Theoretical Analysis And Model Test Study On Cable-stayed And Self-anchored Suspension Combination Bridge With Multi-Tower

With the flourishing development of traffic cause, the long-span bridge receives muchconcern, together with improvement requirements of bridge landscape, cable-stayed andself-anchored suspension combination bridge with multi-tower emerges as the times require.Recently, the lack of research results in the cable-stayed and self-anchored suspensioncombination bridge with multi-tower at home and abroad, it is necessary to systematicresearch on this type bridge.In the engineering background of the building cable-stayed and self-anchored suspensioncombination bridge with three towers, theoretical analysis method, static behavior, ultimatecarrying capacity, nonlinear of suspender anchorage zone of the bridge and the whole bridgemodel test were researched by a method combining theoretical analysis, numerical simulationand model test. The principal results are as follows:（1） Stress calculation formulas of cable-stayed and self-anchored suspensioncombination bridge under dead load were derived by minimum bending energy principle，andmethod of calculating the cable-stayed and self-anchored suspension combination bridge wasgiven by the method of deformation compatibility. The results of analytic solution agreedwith numerical solution of finite element method by taking a simplified cable-stayed andself-anchored suspension combination bridge with three towers as an example.（2）Step-by-step arithmetic for the reasonable finished dead state of the bridge wasintroduced in cable-stayed and self-anchored suspension combination bridge withmulti-tower，and finished dead of cable-stayed and self-anchored suspension combinationbridge and cable-stayed and earth anchored suspension combination bridge were determinedby step-by-step arithmetic. The girder axial force and the main cable tension of the two kindssystems had great difference by comparing analyzed under dead loads, temperature effectsand living loads. The cable-stayed and self-anchored suspension combination bridge under thelive loads whose span is160m can meet the project requirements by deflection theory. Theparameter sensitivity of the structure was analyzed by deflection theory, the results shows thatthe main girder stiffness and the cable stiffness are larger impact on the mechanical behaviorof the structure, and the variation of the main beam axial stiffness the stiffness of the vicetower and main tower are smaller impact on the mechanical behavior of the structure. （3）The ultimate carrying capacity of the bridge was calculated under different loadcases by the methods of linear elastic and elastic-plastic. And the results showed that safetyfactor of the structure under the load from vice tower to main tower was smallest, and thestructure of the actual working conditions can not be reflected by using elastic theory whenthe ultimate carrying capacity of the bridge are analyzed. Meanwhile, the impact ofconsolidation with vice tower and main beam and the material properties variation of mainbeam, vice tower and main beam on the ultimate carrying capacity of the bridge wereresearched by comparison analysis method. And the results showed that safety factor has littledifferences among pier-beams consolidation structure and pier-beam separation structure, theimpact of material properties variation of main beam was significant and the vice tower has agreater impact, but there was less impact of the girder.（4）According to comparative analysis of two anchorages zone structures about fourdiffident anchor segment lengths, the anchor structure along the bridge can be used in a widesingle-box steel girder, and the selection length of anchor segment is at least2times height ofgirder away from anchorage zone in order to response mechanical characteristics of anchorstructure. Ultimate carrying capacity of suspender anchorage zone was analyzed by means oflinear, geometric nonlinear, material nonlinear and dual nonlinear, and the results show thatthe analysis theory of material nonlinearity must be only considered when studying theultimate bearing capacity of such structural modeling using shell elements.（5）The whole bridge model test of cable-stayed and self-anchored suspensioncombination bridge was conducted to simulation force status of each component inconstruction phase. And mechanical behavior of the bridge under live loading in finishedstage was researched. The test results are agreed with the theoretical calculations results,verifying the reliability of calculation theory, and providing reference for constructionmonitoring and design of the cable-stayed and self-anchored suspension combination bridge.