Analytical Method to Estimate the Lateral Restraint for Unbraced Top Chords of Warren-Truss Bridges with Independent Cross-Beam Decks
[ 1 ] Instytut Inżynierii Lądowej, Wydział Inżynierii Lądowej i Transportu, Politechnika Poznańska | [ P ] pracownik
2022
artykuł naukowy
angielski
- chord buckling
- gussetless
- pony truss bridge
EN The assessment of the lateral buckling for the unbraced top chord of a truss bridge (a pony truss bridge) requires a ¯nite element analysis of a three-dimensional model of the whole structure or a method of the chord analysis based on the reliable estimation of the lateral restraint for the chord nodes. The latter alternative becomes crucial if rapid assessment is necessary. Majority of the existing analytical methods of assessment of the stability of top chords of pony truss bridges rely on the sti®ness of U-frames that consist of cross-beams and truss bracing members. The available analytical methods of setting the U-frame sti®ness seem to neglect the existence of independent cross-beam decks that, together with Warren-trusses, constitute contemporary truss bridges. Such structures are analyzed in the paper. The sti®ness of the lateral restraint provided to the truss top chord by the cross-beams, the diagonals and the bottom chord are computed. The in°uence of the cross-beams is re°ected, for the ¯rst time, as an equivalent torsional sti®ness of the truss bottom chord. The analytical method is applied against the method included in the DIN design code to the pony Warren-truss bridges of various height-tospan ratios and various arrangements of their member cross-sections. Then the Timoshenko and Gere model of a compressed bar is adapted to ¯nd the critical load for the top chords of the aforementioned truss bridges. The results are compared to those obtained from the ¯nite element method (FEM) analyses. It is concluded that the analytical method provides lower estimate for the critical load obtained from the FEM analysis provided the smallest values of cross-sectional properties, within the respective groups, are taken as representative for the computations.
30.07.2022
2250189-1 - 2250189-19
Article Number: 2250189
100
3,6