Theoretical Analysis And Experimental Study On Shear-lag Effect Of Prestress Concrete Curved Box Beam

At present, the study on the shear-lag effect of curved box beam is only limited to academic discussion both at home and abroad, which is not included in Chinese design code of bridge structure,but the ignorance of the shear—lag effect may cause hidden troubles to security of bridge. Thus a systematic and theoretical analysis and experimental study on shear-lag effect of curved box beam are carried out in this dissertation,which is of great significance and engineering value.The results and innovative achievement of this study can be concluded as follows.1) The theoretical analysis and test study on the shear-lag effect of curved box beam. Based on the shell finite element theory, an 8-node flat shell element is used to set up space finite element model,and a corresponding analysis program is accomplished, by comparing with the classical cases and the test result of the two models which is based on the current design code,good consistence of theoretical calculation with experimental results is achieved, which indicated that the selection of calculation models and the deduction of calculation formulas are intact in theory, and can reflect the real stress condition of the curved box beam.2) The improvement of parameter analysis of shear-lag effect of the curved box beam and the definition of shear-lag effect coefficient. The derived shear-lag effect equation is used to analyze the shear-lag effect parameters. The result shows that the shear-lag effect of curved box beam is related with the factors of central angle of curvature, width to span ratio, aspect ratio, flakiness ratio, plate thickness to web thickness ratio and the type of loading. Like linear box beam, the influence of flange width to span ratio is obviously. By analysis, the definition of shear-lag coefficient of curved box beam is confused with twist and shear-lag effect, which will influence the tangential stress inhomogeneous distribution. Especially, it can not reflect the variation tendency of stress and the degree of inhomogeneous distribution nearby the web exactly. By improvement, the influence of tangential stress inhomogeneous distribution, which caused by twist, can be neglected, thus the shear-lag coefficient can correctly reflect the distribution condition of tangential stress , which is caused by shear inhomogeneous transfer.3) The analysis of shear-lag effect of curved box beam caused by prestressing force. Space vector theory is used to analyze the function characteristics of prestressing tendons in curved beam, an equivalent load method is developed to calculated the prestressed friction loss of space prestressing tendons and space equivalent load of prestressing tendons, etc, and then analyze the shear-lag effect of curved box beam which is caused by prestressing force in elastic stage. It is compared with the result obtained by model test, of which a consistence is obtained.4) Nonlinear analysis of prestressed curved box beam. A constitutive relation and destructive criterion are established, a software of finite element-ANSYS deployed to carry out a nonlinear analysis on prestressed concrete curved box beam, and obtain the destructive characteristics of prestressed concrete curved box beam under various kinds of test work conditions. By comparing, the theoretical analysis results are in good consistence with experimental results.