STIFFENING THE MANHATTAN BRIDGE

The Manhattan Bridge is a suspension bridge located in New York City. Its lower level carries three lanes of traffic at the center of the bridge and two transit tracks on either side. Its upper level carries two lanes of traffic over each set of tracks. The loads are supported by four cables suspended over four stiffening trusses. After the bridge was opened to traffic in 1909, breaks appeared in the upper laterals. Substituted larger members also broke. The broken pieces were hazardous to the trains, which required the removal of the entire top lateral system. The breaks were attributed to torsional stresses induced by eccentric transit loads. Because it has no top laterals, the bridge has little torsional stiffness and large vertical and lateral motions occur between adjacent trusses during passage of trains, which causes many maintenance problems. Load tests for stresses and deflections were performed on the bridge, and a single-plane 50-scale model, 18 m (59 ft) long was constructed to duplicate the motions and stresses of the prototype. Schemes for stiffening the bridge-stays radiating from the tower tops to the stiffening trusses, tie cables that had small sags from anchorage to anchorage, diagonal ties between the cables and the stiffening truss, and side-span supports--were tested on the model. The side-span supports are efficient and economical in reducing deflections at the main-span center and almost eliminate deflections of the side spans. The tower stays and diagonal ties at the center of the main span are effective in reducing deflections of the main-span quarter points. /Author/

Media Info

  • Media Type: Print
  • Features: Figures;
  • Pagination: pp 14-19
  • Monograph Title: Bridge design, evaluation, and repair
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00195907
  • Record Type: Publication
  • ISBN: 0309028191
  • Files: TRIS, TRB
  • Created Date: Aug 15 1979 12:00AM