This paper is concerned with the problem of ground vibrations induced by railway traffic and its modelling through a decoupled approach, using only the finite element modelling for evaluating the ground waves propagation. The vehicle/track dynamics is calculated separately. An important modelling aspect is undoubtedly the track/soil interaction, which can play an important role in the generation of seismic waves. To avoid excessive computational resources, a coupled lumped mass model (CLM model) of the soil has been recently developed and is considered in this study. The influence of ballast and soil stiffnesses is presented, in order to confirm the range of validity of the CLM model. Combined with a discrete two layer model of the track, it offers the possibility of working with a simple compound track/soil model. A comprehensive analysis is provided to show the benefit of the finite element model with the proper radiation conditions at infinity, for analysing the structural response of a building located in the vicinity of the track. Focusing on typical results based on the tram of Brussels, the effects of track/soil and soil/structure coupling are investigated. Modal analyses of the vehicle and the building are presented in order to understand the effects of seismic wave amplification, especially when the source contains frequencies close to the natural frequencies of the building.
In this study, the stress distribution and stress concentration factor (SCF) of a generic notched wood piece and ASTM D 143:14 notched shear block specimen were analysed. A 2D plane stress finite element model with linear elastic behaviour was assumed for the bulk material and a predefined potential crack path and cohesive behaviour of the crack surfaces were considered. Wood was considered an orthotropic material with transversal isotropy. In the notched wood pieces, the shear stress distribution along the shear plane and the SCF when varying the ratio l/t (length of the heel/depth of the notch) was obtained. The shear stress distribution is not uniform in any situation, approaching a slightly triangular shape. The shear stress concentration increases when l/t is greater and for l/t [ 8 failure occurs due to crack progression. The SCF can be brought fairly close to the natural logarithm of l/t. In the ASTM D 143:14 notched shear block specimen, shear stress distribution only remains a constant value in the central part of the shear plane, while the SCF is greater than 2.
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