ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306855
The State Highway (SH)58 Ramp A Bridge in Golden, Colo., features a state-of-the-art design using curved precast concrete bridge girders to overcome serious challenges that arise when creating complex interchange projects. This latest project, the fifth of six projects to date to use this technique in the state, demonstrates the benefits of this approach to construct cost- effective, complex, long-span structures i n h i g h - p r o f i l e l o c a t i o n s w h e r e aesthetics and urban geometrics are significant design considerations. The ramp connects eastbound I-70 traffic to westbound SH58. As originally designed by CH2M Hill, the bridge was to feature curved, precast concrete girders with unique detailing. Summit Engineering value-engineered the design to feature details and cross-sections similar to those developed for previous projects. This approach provided efficiencies to both the contractor and precaster, which helped meet the numerous construction challenges presented by the difficult urban site. The 11-span bridge crosses Clear Creek, a bike path, three traffic openings, eastbound and westbound I-70, and eastbound SH58. T h e C o l o r a d o D e p a r t m e n t o f Transportation (CDOT) has promoted precast concrete as a viable alternative to structural steel and cast-in-place concrete, which typically have been used for complex interchanges. This project shows how that effort can pay off. Many of the innovative precast concrete design details used on Ramp A were devised for earlier Colorado projects and were further developed and refined during design. The roadway consists of a 38-ft-wide deck that currently accommodates one traffic lane and two large shoulders, but was designed for three traffic lanes. Grades vary from +5.0% to -5.0% and cross slopes vary from +6.0% to -2.0% along the length of the structure. The project includes the state's longest span using constant depth, precast concrete U-girder construction. Its superstructure features two lines of spliced, post-tensioned, precast concrete girders, divided into three units. Unit 1 consists of four continuous spans (153, 205, 235, and 186 ft) that cross Clear Creek, the bike path, and eastbound and westbound I-70. Unit 2 has three spans (147.5, 205, and 186 ft) that cross eastbound SH58. Unit 3 consists of four spans (187.5, 200, 200, and 188 ft). The bridge begins in a spiral curve in Unit 1, which continues through Unit 2 and transitions in Unit 3 to a straight section at the end of the bridge. profile SH58 RAMP A FLYOVER BRIDGE / GOLDEN, COLORADO BRIDGE ENGINEER OF RECORD: Summit Engineering Group Inc., Littleton, Colo. PROJECT ENGINEER OF RECORD: CH2M Hill, Englewood, Colo. PRIME CONTRACTOR: Ames Construction Inc., Aurora, Colo. PRECASTER: EnCon Bridge Co. LLC, Denver, Colo., a PCI-certified producer POST-TENSIONING CONTRACTOR (LONGITUDINAL): VSL, Wheat Ridge, Colo. by Gregg A. Reese, Summit Engineering Group Inc. by Gregg A. Reese, Summit Engineering Group Inc. SH58 Ramp A Flyover Bridge Colorado is using curved precast concrete U-girders to create cost- effective, long-span bridges where aesthetics and urban issues are key factors The SH58 Ramp A Bridge in Golden, Colo., is the state's longest span using constant depth, precast U-girder construction. Photos: Summit Engineering Group. This approach provided efficiencies to both the contractor and precaster. 28 | ASPIRE , Spring 2010 SH587 Flyover Bridge_spr10-1.indd 28 4/30/14 11:11 AM