Vibrações em pisos de edificações induzidas por atividades humanas

Abstract

Nowadays, the new architectural tendency and the market requirements, are leading structural engineering in the search for bolder solutions, which demands great experience and knowledge of the structural designers associated to the use of new materials and technologies. This philosophy of structural conception is inserted in one of the most important trends of project of the last years that means: the search for structural systems of fast execution, endowed with parts of lower weight and that can be successfully large with a minimum of vertical elements, thus allowing a higher flexibility in the ambients adequacy. On the other hand, this project philosophy has lead to structural elements more and more slender and with natural frequencies much and much lower and, therefore, closer to the frequency of the dynamic excitation associated to the human beings activities, such as: walking, running, jumping, etc. Due to the reasons described in the previous paragraph, the structural engineering systems became sufficiently vulnerable to the effects of vibrations induced by small impacts as it is the case of walking of people on floors, resulting in discomfort to the people. It must be highlighted, also, that such project considerations have fulfilled the required limit states. However, the limit states of use for these structural systems need to be analysed, with no doubt, in a more sensible way. In this way, willing to contribute to supply subsidies to the structural engineers, in the dynamic analysis of structures subject to excitation induced by human beings, several loads models are developed to represent the act of walking. The space and time variation of the dynamic load is considered through the analysis and the transient effect of the impact of the human heel on the floor is taken into consideration, as well. In this way, It is considered in this dissertation, several structural models associated to composite floors (steel-concrete). In this study, it was considered the usual techniques of discretization, based on the Finite Element Method (FEM) using the computer program Ansys. An extensive analysis concerning the dynamic response of the floors is made, by means of the application of the developed load models, mainly, in terms of the values of the accelerations. The results obtained are compared to those supplied by the techinical literature available about the subject with the point of view associated to the human comfort. It is also investigated, the influence of the structural parameter variation on the dynamic response of the models, such as: span length, damping ratio, thickness of the slab and, also, rigidity of the beam columns. The results obtained along the study clearly indicate that the structural designers must be alerted to important distortions that may occur when the project rules are used without the necessary caution. Another important remark is regarded to the fact that in several analysed floors it is observed that the criteria of human comfort are not satisfied which demonstrate the importance of the consideration of the dynamic effect caused by human beings in the analysis of this type of problem.