Swing Analysis Of Frame-tube Structure With Strengthened Stories Subjected To Lateral Load

Nowadays, the building heights become higher and higher because of the developments of city, high and new technology. Some times the often-used structural system defined in "Technical specification for concrete structures of tall building" cannot satisfy the needs of multi function architecture. Tall building often adopts the frame-corewall structure system, but its rigidity may be not so enough or economic to against the sidesway loads if the height is a little higher. In this situation, the strengthened story can considered to locate on it. its great rigidity makes the column at one side tensioned and the other compressed which forms a couple and equilibrates part of the overturning moment caused by external loads, thus decreases the moment carried by the core wall and the corresponding sidesway greatly. This thesis makes great efforts in study the sidesway characteristics, overall rigidity, structural parameters effects, match relations and optimization of structural members after setting strengthened story in frame-corewall structure.Firstly, the thesis introduced the action mechanism of strengthened story and the previous analytical models, basic assumptions, and adopted analysis methods. Then in order to cover the shortage of the formal theoretical model, a more reasonable and accurate model was presented. It takes the effects of floor beams and strengthened stories and the shearing action of main members into accounts. Based on researching in the structure analysis methods and the presented model, the static and dynamic analysis approaches are suggested. By simplifying the floor beams into continuous medium along the height and minimum potential energy principle, the governing equilibrium equations of top-strengthened structure under lateral distributed loads was derived as well as top overturning moment and the concentrated action. Then the analytic expression of sidesway curve of top-strengthened frame-tube structure was deduced by powerful functional and variation approach. At last, the sidesway of structure setting some outriggers can be got by the suggested static analysis approach.A simply numerical analysis showed that the influence of floor beams on the sidesway can not be ignored. So, the interesting contribution of general floor beams, outriggers and external frame columns to the entity was study qualitatively and quantitatively. In another hand, the important optical relationship of such members is also explored. Finally, some structural design methods are investigated against the unfavorable factors of earthquake resistance caused by the strengthened story, and recommendations are given on three relative stiffness indexes of this kind of structure. These values can be referenced in the preliminary design stage of the relevant structure.