The free vibration mode shapes have certain special properties, which are very useful in structural analysis, especially in the dynamic analysis. A brief review of eigenvalues eigenvector (natural frequencies at corresponding mode shapes) is presented The static analysis for a numerous number of N-Types and Warren system of trusses with variable parametric studies such as, intensity of loads, number of panels, panel length, interior and exterior heights, types of materials, ... and so on are carried out using stiffness method The eigenproblem equation is solved by common methods with condensation if required The final results for first and second frequencies are fitted to multiple regression programs to get the final empirical formulae. Finally, comparisons between exact and computed values of frequencies are demonstrated.
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