Acoustic Emission and Numerical Analysis of Pine Beams Retrofitted with FRP and Poplar Wood.

Acoustic emission (AE) released by pine beams retrofitted with fiber reinforced plastic (FRP) and poplar planks in bending is analyzed. Basalt fabric (FB), carbon fabric (FC), and carbon pultruded laminate (LC) have been used as FRP. Experimental results and AE behavior are discussed based on an elastoplastic finite-element numerical model. The model demonstrates a strong strain concentration at the end of poplar planks, which causes high AE activity in these areas and acts as a precursor of the delamination of the poplar plank. Based on the experimental results, some AE criteria for predicting the onset of the delamination are tentatively proposed.

Pine Beams Retrofitted with FRP and Poplar Planks: Mechanical Behavior.

The paper presents an experimental analysis of the bending behavior of pine beams (Pinus Sylvester) retrofitted with fiber reinforced plastic (FRP) and poplar planks used as external covering. Poplar wood was chosen because of its rapid growth in planted forests, its homogeneity and attributes for sustainable local development, and high CO2 absorption rate. Vibration tests were also conducted in order to evaluate the stiffness in a non-destructive way and compare it with that obtained by means of the destructive tests. Three types of reinforcement were compared, namely: basalt fabric (FB), carbon fabric (FC) and carbon laminate (LC). In addition, some pine beams were reinforced only with poplar planks and used as control specimens in order to evaluate the improvement provided by the FRP. It was observed that a strong delamination preceded the final breakage of beam. Moreover, the results indicated that stiffness is provided mainly by the poplar plank and not by the FRP, as was expected.

Temporal Acoustic Emission Index for Damage Monitoring of RC Structures Subjected to Bidirectional Seismic Loadings.

This paper shows the acoustic emission (AE) analysis recorded during the loading process of reinforced concrete (RC) structures subjected to bidirectional seismic loadings. Two waffle plates (bidirectional) supported by isolated square columns were tested on a shaking table with a progressive and increasing ground acceleration until the final collapse. Each specimen was subjected to a different loading history. A relevant delay in the beginning of the significant AE energy is observed as the peak value of the ground acceleration increases. Based on this result, a new AE temporal damage index (TDI), defined as the time difference between the onset of the significant AE activity and the onset of the loading that causes this AE activity, is proposed and validated by comparing it with the plastic strain energy released by the concrete, typically used as a reliable damage level indicator. Good agreement was observed for both specimens and seismic inputs.