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Double-beam systems have found many applications in civil and mechanical engineering. Extensive works of research have been conducted on the investigation of double-beam systems in which some have studied the vibration characteristics of general double-beam systems without considering the effect of axial load, whereas others investigated the vibration and buckling of axially loaded double-beam systems with classical boundary conditions. A few previous studies have considered a general axially loaded double-beam system, but none of them have provided a general solution to calculate the critical buckling load of the system with arbitrary boundary conditions. In the present study, free vibration and buckling of an axially loaded double-beam system, which was composed of two nonidentical beams with generalized boundary conditions, were analytically studied by using the Euler–Bernoulli beam theory. A semianalytical method was proposed to calculate the natural frequencies and mode shapes of the system, and an explicit formula was derived to determine the critical buckling load of the system. Parametric investigations were performed to study the influences of the connecting stiffness of the interlayer and axial loads on the dynamic characteristics and critical buckling load of the system. Results show that the proposed method can be used for free vibration and buckling analyses of generalized double-beam systems subjected to axial loads. [ABSTRACT FROM AUTHOR]

Many civil and mechanical engineering structures can be simplified as double-beam systems, i.e., a primary beam and a secondary beam connected to the primary beam. Many studies have investigated the vibration characteristics of double-beam systems. Those studies investigated the influences of boundary and connecting conditions of two beams on vibration frequency, mode shape, and dynamic responses of the system. None of the previous studies considered a tip mass on the double-beam system. Because some structures that support weight on their tip, such as a wind farm tower with a core that supports a nacelle at the top can for analysis be simplified as a double-beam system, it is therefore necessary to investigate the vibration characteristics of double-beam systems with a tip mass. In the present study, free and forced vibrations of an undamped double-beam system carrying a mass with rotary inertia at the tip of the primary beam are analytically investigated, based on the Euler-Bernoulli beam theory. Comprehensive parametric studies are carried out to investigate the influences of the key parameters of the double-beam system, including tip mass, rotary inertia, elastic layer stiffness connecting the two beams, and mass and rigidity ratio of the secondary beam to primary beam, on the vibration frequencies and dynamic responses of the system. Analytical results show that different parameters have different sensitivities on the system's vibration characteristics, and the tuned mass damper (TMD) theory can be used to explain the structural responses. [ABSTRACT FROM AUTHOR]