Composites Offer Solution to Earth Shaking Experiences

By Lori Lovely

CEG CORRESPONDENT

From the land of earthquakes comes a new technology whose benefits can be applied worldwide. Composite Solutions Inc. (CSI), based in San Diego, CA, is marketing a fast, cost-effective process to limit the damage earthquakes or explosions cause to bridges, buildings and other structures.

Charles Lee Powell Structural Research Laboratories at University of California, San Diego (UCSD) and the federal Defense Advanced Research Projects Agency (DARPA) teamed together to develop the process, which relies on lightweight, advanced composite overlay materials wrapped around structures for protection.

Dr. Gilbert Hegemier, Ph.D., is a world-renown expert in seismic retrofitting and structural analysis, with more than 30 years’ experience in aerospace composites and 10 years in research and development of seismic retrofit technologies. He serves as CSI’s chairman and director of the research lab at UCSD, the largest and most sophisticated facility of its kind in the United States.

Hegemier has worked for years to bring the technology of the defense advance project to commercial avenues. He explained that UCSD licenses the technology to companies for both retrofitting and new construction. Not only does the university receive royalties for its technology transfer office, but any company licensing this technology also is obliged to put additional money toward research at the lab.

In addition, because of the relationship, CSI has access to tests conducted at the lab and full access to test new structural designs and materials there. “It’s important for the company to keep ahead of the game,” said Hegemier, “but it’s equally important to continue the research.”

Duane Gee, executive vice president and operations officer of CSI, said his company holds two patents from UCSD to market and apply the process. “We are the only company offering comprehensive service and accurate work,” he added. CSI offers one-stop service that includes structural analysis, retrofit design, material systems design and application, and complete project management, inspection and testing.

What It Is

The composite overlay materials consist of carbon or glass fiber-reinforced polymers — the same materials used in the space shuttle, the Stealth Fighter, armored vehicles, America’s Cup boats and racecars. Originally developed for defense applications, it’s now used predominantly in commercial enterprises.

Gee indicated that the composite industry is large and thriving, as more uses for the material develop all the time. Hegemier concurred, “The more you use it, the more uses you think of.” He added that the cost for carbon has come down in recent years, making the technology more appealing.

Hegemier speaks from experience. Working at Caltech in the aerospace field, he was using composite structures to produce rocket motor casings — using the same materials on the B-2 bomber. In the 1970s he entered a new line of research: earthquakes.

“There are two branches of research now,” he said. “The big labs were doing civil research, but in ’89 the government got interested in new markets. It proposed to move these materials out of the Defense Department and into the commercial realm. Companies like Dupont were very supportive. They were looking for new markets because they were worried about losing defense money — this was at a time when the government wasn’t putting a lot of money into defense.

“But the sports industry really saved the carbon industry,” he concluded.

Uses

Composite material can repair and strengthen a variety of materials, including reinforced concrete, reinforced and un-reinforced masonry, wood and steel. It can be applied to various structural elements, such as walls, columns, floor slabs, beams and joints. It can be used in retrofit situations, or incorporated in the design of new structures, thus reducing project time and cost.

“The material performs like a steel plate,” Gee said. “It can carry heavy loads, but it’s much simpler to apply — you just glue it.”

Applications using this technology include bridge and building repair — with emphasis on hospitals, schools and industrial facilities; aqueducts and related water supply systems; military airbases with antiquated runways; embassies and state departments; chemical and petroleum facilities subject to bombing attacks or accidental explosions; commercial and residential buildings subject to seismic and blast hazards; utilities; tunnels; anti-missile silos; piers chimneys and silos.

Hegemier added that the technology has been used in radar dishes and other space structures, to extend the life of airplanes and for various civil purposes.

CSI’s initial market focus is bridge and building repair. In California, current legislation requires hospitals to be certified as earthquake-safe by 2008, and legislation is pending for schools and other critical structures where loss of life can be extreme.

Outside California, Gee said CSI uses the composites to strengthen and upgrade existing structures to increase their load rate in order to accommodate the addition of floors or heavier service loads. The process can also repair dilapidated structures that would typically require demolition and reconstruction.

Hegemier said that because the process doesn’t change the architectural structure of buildings, it’s perfect for refurbishing historical sites. “It doesn’t add thickness or weight — in fact, it saves weight and mass. It won’t alter the look of a building,” he said.

Gee indicated the technology also is effective in the revision of AASHTO loads, benefiting bridges and parking garages that see increasing heavy truck traffic.

It’s equally effective in protecting structures from blasts and bombs. Federal buildings and embassies understand the significance of that after seeing the damage the Oklahoma City bombing wreaked in 1995.

How It Works

Hegemier indicated that the composites can be used for retrofit and repair as well as new construction. The application process varies only slightly.

“The composite fabric is saturated with resin, then wallpapered by hand to the existing structure,” Hegemier described. Trained engineers determine how many layers are necessary.

“Instead of using a steel jacket, the composite is the jacket. It’s easy, fast and cheap,” Hegemier continued. “If you were retrofitting a column the standard way, you’d have to build a jacket to confine the concrete. But because you’re not counting on a bond between the concrete and the composite, you don’t have to build a jacket. You don’t even have to take the paint off.”

A four-man crew can strengthen four to five 2.4-meter (8 ft.) tall columns per day. Paint, plaster or dry wall can be added as aesthetics dictate.

