The Creative Use of Precast Awards competition highlights the innovative uses and versatility of precast concrete as the world’s premier building material. Awards were submitted for projects completed in 2009, and were judged by a team of engineeering instructors and precast concrete experts. The awards were presented at the Salute to Excellence Feb. 20, 2010, in Phoenix.
1st Place Above-Ground
U.S. Concrete Precast Group – San Diego
Project: Bicycle-Pedestrian Bridge
Location: San Diego County, Calif.
Stress-Ribbon Bridge Ties Trails Together
Precast concrete played a prominent role in the building of the world’s longest stress-ribbon bridge as part of the David Kreitzer Lake Hodges Bicycle-Pedestrian Trail near San Diego. Built in an environmentally sensitive area, the three 330-foot spans of ultrathin precast concrete deck was chosen because it minimized disruption to the local ecology and blended well into the sensitive surroundings. The bridge provides a vital link to the Coast to Crest Trail, eliminates a nine-mile (15 km) detour, and furnishes a safe route for bicycle commuters who otherwise would ride on the shoulder of the busy and dangerous interstate freeway. The stress-ribbon bridge resembles a suspension bridge with cables embedded in an ultra-thin concrete deck. All together, 87 precast panels (29 in each span) were used in the deck. The deck panels were post-tensioned to ensure continuity in the spans, close the transverse joints and give the bridge its required stiffness for live loads.
Once the precast concrete panels were in place and the closure pours filled with concrete, the entire length of the bridge was post-tensioned by a second set of prestressing tendons. The completed bridge features widened decks (or belvederes) over the two intermediate pier supports on the lake, benches and informative displays of the lake.
Only six stress ribbon bridges exist in North America, with just 50 worldwide. The longest prior to the Lake Hodges Bridge is a 500-foot stress- ribbon bridge in Bulgaria.
1st Place Underground
Atlantic Precast Concrete Inc.
Project: Repaupo Creek Floodgate
Location: Greenwich & Logan Townships, Gloucester County, N.J.
Greenwich and Logan Townships, N.J., lie on the east side of the Delaware River just south of the Philadelphia International Airport. These communities have had a history of flood damage caused by the Delaware River and its tidal fluctuations since the 1700s. In 1919, a dike and floodgates were installed to protect against flooding. But the floodgate where Repaupo Creek flows into the Delaware River has been in poor condition since the middle of the 20th century.
A recent $3.6 million project using precast concrete now protects properties, even from a 100-year storm event.
Time and cost were important considerations, and so the solution was to use steel sheeting (to provide a watertight site) with precast concrete sections. Once the site was prepared, 27 precast units were installed in five working days. Once all 27 units were set, they were post-tensioned and then cross- bolted.
The project consisted of three parallel runs of box culverts. Each run contains a “flap” gate that allows water to flow to the river. As the tide or level of the river rises, the gates close, preventing the backflow of water and possible flooding in the creek.
2nd Place Above-Ground
Project: J Street Lofts
Location: City of Sacramento, Calif.
Art and Frame All in One
In a city that has made history with its earthquakes, seismic stability is one of the most important features of new construction. When City of Sacramento officials initiated revitalization of a downtown infill lot that had been vacant for 15 years, they wanted a structure that would not only withstand earthquakes but would also be an architectural gem.
The result was the design of the J Street Lofts, an eight-story, 340,000-square-foot, mixed-use project with a parking garage, street-level retail space and residential apartments.
The all-precast hybrid moment frame system has a special post-tensioned, self-righting mechanism that protects the building’s structural frame from damage in the event of an earthquake. The standard reinforcing steel and high-strength, post-tensioned cables in both the columns and beams allow more prestressing than with traditional precast.
Another key feature is its design flexibility. The double-tee floor system of the structure allows for extensive open space in the residential units, creating a loft feel that mimics a converted warehouse building.
2nd Place Underground
Garden State Precast
Project: Internal Combustion (ICE) Engine Green
Location: New Jersey
The ICE Manifold Cometh
This Green Energy Co-Op project is a collaboration of nine local New Jersey municipalities to generate electrical power from methane gas collected at the local sewage treatment plant.
Garden State Precast designed, manufactured and shipped an underground utility manifold for the project. This 55,000-pound cross-shaped manifold has a footprint of 19 by 25 feet. The manifold unit was shipped complete with stainless steel seating and multi-part aluminum covers.
Due to the showcase nature and sensitive timelines posed by the project, the contactor chose to use precast concrete construction. Various other project benefits were realized by using precast for the manifold, which was produced under controlled conditions to ensure the proper delivery date. Weather dates were reduced in the project timeline, and the staging area provided to the contractor was minimized. This reduced the overall site impact and contributed to the “green” nature of the project. The choice to use precast concrete allowed the contractor to minimize site labor at the high prevailing wage rate. The ICE manifold was installed Dec. 1, 2009, in less than 15 minutes. This compared with the contractor’s estimate of six field casting days.
