Larson Design Group (LDG) provided design and construction engineering services for the bridge rehabilitation of the 221’ long steel riveted through truss. Columbia County Bridge #42, located near the town of Mainville, serves as the main access for approximately 30 residents across Catawissa Creek. An abandoned railroad grade, updated during the bridge rehabilitation, was utilized as the detour during construction and will be maintained as a secondary access route.
The bridge rehabilitation included the design of a new floor system, strengthening of existing truss members, substructure repairs, and minor roadway improvements. The new floor system consisted of floor beams, stringers, open steel grid deck, and structure mounted guide rail. All new members were galvanized and painted to match the truss. The open steel grid deck was attached to the stringers by placing shear studs across the top flange of each stringer and pouring the area full of concrete. LDG analyzed the truss with BAR7 and included additional tension rods throughout the trusses, and low chord and diagonal tension members to meet a minimum inventory rating factor of 1.0, allowing the truss to carry legal loads.
New reinforced concrete abutment seats with backwalls and wing caps were constructed over the existing large stoned masonry abutments. Roadway widening with stop conditions at each end of the single-lane bridge were added as a safety feature for motorists.