The owner of a major mall in South Florida wanted to convert the mall to a communications center. The one million plus square foot area structural floor of the structure consists of a one-way cast-in-place slab on precast prestressed joist system, simply supported on continuous cast-in-place concrete beams with precast prestressed soffits running between columns. For the new use, the structural floor required an upgrade from a live load capacity of 100 psf to new loads consisting of 25 psf super-imposed dead load and 150 psf live load.

When it comes to operating these technology centers, time is money and fast track upgrade techniques are desired. To this end, SPS used Rapid Load Testing as a mean to evaluate the in-place strength of the unstrengthened floor components and to develop an optimized and economical strengthening solution. Based on the results of the load test it was concluded that the slab was adequate for the new loads, the joists could be rated for 125 psf live load, the beam could be rated for 135 psf live load - all larger than the theoretical load capacity.

To meet new load demands, SPS proposed an externally bonded carbon FRP strengthening system consisting of multiple plies of FRP strips attached to joists soffit to increase the positive bending moment capacity. Additional FRP strips were wrapped around the joists at each end to anchor the FRP strips. The beams were strengthened to improve their positive and negative moment capacity. For positive moment, FRP strips were installed on the soffit of the beam. For negative moment, FRP strips were installed on top of the slab. On top of the slab, the required amount of FRP for beam upgrade was equally divided and installed of each side of the column in the direction of the beam. For shear, CFRP strips were wrapped around the beam sides. The capacity improvement of the upgraded structural elements was then verified through full scale in-situ load testing. The use of this novel design-build-verify (through load testing) approach resulted in savings of approximately $750,000 to the owner when compared to the original strengthening design.