Experimental assessment of CFRP reinforced wooden beams by 4-point bending tests and photoelastic coating technique

Abstract

The article presents selected results of experimental investigations into carbon fibre reinforced plastic (CFRP) strips for strengthening wooden beams. About 100 years old beams were tested under four-point bending load. Electrical-resistance strain gauges (ERSG) together with the photoelastic coating technique (PCT) were used to determine strain distributions (also in the inserted strips). A comparison of the strain values measured by, respectively, ERSG and PCT showed significant differences (amounting to 2.2–72.5%) due to the different character of the two kinds of measurement, connected with the significant effect of wood structure on local strain distributions. Generally, the strain measurement results suggest that the proposed methods of reinforcing wooden beams with CFRP strips are useful for restoration purposes. The effectiveness of the reinforcement significantly depends on the quality of the wood-CFRP strip bond, which means the preparation of the surfaces for bonding plays an important role.