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A platform for research: civil engineering, architecture and urbanism
Through-girder bridges consist of two parallel I-section plate girders connected near their soffits by a steel or concrete deck. These bridges are attractive when height limitations prohibit the use of a deck supported on steel girders placed below the deck. Unlike the more conventional bridge, the top flanges of the girders of a through-girder bridge are subjected to regions of compression. Because the top flanges are restrained only by the stiffness of the webs, the buckling mode is necessarily lateral-distortional. Such lateral-distortional buckling cannot be predicted accurately by routine lateral-torsional buckling solutions, and recourse is generally made to the so-called 'U-frame' approach. An efficient element method of analysis that is capable of analysing the elastic lateral-distortional buckling of through-girder bridges has been described. The method may include the presence of web stiffeners. A particular girder was analysed, and it was shown that the predictions of lateral-torsional buckling, presented in detail in building standards, do not enable the buckling load to be calculated with any accuracy. Moreover, recourse to the U-frame method deployed in bridge design can also lead to inaccuracies in determining the elastic buckling load. When the buckling twist restraint afforded by the deck is negligible, web stiffeners positioned within the span of a through-girder have little effect on the buckling load. However, web stiffeners provided at the other extreme when the deck restrains the tension flange against lateral deflection and twist may have a significant effect on the buckling of through-girders. The position of the web stiffeners can be ascertained through an examination of the buckling mode of the unstiffened girder, and, not surprisingly, their effect in delaying the onset of buckling is greatest when placed at positions of maximum buckling displacement in the unstiffened girder.
Through-girder bridges consist of two parallel I-section plate girders connected near their soffits by a steel or concrete deck. These bridges are attractive when height limitations prohibit the use of a deck supported on steel girders placed below the deck. Unlike the more conventional bridge, the top flanges of the girders of a through-girder bridge are subjected to regions of compression. Because the top flanges are restrained only by the stiffness of the webs, the buckling mode is necessarily lateral-distortional. Such lateral-distortional buckling cannot be predicted accurately by routine lateral-torsional buckling solutions, and recourse is generally made to the so-called 'U-frame' approach. An efficient element method of analysis that is capable of analysing the elastic lateral-distortional buckling of through-girder bridges has been described. The method may include the presence of web stiffeners. A particular girder was analysed, and it was shown that the predictions of lateral-torsional buckling, presented in detail in building standards, do not enable the buckling load to be calculated with any accuracy. Moreover, recourse to the U-frame method deployed in bridge design can also lead to inaccuracies in determining the elastic buckling load. When the buckling twist restraint afforded by the deck is negligible, web stiffeners positioned within the span of a through-girder have little effect on the buckling load. However, web stiffeners provided at the other extreme when the deck restrains the tension flange against lateral deflection and twist may have a significant effect on the buckling of through-girders. The position of the web stiffeners can be ascertained through an examination of the buckling mode of the unstiffened girder, and, not surprisingly, their effect in delaying the onset of buckling is greatest when placed at positions of maximum buckling displacement in the unstiffened girder.
Stability of through-girder bridges
Stabilität von Stahlbrücken mit durchgehenden Stahlträgern
Bradford, M.A. (author)
1996
8 Seiten, 4 Bilder, 7 Quellen
Conference paper
English
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