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Shih Toh Chang - One of the best experts on this subject based on the ideXlab platform.
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Shear Lag effect in simply supported prestressed concrete box girder
Journal of Bridge Engineering, 2004Co-Authors: Shih Toh ChangAbstract:In this paper, derivation and computed formulas are provided for the Shear Lag coefficient in a simply supported prestressed concrete box girder under dead load. In the case of prestressed tendons having parabolic configurations, formulas to compute the Shear Lag effect are also developed. The magnitude of upward loading intensity caused by prestress as well as the relationship between the height of the box girder and the sag of prestressed tendons have been fully treated. Conclusions are drawn that the Shear Lag effect caused by dead load and prestress force is equivalent to dead load acting alone, provided that the prestressed tendon is set up with a parabolic profile. Shear Lag effect caused by movable load is also analyzed according to the eccentricity of the load to the half-width ratio of the box girder. Charts were prepared to predict the Shear Lag coefficient for live load. Finally, having considered the Shear deformation of flanges, the deflection of box girders is studied for both uniformly distributed load and concentrated load. Examples are given for illustrative purpose.
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Shear Lag effect in simply supported prestressed concrete box girder
Journal of Bridge Engineering, 2004Co-Authors: Shih Toh ChangAbstract:In this paper, derivation and computed formulas are provided for the Shear Lag coefficient in a simply supported prestressed concrete box girder under dead load. In the case of prestressed tendons having parabolic configurations, formulas to compute the Shear Lag effect are also developed. The magnitude of upward loading intensity caused by prestress as well as the relationship between the height of the box girder and the sag of prestressed tendons have been fully treated. Conclusions are drawn that the Shear Lag effect caused by dead load and prestress force is equivalent to dead load acting alone, provided that the prestressed tendon is set up with a parabolic profile. Shear Lag effect caused by movable load is also analyzed according to the eccentricity of the load to the half-width ratio of the box girder. Charts were prepared to predict the Shear Lag coefficient for live load. Finally, having considered the Shear deformation of flanges, the deflection of box girders is studied for both uniformly distributed load and concentrated load. Examples are given for illustrative purpose.
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PRESTRESS INFLUENCE ON Shear-Lag EFFECT IN CONTINUOUS BOX-GIRDER BRIDGE
Journal of Structural Engineering-asce, 1992Co-Authors: Shih Toh ChangAbstract:The Shear-Lag effect in a thin-walled box girder has been recognized and introduced in the technical literature. In contrast however, a discussion of Shear-Lag effect caused by the combination of prestress force and self-weight of a box girder is limited. In this paper, the Shear-Lag effect is treated by the principle of superposition by considering that the configuration of a prestressed tendon takes the form of a broken straight line. Two equal spans of a continuous box girder of constant depth with a Shear-Lag effect are used as an illustrative example. If λ\N denotes actual stress due to bending under symmetrical loading over the stress computed by elementary beam theory, a compound parameter \IN\N\I\dy\Nθ\N/ω\N\IL\N is a measure of the Shear-Lag effect in this particular example, where \IN\N\I\dy\N is effective prestress force, θ\N is the inclined angle of tendon at support, ω\N is the intensity of uniformly distributed load, and \IL\N is the span length of bridge. On the \IN\N\I\dy\Nθ\N/ω\N\IL\N and λ\N diagram, an asymptote exists. Usually in engineering practice \IN\N\I\dy\Nθ\N/ω\N\IL\N is equal to or greater than unity. Based on this approach, some preliminary conclusions are presented for this study.
John A. Nairn - One of the best experts on this subject based on the ideXlab platform.
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on the use of planar Shear Lag methods for stress transfer analysis of multilayered composites
Mechanics of Materials, 2001Co-Authors: John A. Nairn, D A MendelsAbstract:Shear-Lag equations for analysis of stresses in a multilayered composite were derived using a series of approximations to exact two-dimensional elasticity methods. The Shear-Lag equations derived with the fewest assumptions were termed the optimal, Shear-Lag analysis for planar problems in composites. A solution method for these equations was outlined based on eigenanalysis of a matrix of Shear-Lag parameters. The optimal, Shear-Lag analysis differs from most prior Shear-Lag methods in the literature. By adding more assumptions, we could reduce the optimal analysis to two common, prior Shear-Lag methods. These prior methods were labeled as interlayer, Shear-Lag analysis and parametric, interlayer, Shear-Lag analysis. Because these two interlayer methods required more assumptions than the optimal method, they are less accurate than that method. Several examples illustrated the types of problems that can be accurately solved by Shear-Lag analysis and the differences in accuracy between the various Shear-Lag methods. The results of this paper can be used to guide the derivation of future, improved Shear-Lag models or to evaluate the quality of prior Shear-Lag models.
