A Study Of Dynamic Response For Self-anchored Cable-stayed Suspension Bridge

As a new type of bridge, self-anchored cable-stayed suspension bridge has not only some advantages of traditional cable-stayed suspension bridge, but also is more adaptive to being built in deeper sea and soft soil base owing to canceling giant anchor block, so is highly competitive under bad geologic conditions and has been adopted by engineering filed so far. However, there is little research on dynamic behavior for the type of bridge from the documents that have existed. Combined the scientific research question, i.e. the study on cable-stayed suspension bridge which is scientific and technological item of Ministry of Communciation for traffic construction of west region with the engineering background of Dalian harbor across sea bridge, the dynamic characteristic and seismic response as well as buffeting response of the new structural system are investigated in this dissertation, the main research work covers the following aspects:(1) Dynamic characteristics of self-anchored cable-stayed suspension bridge mainly include natural vibration frequencies and principal modes, which are the base and precondition of dynamic response analysis for the kind of the system bridge. Dynamic characteristics of Dalian harbor across sea bridge, belonging to self-anchored cable-stayed suspension system, are analyzed and compared with those of earth-anchored cable-stayed suspension bridge with the same span and structure parameters by using spatial finite element model, some new traits of dynamic characteristics for the system bridge are summarized and the reasons are discovered. Meanwhile, the vibration-restraining measure setting intersecting inclined cable, aiming at the trait of being subjected to vibration of the main cables at main span, is proposed and finds that the reasonable setting position should match the dynamic characteristics of the structural system. As for as the example is concerned, the best setting position is not 0.25 position but 0.2875 position of main span length. Besides, effects on dynamic characters due to different restriction ways to girder, setting conditions of accessorial piers, varieties of dead load and rigidity of stiffing girder as well as stiffness of tower are studied, and the influence regulations are discussed in detail.(2) By applying highly efficient pseudo excitation method, the dissertation analyzes random seismic response of self-anchored cable-stayed suspension bridge under P. wave, SH wave and SV wave excitation and the influences on the peak values of internal forces and displacements of some factors such as multiple-support excitation and seismic spatial effect and varieties of damping ratio are considered. Subjected to multiple-support uniform and non-uniform excitation, the traits and regulations of seismic response for Dalian harbor across sea bridge are compared on basis of the equivalent power spectrum density function made by criterion response spectrum, conclusions drawn provide some valuable references for the anti-seismic design of the new type of bridge. Beside, through the comparison with the seismic response of earth-anchored cable-stayed suspension bridge, the reason that the different anchored measures of main cables lead to the differences of seismic response between two systems is revealed.(3) Based on the consideration that the nonlinear behaviors of self-anchored cable-stayed suspension bridge will become more complex due to huge axial pressure applied on beam, four groups of artificial seismic waves are utilized to study the linear and nonlinear seismic response of Dalian harbor across sea bridge under longitudinal, vertical and lateral seismic excitation, and the response time histories of internal forces and displacements of controlling section such as main beam, tower, side piers are analyzed and compared in the condition of linear and nonlinear behavior. The effect regulation is discussed in detail. Since the HPD(High Precision Direct integration) method is applied in time domain analysis, the results are more accurate. Conclusions drawn provide some valuable references for the anti-seismic design of the new type of bridge.(4) On basis of improving on the former method of time domain buffeting response analysis carried out in ANSYS software, combined the opened trait of Matrix27 element with APDL language, the dissertation obtains a particular and applied kind of method which performs time domain buffeting response analysis of long span bridge in ANSYS software. Then, effects on buffeting response of some factors such as geometrical nonlinear, lateral aerodynamic memory effect, aerodynamic admittance, initial attack angle and fluctuating wind of cables are mainly researched. The results reveal that the above factors have a considerable impact on the precision of buffeting response for the structural system. It is notable in especial that fluctuating wind of cables causes the vibration of main cables and coupling vibration with stiffing girder, which has a bigger effect on beam of self-anchored cable-stayed suspension bridge than this of general suspension bridge.