Numerical prediction of building correction factors for the hybrid prediction of urban-scale ground-borne vibration in buildings

Within the project QuieterRail, one of the objectives is to develop an enhanced software tool for the urban-scale prediction of ground-borne noise and vibration in buildings. The aim is to improve and extend the hybrid vibration prediction tool that was originally developed in the project SILVARSTAR, based on the empirical analysis procedure of the US Federal Railroad and Transit Administrations, in which the vibration velocity level in a building, expressed in decibels in one-third octave frequency bands, is written as a sum of a force density, a line source transfer mobility and a building correction factor. As a hybrid procedure, each of these terms representing the source, propagation path and receiver may be derived from either measured data or predictions from a numerical model. This paper presents the methodology behind the numerical prediction of building correction factors to cover a wider range of soil properties and building types, which range from large multi-storey buildings founded on piles to small residential dwellings founded on footings. The modelling is based on a combination of three-dimensional finite-element, boundary-element and singular-boundary methods, which account for the dynamic soil-structure interaction between a building and its foundation. The approach is outlined with reference to a combined finite-element / boundary-element model, and some example results are presented that illustrate the impact of three different foundations for a framed building.