on it shows that its dynamic response characteristics meet the design cods well, although its failure mechanism is unreasonable. It is shown that vertical distribution of interaction between primary and secondary frame has the mode of its inter-story rotation distribution, i.e., the curve of distribution of end small middle large with decrease at each mega-beam position.(7) It was proposed that, in aim of seismic energy response analysis, record selecting methods like energy spectrum fitting method for real record and spectrum-match method for the artificial ground motion record, should be used. It was an effective way to evaluate structural seismic performance using single IDA seismic analysis method based on input of artificial ground motion record from spectrum-match method. Using this method, it was pointed out that the designed mega-frame structure has good seismic performance, while its energy and damage distribution are unreasonable, as damage distribution evaluation index staying very low. However, with the idea of component energy dissipation and energy transferring, constructive suggestions on the improving of seismic performance of mega-frame structure were made, among which the multi-function controlled mega-frame structural system should be the best.(8) Finite element model with micro-element for a steel mega-frame structure was established. Research on it showed that the hysteretic energy distribution was consistent with the damage distribution, as aforementioned. Similar results on energy and damage distribution were also received, which reflects that the unreasonable distribution of seismic energy and damage can be applicable widely to some extent.In summary, this paper studied general law of seismic energy response method, focused on characteristics of structural seismic energy distribution. Applying this method to a designed super-high mega-frame structure, comprehensive evaluation of the seismic performance of mega-frame structure was received and improvement measures were suggested. Results and conclusions can be referred in seismic analysis and design using energy response method.