Dynamic Impact Factor Determination of an Existing Pre-stressed Concrete I-Girder Bridge Using Vehicle-Bridge Interaction Modelling

The dynamic Impact Factor (IM) of a bridge is influenced by many factors, including Vehicle-Bridge Interaction (VBI), vehicle speed and road roughness. This paper represents the dynamic effects of moving vehicles and the determination of IM of an existing Pre-stressed concrete I-girder bridge utilizing VBI modeling. Evaluation of the IM is expected to provide valuable information for condition assessment and management of the existing bridge. The interaction problem between the vehicle and the bridge includes a dynamic model for the bridge structure subsystem, a dynamic model for the vehicle subsystem, interaction constraints, road roughness modelling and numerical solution techniques for the dynamic systems. The Half-car model is utilized for modelling of the vehicle dynamics and the bridge dynamic model is idealized according to Finite Element Method (FEM). Then FEM along with the mode superposition method are utilized for determining the Equation of Motion (EOM) for the bridge subsystem. D’Alembert’s principle is used for developing EOM for the vehicle subsystem. The interaction between vehicle vibration and bridge vibration is established through the contact forces between the wheels and the bridge by employing the compatibility relationship between the contact points and by applying the static equilibrium condition. Lastly, Newmark’s-β method is used for solving the coupled mathematical model of the vehicle and bridge interaction problem to determine the responses of the two sub-systems. The whole procedure is then performed for different vehicle speeds and various bridge deck surface roughness conditions to determine the dynamic impact on the existing I-girder bridge named Teesta Bridge located in Bangladesh.

A study of the influence deformation of the drilling riser on the longitudinal oscillations of the drill string

The article deals with the study of the effect of drilling riser transverse vibrations on the longitudinal vibrations of the drill string and the change of the dynamic component of weight on the bit when drilling wells from floating drilling vessel in deep sea conditions. The impact assessment was carried out by comparing the results of the simulation of the drilling system in the software based on the Modelica language. For this purpose, a simulation model has been created to enable the study of the operation of the «drill ship – riser wire tension system – drilling riser – drill string heave compensator – drill string» system in the case of irregular sea agitation obtained from decomposition the JONSWAP energy spectrum. The influence of the deformation of the drilling riser on the axial vibrations of the drill string is taken into account by introducing into the "classical" equation of the axial vibrations of the drill string the nonlinear term of the longitudinal-transverse strain. The drill string transverse deformation was determined based on the assumption that the axes of deformation of the drilling riser and drill string were coincident in the course of operation. A series of simulation experiments was carried out in the case from three to six WMO sea state code, absence of action of sea currents and active mode of work of the drill string heave compensator. The obtained results show that the greatest influence of the deformation of the drilling riser on the axial vibrations of the drill string is observed in the section at the level of the well head, where the amplitude of longitudinal vibrations increases up to 4 times. In general, the deformation of the drilling riser causes the growth of the dynamic impact factor of weight on the drill bit to increase by 4-7% for the investigated structure of the drilling system.