Commercial Building Retrofitting & Strengthening

Project Background

The building is an aging commercial structure scheduled for renovation and functional conversion. As the building transitions to a new use with different loading conditions, the existing reinforced concrete frame was subjected to a structural appraisal. The appraisal identified the typical deficiencies of older commercial construction: insufficient column confinement, inadequate shear capacity at beam ends, and limited in-plane shear capacity of the walls — all compounded by increased service loads and current seismic requirements.

Material and Specification

The strengthening system is a two-component wet lay-up:

• Carbon fiber sheet — high-strength unidirectional fabric, supplied in rolls, saturated on site;

• Carbon fiber saturating adhesive — a low-viscosity epoxy that impregnates the fabric and bonds it to the concrete substrate, together with a compatible primer and leveling putty.

Strengthening Scheme by Element

• Columns — full wrap confinement. Carbon fiber sheets were wrapped around the columns in continuous circumferential bands. The wrap confines the concrete core, raises axial capacity, and improves ductility, eliminating the brittle failure risk of poorly confined older columns.

• Beam ends — local strengthening at beam-column joints. Carbon fiber sheets were applied only at the beam ends, adjacent to the beam-column joints, to resist the higher shear and moment demand concentrated in these critical regions.

• Shear walls — horizontal band strengthening. Horizontal carbon fiber bands were applied across the wall surfaces in overlapping strips, increasing in-plane shear capacity and improving the wall's contribution to the overall seismic system.

Results and Benefits

• Capacity gains in columns, beam ends, and shear walls without section enlargement;

• Near-zero added weight, protecting the existing foundations;

• No loss of usable floor area, important for a commercial renovation;

• Fast, low-noise installation running in parallel with the fit-out, shortening the overall schedule.