Phil Sheridan, PE, has been working with design-build projects for 10 years at Clark Design-Build LLC. Since the earliest days, he’s used reinforced concrete in these projects, because of the variety of benefits it offers for design-build delivery systems.
“Concrete is a very adaptable product,” says Sheridan, project executive with the Bethesda, Md.-based construction services company. That adaptability is at the essence of design-build projects, which adjust and respond rapidly to new information and situations. Reinforced concrete’s flexibility was demonstrated on Sheridan’s first design-build contract, the 1998 construction of the Bath Iron Works’ Land Level Transfer Facility in Bath, Maine, a 14-acre marine pier. The project used both cast-in-place reinforced concrete and prestressed, precast concrete.
Six acres of the project had to be constructed over a tidal river, creating extremely difficult conditions. Much of the work was accomplished by optimizing the project’s specifications to allow more than 4,000 precast concrete components to be erected on the tidal portions, with cast-in-place closure pours.
“The flexibility of concrete allowed us to use both precast and cast-in-place concrete where it was most efficient,” he says. “The design-build method gave us the flexibility, and concrete was adaptable to that need while letting us keep the same design criteria. The project would have been an order of magnitude more difficult without the adaptability that concrete provided.”
Whether designing large or small buildings, or transportation projects, designers are finding the benefits supplied by reinforced concrete work well with the goals that design-build teams want to achieve. Those advantages include enhanced constructability, faster completion speed, improved economics, and sustainable design concepts.
Early Impact
Reinforced concrete is positioned perfectly in the construction schedule to have a major impact on the success of a design-build project, says Mario Garza, Jr., pre-construction manager for the Concrete Division of Barton Malow, a design and construction services firm in Oak Park, Mich. “Ninety percent of a project’s cost savings can be found in the first 10 percent of the job,” he says, quoting statistics from a speech by Tom Verti of Pankow Builders at the Spring 2008 meeting of the American Concrete Institute. “Once the structure is set, there’s not much to impact. You have to make value-engineering decisions early in the process to save the owner money.”
Design-build’s emphasis on adaptability and efficiency allows contractors to make effective use of their own expertise and talents, as well as the project’s performance needs. “We know what saves us money and what costs us money,” Garza explains. “We want to come to the table and share that information with the owner, to eliminate a lot of risk. That will help our pricing and theirs.”
On a recent design-build project, Garza’s team needed to pour an eight-foot-thick foundation, which site conditions made difficult. The crew suggested splitting the pour in two segments, allowing reinforcing steel to be added more efficiently without as much support, and placing anchor bolts more easily. The two-pour system also reduced concerns with issues of heat and hydration associated with mass concrete. “Taking our own approach greatly reduced man-hours to install the reinforcing steel and embedments,” he says. “When we can take their design and show them what we think will work better, we all benefit.”
Advanced Technology
Forming, pumping and placing technologies have evolved dramatically, making reinforced concrete even more adaptable. “What has really made the difference for concrete construction [is] the development of high-strength concrete mixes, the greatly increased efficiency of concrete pumps and placing booms, and the development of forming systems that can be erected safely and quickly, then moved to the next location,” says Stan Korista, the now-retired structural engineering director at Skidmore, Owings & Merrill LLC in Chicago.
The design firm has significant experience with extending the boundaries for reinforced concrete, most recently on the 92-story Trump International Hotel & Tower in Chicago. Although not produced as a design-build project, the setback design pushed steel-reinforced concrete technology to the edge and included a marathon 24-hour pour of 10,000-psi cast-in-place concrete for the foundation. This created a mat 65’ x 300’ requiring 500 truckloads of concrete. This presently is the largest single placement of self-consolidating concrete in North America.
“Ready-mix concrete has come a long way in the last 20 years,” adds Sheridan. “Every day, someone is pouring 15,000-psi concrete. And it can be formulated and refined to address a lot of different issues — aesthetics, durability, strength. It’s very flexible and can respond to a lot of challenges with the right engineering.”
Design-build projects can take full advantage of those efficiencies, especially leveraging the local market’s skills. “The contractor may have a traveling-form system or a launching truss for bridge girders,” Sheridan explains. “There are a lot of ways to skin the cat, and design-build systems allow us to maximize concrete’s flexibility to find the best one.”
Garza agrees. “The biggest risk and cost to owners and contractors is change orders,” he says. “We want to eliminate them. If we can hash out everything in advance, before drawings are complete, rather than doing field changes, we’re in better shape.” That requires close communication, which thrives in the design-build format, he adds. “It involves the concrete supplier working out with the contractor what will work and especially what works best in his region and what doesn’t.”
For a recent series of four industrial facilities built in Michigan, the team set up offices on the company’s fourth floor, providing space for the owner’s rep, structural engineers, its own project team and others. “Everybody worked in the same area for the duration of the project. There was no need for an RFI, we could just ask the person next door.”
