Experimental study on bond and anchorage behavior of glued-in rebar in glulam

This paper describes an experimental program of 25 glulam specimens with glued-in rebar which aim to investigate the influence of slenderness ratio (λ= l_a/d) of rebar and glue-line thickness on the pull out load, and bond behavior of glued-in rebar axially loaded parallel to the grain. The failure modes and mechanics of specimens were analyzed. Moreover, in order to obtain the bond stress distribution along the anchorage length of rebar, specimens with strain gauges attached to steel rebar internally were designed. The experimental results show that failure occurs mainly due to pull-out of rebar, shear failure of timber around the glue-line, splitting of timber and yielding of rebar. The pull out load of glued-in rebar increases with the increasing of both the anchorage length and glue-line thickness. The ductile failure of yielding rebar occurs with the slenderness ratio of rebar up to 12.5. Anchorage length and glue-line thickness have obvious influence on the bond behavior of glued-in rebar. The distribution of bond stress at rebar/adhesive interface is not uniform, but rather accentuated near both the loading end and the anchorage end, which confirms the theory of Volkersen (1938). The variation of bond stress at rebar/adhesive interface is different from adhesive/timber interface with the increasing of glue-line thickness. With glue-line thickness increased from 2 mm to 6 mm, bond stress at rebar/adhesive interface increases, while decreases at adhesive/ timber interface. Appropriate increasing of glue-line thickness is beneficial to the decreasing of peak value of bond stress.