Acoustic emission monitoring during elastic bending of cross laminated timber-steel composite beams

Abstract

Reinforcement of cross laminated timber (CLT) floors by a composite design with steel girders can provide an innovative and sustainable alternative for highly stressable floor systems made of steel and concrete for spans exceeding 8 m. To make this construction method economical and resource efficient, a significant contribution of the CLT panel to the composite stiffness is necessary. One key aspect of the composite design is the formation of the shear-resistant connection between CLT panel and steel girder. The effect of both composites on the bending stiffness of CLT-steel composite beams was investigated in large-scale 4-point bending tests with spans of 8.1 m and 10.6 m. To monitor the damage of the specimen using acoustic emission (AE), a network with 16 AE sensors were attached to the surface of the specimen in area of largest deflection and highest load. For this purpose broadband AE sensors with a measurement frequency of up to 200 kHz were used. The ultimate failure of the specimen occurred at a maximum test load of approximately 197 kN. The highest deflection at this force was about 192 mm. During the tests, which lasted about 50 minutes, more than 8,500 AE events were detected. In this contribution, the relationship between the mechanical quantities and the AE activity is shown.