مهندسی عمران شریف (Feb 2018)
Multi-span bridge, multi-span beam, moving oscillator, accelerated movement, dynamic response.
Abstract
Vibration of structures under moving loads has been extensively dealt with by numerous researchers. In particular, this problem is of importance to bridge engineers. In this regard, there are a great number of studies on vibration analysis of single - span thin beams under moving loads. It is noteworthy to highlight that there is lack of research on the dynamic behavior of multi-span beams under moving inertial loads. Moreover, most of these studies neglect the inertia of the moving vehicle and consider the moving force approach. However, several investigations using moving mass approach highlighted the considerable contribution of load/structure inertial interaction for heavy masses moving at high speeds. In moving mass simulation framework, a solid mass is considered to slide on the base structure while remains directly in contact with the base structure. Therefore, the transverse acceleration of the moving object corresponds to that of the beam beneath the traveling load and the effects of vehicles flexibility are neglected. Moving oscillator model is composed of a mass supported by a spring-damper system in order to allow for the vehicle suspension system. Hence, moving oscillator can capture a wider range of possible structural behaviors with regard to the variation of vehicle stiffness. In this research, dynamic behavior of a multi-span continuous beam subjected to the excitation of an accelerated moving oscillator is studied to simulate vibration of a multi-span bridge acted upon by the accelerated movement of a vehicle. Euler-Bernoulli beam theory is employed as the governing equation for each span of the beam. The proposed solution is applicable to general beam fixity conditions. Moving oscillator model, as a reduced order model of a moving system, is of higher accuracy rather than old-fashioned methods of moving force and moving mass due to importing suspension system effects on the corresponding computational model. The solutions are verified and very close agreement is observed with published results via other methods in the asymptotic states of moving oscillator, where soft and rigid springs correspond to moving force and moving mass, respectively.