3rd Place Above-Ground
Rocky Mountain Prestress
Project: CH2M HILL Campus
Flexible and Sustainable Design
When CH2M HILL, a leading international engineering firm, set out to build a new corporate headquarters, Leadership in Energy and Environmental Design (LEED) certification was a goal right from the start. CH2M HILL wanted a headquarters campus that met three important goals: environmentally sustainable design, ease and speed of construction, and flexibility for the future. The design team chose precast concrete not only for its reduced cost but also for its sustainability features, ease of installation, and the idea that structure and architectural detail can be melded into one component.
The original plan called for only two buildings, but over time the campus project developed into four structures – all of them similar in design, all of them made from precast wall systems that would serve as both structural and architectural panels.
3rd Place Underground StructureCast
Project: Mill Creek Linear Park
Location: Bakersfield, Calif.
Mill Creek Linear Park is a $13.3 million project located in Central Park in Bakersfield, Calif., along 1.5 miles of the Kern Island agricultural canal. The five-phase waterway project called for precast concrete culverts to create a recreational park with a natural creek and pedestrian corridor through the heart of downtown Bakersfield. The park was opened to the public May 29, 2009. The city’s mayor called the park one of the more outstanding community assets and enhancements for the city that has taken place in quite some time.
Mill Creek is unlike any other amenity in Bakersfield. Once a fast-moving canal in a dirt ditch, it is now a lined, natural-looking creek running through downtown Bakersfield, and links housing, commercial, entertainment and recreational venues along a safe and healthful path. The pedestrian bridge/architectural precast culverts had to be installed in less than two weeks. The canal is drained only two weeks each year for regular maintenance, and it was within those two weeks that this critical change had to occur to avoid interrupting the agricultural market that relies on the canal water to sustain crops.
The precast culvert provided ease of construction, an accomplishment that would have been impossible with a cast-in-place culvert. This precast solution also created significant cost benefits in terms of reduced installation labor.
Above-Ground: Honorable Mentions
Project: Advanced Technology Center
Location: Blue Bell, Pa.
A Step Up in Technology
The Advance Technology Center in Montgomery County Community College, Blue Bell, Pa., used nothing less than the most advanced in architecture and engineering design to match the school’s leading-edge technology in astronomy, biotechnology programs, computer design, animation, digital audio and video design, and state-of-the-art observatory and observation deck.
Viewed from outside through glass enclosures, the precast concrete stairs within the 10 stairwells seem to float in mid air around architectural walls fitted with large, round viewing ports strategically located to allow light through and to create an illusion of a wide-open area in the enclosed space.
The one precast concrete stair system supporting the observatory eliminated all vibration in the observatory and reduced traffic noise. The main landings were fabricated separately to further isolate vibration within the stairwell. Ten stairs with integral landings and 10 main landings were fabricated within three weeks.
Project: I-35W Bridge Gateway Monuments
In the center median at each end of the new I-35W bridge in Minneapolis are three individual precast waves flowing upward. Each precast wave is 1.5 feet wide, 5 feet deep and 30 feet high. The natural contour of the design blends into the bridge rather than overtly projecting its presence. The project description best explains the design: “The symbol for water, inverted on its side, simply defines the transitions of the road on land to a bridge over water – a sound pairing to the quiet design of the bridge.”
Another unique attribute of the monuments was the use of TX Active, a white photocatalytic cement. Natural sunlight activates the photocatalytic reaction within concrete made with TX Active cement. The reaction accelerates the oxidation of pollutants and prevents them from accumulating, obtaining a “self-cleaning” effect.
Underground: Honorable Mentions
Project: Sewer Treatment Plant
Location: Hammond, La.
Making Room in Small Spaces
When a construction company set out to develop a sewer treatment plant for a subdivision in Hammond, La., the firm had several major challenges to overcome, not the least of which was a very tight place in which to locate the plant. A conventional above-ground plant with steel would have cost more than precast concrete, and the steel plant didn’t have the flexibility to fit the space. Plus the above-ground plant would have been unsightly to residents.
Gainey’s Concrete Products designed thin-walled cells for an underground plant at half the price of a steel tank. The precaster also built a custom grease interceptor to fit the limited space.
Project: Forester Creek Channel Improvement Project
Location: City of Santee, Calif.
The $36 million Forester Creek Channel Improvement Project is the City of Santee’s largest capital improvement project to date, which has received multiple awards for concept and design as a pinnacle for creek restoration to improve urban water quality. The project involved the widening and realignment of the creek in order to withstand a 100-year flood level while facilitating the restoration of riparian and wetlands habitat.
The Enviroflex protection system was utilized in three areas along the channel alignment. Approximately 75,000 square feet of Enviroflex were installed within 25 days.
Project: St. Cloud Water Treatment Plant
Location: St. Cloud, Fla.
This project originally was designated for cast-in-place concrete, which called for six months of construction time. By convincing the on-site contractor that the product could be precast, the time was cut in half. In only three months, the product was designed, manufactured and installed – with total installation of the precast structure in less than one day.
Precast eliminated the waste of on-site forming and disposal of forming materials. It also eliminated cleanup, carpentry costs, painters, concrete truck traffic and multiple laborers. Overall savings exceeded $150,000.