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on the use of Shear Lag methods for analysis of stress transfer in unidirectional composites
Mechanics of Materials, 1997Co-Authors: John A. NairnAbstract:Abstract The ‘Shear-Lag’ analysis method is frequently used for analysis of stress transfer between the fiber and the matrix in composites. The accuracy of Shear-Lag methods has not been critically assessed, in part because the assumptions have not been fully understood. This paper starts from the exact equations of elasticity for axisymmetric stress states in transversely isotropic materials and introduces the minimum assumptions required to derive the most commonly used Shear-Lag equations. These assumptions can now be checked to study the accuracy of Shear-Lag analysis on any problem. Some sample calculations were done for stress transfer from a matrix into a broken fiber. The Shear-Lag method did a reasonable job (within 20%) of predicting average axial stress in the fiber and total strain energy in the specimen provided the Shear-Lag parameter most commonly used in the literature is replaced by a new one derived from the approximate elasticity analysis. The Shear-Lag method does a much worse job of predicting Shear stresses and energy release rates. Furthermore, the Shear-Lag method does not work for low fiber volume fractions.
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a revised Shear Lag analysis of an energy model for fiber matrix debonding
Advanced Composites Letters, 1996Co-Authors: John A. Nairn, Daniel H WagnerAbstract:A Shear-Lag analysis based on energy is used to predict the amount of debonding thatoccurs when a flber fragment breaks into two fragments. The Shear-Lag analysis repro-duces all features of more sophisticated analyses. A drawback of the Shear-Lag analysis,however, is that it depends on an unknown parameter which can be expressed in termsof an
Jaturong Sanguanmanasak - One of the best experts on this subject based on the ideXlab platform.
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stress concentration and deflection of simply supported box girder including Shear Lag effect
Structural Engineering and Mechanics, 2008Co-Authors: Eiki Yamaguchi, Taweep Chaisomphob, Jaturong Sanguanmanasak, Chartree LertsimaAbstract:The Shear Lag has been studied for many years. Nevertheless, existing research gives a variety of stress concentration factors. Unlike the elementary beam theory, the application of load is not unique in reality. For example, concentrated load can be applied as point load or distributed load along the height of the web. This non-uniqueness may be a reason for the discrepancy of the stress concentration factors in the existing studies. The finite element method has been often employed for studying the effect of the Shear Lag. However, not many researches have taken into account the influence of the finite element mesh on the Shear Lag phenomenon, although stress concentration can be quite sensitive to the mesh employed in the finite element analysis. This may be another source for the discrepancy of the stress concentration factors. It also needs to be noted that much less studies seem to have been conducted for the Shear Lag effect on deflection while some design codes have formulas. The present study investigates the Shear Lag effect in a simply supported box girder by the three-dimensional finite element method using shell elements. The whole girder is modeled by shell elements, and extensive parametric study with respect to the geometry of a box girder is carried out. Not only stress concentration but also deflection is computed. The effect of the way load is applied and the dependency of finite element mesh on the Shear Lag are carefully treated. Based on the numerical results thus obtained, empirical formulas are proposed to compute stress concentration and deflection that includes the Shear Lag effect.
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deflection of simply supported box girder including effect of Shear Lag
Computers & Structures, 2005Co-Authors: Chartree Lertsima, Eiki Yamaguchi, Taweep Chaisomphob, Jaturong SanguanmanasakAbstract:The Shear Lag has been studied for many years. Nevertheless, most of the studies are related to the effect of the Shear Lag on stress distribution and very few have investigated the effect on deflection, although some design codes have formulas for the effect of the Shear Lag on deflection. In this conjunction, the present study carries out three-dimensional finite element analyses for various box girders to investigate the deflection at the mid-span. The multimesh extrapolation is employed to ensure the accuracy. The present study thus reveals the influence of the parameters that characterize the geometry of a box girder on the deflection. It is also shown that the formulas adopted in the design codes underestimate the deflection considerably. Based on the present numerical results, empirical formulas are proposed to compute the deflection magnification factors that account for the difference between the deflections due to the finite element analysis and the beam theory.
