The prediction of damping remains an important research challenge in structural dynamics. This paper deals with the energy losses caused by friction in assembled structures. From previous analytical works and experimental studies of the bending vibrations of a clamped–clamped beam with original positions of the interfaces, the objective of this work is to compute the damping of the structure taking into account the local properties of the joints. The purpose is to understand and analyze the contribution of the surface defects on the damping due to the joints based on multi-spherical contacts governed by Hertz' and Mindlin's theories. A design of experiments based on the model parameters is proposed and the final results are compared to the experimental's ones.