Pull-out behaviour of steel rods bonded into timber

Connections for timber structures using concealed bonded-in rods offer one possible solution to the development of more efficient joining methods. However the importance of certain basic joint characteristics, and the influence of adhesive type and properties, are not yet fully understood and as such design criteria are lacking. This paper describes a comprehensive experimental and numerical investigation into the fundamental material and joint geometry characteristics of rods bonded in to timber. The adhesive type and performance are both considered, along with test configuration and joint parameters that included rod embedment length, rod diameter, annular bondline thickness, multiple rods and rod spacing. A navel approach that involved end-profiling of the bond area was also investigated. It was found that epoxy adhesives out-performed all other types investigated, and pull-out strengths can be significantly improved through careful selection and optimisation of the joint geometry.