In order to maintain its five-star rating, the Four Seasons Hotel - a popular hotel for businesspeople, dignitaries and celebrities located in the Georgetown district of Washington, D.C. - underwent an extensive upgrade of approximately 120,000-square-foot floor areas in 2005. One of the key aspects of the project was reconfiguring room layouts on each floor, specifically enlarging the bathrooms and relocating associated plumbing. During the construction process, it was necessary to install new penetrations into the concrete slab to run new plumbing and other mechanical and electrical equipment from floor to floor. During this process, more than 900 existing steel reinforcing bars were to be cut or damaged, compromising the structural capacity of the concrete slab in many locations.

With extensive strengthening expertise, Structural Preservation Systems (SPS) was brought in to quickly develop an effective remediation solution. After evaluation, SPS selected carbon fiber reinforced polymer (CFRP) - paper-thin fabric sheets bonded to concrete members with an epoxy adhesive - to strengthen the slabs. With a tensile strength 10 times stronger than steel, approximately 15,000 square feet of carbon reinforcement was utilized on the top and underside surfaces of the reinforced concrete slabs.

For this type of strengthening application, the General Contractor and the electrical and mechanical subcontractors typically identify the locations where it is necessary to drill the new holes into the concrete slab. A Ground Penetration Radar (GPR) survey is then performed to determine how many bars will be cut. Based on this information, the Engineer designs a repair solution and a specialty repair contractor completes the repair. With multiple parties involved, continuous revisions to layout and scheduling concerns, this process can become very time-consuming and expensive. However, because this project required a series of somewhat common slab penetration patterns that were already identified, SPS was able to develop a series of FRP repairs that would address all conditions and be based on the amount of bars cut per hole. This would save the Owner and General Contractor time and money.

The SPS team categorized the proposed slab penetrations, taking into account the "worst case" scenario of how many bars could possibly be cut for each category. Based on this, the team was able to design a conservative repair strategy before any holes were cut. Since the repair was established and approved before the holes were cut, significant time was saved. In addition, because the team was working based on a "worst case" scenario, it was not necessary to perform a GPR survey, saving the General Contractor valuable time and money on the project. Although in some instances slightly more CFRP was installed than necessary, this was greatly offset by the cost savings provided by using this expedited process.

It was vital for SPS to complete the strengthening upgrades as other contractors on the job worked to finish the rest of the repairs on each floor. SPS began working in February 2005 and completed the fifth and sixth floor upgrades on schedule by April. SPS then worked on strengthening the second, third and fourth floors. By using this unique design/repair process, SPS saved the Owner and General Contractor significant time and money. In addition to strengthening work, SPS also performed exterior faced repair work.