4.5 Repair of a damaged circular column using carbon fiber sheet (Reno system)

Bridge columns designed before 1971 in the United States contained very little transverse reinforcement. As a consequence of the damage observed after the 1971 San Fernanado earthquake, some major problems were identified [1, 2]: 1), the moments and lateral forces induced by seismic loads results in large shear forces, 2) a concrete column is subjected to a large range of varying lateral loads during an earthquake, 3) a column/footing joint suffers from a large shear stress, leading to failure of the column in the plastic hinge region. A column was designed and constructed as part of a research project to consider the effects of seismic loads and the configuration of the column is presented in Figure 1. This column was subjected to a constant compressive load and a series of lateral loads (push and pull action) to simulate the seismic conditions. Because of the strong footing, the tested column exhibited damage on the bottom of the column, especially within the plastic hinge region, see Figure 2.

Application of carbon fiber reinforced plastic (CFRP) composites in infrastructure repair has received a lot of attention in the past decade, both for retrofitting and strengthening of deteriorated reinforced concrete structures. CFRP has superior properties such as high specific tensile strength and modulus and high corrosion resistance. In column applications, the hoop wrapped carbon fiber composite material is used for circumferential confinement, greatly increasing the compressive strength of the column. In this study, the strength and the ductility of a damaged column repaired with CFRP were investigated. The specific objectives of this study were as follows:

a) to gain practical experience in handling a Reno CFRP material system

b) to establish repair procedures for damaged columns

c) to determine the maximum lateral load and the maximum deflection

The following sections describe in detail the design, testing and evaluation of the performance of a damaged concrete column repaired with carbon fiber reinforced plastic. The material system was a Reno carbon fiber sheet (ASMT Co.'s product)

• DESIGN REQUIREMENTS FOR THE REPAIR OF A COLUMN USING ADVANCED COMPOSITE MATERIALS

• EXPERIMENTAL PROGRAM: CONFIGURATION, CONSTRUCTION AND MATERIAL PROPERTIES OF THE COLUMN SPECIMEN

• PREPARATORY WORK AND PROCEDURES

• APPLICATION OF CARBON FIBER SHEET (RENO CARBON FIBER SHEET SYSTEM)

• TEST SETUP AND TESTING

• GENERAL OBSERVATIONS, TEST RESULTS AND DISCUSSION

• CRACKING AND FAILURE MECHANISM

• LOAD-DISPLACEMENT CHARACTERISTICS

• CONCLUSIONS

• REFERENCES