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Abstract
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The problem of the effect of traffic-generated vibrations on buildings, particularly masonry-built and historical buildings, has been in the centre of interest in recent years when traffic intensity and axle loads have grown considerably. The problem has been studied systematically, by the team of the Chair of Structural Mechanics of the Technical University in Prague, since 1964.
The vibrations generated by passing vehicles cause, through the movement of foundations, forced vibrations of the building. The accuracy of the investigation of the natural vibrations of buildings depends on the suitable selection of the design pattern. The general form of the solution of the equations of motion describing the effect of the traffic-generated vibrations of the foundations of a symmetrical building as a system with n degrees of freedom in matrix form and when using normal coordinates can be obtained by means of Laplace transformation. The equations of motion in the case of an asymmetrical building and the expression of the matrix of masses, rigidities, attenuation, displacement vector and particularly the driving forces are introduced in this case.
The problem of the determination of the matrix of the driving forces [F] is considered. Their forecast is based on experience and test results. In the framework of the solution of this problem a whole number of measurements of traffic-generated vibrations was carried out both on the roads, foundation soil, building foundations, and the buildings themselves as well as the moving vehicles invarious parts of Prague, Brno, in the urban architectural reservation of Cesky Krumlov and elsewhere. The most suitable pickups and measuring apparatus are described. The results are presented in the form of a probability histogram and tables of basic characteristics of the investigated statistical sets. Examples of some results are introduced.
The danger of traffic-generated vibrations lies in that they are vibrations with very short periods varying between 0.005 and 0.5 seconds and very small amplitudes ranging between 0.1 and 20 [mu]m, but considerable acceleration. Large frequency of occurrence of these minor vibrations manifests itself as a fatigue phenomen and influences unfavourably the urban living environment. It is necessary to coordinate and harmonize the requirements of modern transport with the requirements of the safety of buildings, particularly with the requirements of the protection of historical and cultural memorials and, last but not least, the requirements of a satisfactory living environment in cities. |