Structural effects on externally induced building vibrations

Abstract: Much focus is being laid on vibrations in the building industry today. Many times these vibrations are externally induced and caused by placing buildings closer to existing sources, such as railways and roads, or new transportation systems closer to existing buildings. Vibrations can be disturbing to both humans and sensitive equipment in, for example, hospitals and laboratories. The simulations needed to investigate the effects of these vibrations are complex. Because of this it is important to know which studies are needed in a project and what parameters need to be evaluated. In the Master's dissertation, the important parameters for a building and its surrounding materials, when analysing externally induced vibrations in the built environment, are investigated. The focus of the study is on the effects of surrounding buildings in numerical models, i.e. how multiple buildings will respond to external vibrational sources compared to the response of a single building. Numerical parametric analyses were performed in the commercial software Abaqus using twodimensional finite element models with different geometry, mass, stiffness and damping. Plain strain conditions were used in the layered ground model and the concrete buildings. Steady-state analyses were performed for the frequency spectrum between 1 and 80 Hz, with a linear step size of 0.5 Hz applying a unit load of 1 N, 50 m from the studied building. Both the effects of a building being placed in front of a studied building and a building being placed behind the studied building was investigated. How nearby buildings affect the response to external vibrations on a building is difficult to predict and it's hard to find general principles that describe it. It is, however, clear that nearby buildings have an impact on the vibrational response. A large reduction in vertical response amplitude can be observed when a building is placed in front of a building that is similar in geometry. The largest reductions in displacement seem to coincide with the resonance frequencies of the buildings. A heavy building and a building with low damping being placed between the load and the studied building yielded similar results in that they both corresponded to a lowering of the vertical displacement amplitude. A building placed after the studied building in the direction of the propagating waves does not have a large impact on the vertical vibrational response. Only when the building behind is partly submerged into the soil i.e. having a cellar, is the difference in response for the studied building noticeable but still low.