On April 16, the Susquehanna Chapter of the Association for Bridge Construction and Design (ABCD) honored Larson Design Group (LDG) as the winner of the Short Bridge category at ABCD’s annual awards ceremony.
The design was created by bridge engineers in the Lititz, PA branch of LDG for the Strasburg Railroad Company; a 4.5-mile short-line railroad located in scenic Lancaster County, PA. Strasburg is known for its meticulous portrayal of historic 20th century railroading to 325,000 sightseeing passengers each year.
Due to the scenic nature of the bridge, aesthetics were a key consideration for the LDG team. The railroad reviewed historic bridges and determined that a plain concrete surface was consistent with early century bridges and was more appropriate for this site than using formliners to create a stone appearance. Placing the date above the arch is a classic railroad bridge feature included in the plan. The headwalls and wingwalls were also recessed as an architectural feature. LDG Bridge Group Project Manager Quentin Rissler, P.E., noted, “Since the existing bridge abutments are believed to be from the Civil War era on the historic railroad, the large stones were salvaged during demolition and retained by the railroad to use on future projects.”
Historical accuracy wasn’t the only consideration for the team. According to Rissler, “This was a challenging project with a 4-month schedule. Normally, the process will last a year or longer from the start of field survey to geotechnical investigation, permit submissions, design, development of bid documents, and bidding of the project.” The construction was limited to a 15-day track outage based on Strasburg Railroad’s need to make timely freight deliveries. The project also needed to be constructed outside of the normal construction season to minimize impact on tourism. To meet these requirements, LDG developed an innovative structure composed entirely of precast concrete that could be fabricated before the track shutdown and then assembled on-site within the required time frame. Rissler says, “We partnered closely with the railroad staff, precast fabricator and contractor to ensure that the result was reasonable, cost-effective and constructible.”
The concerns of local residents were also important. The bridge crossed an Amish farm lane, so the vertical underclearance was increased by 3′ to accommodate both Amish equipment and future users. The Amish neighbors were consulted during design and included in the preconstruction meeting, which led to partnering for tree removal and developing the access road.
Rissler says, “LDG was selected for the project by Strasburg Railroad because they wanted to work with a local firm who shared their core values and was interested in working collaboratively. We listened carefully to understand the railroad’s needs and then worked as a team to develop this innovative solution that met their requirements.”
The design team will give a presentation at the ABCD technical conference in August.