Earthquake-Reduced Analysis Of Core-Tube Suspended Building And Design Of CFRP Cable Structure

Suspended building structure that conforms to nature laws is a new kind of system in highrise buildings. The high-strength building materials are of full use in this system. Because it can bring us a big room in the building, it is possible to relax the contradiction between usable function and structural construction. Suspended system can be propitious to resist wind loads and seismic effects and realize the unity of safety, suitability and beauty, so it is of good benefit to the society and economy. Core-tube suspension building structure control system, combining the structural control devices with the structural layout, can reduce the reaction under earthquake loads effectively, which is a new control method for the development of highrise buildings. Because of this, this paper discusses several problems about core-tube suspended building earthquake-reducibility and the application of CFRP.Firstly, design points for an analytical model for single-section hanger on core-tube are briefly listed. The frequency transfer functions of relative displacement and absolute acceleration are derived under action of harmonic and white noise ground excitation. Some parameters, such as the damping, frequency and suspended mass ratio, have an important effect on structure design. Based on the recent achievements, analytic expressions about influencing factors are given when the structure is optimized and the primary structure without the damp. numerical values are presented when the primary structure with the damp. The objective, constraints and basic measure are summarized about the design of structural parameters. Secondly,Frequency-domain and time-domain analysis methods are applied. The rules of reactions of suspended structures under the earthquake excitation have the similar features. By proper design and optimization, suspended structures can reduce the reactions remarkably. The effect is relative to the frequency and damping ratio. With the increment of the frequency ratio, the top displacement of the core firstly declines and then increases, and the relative displacement between the core and the suspended floors descend;The optimum frequency ratio must exist and leads to that the top displacement is minimum; with the increment of the damping ratio, the top displacement change a little, and a relative displacement descends.Thirdly, finite element analysis model about core-tube suspended structure is constructed. Modal analysis shows that suspended structure's modes are mainly made up of each vibration between core and suspended floors. The time history analysis shows that the top displacement of the core decreases to 55% and the base shear force of the core decreases to 65% in comparison with the uncontrolled suspended structure. The measures and steps of parameter setting are summarized, with which we can rapidly solve key parameters of the suspended structure.Finally, the suspending girder of the core-tube suspended structure is analyzed, and the methods of analysis and design are given for the suspending girder which is prestressed by CFRP cable. The design steps are illuminated by an example for the girder in elastic stage.