Research On Mechanical Performance And Design Parameters For Steel-concrete Mixed Beam Combined Section

As a type of hybrid structures, the steel-concrete mixed beams are systems that usingsteel-concrete combined sections contact concrete beams and steel beams with joint structuresat proper position in vertical. The steel-concrete combined sections are key parts of mixedbeams, and determine the success or failure of structural design. So that, with wider use ofhybrid structures, the problem of design on steel-concrete combined sections is becoming newfocus of research in the field of engineering. And then, the research on behavior and designparameters of combined sections has a positive significance for promoting technologicaldevelopment of hybrid structures.In this paper, relaying on the design and optimization for mixed beam combined sectionof Weihe Bridge, the mechanical performance and design parameters of steel-concrete sectionwere studied. This thesis introduced the composition, type, feature and application ofsteel-concrete combined section; explained the selecting and determining method forreasonable location and structure in the course of steel-concrete combined section overalldesign; studied on the load transmission mechanism, deformation characteristics andmechanical performance of combined section; discussed about the mechanical performanceand engineering features of various connectors; put forward some design parametersaccording to analysis on the mechanical behavior of Perfobond Leiste（PBL）connector;illustrated the overall design ideas, methods and processes on the base of real bridge designand analysis.1. Research on overall design of combined section. It pointed out that the reasonablelocation should consider about the load-carrying, cost and construction comprehensively withthe key elements evaluation method that combined qualitative evaluation with quantitativeevaluation. It also pointed out that the basic guideline of reasonable structure is the damagedoes not result in combined sections which should be in normal working condition during thestructure bearing loads. That was the first innovative point of this paper.2. Research on mechanical performance of combined section. Combined section couldtransfer internal forces, but should increase stiffness for being good for connector andreducing relative displacement; axial tensile was the adverse force condition to combinedsection, so it should be in preloading state; connectors should be symmetrical arranged, andshould be analyzed using Spatial Finite Element Method. That the analysis and conclusions on the load transmission mechanism and deformation characteristics of combined section, wasthe second innovation point of this paper.3. Research on structure characteristics, mechanical and application performance ofvarious connectors. The welding screw and Perfobond Leiste（PBL）connector had obviousadvantages comparing with other connectors, and the longitudinal prestress was a widely usedconnection measure. The joint effect of PBL connector was determined by the embedded rolebetween concrete columns and steel-plate openings, and the PBL connector should bepreferred in civil engineering for its better ability of force transferring and reliability.4. Research on design parameters of PBL connector. This thesis studied particularly themechanical performance of the PBL connector using Spatial Finite Element Method, whichanalyzed every factor’s influence on the laws of stress distribution, stress concentration anddeformation. The thesis systematically put forward design parameters of PBL connector suchas the plate thickness, holes diameter, opened location and connection length, also point outthe basic principle and key points of design optimization for connector such as “strengthenedend-part, simplified middle-part and refined corner-part”. That was the third innovation pointof this paper.5. Proposed two kinds of new PBL connectors creatively. This thesis creatively came upwith the trapezoid and U-shaped PBL connector on the basis of research on rectangle PBLconnector. The results of FEM numerical calculation indicated the obvious improvement forstructural optimization. These studies have offered reference to further development andapplication of new connectors. That was the fourth innovation point of this paper.6. Summarized design thoughts and analysis method for combined section. It clarifiedthe application of research results to the project, and illustrated the ideas, processes andmethods about overall design, structural choosing, design optimum, mechanical analysis forsteel-concrete combined section by taking Weihe Bridge as an example. The numericalcalculation results showed that the design met the requirements and the structure wasfeasible.