Rapid Construction
Made with local materials and local labor, and with components either cast on site or at local precasting plants, reinforced concrete’s ability to speed construction schedules plays to design-build projects’ goals and cuts construction time in a number of ways. New construction methods shave construction time by using high-early-strength concrete, while advances in forming methods produce faster floor turnaround cycles.
New placing techniques minimize costs and constraints of limited site access and material staging. By enclosing the shell quickly, interior trades gain access faster, creating a domino effect that speeds every project facet.
Steel construction can require long lead times for fabrication and delivery, which can change between design and construction. Garza notes that reinforced concrete sometimes will be specified during the design-build process for structural frames because steel isn’t available on the schedule that’s planned during the bid phase. “The projects are designed using existing form systems to turn the schedule around so they aren’t waiting on steel to arrive.”
Precast concrete’s ability to begin fabrication off-site while preparation work progresses at the project site also speeds construction. Sheridan leveraged that benefit on the Washington Metropolitan Area Transit Authority Blue Line Extension projects in Largo and Landover, Md., which won DBIA’s 2005 Design-Build Excellence Award for Transportation Projects over $50 million. Clark’s designers used reinforced concrete on the project for aesthetic reasons, he notes, but it significantly cut the schedule, especially for the 600-foot-long passenger platform, which was fabricated with precast concrete components.
“While doing major site development and getting drilled shafts in, we were able to create an early-release structures package and had the precast concrete components cast concurrently,” he explains. Once the site was ready, crews erected the waiting precast components for the 20,400-square-foot platform in six weeks.
The company also used a just-in-time delivery system, eliminating storage requirements at the site. “It created a really nice system,” he says. “We took advantage of reinforced concrete’s speed and off-site production, while we overcame site challenges.” The result was that both stations opened in 27 months — when WMATA previously had never opened a station in under four years. “Being able to be innovative with the platform construction is what helped us get there.”
Speed Factors
Administrators at the Federal Energy Regulatory Commission in Washington, D.C., also recognized these benefits when they awarded the contract for their new office space. Under pressure to gain occupancy quickly into the 11-story, 900,000-square-foot building, they used a design-build system that had the building ready to open in only 22 months.
The building, which earned a Washington Building Craftsman Award for high-quality construction, features a structural reinforced concrete frame. Its shallower depth helped maximize usable space under the city’s height-restricting building code, and its fast startup time and on-site adaptability were essential to keeping the project on track, according to William F. Faschan, a partner at Leslie E. Robertson Associates, the project’s New York-based structural engineering firm.
“Mobilization and excavation started at the same time as design,” says Faschan. “Final structural drawings were issued, shop drawings were made, and concrete was cast on a rapid floor-by-floor cycle. Only with the team effort of the developer, the designers, and the builder was this schedule possible.” Specifying structural reinforced concrete cut an estimated five to six months from the schedule.
Government agencies, as well as many other building owners using design-build systems, also want to maximize the sustainable-design concepts they can incorporate. Reinforced concrete systems provide these attributes for design-build projects in an inherent way, without needing to adapt the project.
Attributes that help reinforced concrete contribute to a “green” building are focused especially in its ability to aid energy efficiency. Reinforced concrete’s inherent thermal mass absorbs heat during the day and releases it at night, reducing HVAC costs and enhancing energy efficiency. Other areas where reinforced concrete contributes to a building’s sustainable design include providing recycled and recyclable materials, reduced waste, and improved indoor air quality, and high energy efficiency.
Cost Savings
Concrete’s adaptability and speed save design-build projects significantly in budgeting, especially as the savings often can be pinpointed and confirmed early in the process, freeing money for other areas. Concrete producers can provide pricing during the bid process that usually won’t change significantly before construction starts. Sheridan, for instance, recently shifted the design for seven bridges on a $500-million highway project underway in Maryland from steel to reinforced concrete.
“With the time to market that we need and today’s commodity prices, we decided to use precast concrete AASHTO girders for the shorter-span bridges,” he says. “The economies of concrete in the forms and functions we need are much more competitive today than steel. And design-build allows us to make that decision closer to construction time. I can bid the projects with one product, and then, if the market changes from the time I bid until I’m designing it, I can change the design.”
Those budget savings are enhanced by reinforced concrete’s savings through the construction process, bringing the project online quicker to cut interim financing costs and producing revenue faster.
To make full use of reinforced concrete’s capabilities, Sheridan stresses, owners must create performance standards that allow flexibility, rather than stating prescriptive standards. “The owner must have the vision to let the industry and the local contractors decide how to provide the best economics to reach his goals. He’s got to be open to performance specifications for it to work.”
Garza agrees. “Design-build requires an open-book relationship and a desire to share cost data and skills. In the end, the projects will come in cheaper and on time.” The proof for his Concrete Division, he notes, is in the pudding. “We’ve had a number of clients who agree to try a design-build approach once, and then they want to keep doing it. Once they open their minds, we’ve found they typically don’t go back.”
Craig A. Shutt is a contributing editor to the Concrete Reinforcing Steel Institute. To learn more about reinforced concrete and access the organization’s design guides, research studies, and training programs, visit www.crsi.org.