L. Van Parys

Using three-dimensional finite element analysis in time domain to model railway-induced ground vibrations

For the prediction of ground vibrations generated by railway traffic, finite element analysis (FEA) appears as a competitive alternative to simulation tools based on the boundary element method: it is largely used in industry and does not suffer any limitation regarding soil geometry or material properties. However, boundary conditions must be properly defined along the domain border so as to mimic the effect of infinity for ground wave propagation. This paper presents a full three-dimensional FEA for the prediction of railway ground-borne vibrations. Non-reflecting boundaries are compared to fixed and free boundary conditions, especially concerning their ability to model the soil wave propagation and reflection. Investigations with commercial FEA software ABAQUS are presented also, with the development of an external meshing tool, so as to automatically define the infinite elements at the model boundary. Considering that ground wave propagation is a transient problem, the problem is formulated in the time domain. The influence of the domain dimension and of the element size is analysed and rules are established to optimise accuracy and computational burden. As an example, the structural response of a building is simulated, considering homogeneous or layered soil, during the passage of a tram at constant speed.

Compatibility Assessment for Repair Mortars: An Optimized Cement-Based Mix for Tuffeau de Lincent

Mortars developed for the reconstitution and ‘plastic repair’ of natural stones have become increasingly popular. They are an alternative for the replacement of deteriorated stones, since they are capable of preserving the (memory of) diversity in building materials. This article addresses some key elements for the compatibility between repair mortars and stones. This research accordingly studies the compatibility of a repointing mortar designed for the Tuffeau de Lincent (Belgium), a friable stone in need for restoration and replacement, which was developed using an auto-formulation tool, based on strength and colour compatibility. The selected repointing mortar was further tested in order to assess its use as plastic repair mortar for the Tuffeau de Lincent stone. The developed mortar was considered compatible in colour with the stone and had a strength of 14 MPa, which falls within the strength range of the stone (8–18 MPa). However, porosity and pore size distribution measurements indicated that the stone and the mortar were different. This study compares the first product of the prototype formulation tool and lays the foundations for a more expanded and larger auto-formulation tool for the repair of natural stone.