| In this dissertation, experimental researches and theoretical analyses on the new multi-cantilever prestressed composite beams with corrugated steel webs and steel-concrete composite castellated beam, including the shrinkage and creep effect of composite cantilever beam, the load distribution pattern among cantilever beam and the stability behavior of flanges in composite cantilever beam with corrugated webs, the stress and flexibility computation of composite castellated beam, the elastic buckling of perforated web under shear, the shear strength of perforated web, the ultimate bearing capacity of composite castellated beam, were made. The main contents of this dissertation are described as following:(1) A static test has been conducted on two large-scale specimens of composite cantilever beam and steel-concrete composite castellated beam, respectively. The load distribution pattern among cantilever beam and the ultimate bearing capacity of composite cantilever beam, the stress and flexibility distribution patterns, the ultimate bearing capacity of composite castellated beam, were studied. The test results can be referenced by design of the two new composite structures.(2) The reduced calculation formulas of section stress induced by creep and shrinkage effect for pre-stressed cantilever composite beam with corrugated steel webs are proposed. The investigation validate that compared with general composite beam, the loss of prestressing induced by creep and shrinkage effect in concrete slab of pre-stressed cantilever composite beam with corrugated steel webs is greatly reduced. The multi-cantilever prestressed composite beams with corrugated steel webs have good prestressing efficiency.(3) Based on the existing theory of lateral load distribution patterns, modified elastic supported continuous beam method and modified rigid-joint girder method are proposed with considering the structure characteristic of multi-cantilever prestressed composite beams with corrugated steel webs. The validity of theoretical analysis is demonstrated by comparing with experimental study and spatial finite element analysis.(4) The stability behavior of flanges in composite cantilever beam with corrugated webs is studied by adopting finite element method. Considering the influence of profile parameter of corrugated web to elastic buckling stress, the flakiness ratio limit of compression flange is proposed. Analysis on ultimate load resistance of flange are carried out, the influence of initial geometrical imperfections on ultimate load resistance of flange is also discussed. Moreover, according to the model test, the deformation performance, failure modes, load capacity and limit states of two-type composite cantilever beams are analyzed.(5) Based on vierendeel truss theory, reduced calculation formulas of stress for steel-concrete composite castellated beam are deduced. Test results shows the formulas can predict accurately the value and position of critical stress on the edge of web hole, the formulas is applicable to analyze the strength of composite castellated beam in elastic stage. Also, the calculation formulas of deflection for steel-concrete composite castellated beam are proposed based on vierendeel truss theory, it is found that this method can satisfy engineering requirements by comparing theoretical results with both experimental and FEM ones.(6) On the basis of investigation on elastic buckling of plate girder web panels under shear, the elastic buckling behavior of perforated web under shear in different boundary condition is analyzed with finite element software. Based on the formulas of the shear buckling coefficient for plate girder web panels, formulas are suggested to evaluate the elastic buckling coefficients of the perforated web are proposed, by introducing the parameters which consider the influence of radius-height ratio and width-height ratio. The elastic restraints to perforated web provided by the flanges are taken into account in this study. Besides, using universal finite element program the spatial finite element model of perforated web is established, detailed analysis on shear strength of perforated web are carried out with consideration of material and geometrical nonlinear. Also, the influence of flange rigidity, initial geometrical imperfections and residual stress on shear strength of perforated web is discussed, some useful conclusions are reached.(7) The ultimate bearing capacity of steel-concrete composite castellated beam is studied by theoretical analysis, spatial finite element analysis and experimental research. The calculation formulas of ultimate bearing capacity for steel-concrete composite castellated beam are proposed. Moreover, according to the characteristics of composite castellated beam, the spatial finite element model is built with suitable elements and material constitutive laws, nonlinear finite element analysis on ultimate bearing capacity of composite castellated beam are done. Besides, test results of ultimate bearing capacity test of composite castellated beam are analyzed, the test results are consistent with the theoretical and FEM results. |
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