Assessing the behaviour of a cross half joint using different methods of reinforcement to enhance its flexural capacity

Abstract

In today's timber diagrid roofing system, the Cross Half Joint is being superseded by terminating one of the beams and re-connecting it using various methods, hence disrupting its continuity. Thus, in this study, an investigation was conducted to assess the flexural performance of a Cross Half Joint and assess alternative methods of reinforcement to enhance its flexural capacity. Six reinforcement configurations were tested on glulam beams having a notch within the bottom half. Reinforcement applications were composed of Self-Tapping Screws, bolts with trapezoidal end plates, and flat steel plates. The beam specimens were tested on a four-point bending test using a manualy operated hydraulic jack to exert the load. Results from this study show that even though the beam exhibit a lower flexural capacity when having the notch situated within the top or bottom half of it, the latter configuration exhibits a further reduction in its flexural capacity. Moreover, the two failure mechanisms exhibited within this configuration were crack formation at the notched corner due to tensile forces acting perpendicularly to the grain and widening of the bottom notch opening due to the disruption in the continuity of the tension face. More importantly, Self-Tapping Screws at 45 degrees to the horizontal applied to control the tensile forces acting perpendicularly to the grain at the notch corner exhibited the highest flexural capacity enhancement. Thus, it was concluded that among the different configurations and methods analysed, this method is the most ideal one to enhance the flexural capacity of the Cross-Half Joint.