Abstract
This paper proposes the monitoring of old timber beams with natural defects (knots, grain deviations, fissures and wanes), reinforced using carbon composite materials (CFRP). Reinforcement consisted of the combination of a CFRP laminate strip and a carbon fabric discontinuously wrapping the timber element. Monitoring considered the use and comparison of two types of sensors: strain gauges and multi-resonant acoustic emission (AE) sensors. Results demonstrate that: (1) the mechanical behavior of the beams can be considerably improved by means of the use of CFRP (160% in bending load capacity and 90% in stiffness); (2) Acoustic emission sensors provide comparable information to strain gauges. This fact points to the great potential of AE techniques for in-service damage assessment in real wood structures.
Highlights
In Europe, after decades of concrete culture, wood is witnessing a relative boom for the construction of houses and unique buildings
Acoustic emissions (AE) are the stress waves generated by the sudden internal stress redistribution in materials or structures when changes in their strain field are produced by crack initiation and growth, crack opening and closure, deformation, dislocation movement, void formation, interfacial failure, corrosion, fiber-matrix debonding in composites, etc
This sub-section shows the results of the acoustic emission data analysis by using the elastic waves recorded by the AE sensors
Summary
In Europe, after decades of concrete culture, wood is witnessing a relative boom for the construction of houses and unique buildings. Acoustic emissions (AE) are the stress waves generated by the sudden internal stress redistribution in materials or structures when changes in their strain field are produced by crack initiation and growth, crack opening and closure, deformation, dislocation movement, void formation, interfacial failure, corrosion, fiber-matrix debonding in composites, etc. The present paper uses a layout proposed by our research group for reinforcing timber beams with carbon composite materials (CFRP), tentatively named Braided Reinforcement. It consists of the combination of a laminate strip attached on the tension side and a CFRP fabric discontinuously wrapping the timber element. Results of accumulative AE energy released by the specimen during the test and its location are compared with the visual observation of cracks and with the measurements carried out with strain sensors
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