Prestress Influence on Shear‐Lag Effect in Continuous Box‐Girder Bridge
Publication: Journal of Structural Engineering
Volume 118, Issue 11
Abstract
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 γ denotes actual stress due to bending under symmetrical loading over the stress computed by elementary beam theory, a compound parameter is a measure of the shear‐lag effect in this particular example, where is effective prestress force, θ is the inclined angle of tendon at support, ω is the intensity of uniformly distributed load, and L is the span length of bridge. On the and γ diagram, an asymptote exists. Usually in engineering practice is equal to or greater than unity. Based on this approach, some preliminary conclusions are presented for this study.
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References
1.
Chang, S. T., and Fang, Z. Z. (1987). “Negative shear lag in cantilever box girder with constant depth.” J. Struct. Engrg., ASCE, 113(1), 20–35.
2.
Moffatt, K. R., and Dowling, P. J. (1975). “Shear lag in steel box girder bridges.” Struct. Engrg., 53(10), 439–448.
3.
Reissner, E. (1945). “Analysis of shear lag in box beams by the principle of minimum potential energy.” Q. Appl. Math., 4(3), 268–278.
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Copyright © 1992 ASCE.
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Published online: Nov 1, 1992
Published in print: Nov 1992
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