Elisabet Suarez

Concrete-Galvanized Steel Pull-Out Bond Assessed by Acoustic Emission

AbstractThis paper experimentally investigates the steel-to-concrete bond phenomenon in two kinds of deformed bars: black steel and hot-dip galvanized steel. The differences in the steel-to-concrete bond behavior are identified in terms of the load-slip curves and the acoustic emission (AE) patterns measured during pull-out tests. Test results show that the bond capacity and the initial stiffness of the bond stress–slip curve of black steel are approximately 20 and 50% greater, respectively, than those of galvanized steel, and the slip corresponding to the maximum bond stress is approximately 20% times larger in the latter. By measuring the AE activity, it is possible to identify the transitional points between the four stages characterizing interaction between the concrete and the bar subjected to pull-out force. Each transition coincides with a sudden drop in the AE activity.

Experimental Comparison of Different Carbon Fiber Composites in Reinforcement Layouts for Wooden Beams of Historical Buildings

This paper offers a detailed, quantitative and exhaustive experimental comparison in terms of mechanical properties of three different layouts of carbon composite materials (CFRP) used to strengthen existing old timber beams highly affected by diverse natural defects and biological attacks, testing the use of pultruded laminate attached on the tension side of the element (LR), CFRP fabrics totally U-shape wrapping the timber element (UR), and the combined use of both reinforcement solutions (UR-P). Moreover, unidirectional and bidirectional fabrics were considered and compared. Timber elements used for the experimental program were extracted from a recent rehabilitation of the roof of the current Faculty of Law building, University of Granada (Spain), catalogued as a historical edifice. Experimental results from bending tests show that in all cases reinforcement provides a clear improvement in terms of bending capacity and stiffness as compared with the control specimens (without reinforcement). However, improvements in terms of ductility differ considerably depending on the kind of layout.

Experimental validation of a CFRP laminated/fabric hybrid layout for retrofitting and repairing timber beams

ABSTRACT This paper proposes a new hybrid layout to retrofit and repair timber beams by means of carbon composite material. It is based on the combination of a carbon laminate strip attached on the tension side, and a carbon fabric discontinuously wrapping the timber element. This layout has been experimentally validated by means of a study involving large-scale timber beams with many years in service. Results demonstrate not only that the bending load capacity of the broken beams can be totally recovered, but that it may even be increased by 70% with respect to the non-broken ones.

Monitoring of Carbon Fiber-Reinforced Old Timber Beams via Strain and Multiresonant Acoustic Emission Sensors

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.