Shear Lag Analysis of Thin-Walled Box Girders Adopting Additional Deflection as Generalized Displacement
Publication: Journal of Engineering Mechanics
Volume 140, Issue 4
Abstract
The shear lag effect is one of the very important mechanical characteristics of thin-walled box girders and has been studied over several decades. However, the generalized displacement adopted in many papers is not very simple or clear, and the analytical procedure is somewhat complicated. In this paper, a new method for analyzing the shear lag effect in thin-walled box girders is proposed in which the additional deflection induced by the shear lag effect is adopted as a generalized displacement to describe the shear lag deformation state. Based on the generalized moment for shear lag defined in this paper, the shear lag deformation state is separated from the flexural deformation state of the corresponding elementary beam and analyzed as a fundamental deformation state. The governing differential equation and boundary condition for the additional deflection are established by applying the principle of minimum potential energy, and the initial parameter solution to the differential equation is given. A very simple and convenient formula of shear lag warping stress is proposed that has the same form as that of the bending stress of the elementary beam. A finite beam segment element with eight degrees of freedom is developed to analyze the shear lag effect in complex continuous box girders with varying depth. An example of a simply supported concrete box girder is provided in which the results obtained by the present method are compared with those by FEM, finite-strip method, and other existing analytic methods. A three-span continuous box-girder model with varying depth is also analyzed, and the calculated results are in a good agreement with the test results on the whole, which validates the analytical method and the element presented.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China (Grant Nos. 51268029 and 51068018). The present research is also supported by the Program for Changjiang Scholars and Innovative Research Team in University of the Ministry of Education of China (IRT1139).
References
Chang, S. T., and Yun, D. (1988). “Shear lag effect in box girder with varying depth.” J. Struct. Eng., 2280–2292.
Chang, S. T., and Zheng, F. Z. (1987). “Negative shear lag in cantilever box girder with constant depth.” J. Struct. Eng., 20–35.
Dezi, L., and Mentrasti, L. (1985). “Nonuniform bending-stress distribution (shear lag).” J. Struct. Eng., 2675–2690.
Kuzmanovic, B. O., and Graham, H. J. (1981). “Shear lag in box girders.” J. Struct. Div., 107(9), 1701–1712.
Luo, Q. Z., and Li, Q. S. (2000). “Shear lag of thin-walled curved box girder bridges.” J. Eng. Mech., 1111–1114.
Luo, Q. Z., Li, Q. S., and Tang, J. (2002a). “Shear lag in box girder bridges.” J. Bridge Eng., 308–313.
Luo, Q. Z., Wu, Y. M., Li, Q. S., Tang, J., and Liu, G. D. (2004). “A finite segment model for shear lag analysis.” Eng. Struct., 26(14), 2113–2124.
Luo, Q. Z., Wu, Y. M., and Liu, G. D. (2003). “Shear lag of the thin-wall box girder with varying depths.” J. Chin. Railway Soc., 25(5), 81–87 (in Chinese).
Luo, Q. Z., Wu, Y. M., Tang, J., and Li, Q. S. (2002b). “Experimental studies on shear lag of box girders.” Eng. Struct., 24(4), 469–477.
Reissner, E. (1946). “Analysis of shear lag in box beams by the principle of the minimum potential energy.” Q. Appl. Math., 4(3), 268–278.
Salim, H. A., and Davalos, J. F. (2005). “Shear lag of open and closed thin-walled laminated composite beams.” J. Reinf. Plast. Compos., 24(7), 673–690.
Wu, Y. P., Liu, S. Z., Zhu, Y. L., and Lai, Y. M. (2003). “Matrix analysis of shear lag and shear deformation in thin-walled box beams.” J. Eng. Mech., 944–950.
Wu, Y. P., Zhu, Y. L., Lai, Y. M., and Pan, W. D. (2002). “Analysis of shear lag and shear deformation effects in laminated composite box beams under bending loads.” Compos. Struct., 55(2), 147–156.
Zhang, Y. H. (2012). “Improved finite-segment method for analyzing shear lag effect in thin-walled box girders.” J. Struct. Eng., 1279–1284.
Zhang, Y. H., Bai, X., and Lin, L. X. (2012a). “An improved approach for analyzing shear lag effect of box girders.” Chin. Civ. Eng. J., 45(11), 153–158 (in Chinese).
Zhang, Y. H., and Li, Q. (2009). “Flexural-torsional analysis of thin-walled curved box girders with shear lag and secondary shear deformation in restraint torsion.” Chin. Civ. Eng. J., 42(3), 93–98 (in Chinese).
Zhang, Y. H., and Lin, L. X. (2012). “A method considering shear lag effect for flexural-torsional analysis of skewly supported continuous box girder.” Eng. Mech., 29(2), 94–100 (in Chinese).
Zhang, Y. H., Su, Y. D., and Lin, L. X. (2012b). “Finite beam element analysis on shear lag effect of skewly supported continuous box girder.” J. Chin. Railway Soc., 34(10), 85–90 (in Chinese).
Zhang, Y. H., Wang, L. L., and Li, Q. (2010). “One-dimensional finite element method and its application for the analysis of shear lag effect in box girders.” Chin. Civ. Eng. J., 43(8), 44–50 (in Chinese).
Zhou, S. J. (2008). “Shear lag analysis of box girders.” Eng. Mech., 25(2), 204–208 (in Chinese).
Zhou, S. J. (2010). “Finite beam element considering shear-lag effect in box girder.” J. Eng. Mech., 1115–1122.
Zou, B., Chen, A., Davalos, J. F., and Salim, H. A. (2011). “Evaluation of effective flange width by shear lag model for orthotropic FRP bridge decks.” Compos. Struct., 93(2), 474–482.
Information & Authors
Information
Published In
Journal of Engineering Mechanics
Volume 140 • Issue 4 • April 2014
Copyright
© 2014 American Society of Civil Engineers.
History
Received: Jan 30, 2013
Accepted: Sep 3, 2013
Published online: Sep 5, 2013
Published in print: Apr 1, 2014
Discussion open until: Jun 6, 2014
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.