J. Tang - One of the best experts on this subject based on the ideXlab platform.
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Membrane forces acting on thin-walled box girders considering Shear Lag effect
Thin-walled Structures, 2004Co-Authors: J. Tang, Qiusheng Li, J R WuAbstract:Abstract A new method for the determination of membrane forces acting on box girder bridges considering Shear Lag effect is proposed in this paper. A box girder is divided into four thin plate elements: top plate, bottom plate, cantilever and web. Using the equilibrium conditions of the plates, the membrane force equation for each plate element is established. The analytical formulas for calculating the membrane normal, transverse and Shear forces of each plate element considering Shear Lag effect are derived. The proposed method is easy to implement in the design of thin-walled box girders considering Shear Lag effect. Through examples using the high order finite strip element method and the experiment, the results obtained by the proposed method are examined and the accuracy of the proposed method is verified. The discussions on the Shear Lag effect on the membrane forces acting on cantilever box girders are given considering the variations of span to width ratio, width to height ratio and various loading conditions.
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Shear Lag in box girder bridges
Journal of Bridge Engineering, 2002Co-Authors: Q Z Luo, J. TangAbstract:A finite-segment method for analyzing Shear-Lag effects in box girders is presented in this paper, with an assumption that the spanwise displacements of the flange plates are described by a third-power parabolic function. The governing differential equations for two generalized displacements are established according to the principle of minimum potential energy. In order to obtain the longitudinal stresses under the Shear-Lag effect, the element stiffness equations are developed based on the variational principle by taking the homogeneous solutions of the differential equations as the displacement functions of the finite segment. The effect of two major parameters on Shear Lag is investigated for cantilever and continuous box girders with varying depth under three kinds of loads. It is shown that the height ratio, in addition to the flange width to span length ratio, has a significant influence on the Shear Lag. The solutions based on the present method are compared with the results of model testing and the finite strip method. The accuracy of the present method is proved to be satisfactory.
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negative Shear Lag effect in box girders with varying depth
Journal of Structural Engineering-asce, 2001Co-Authors: Q Z Luo, J. TangAbstract:A study on negative Shear Lag effects in box girders with varying depth is performed using a modified finite segment method developed by the writers. Three types of structuressimply supported, cant...
Chartree Lertsima - One of the best experts on this subject based on the ideXlab platform.
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stress concentration and deflection of simply supported box girder including Shear Lag effect
Structural Engineering and Mechanics, 2008Co-Authors: Eiki Yamaguchi, Taweep Chaisomphob, Jaturong Sanguanmanasak, Chartree LertsimaAbstract:The Shear Lag has been studied for many years. Nevertheless, existing research gives a variety of stress concentration factors. Unlike the elementary beam theory, the application of load is not unique in reality. For example, concentrated load can be applied as point load or distributed load along the height of the web. This non-uniqueness may be a reason for the discrepancy of the stress concentration factors in the existing studies. The finite element method has been often employed for studying the effect of the Shear Lag. However, not many researches have taken into account the influence of the finite element mesh on the Shear Lag phenomenon, although stress concentration can be quite sensitive to the mesh employed in the finite element analysis. This may be another source for the discrepancy of the stress concentration factors. It also needs to be noted that much less studies seem to have been conducted for the Shear Lag effect on deflection while some design codes have formulas. The present study investigates the Shear Lag effect in a simply supported box girder by the three-dimensional finite element method using shell elements. The whole girder is modeled by shell elements, and extensive parametric study with respect to the geometry of a box girder is carried out. Not only stress concentration but also deflection is computed. The effect of the way load is applied and the dependency of finite element mesh on the Shear Lag are carefully treated. Based on the numerical results thus obtained, empirical formulas are proposed to compute stress concentration and deflection that includes the Shear Lag effect.
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deflection of simply supported box girder including effect of Shear Lag
Computers & Structures, 2005Co-Authors: Chartree Lertsima, Eiki Yamaguchi, Taweep Chaisomphob, Jaturong SanguanmanasakAbstract:The Shear Lag has been studied for many years. Nevertheless, most of the studies are related to the effect of the Shear Lag on stress distribution and very few have investigated the effect on deflection, although some design codes have formulas for the effect of the Shear Lag on deflection. In this conjunction, the present study carries out three-dimensional finite element analyses for various box girders to investigate the deflection at the mid-span. The multimesh extrapolation is employed to ensure the accuracy. The present study thus reveals the influence of the parameters that characterize the geometry of a box girder on the deflection. It is also shown that the formulas adopted in the design codes underestimate the deflection considerably. Based on the present numerical results, empirical formulas are proposed to compute the deflection magnification factors that account for the difference between the deflections due to the finite element analysis and the beam theory.
