Abstract Summary
The reassessment of existing mechanical bridge machineries in The Netherlands has created the need for the development of acceptance/rejection criteria to assess their structural safety. The existing design code in The Netherlands [1] defines an ultimate limit state, meant for new torque regulated machineries, which is based on a linear single degree of freedom (SDoF) dynamical system [2]. Observations show that the SDoF model fails to predict the dynamic response of existing machineries during all load cases. Nowadays, movable bridge machineries are speed regulated and they are in fact nonlinear systems consisting of many mechanical components connected to each other while each movable bridge is characterized by a unique set of fixed parameters. Thus, on-site measurements of a single bridge do not always provide the generic information that one needs for design and/or reassessment of existing structures. In this paper, a novel experimental setup is presented which allows the investigation of a large number of variations in order to capture the dynamics of the powertrain in a class of bridge machineries. A model is also developed that overcomes the limitations of existing SDoF systems, i.e. it accounts for base excitations, damping, and some additional variables of the physical system which are neglected by the current code. A comparison of model predictions with measured data shows that the proposed model provides an upper bound of the peak torque occurring in the powertrain during an emergency braking. Keywords: Dynamics of movable bridges, bridge machinery, powertrains, torque measurements. REFERENCES [1] NEN 6786, Rules for the design of movable bridges, 2001. [2] K. Sektani, A. Tsouvalas, A. Metrikine, Heron Journal, Volume 67, Issue 1: Dynamics. A mathematical model to quantify dynamic forces in the powertrain of torque regulated movable bridge machineries, 2022.
