Seismic-Repair-and-Strengthening-of-Tilt-up-Walls-with-Glass-or-Carbon-FRP

Seismic Repair and Strengthening of Tilt-up Walls with Glass or Carbon FRP

Glass or Carbon FRP offer ideal solutions for seismic repair or strengthening of tilt up walls. Glass FRP (GFRP) and Carbon FRP (CFRP) can also be used for strengthening walls around door or window openings to create lintels or piers that are reinforced with FRP. Many existing and older tilt up walls are inadequately reinforced, resulting in cracking of the wall panels under severe loads such as an earthquake. Tilt up walls can be strengthened with Glass or Carbon Fiber Reinforced Polymer (FRP). In some cases, fire damage could lead to weakened wall panels that may require strengthening; such fire-damaged walls could also be strength ned with Glass FRP (GFRP) or Carbon FRP (CFRP).

Crack Injection vs. Strengthening with FRP

Injection of resins into cracks is a common approach to strengthen cracked tilt-up panels. The epoxy is intended to penetrate the full depth of the crack and bond the separated pieces of concrete together. If done correctly, it can also serve as a protection measure against moisture penetration and corrosion of reinforcement. However, such repairs do not increase the strength of the tilt-up panel and similar cracks may be observed in the future at relatively short distances from the current cracks.

Better results can be achieved by strengthening the wall panel with carbon or glass FRP fabrics. This repair system offers the following advantages:

FRP covering the crack protects the internal steel reinforcement against corrosion.
FRP can significantly increase the strength of the wall (in flexure and shear); thus the causes of distress can be directly addressed and corrected.

Flexural Behavior

The flexural strength of tilt-up wall panels is enhanced in accordance with the same principles discussed for concrete beams and URM walls.

Our tests for two wall panels are shown on the right. The panels were subjected to out-of-plane cyclic loading similar to that experienced during an earthquake.

The hysteretic response shown on the left is for the control specimen. The graph on the right is for a similar specimen that was strengthened by applying a layer of glass FRP on each face. Clearly, the strength of the retrofitted specimen is significantly improved and it shows very good hysteretic behavior.

Shear Behavior

The shear strength of tilt-up wall panels is enhanced in accordance with the same principles discussed for concrete beams and URM walls.

A more detailed description of the benefits of this strengthening approach and details of a filed application are presented in a paper that appeared in Earthquake Spectra.

Case Studies

Several tilt-up buildings have been strengthened using QuakeWrap™ glass FRP products. A sample of projects are listed below. By clicking on each project, you will be able to view specific information on each project.

For detailed field installation procedures click here.