Study On The Pull-out Capacity Of Timber Connections With Glued-in Rods

Timber connections with glued-in rods has high strength,stiffness and good fire resistance,which is a very effective form of connection in timber structures.When the connections with glued-in rods are subjected to axial load,it may occur tensile failure of timber,yielding of the rod,splitting failure of timber,shear block failure and pull-out of the rod.To determine the load-carrying capacity of the connections with glued-in rods,it is necessary to determine the pull-out capacity when the pull-out of the rod occurs.The pull-out capacity of the connections with glued-in rods is affected by several factors such as the diameter of rod,anchorage length,bond-line thickness and spacing and distance of rods.At present,the research on the connections with glued-in rods mainly focuses on the single glued-in rod parallel to the grain.However,in actual engineering,the rods are not always parallel to the grain,and the connections with multiple glued-in rods are often used.Therefore,it is necessary to study the pull-out capacity of the connections with single glued-in rod at an angle to the grain and the connections with multiple glued-in rods.Firstly,this paper summarized the experimental results of the connections with single glued-in rod perpendicular to the grain in the literature,and analyzed the effects of diameter of rod,anchorage length and slenderness ratio on the pull-out capacity of the connections with glued-in rods.An empirical formula of the pull-out capacity of the connections with single glued-in rod perpendicular to the grain was proposed,and compared with the existing formulas in the literature,it is found that the prediction ability of the formula proposed in this paper is better than those in the literature.Subsequently,an experimental study was carried out for the connections with single glued-in rod at an angle to the grain,the diameter of the rod is 10 mm,the anchorage length is 100 mm,the bond-line thickness is 2 mm,and the angles of rod are 0°,30°,45°,60° and 90°.Combined with the experimental results of the connection with single glued-in rod at an angle to the grain in the literature,and proposed the formula of the pull-out capacity of the connections with single glued-in rod at an angle to the grain.The pull-out capacity of each rod in the connections with multiple glued-in rods is lower than the connections with single glued-in rods.When checking the pull-out capacity of the connections with multiple glued-in rods,the group effect of rods needs to be considered.This paper summarized the experimental results of the connections with multiple glued-in rods in the literature,and analyzed the effects of the diameter of rod,anchorage length and slenderness ratio on the effective number of rods.The experimental study on the connections with multiple glued-in rods was performed,the diameter of rods is 10 mm,the anchorage length is 100 mm,the bond-line thickness is 2 mm,the number of rod is two and four,and the spacing of rod is 40 mm,50 mm and 60 mm.Combined with test results in the literature,and the effects of diameter of rod,anchorage length,slenderness ratio,spacing of rods and the number of rods on the effective number of rods were analyzed.An empirical formula of the effective number of rods of the connections with multiple glued-in rods was proposed,and compared the existing formulas in the literature,it is found that the prediction ability of the formula proposed in this paper is better than those in the literature.Finally,The calculation formula of the load-carrying capacity of the connections with multiple glued-in rods was proposed.Compared with the experimental results in the literature,it is found that the calculation formula can accurately predict the load-carrying capacity and failure modes of the connections with multiple glued-in rods.