An experimental and theoretical investigation into the influence of hysteretic damping on the dynamic behavior of a three-beam structure

Abstract

In this thesis, we theoretically and experimentally investigate the linear and nonlinear dynamic behavior of a frame structure, which frequently occurs in engineering applications. The structure consists of three continuous steel beams that are connected by two brass hinges. Experimental modal analysis indicates that the obtained natural frequencies are highly sensitive to changes in the oscillation amplitude, even for small motions. Thus, the amplitude range where linear responses can be expected is, in practice, very small. Instead, a strong nonlinear behavior is exhibited by the experimentally obtained backbone curves for small vibrations. Furthermore, the experimentally obtained frequency-response curves exhibit jump phenomena. We investigated experimentally whether the nonlinear dynamic characteristics of the structure are the result of modal interactions, such as internal and combination resonances. We were unable to activate any of these resonances. Next, we investigated whether these characteristics are due to geometric, inertia, material, or damping nonlinearities. The answer is again negative. Finally, we examined the nonideal dynamic characteristics of the hinges. We found that stiffness degradation hysteretic damping in the hinges is the best model that explains the observed nonlinear dynamic behavior. A multilinear stiffness degradation model was used to describe the overall hysteretic load-displacement relation. An approximate analytical approach was used to compute the steady-state response of the structure to a harmonic excitation. A good qualitative agreement between the computations and the experimental results was obtained.