Workers install FRP sheets to topside of concrete deck
Installed FRP system

FRP Utilized to Convert Parking Area to Conference Rooms for a West Coast Hotel

Project Description 

The owner of a west coast hotel wanted to convert an elevated post-tensioned parking area located on a conference room level into additional conference rooms.  The structural engineer hired by the owner determined that the existing concrete deck live load capacity was not sufficient to support the design load for conference space, which was specified at 100psf.  As a result, the owner needed a solution to increase the elevated deck load capacity, maximize use of existing space and keep the ongoing renovation project on schedule.

Initially, STRUCTURAL was contacted by the owner to repair existing post-tensioned cables that were damaged due to new slab penetrations that had been installed as part of the new renovations.  While performing the repairs, the owner, general contractor and structural engineer consulted with STRUCTURAL for options to strengthen additional areas of concrete deck slab.  After a quick preliminary evaluation, STRUCTURAL recommended the use of externally bonded fiber reinforced polymer (FRP) reinforcement as an effective and economical solution that would meet the following requirements by the owner:

  • Maximize use of space -The owner did not want to have to take away any usable new conference space as this would result in smaller rooms and ultimately affect revenue.
  • Keep the project on schedule - the tight renovation schedule could allow for only one month to perform the strengthening of the entire deck.
  • Affordability - the upgrade project had to stay within the estimated budget.

Other solutions that were considered included installation of shallow RC beams (enlargement) and external post-tensioning. These conventional techniques would take up more space and headroom, and would require longer time to install. These conventional strengthening options were also more expensive than using FRP. Externally bonded FRP was the solution of choice and STRUCTURAL was contracted to perform the slab strengthening portion of the renovation project.

STRUCTURAL began the strengthening phase by performing concrete repairs on the existing slab to restore the integrity and improve the durability of the concrete deck. The slab surface (top & bottom side) was then roughened to optimize bond of the FRP system, using shotblasting on the top side of the slab and sandblasting on the bottom side. Shotblasting was used on the top side because it requires minimal cleanup as it includes a self-vacuuming process. The objective of surface profiling was to achieve a concrete surface profile (CSP) of 3 or better, per the International Concrete Repair Institute (ICRI) and the American Concrete Institute (ACI) guidelines. This is the minimum requirement to ensure that the FRP system is properly bonded to the existing concrete. FRP sheets were bonded to the topside of the slab in both directions within the column strip areas. Sheets on the soffet side of the slab were installed in both directions within the middle strip areas.  After the FRP strengthening system was installed per the manufacturer's recommended procedure, an additional coating of FRL intumescent paint was applied on top of the system to provide additional flame/smoke spread resistance as required per local code.

In all, 5,000 square feet of FRP was installed to strengthen approximately 8,000 square feet of slab.  The strengthening part of the project was completed one week ahead of the scheduled completion date, and because the FRP can achieve initial cure within 24 hours, the next contractor was able to begin work the next day.  As a result of STRUCTURAL's efforts, the owner, general contractor and structural engineer were extremely pleased that STRUCTURAL was able to develop and install an affordable strengthening solution under budget that met all the owner's requirements and was completed one week ahead of schedule.