Analysis On General Working Characteristics Of Structures Based On Structural Stressing State Theory

This thesis states the status and the isuues presented in the field of structural analysis,evidences the background and significance of the theory and method for analyzing structural stressing state,and sums up the contens of the theory and method.Then,by modeling the experimental and simulative data of concrete-filled steel tubular(CFST)short columns,CFST arch structures and curved box-girder bridges using the theory and method,it reveals their common/general characteristics of structural global working behavior and structural stressing state submodes formed by different components and internal force types(1)The theory for analyzing structural stressing state is systematized by summing up the the involved concepts,theories and methods: Based on the concept of generalized strain energy density(GSED),structural stressing state is modeled by using the methods in mechanics and mathematics.According to the natural law that quantitative changes lead to qualitative changes,the Mann-Kendall(M-K)criterion in statistics is introduced to distinguish the critical load of the structures mutating from stable stressing state to the unstable one,in other words,to determine the load at the beginning of structural failure to update the definition of structural failure load.The M-K criterion is again applied to detect the other working behavior characteristics,such as,the characteristics of elasticplastic branch and structural progressive failure.The experimental data is extended by combining the corresponging numerical simulation,which will derive the formulas for predicting structural failure loads.(2)The mutation characteristics in the GSED-load curves on two types of short columns(CFST and CCFST)subjecting axial compression are detected by the M-K criterion,which verifies the effectiveness and practicability of structural stressing state theory.Meanwhile,it reveals the failure loads of short columns characterized by the qualitative change of structural stressing state modes.Finally,the formulas are formed to predict the failure loads and ultimate loads of CFST short columns through fitting the experimental and simulative data.(3)Investigation on structural stressing state of CFST arch models is launched by using experimental data.And M-K criterion is used to distinguish the mutation from structural working characteristic curves(the sum of GSED values-load curves),which reveals the structural failure loads and the characteristics of different stressing state stages of experimental arches.Then,structural stressing state modes and submodes formed by strains and displacements are used to verify the rationality of the updated failure load.Furthermore,the numerical simulation is used to analyze the influence of different configurational and material parameters on the failure loads and ultimate loads of arches.Finally,a unified formula for predicting the failure loads of CFST arches is put forward by using simulative results and verified by experimental data.(4)Investigation on structural stressing state of a 1/10 scaled large-curvature continuous steel box-girder bridge model is launched by using its experimental data.The M-K criterion is also used to distinguish the stressing state mutation from its characteristic curve(the GSED sum-load curve)to reveal the failure load and the characteristic of structural progressive failure.The yield process of the bridge model is analyzed by comparing uniaxial yield strains with the corresponding experimental strains to see its yield behaviors before and after the updated failure load as well as the failure characteristics once the structural plasticity accumulates to a certain degree during the structural elastic-plastic stage.Because the bridge model mainly withstands bending and torsional deformation,the average sectional deflections and the sectional displacement differences between the measured interior and exterior deflections are modeled as the structural stressing state submodes,which reveals the characteristic of branch distortion between the submodes.Furthermore,the concept of coordinative working performance is deepened according to the developing trend and sensitivity analysis between the stressing state submodes.Accordingly,the ratios between the GSED values is modeled to characterize the distribution modes of structural energy and to reflect the coordinative working performance among structural components.(5)Numerical shape functions are constructed with the physical features of the model.And the experimental data is expanded by the interpolation in a linear combination which is weighted by experimental data and takes the numerical shape function field as basis vectors.Then,the finite element simulative results are used as the basic state shape which is adjusted with conventional numerical shape function field;thus a new experimental data interpolation method,called as the state shape interpolation method,is established so that the interpolated experimantal data field can be closer to the real one.What's more,the state shape interpolation method is also applied to extend the measured sectional strain data to obtain the interpolated sectional strain field;in this way,the sectional axial force and bending moments can be derived from the interpolated sectional strain field based on constitutive relations of materials and numerical integration.Finally,the concept of structural failure and the corresponding working behavior characteristics are verified by investigating these numerical results according to the theory of structural stressing state.The stressing state characteristic analysis of these typical structures in their whole load-bearing processes reveals their general characteristics that the structural stressing states mutate at the critical load values.The general mutation characteristic of the structures is the embodiment of the natural law that quantitative changes lead to qualitative changes.These achievements enrich the theory and method of structural stressing state.The failure loads of different structures can be determined by employing the modeling method and characteristic discrimination criterion of structural stressing state,indicating that this thesis founds a unified judging criterion of structural failure and a preliminary method for investigating the coordinative working performance of the structure.If applying these theories and methods to structural design codes,the structural design will be more reasonable,even it may promote or contribute an advanced basis and specification for structural design.