Research On The Effects Of Construction Progress And Dynamic Behavior Of Tall Hybrid-Structures

In China, tall building hybrid structures, which are composed with steel frames and concrete core-tubes or with composite steel frames and concrete core-tubes, have been widely applied recently. It is rational to research the problems of creep and shrinkage and the seismic response of tall building hybrid structures. In this thesis, combined with the research project"Research on the behavior of the tall building hybrid structures"financed by the Natural Science Foundation of China (NSFC), the problems of creep and shrinkage and the seismic response of hybrid structure are studied. Productions obtained are as follows.1. Defects of methods available at present to determine the vertical load effects of tall building are analyzed. Taking into account the facts of construction, a more accurate method than present methods to simulate the construction process of tall building structures is presented. Corresponding FORTRAN program is made also. The analysis results of a tall frame structure and a tall hybrid structure use this method and other methods are compared, respectively.2. Based on linear creep and superposition principle, adopting creep and shrinkage formula in ACI code, a new method to calculate displacement of axial-compress reinforced concrete member under multi-grade loading is first established. In this method, based on age-adjusted effective module method, the formula to calculate steel ratio effects on member deformation is deduced.3. Based on the new method of calculating displacement of axial-compress RC member under multi-grade loading, the practical analysis method of tall building structures is first established, which can take into account the effects of construction process, creep and shrinkage. This method can fast and easily calculate the vertical displacements and different vertical displacements of tall hybrid structures. Furthermore, the effects of construction speed, surroundings humidity, member dimension, steel ratio and the fact core-tube constructed in advanced are also considered. The vertical load effects of a tall frame structure and a tall hybrid structure are analyzed use this method. Based on the calculation results, some measures are proposed from three aspects, namely material, structural design and engineering construction, to reduce the different vertical displacement of hybrid structures. 4. The higher mode effect cannot always be ignored in pushover analysis of tall building hybrid structures. Therefore, in this thethis, an improved multi-mode pushover analysis, which combines the advantage of the modal pushover analysis and the adaptive pushover analysis, has been proposed to take the higher mode effect and history of load into account. In the multi-mode pushover analysis procedure, the multiple degree-of-freedom system can approximately be decomposed into equivalent single degree-of-freedom system of multi-mode. The response of each modal pushover analysis can be attainde by using adaptive load pattern when the structure enters into nonlinear stage.5. The displacement demand of each modal pushover analysis is obtained by using the improved capacity spectra method. The seismic response of different height of tall building hybrid structures are firstly evaluated by this method.6. The tall building hybrid structure designed by myself are analyzed in many means, such as taking into accout the construction process ,the creep and shrinkage of concrete, nonlinear time history , pushover analysis procedure, and so on. The numerical results show that these methods are reliable.