scholarly journals A Minimal GBT Model for Distortional-Twist Elastic Analysis of Box-Girder Bridges

2021 ◽  
Vol 11 (6) ◽  
pp. 2501
Author(s):  
Francesca Pancella ◽  
Angelo Luongo
Keyword(s):  
Cross Section ◽  
Closed Form Solution ◽  
Beam Theory ◽  
Form Solution ◽  
Box Girder Bridges ◽  
Torsional Mode ◽  
Box Girder ◽  
Girder Bridges ◽  
Order Of Magnitude ◽  
The Cross

A simple and efficient method is proposed for the analysis of twist of rectangular box-girder bridges, which undergo distortion of the cross section. The model is developed in the framework of the Generalized Beam Theory and oriented towards semi-analytical solutions. Accordingly, only two modes are accounted for: (i) the torsional mode, in which the box-girder behaves as a Vlasov beam under nonuniform torsion, and, (ii) a distortional mode, in which the cross section behaves as a planar frame experiencing skew-symmetric displacements. By following a variational approach, two coupled, fourth-order differential equations in the modulating amplitudes are obtained. The order of magnitude of the different terms is analyzed, and further reduced models are proposed. A sample system, taken from the literature, is considered, for which generalized displacement and stress fields are evaluated. Both a Fourier solution for the coupled problem and a closed-form solution for the uncoupled problem are carried out, and the results are compared. Finally, the model is validated against finite element analyses.

Effect of diaphragms on stress reduction in box girder bridge sections

1988 ◽  
Vol 15 (1) ◽  
pp. 127-135 ◽  
Author(s):  
A. H. Siddiqui ◽  
S. F. Ng
Keyword(s):  
Cross Section ◽  
Stress Reduction ◽  
Box Girders ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Girder Bridges ◽  
Loading Tests ◽  
The Cross ◽  
Girder Bridge ◽  
Determine Effect

The purpose of this study is to examine the effect of rigid diaphragms in reducing warping and distortion stresses developed in box girders due to deformation of the cross section. Tests were conducted for two Plexiglas box girder models to determine effect of diaphragms on the behaviour of box girder sections. The results of the tests were compared with values obtained from the so-called “beam on elastic foundation (BEF) analogy,” an analytical procedure that permits the calculation of warping and distortion stresses in box sections due to deformation of the cross section.Each box girder model was tested as a simply supported beam with a 1168.4 mm (46 in.) span. Six separate loading positions were used for each of the three predesigned diaphragm spacings. Thus, 18 separate loading tests were conducted for each model in order to obtain sufficient data to determine the amount of reduction in both warping and distortion stresses. Test measurements included the applied load, deflections, and strains at various locations on the webs and bottom flanges.The results indicate that deformation of a box girder cross section due to eccentric loading may cause substantial warping and distortion stresses, and that these stresses can be effectively controlled by judicious installation of rigid diaphragms along the span of the girder. Also, experimental warping and distortion stresses obtained from both tests compare reasonably well with those predicted by the BEF analogy. Key words: warping, torsional, stresses, deformations, box girder bridges, diaphragms.

scholarly journals Closed form solution in buckling optimization problem of twisted rod

2021 ◽  
Author(s):  
Vladimir Kobelev
Keyword(s):  
Closed Form ◽  
Cross Section ◽  
Cross Sections ◽  
Optimization Problem ◽  
Closed Form Solution ◽  
Form Solution ◽  
Optimal Shape ◽  
Actual Problem ◽  
The Cross ◽  
Simply Connected

Abstract The applications of this method for stability problems are illustrated in this manuscript. In the context of twisted rods, the counterpart for Euler’s buckling problem is Greenhill's problem, which studies the forming of a loop in an elastic bar under torsion (Greenhill, 1883). We search the optimal shape of the rod along its axis. A priori form of the cross-section remains unknown. For the solution of the actual problem the stability equations take into account all possible convex, simply connected shapes of the cross-section. Thus, we drop the assumption about the equality of principle moments of inertia for the cross-section. The cross-sections are similar geometric figures related by a homothetic transformation with respect to a homothetic center on the axis of the rod and vary along its axis. The distribution of material along the length of a twisted rod is optimized so that the rod is of the constant volume T and will support the maximal moment without spatial buckling. The cross section that delivers the maximum or the minimum for the critical eigenvalue must be determined among all convex, simply connected domains. We demonstrate at the beginning the validity of static Euler’s approach for simply supported rod (hinged), twisted by the conservative moment. The applied method for integration of the optimization criteria delivers different length and volumes of the optimal twisted rods. Instead of the seeking for the twisted rods of the fixed length and volume, we directly compare the twisted rods with the different lengths and cross-sections using the invariant factors. The solution of optimization problem for twisted rod is stated in closed form in terms of the higher transcendental functions. In the torsion stability problem, the optimal shape of cross-section is the equilateral triangle.

