ASPIRE Summer 08 - Aspire - The Concrete Bridge Magazine

PERSPECTIVESustainableConcrete Bridge Designby Jay Holombo, Vinh Trinh, and Maher K. Tadros, PBS&JAs with many states, California isfaced with diminishing open spaceto improve congested transportationnetworks. Therefore, most of theseimprovements involve heavily-congestedurban interchanges, where trafficdisruption is not acceptable. Efforts arefurther hampered with constructioncost increases in recent years that havelargely outpaced inflation; thus delaysin project delivery effectively diminishavailable budgets. All of this underscoresthe importance of delivering sustainableconcrete bridges both cost-effectivelyand in an accelerated schedule. Bridgeconstruction is often in the critical pathof larger transportation improvementprojects and is a significant portion ofthe overall project cost.When owner agencies and industrycollaborate, the cost benefits ofsustainable concrete bridge deliveryare maximized, as demonstrated by therecently completed widening of theState Route 22 freeway in SouthernCalifornia. Twenty-two bridges werewidened, nine bridges were replaced,and three new bridges were added in anaggressive design-build schedule. Thesebridge improvements were part of anoverall project to eliminate bottlenecks,reduce congestion, and improve safetyon a 12-mile stretch of Route 22,located in Orange County, California,extending from Valley View BoulevardFormwork is placed around precastgirders in the construction of a seismicresistantintegral connection with thecolumns. Photo: Jay Holombo, PBS&J.Completed low-profile precast concrete girder undercrossing on SR 22.Photo: Vinh Trinh, PBS&J.to its terminus at State Route 55. Thisproject added a high-occupancy vehicle(HOV) lane, auxiliary lanes, shouldersalong with ramp replacement, andinterchange reconfiguration.The $670 million project was fundedby the Orange County TransportationAuthority (OCTA), and delivered usingdesign-build, led by the Granite-Myers-Rados (GMR) joint venture. The GMRteam hired PBS&J as the lead structuralengineer in design and constructionsupport. A collaborative environmentfacilitated by innovative project deliverymethods was crucial in not only meetingthe aggressive design-build schedule butalso maximizing economy.A significant challenge on the projectwas maintaining acceptable verticalclearance of the undercrossing andseparation widening because widenedbridge structures had to match theexisting cross-slope and profile. Further,the widened structures had to matchthe structural seismic and gravityresponse characteristics of the existingcast-in-place box girder bridges thatare both continuous longitudinally andmonolithic with the substructure. Andfinally, disruptions to traffic had to beminimal during construction.14 | ASPIRE, Summer 2008