engleski

Fracture Behaviour of Bolted Joint Using Steel Threaded Bars Glued In Oak elements

The procedure of strengthening the Oak girders by reinforcing the places of lower strength by steel glued bars is often applied [3]. Joints with glued– in steel bars in timber frames are also potentially very acceptable solution for connections between its columns and beams [4] especially when a large load capacity is needed [5]. EC5 standards, with a little exception of their informative annexes, do not regulate this type of joints in a legal way. The paper presents the comparison of results obtained experimentally, numerically and analytically. Joint specimens have been tested in the laboratory using destructive one– side pull– out test. Test method together with test results is very briefly described in further text. The experiment was the starting point of the whole process with purpose of determining the tensile strength of joint. As their final result, tests carried out the (Fracture) Force– Displacement diagrams. Experimental models have their basis in fracture mechanics approaches to study of modes of strength failure. FE parametric numerical models of an experiment using COSMOS/M had also been prepared. Comparison of results of experimental test with results of analysis of 3D FE models was the next step of this researching. Numerical FE analysis is based on linear fracture mechanics analysis of the model of the adhesive layer's behaviour. Satisfactory correlation between experimentally obtained results and those that numerically produced was an ultimate issue we have intended to achieve. Confirming of numerically results by analytic model with rational theoretical bases was the final goal of comparison. The models have their bases in fracture mechanics and the key material property is the strength failure characteristics of the decisive fracture area [2]. During the experiment and linear analysis of FE models, as well, the following parameters had been varied: the diameter of the bars, an anchorage depth of threaded steel bars and an angle of the bars in comparison with wooden grains (0 and 90deg). The thickness of the glue to fill provided holes was kept constant (1, 5mm) as well as the type of an adhesive layer (two– component epoxy glue). The decisive thesis we try to verify is: if we could find the validity of relationship between results obtained experimentally, numerically and analytically, then we can use only numerical model to continue researching and make it extensively. We use then only numerical FE model to explore an influence on joint strength capacity caused by variation of diameters and anchorage depths of threaded bars, as well.

bolted joints; steel threaded bars; glue; oak; experiment; FE; theory; analysis

nije evidentirano