Dynamic property control of bridge girders

Abstract

   The dynamic properties of bridge girders depend on the design solutions, namely the replacement of the roadway slab by the orthotropic, deviation from standard solutions in the formation of longitudinal schemes, and the use of a new type of supports causing the dissipation of vibration energy and gyropendulum effect.The control for dynamic properties with regard to multifactorial defects, is characterized by ignoring the shock dampers of vehicles moving on the roadway. In this case, it is advisable to control the dynamic properties with regard to the energy dissipation of oscillatory processes within the internal and external strain boundaries, each of which can be functionally solved by the dependencies between the parameters of static and dynamic conditions of elasticity and plasticity. Long experience in diagnosing bridges under varying conditions of moving load allows identifying critical moments and limiting values of dynamic properties, at which the integrity of the span-vehicle system is violated. The difference in the operation of the system elements is complicated by the influence of a wide range of dynamic impacts, whose nature is opposite to the mechanical impact of vibra-tion dampers such as all-round moving supports. In this case, the criterion for the dynamic property control are anti-phase vibrations of the girder and supports and their stiffness ratio. Based on the results, the dynamic property control includes the identification of the critical speed of the moving load based on various forms of energy of the deformed state of the structure, including resonance; conditions of the energy dissipation of the vibration process of the span-vehicle system; new parameters and requirements for bridge structures with controlled dynamic properties adequate to those of numerical simulation of bridge girders of 40 to 60 or 80 m and longer; optimization and modernization of bridge vibration-based diagnostics.