The Mechanics Analysis Of Prestressed Mega-Frame Structure During The Construction Process

With the development of high rise-building, more and more structures with new structural forms, such as structures with complex facades or structures with straggered floor, door-like structures multi-tower conneted structures etc., begin to develop, which high-rise building are developing towards the structures with higher height. The Mega-Frame structure studied in this thesis is a representative type. Although the mega-frame structures will be widely used because they accord with the demands of trends and characteristics of high-rise buildings, few research materials on their calculation theory and design methods can be seen now, especially there are no articles about construction of mega-frame. So, how can we analyze the high-rise building's reality behavior and make the results safe and economic to structure, which is the newly theme that construction mechanic of structures want to be solved. In view of the above situation, this dissertation makes systematically research on mega-frame during construction process and the results can be a useful reference to engineering design. The contents include the following key points,Firstly, this paper makes a study of the construction process of prestressed concrete mega-frame structure and presents a new method of analysis for simulating the construction process. The method is effect to reality. It can consider different construction process as well as different concrete age.Secondly, to the special type of this prestress concrete mega-frame structure, the different prestress losses were calculated during construction process because of batch pretension. By analyzing traditional method of prestress losses, this paper derives a precise long-term prestress lossess formula for evaluating the effect of the shrinkage creep considering the variation of stress, the variation of elastic modulus in different age, and the influence of reinforcement on shrinkage creep. Meanwhile, the effective prestress of beam was obviously when the lateral stiff of column was taken into account. The results indicate the prestress loses between additional method and the method in this paper considering construction process are different. It also indicated that the calculation regardless the effect of lateral stiff would induce great inaccuracy.In the aspect of studies design of mega-frame, by considering construction progress of the prestressed mega-frame structure, using example of the analysis and compare to the result of integral model, the trend of secondary moment was found, we can solve it by integral modelfor the results of two methods are similar.Finally, to find the difference of stress and strain between the two methods, the author used finite element method to simulate the construction process of the mega-frame structure though the soft ware of ANSYS. It's effective to the reality structure.