Sheer walls require a little more preparation. “To bridge cracks in concrete, much like you would do with rebar, you need to get a good bond,” explained Hegemier. “First we have to clean the surface with a dry ice blaster, which is very clean. There’s no sand residue or water to clean up, like there is with other blasters. And this even has a vacuum to get rid of any residue.

“You have to wear gloves and use a ventilation system, but it’s not toxic. It’s clean and non-invasive,” he insisted. In fact, one of its selling points is the speed with which it can be applied, and the minimal disruption it causes. Composite retrofitted facilities can typically return to full use within 24 hours of application.

Gee said CSI’s intention is to cut the duration of a retrofit by a third, saving an estimated 25-30 percent in project costs. “Our intention is to keep the operation functional [during a retrofit],” he said. “We have a high satisfaction rate. The owners appreciate the lack of impact on their facility. There’s no shutdown during a retrofit.”

Benefits for New

Construction

New construction can take advantage of this technology, and end up saving money in the long run, according to Hegemier. Although initially the composite materials cost up to 20 percent more than conventional retrofit materials such as steel rebar and metal jackets, the ease and speed of application reduce installation costs, reduces or eliminates shutdown, requires no heavy equipment and causes no loss of facility space. These factors can decrease overall project cost up to 50 percent.

Hegemier said the benefit of this technology in savings of both time and labor is very real. While in retrofit overlay applications, the fabric is woven in a factory and applied on existing structures in a wet lay-up manner, for new construction the same materials are formed into composite molds or shells for lightweight, high-strength building supports such as columns or crossbeams.

In addition to offering earthquake resistance, the composite molds allow for faster construction of multistory buildings. As Hegemier indicated, the molds are placed in position and the concrete is poured inside. Steel rebar cages are not necessary.

In addition, the higher strength of the composite shell construction permits smaller columns and support beams to be installed. The amount of concrete is reduced, decreasing the overall weight of the structure.

Gee explained that the stay-in-place forms replace rebar, but added that this new technology needs further research. Nevertheless, Hegemier related that Granite Construction used the process on the King Stormwater Bridge, a short-span bridge, in Palm Springs, CA. “You put the tubes in place, pour the concrete, and you’re done,” he said. “The 40-foot tubes are so light, two people can lift them.”

Not merely for seismic-prone areas, the technology is effective everywhere. “It’s a good product to upgrade buildings, carry heavy loads and resist wind — like tornadoes and hurricanes,” said Hegemier. Fyfe Co. LLC supplied composites for non-seismic projects such as the Interstate 60 overpass in Fort Wayne, IN, 10 concrete columns on Route 64 in Illinois, and a parking garage in Oklahoma City, OK.

Gee included another use for the technology: composite rebar. “It works better than a grid of steel in a bridge deck because it doesn’t corrode,” he claimed. Indeed, maintenance and upkeep of composites is very limited because they aren’t subjected to corrosion or environmental attack.

Weight and corrosion are not always the obstacles to overcome. Gee indicated that hospitals prefer using the composite rebar in MRI rooms because the steel used in most structures can alter readings, according to Gee. Composite rebar doesn’t interfere with the magnetic soundings.

On-Going Testing, Development and Approval

As the lab’s director, Hegemier is instrumental in testing. Structures have been tested for earthquake response in the lab since 1989. The lab features a reaction floor and wall, each made of five-foot thick reinforced concrete. These are the fixed, or immovable, structures in the Lab, allowing the transfer of earthquake forces directly into test elements.

Hegemier indicated that full-scale walls are tested. A five-story building is erected in the lab and bolted to a giant actuator system, the reaction floor and the wall. A computer program runs the actuators to simulate specific quakes in pattern, speed, time and other influential conditions. They can release up to 300 KIPS, one KIPS equaling 450 kilograms (1,000 lbs.) of force.

According to Hegemier, UCSD also utilizes White Sands as a testing facility for hazard mitigation. This allows the research team to test the effects of blasts similar to that of the Oklahoma City bombing. “It’s been very successful,” said Hegemier.

Currently there are no national codes for retrofitting buildings. The Office of Statewide Health Planning and Development in California considers the use of composites in compliance with their new seismic standards.

Although composites have not been included in national and local building codes, some industry organizations have approved use of them. The International Conference of Building Officials has published an acceptance criteria as a link to its Uniform Building Code, and the American Concrete Institute has published guidelines for the use of composites.

CSI’s Role

As UCSD continues to test and develop the technology, CSI puts it to use. As the only company currently licensed to use the patented and proprietary technology, CSI markets its services to facility owners, typically by word of mouth through various contractors.

CSI offers full-scale structural testing, proprietary software that assists construction project management teams make calculations. Relying on 10 years of research, Hegemier and his team developed the only comprehensive design and analysis software in the industry. The software program is used to select overlay thickness and application method, the resin type and additives, and the fabric and its architecture

Gee, who has designed and managed more than 100 strengthening projects using the composite materials, explained the company’s role, “We’re a turnkey solution, offering risk assessment, analysis, design and implementation. We look for the failure mechanism. We’re a one-stop shop. Our scheme is to have all the necessary services under one umbrella and let the client chose what he needs.

“We try to be flexible and give the customer what he wants. There are three ways we can work with a client. We can do the complete design, engineering and building process; we can act as a consultant by working with a facility owner’s on-staff engineer; or we can allay with an architectural firm who has a close relationship with the facility owner.

“Quality control is our responsibility,” he continued. “We either bring in an experienced crew or we will train and supervise a new crew.” Hegemier added that only qualified people are used for this specialized work. “We use only a few, trained contractors at the moment,” he said.


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