Numerical assessment of effective width in steel-concrete composite box girder bridges

2020 ◽  
pp. 136943322097174 ◽  
Author(s):  
Renato Silva Nicoletti ◽  
Alexandre Rossi ◽  
Alex Sander Clemente de Souza ◽  
Carlos Humberto Martins
Keyword(s):  
Cross Section ◽  
Specific Recommendation ◽  
Effective Width ◽  
Technical Standards ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Girder Bridges ◽  
Transversal Section ◽  
Numerical Assessment ◽  
Girder Bridge

The present paper aims to determine numerically in the Abaqus® software the parameters that have the greatest influence on the effective width of steel-concrete composite box girder bridges. In the technical standards and in the literature, there is no specific recommendation for calculating the effective width in steel-concrete composite box girder bridge. As an alternative, the existing recommendations for steel-concrete composite I-girders are adopted. Therefore, in the absence of standards recommendations for steel-concrete composite box girder bridges, there is a need for an investigation into the distribution of stresses at the steel-concrete interface, because if the effective width was admitted incorrectly, may result in costly or even unsafe solutions. For this purpose, the effective numerical width of 160 models of steel-concrete composite box girder bridges was determined, in which the study variables were the configuration of the transversal section, the slab height, the span length and the elements arrangement in the cross section. After analyzing the results, it was proposed a recommendation to determine effective width of steel-concrete composite box girder bridges.

Longitudinal stress over supports of concrete box-girder bridges

1981 ◽  
Vol 8 (2) ◽  
pp. 155-164 ◽  
Author(s):  
A. Ghali ◽  
M. S. Cheung ◽  
W. H. Dilger ◽  
M. Y. T. Chan
Keyword(s):  
Finite Element ◽  
Beam Theory ◽  
Type Equation ◽  
Box Girder Bridges ◽  
Element Analysis ◽  
Box Girder ◽  
Girder Bridges ◽  
Beam Type ◽  
Concrete Box Girder Bridges ◽  
Classical Beam Theory

This paper describes a study of the values of longitudinal moments/stresses and their distribution at sections over the supports of continuous box-girder bridges. A series of continuous box-girder bridges are analyzed using the finite element method. Results from the finite element analysis are compared with the classical beam theory which is commonly used in the design office for this type of bridge. It is found that the use of the classical beam theory assuming knife-edge supports usually results in an overestimation of the support moments. A modified beam-type equation for the support moments is proposed here for the design of continuous box-girder bridges.

The significance of warping torsion in the design of straight concrete box-girder bridges

1988 ◽  
Vol 15 (5) ◽  
pp. 879-889 ◽  
Author(s):  
Peter Waldron
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Design Stage ◽  
Assessment Procedure ◽  
Box Girder Bridges ◽  
Cross Sectional ◽  
Box Girder ◽  
Girder Bridges ◽  
Concrete Box Girder ◽  
Concrete Box Girder Bridges

Out-of-plane warping, resulting from torsional loading, is an important feature of box-girder bridges of thin-walled cross section. This may be of some consequence in girders where warping is restrained, since it may alter the level of stress both around the cross section and along the entire length of the beam. It is well known that some girders with very thin walls are not susceptible to warping, whereas others, with thicker walls, warp significantly when twisted. It is shown that the degree of warping is not governed by wall thickness alone; cross-sectional geometry, girder configuration, and loading must also be considered. The significance of these various factors in estimating the effects of warping restraint is assessed. In many cases this will permit the selection of box-girder cross sections at the conceptual design stage for which torsional warping effects are negligible. A simply supported concrete box girder is used as an example to demonstrate the importance of cross-sectional geometry, girder configuration, and loading in the assessment procedure. This is extended to the more general case of multi-span girders subjected to realistic patterns of loading. Key words: torsion, warping, box-girders, bridges, concrete, design.

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