The Shear Strength Of Tapered Web Panels Of Steel Plate I-Girders | Posted on:2011-06-01 | Degree:Doctor | Type:Dissertation | Country:China | Candidate:Y Jin | Full Text:PDF | GTID:1102360305462655 | Subject:Structural engineering | Abstract/Summary: | PDF Full Text Request | It is well known that the structural behaviour of web plates subjected to an increasing shear load up to failure may be divided to three phases, the pre-buckling, post-buckling stages and collapse. Extensive studies on the post-buckling behaviour of web panels of prismatic plate girders have revealed that the increment of shear strength after web buckling is considerable. Unfortunately, the theoretical and experimental investigation into the behaviour of tapered plate girders under shear is very limited and the practical formula has not yet been developed to predict the ultimate shear resistance of tapered web plate. In this paper, the finite element analysis and experimental study are conducted to estimate the ultimate shear strength of tapered web panels. Based on this study, a modified formula for the shear strength of prismatic girder web plates is presented, amd a simple and practical method is proposed to evaluate the ultimate shear resistance of tapered web panels.Elastic buckling of plates under linearly distributed stresses is investigated using the finite element method. A brief review on various formulas for the buckling coefficients of simply supported plates from different codes is presented firstly. Then the formulas for the plates with two unloaded edges fixed are proposed by changing the boundary conditions of two unloaded edges. The difference between the restraint by the flanges and the traditional rotational restraint is pointed out. A simple and accurate formula for the buckling coefficients of the web plates restrained by flanges is presented by introducing the ratio of flange's free torsional stiffness to the bending stiffness of the web as a parameter representing the restraint from the flanges. A series of finite element analyses of web plates subjected to combined bending and shear stresses are carried out to validate the applicability of the traditional interaction formula for the buckling of plates under bending and shear.The elastic buckling of tapered web plate under pure shear is studied with the finite element analysis using the rectangular plate model with inclined stiffeners. Based on the formulas of the shear buckling coefficient for rectangular plate, this paper derives formulas of the shear buckling coefficient for tapered web plates. Two boundary conditions are considered:simply supported condition for four edges, and simply supported condition for two opposite edges and fixed condition for the others, by introducing the parameters accounting for the influence of tapering ratio. The results of the proposed formulas are compared with those from the finite element analysis. Taking the ratio of free torsional rigidity of the flanges to bending rigidity of the web as a non-dimensional parameter, the formula of the shear buckling coefficient for tapered web plates is obtained, which could consider elastic restraint provided by the flanges.A detailed review is presented on several existing methods for assessing the failure shear load of tapered web plates. It is found that the solution by Davies has relatively better accuracy than the other analytical models. Employing the elastic shear buckling coefficient of tapered web panels proposed in this thesis in calculating the critical shear buckling stress, the performance of the existing methods is obviously improved.In this study,10 tapered plate girders subjected to vertical load in mid-span are tested to investigate the shear behaviour of tapered web panels. The main objective of the present experimental study is to investigate the effects of aspect ratio, tapering ratio and relative flange rigidity on the shear strength of tapered web plates. A finite element (FE) modeling using thin shell elements of ANSYS is carried out to predict the ultimate shear strength of tapered web panels in plate girders. Very good agreements are found between the results employing this FE modeling and the test results, which confirms the validity of the FE modeling for the further theoretical research.The procedure for obtaining the ultimate shear load by traditional tension field theories is too complicated for use in practice. An interesting phenomenon is observed in the experiments that the tension band instantaneously formed as long as the applied load reached the ultimate shear load of tapered girder, which is inconsistent with the traditional tension field theories. Based on a parametric study using the proposed FE modeling, a new design method is proposed for the ultimate shear strengths of tapered web panels by accounting for the resistance contribution from the web and from the flanges. This thesis present a modified formula for the ultimate shear load of prismatic web plates and a good accuracy formula for the ultimate shear resistance of tapered web panels. | Keywords/Search Tags: | web plate, buckling, web tapered girder, I-section, buckling coefficient, interaction formula, tension field, shear strength | PDF Full Text Request | Related items |
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