Mechanical Performance And Seismic Failure Control Research On High-Rise Diagrid Tube Structures

In the early 21st century, the diagrid tube was applied to the Swiss Re Tower(2004) and Hearst Tower (2006) by Norman Foster which attracted attentions ofarchitects and structural engineers all over the world. In the next few years, more andmore of this kind of high-rise structures were built, however, the seismic behaviourssuch as structure failure mode and failure control index were not clear. In order tosolve the problem of seismic theory of diagrid tube structures being far behind theengineering practice, the mechanical property, cooperative working performance ofinner and outer tubes, seismic performance, structure failure mode under rareearthquake and failure control index were studied in the thesis.(1) The mechanical properties of high-rise diagrid tube under vertical and lateralforces were reaserched, the mechanical characteristics of beams and inclined columnsof the diagrid tube were presented and the influences of the tube plane shapes weretalked about. The bending rigidity of the web was proposed and the bending rigidityof the diagrid tube module is modified. Then the formulas to calculate the top lateraldisplacement under three typical lateral forces were proposed. The sensitivityanalysis of the diagrid tube main parameters was carried out and the sensitivity orderof these parameters was given.(2) A simplified analysis method on linear elastic interaction behavior of diagridtube-core tube structures under lateral loads was presented, considering the flexuraldeflection and shear deflection of both inner and outer tubes. The analytical solutionsof structure lateral deflection and distribution of the applied lateral load betweeninner and outer tubes under typical lateral loads are obtained based on the equilibriumdifferential equations of the tubes through the continuum approach. The interactionbehaviors of tubes are summarized and the effects of grid forms are researched.Besides this, the crucial parameter to judge the optimal diagrid forms is obtainedfrom the structure lateral deflection and material usage point of view. The method toobtain the optimal inclined column angle from diagrid tube height-width aspect ratiois proposed at last.(3) The typical CFST diagrid tube-cocrete core tube structures were analyzed byModal Pushover method and elastic-plastic time history analysis method. Thestructure plastic development process and the component yield order weresummarized. The failure path and the space performance of the diagrid tube werepresented. The force distributions of diagrid and core tubes were researched and thereasons of force redistributions between them were explained by analyzing the changes of diagrid tube forces. The reason for structure lateral stiffness degradationwas discussed based on the development process of diagrid and core tube lateralstiffness. The key components of structure lateral stiffness and plastic energydissipation were achieved and the anti-seismic concepts were given.(4)Pseudo-static test of diagrid tube structure typical model was carried out,theresearch results of structure seismic perfomanc such as components plasticdevelopment process, diagrid tube faiure path and the column yield mechanism wereproved to be correct. The research results were applied to an actual project and againthe research results were proved to be correct and guided the practical applicationeffectively.(5)The main parameters that affect the structure seismic performance werediscussed and the structure failure modes were analyzed based on plastic energydistribution. At last the structure optimal failure mode uner rare earthquake wasachieved base on structure seismic conceptual design.(6)The mechanism of the diagrid tube structure was researched and the harmfulstory drift was used as structure failure control index. The method to calculate theharmful story drift was proposed and the main parameters were discussed. After thata method to get the diagrid tube lateral force degradation performance index fromdiagrid tube parameters was presented. Then the structure failure control index of thecore tube was given to reach the seismic fortification goal of"no collapsing withstrong earthquake".