U radu je provedena analiza izobara glavnih naprezanja na jednostavnom primjeru slobodno oslonjene grede. Analiza je provedena na analitički način koristeći se programskim paketom Wolfram Mathematica te na eksperimentalni način pomoću refleksijskog polariskopa. Pojašnjen je princip rada samog polariskopa te je prikazana priprema uzoraka za ispitivanje ovom vrstom polariskopa. Zatim su dane usporedbe rezultata dobivenih analitički i eksperimentalno, kao i krajnji zaključci i prijedlozi za daljnja istraživanja.

This paper deals with the estimation of the design force in self-tapping screws used as a reinforcement of notched cross laminated timber plates (CLT). With the reinforcement, apart from an increased load-carrying capacity, a more ductile behaviour of this detail can be achieved. An analytical model based on the Timoshenko Beam Theory was developed, enabling the estimation of the axial force in the reinforcement. A parametric numerical analysis was conducted to verify the model and to provide possible ways for the calibration. The results show a good matching of the model with the numerical results. The load-bearing capacity is analysed using a simple fracture mechanics model taking into consideration the effect of the reinforcement to correctly depict the increase in performance. Theoretical and numerical results are compared with experimental findings and show acceptable correlations encouraging a further development and a subsequent implementation in EN 1995-1-1.