Study On Some Problems Of Prestressed Mega-frame-tube With Suspended Damper Control Structural System

In this paper, based on concepts of the structure control theory and the behavior of prestressed concrete system, mega-frame-tube structural system, suspended system and tube structural system, a new structural system composed of prestressed mega-frame-tube suspended damper control structure is presented. At first, the working behavior of this structural system is analyzed in terms of concepts, possible placing styles of steel bars in beams and columns of mega-frame structure are studied and some key problems worthy of being studied of this structural system are put forward. The wind-resistant behavior and aseismic behavior of the prestressed mega-frame-tube suspended damper control structural system, the effect of structural control and concrete shrinkage creep on this system and its analyses methods, and the prestressed mega-frame connections are especially studied in this paper.In the aspect of the analysis about dynamic response and the study on structural control, the aseismic principle of the suspended structural system and its structure control methods are analysed, a control model of the system is established, the structural system is dynamicly analysed using random vibration method and dynamic time-history method. And the prestressed mega-frame-tube suspended damper control structural system has perfected a seismic performance compared with supported mega-frame system. The main factors that the control effect of the prestressed mega-frame-tube suspended damper control structural systeminclude the mass of the suspended structure, the stiffness and the connection of suspenders, the stiffness(A^) and the damping(Q) of spring damper control. The installation of spring damper in suspended floors can effectively control both the horizontal displacement of suspended floors at serviceability limit state and their too large horizontal displacement under earthquake, and it can greatly reduce the horizontal seismic force of mega-frame columns as well. The paper raise the design concepts of mega-frame-tube suspended structural system, and analyses show that the arrangement of suspended floors at 1st ~ 3rd story can greatly exhibit the a seismic behavior of suspended floors, which offers a new practical path for the prestressed mega-frame-tube suspended damper control structural system. Using Davenport wind velocity spectrum, this paper analyzes the random vibration of the structural system subjected to wind loads, and the results predict that the free suspended floors makes large standard deviation of both displacement and acceleration, which influence normal use requirement. The control methods that increasing the stiffness of dampers, can effectively control the dynamic response of suspended floors to wind vibration.In the aspect of studies the influence of shrinkage creep on the structural system and its analysis methods, based on analyzing theoretic studies on concrete shrinkage creep behavior and its calculating, construction is introduced to analyze the influence of shrinkage creep on structural system for the first time. According to the fundamental equation methods of creep mechanics and the mid-parameter method, this paper derives a formula for evaluating the effect of the shrinkage creep of arbitrary section in two-way eccentric compressed members on the redistribution of its inner force, considering the variation of stress, the variation of elastic modulus in different age, and the influence of reinforcement on shrinkage creep. Based on the property of the mega-frame-tube structural system under vertical loads, the shrinkage creep equation of mega-frame-tube suspended structural system isbrought forward, considering the effect of construction and reinforcement. Based on the property that construction and shrinkage are quite relative with time, a formula for calculating vertical deformation is proposed. The formulae presented in this paper have been applied to calculate the mega-frame-tube suspended structural system, and the results indicate that giant structural system makes great vert...