When the Stillwater Viaduct was rehabilitated in 2012, designers had to be careful to maintain the original design aesthetics, mainly because of its historical significance. A precast concrete design allowed the team to seamlessly replicate the original features of the architecturally significant bridge with a high-performance solution that will stand the test of time. The use of precast concrete was also critical to completing the project within the very limited schedule established by the owner.
Despite the massive rework and short time frame, the bridge was substantially completed in just seven months and reopened to traffic one month ahead of schedule. The use of precast concrete to create the slender beam design and interesting details resulted in a beautiful and elegant bridge that still fit the budget. Precast proves you don’t have to spend a lot of extra money to get a bridge that is attractive and will last for a very long time.
The team replaced the severely deteriorated superstructure with precast concrete stringers, pier caps, floor, and spandrel beams at the arch span, as well as fascia beams with cantilevered brackets and decorative bridge rail with spindles. The bridge deck is 8 in. (200 mm) thick cast-in-place concrete with a waterproofing membrane followed by a 3 in. (75 mm) asphalt overlay. All of the precast concrete was pigmented to match the old structure.
The existing arch rings and pier columns were also restored during construction, which included patch renovating arch ribs and pier columns, partially replacing tops of existing pier columns, crack sealing, and fiber wrapping arch ribs to improve seismic performance. In fact, to control cracking and increase the stiffness of the longer units during shipping and erection, high-strength concrete in excess of 8000 psi (55 MPa) was utilized and prestressed strands were added.