Contemporary truss structures must maintain appropriate strength requirements for safe use. This may result in the fact that the influence of vibrations on a truss structure exposed to horizontal forces as well as transverse forces caused by wind may be dangerous for safe use (e.g. bridge structures). Recognizing the need to improve methods of testing truss elements for the purpose of assessing their condition as well as assessing the safety factors in this work, an attempt was made to examine the destruction of the modelled bridge span element using the theoretical modal analysis method.