Probabilistic Analysis and Optimization of Roof Trusses

The influence of gap between wooden members and displaced nail-plates in roof trusses is investigated by means of probabilistic calculations and structural optimization. The employed mechanical model, using the finite element method, captures the non-linear behaviour of the nail-plate joints. The joint stiffness involves the size and location of the nail-plate, and the presence of contact or gap respectively between the wooden members. The analysis shows that even small initial gaps considerably increase the deflection of a roof truss. Misplaced nail-plates also effect the deflection negatively, but it is also shown that the deflection can be significantly decreased, and the utilization of nail-plates improved, by optimizing the nail-plate positions with respect to critical load cases and requirements.