Practice of Restoring Damaged Historical Truss Bridge

Abstract

Keysville Road Bridge is an 1880 wrought-iron truss bridge listed on the U.S. National Register. The bridge is across Tom's Creek, located in Frederick County, Maryland. This 31.4-m-(103 ft)-long structure has an overall width of 4.57 m (15 ft 0 in.) c/c of the trusses and 3.66 m (12 ft 0 in.) clear roadway between timber curbs. The trusses are wrought-iron Warren trusses with eight panels spaced about equally. This historical bridge was damaged by the previous year's flooding. During the flood, the bridge, which was then covered with canvas for painting, was uprooted by the high water and displaced several yards downstream. The bridge was recently rehabilitated and repainted. Several bent and damaged truss members, including all of the deck, were restored. All the replaced truss members are A36 steel and the deck panels are treated glue-laminated woods. Some of the truss members were recovered from damage and the integrity of the whole truss structure was the concern of the county officials. A field test by using strain gauges was conducted by the Bridge Engineering Software and Technology (BEST) Center, Department of Civil Engineering, University of Maryland. While the bridge was undergoing testing, rehabilitation was nearly completed except for the railing. The complete test was done and with the load-proofing the bridge was opened to traffic.