CFRP Fabric Strengthening for R&D Office Floor

The floor slabs of this 10-year-old reinforced concrete (RC) office building were originally designed based on standard office live loads. Due to changes in tenancy, centralized server equipment needed to be installed in designated areas, thereby increasing the localized design live load.

Background: The floor slabs of this 10-year-old reinforced concrete (RC) office building were originally designed based on standard office live loads. Due to changes in tenancy, centralized server equipment needed to be installed in designated areas, thereby increasing the localized design live load.

Solution: CFRP Fabric Strengthening System

Unidirectional CFRP fabric strips are externally bonded to the underside of the concrete slab to enhance flexural capacity in the positive moment zones. The width, number of layers, and center-to-center spacing of the strips were precisely calculated and verified based on the bending moment envelope for the high-load server area.

All design calculations adhere to the ACI 440.2R-17 standard. To account for long-term environmental degradation, the upper limit for the effective tensile strain of the CFRP fabric is set at 0.004, thereby preventing premature debonding and rupture of the carbon fiber fabric.

Test Item	Measured Result	Specified Acceptance Limit
CFRP fabric-concrete pull-off bond strength	2.8 MPa	Minimum 2.5 MPa (EBR fabric standard)
Maximum CFRP fabric tensile strain under full service load	0.0025	Maximum allowable effective strain 0.004
Slab deflection under full service dead load (SDL)	L/450	Code limit L/250 (stricter control adopted for vibration-sensitive server equipment)
Static load plate bearing test	Fully passed	Successfully sustained 1.2 times the ultimate design load of server zones