Model test of double-deck steel truss bridge with arched stiffening chord

Abstract

This study investigated the mechanical performance of double-layer steel truss bridges with arched stiffening chords and their impact on the truss structure. Based on the 1412 m Xi'an Metro Line 10 bridge over the Wei River, a 1:30 scale test model of the three central spans (168 + 300 + 168 m) was established using similarity theory. A model test was conducted to investigate the overall mechanical performance of the double-layer steel truss continuous beam as well as the interaction mechanism and failure modes between the beam and the upper arched stiffening chord. The results indicated that under full-span loading, the upper arched stiffening chords increased the stiffness of the midspan by 37.9 %, effectively reducing the midspan displacement. The addition of arched stiffening chords altered the load path and transferred some forces from the truss structure through the montants at mid-span to the stiffening chords, and finally to the montants above the supports. This results in increased stress in the web members above the supports and reduced stress in the upper chords. The initial failure occurred via buckling of the web members above the supports, followed by yielding of the lower chords, ultimately leading to overall structural failure, at which point the arched stiffening chords remained in the elastic stage.