Pull-out strength and bond behaviour of axially loaded rebar glued-in glulam

This paper presents an experimental program for testing glued-in rebar timber joints. Twenty five glulam specimens, each with a single glued-in rebar parallel to the grain were tested to evaluate the effects of anchorage length and glue-line thickness on pull-out strength and bond behaviour of glued-in rebar timber joints. Tests were conducted in pull-pull configuration. The test results showed that both the anchorage length and glue-line thickness had a significant influence on these two properties. Failure modes were characterized by pull out failure of the rebar, either alone or combined with the shear failure of timber along the glue line, longitudinal splitting of wood and bar yielding. For the same anchorage length, the average bond stress at both interfaces showed different variations (increasing by 11.6% at the bar/adhesive interface, and decreasing by 12% at the adhesive/timber interface) since the glue-line thickness increased from 2 mm to 6 mm. The load–slip relationship and initial stiffness of specimens were analysed in terms of anchorage length and glue-line thickness. An empirical bond–slip model for glued-in rebar timber joint was proposed by regression analysis based on the experimental data. It was observed that the proposed model fit the bond–slip relationship of glued in rebar timber joints with less than 15% deviation. Finally, the test results were compared with the design proposals reported in the literatures. It can be concluded that the prediction of Rossignon design proposal was more closely to the test results, and the Steiger design equation was unsafe, however, the Riberholt design equation was too conservative for the joint design.