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This paper describes the design of a system to monitor floor vibrations in an office building and an analysis of several months’ worth of collected data. Floors of modern office buildings are prone to occupant-induced vibrations. The contributing factors include long spans, slender and flexible designs, use of lightweight materials and low damping....
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... were taken into account for optimal sensor placement simulations as they were in the range that could be excited by footfall harmonics. Figure 3 shows three examples of the lowest frequency modes. It can be seen that due to irregularities and openings in the floor they are localized in either the lower part of floor, where several small classrooms are located, or in the upper corners used for offices and galleries. ...
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In this research, realistic models were developed using experimental approach and statistical or
deterministic analysis in the relationship between bending amplitudes and bending stress (strain)
of the overhead line conductor. This was rigidity clamped and subjected to Aeolian vibration
(1Hz-150 Hz). The experiments were performed at the Vibration...
Citations
... The influence of the cracks developing in the concrete slab and the deflections of the supporting beams are also considered as one of the influencing parameters. At present, plenty of studies focus on such dynamic characteristics as natural frequencies, damping ratios, and mode shapes of TCC floor systems; in among the others mentioned here, there are more studies [15][16][17][18][19][20][21][22][23][24][25][26][27]. If a fixed-length system is considered, it can be concluded that the thickness of the concrete slab contributes to stiffness as well as mass, but the increased mass can outweigh the improvement to stiffness, thus causing the fundamental frequency to decrease. ...
... The permanent and imposed load was determined following [66], while the shrinkage effect (Figure 4) was taken as follows [38]: ∆T = ε cs oo/αT (22) Finally, the load combinations [37] are made as follows: ...
... winst = G + Q1 (24) wnet,fin = Gkdef + ∑〖ψ2•Qi,k,def − wc〗 (25) wnet,fin = Gk,def The permanent and imposed load was determined following [66], while the shrinkage effect (Figure 4) was taken as follows [38]: ∆T = ε cs oo/αT (22) Finally, the load combinations [37] are made as follows: ...
The TCC concept has been studied and developed over the past decades. The variety of solutions shows the meaningfulness and functionality of this system, as well as the continuous work of scientists over time. To benefit from these advantages, the composite needs to provide sufficient stiffness to meet the serviceability criteria and load capacity to resist loading at every stage of the building life. An example of connector types and load slip curves according to EN 1995 is given. This paper discusses possible limitations related to residential areas, and additionally, the possible solutions that EN 1995 does not discuss in the case of resonant response (f1 < 8 Hz). The theoretical studies were accompanied by numerical analyses considering certain simplifications suitable for practical use.
Timber-concrete composite (TCC) is a well-approved technology for revaluation or strengthening of existing timber beam ceilings. In this process, shear connectors are assembled at the top of the timber beams and subsequently a concrete slab is casted resulting in a composite member in consequence of hardening of concrete. Normally, the boarding can stay in place and the bottom side of the floor may be unchanged. This fact is a huge benefit in the context of heritage protection and revaluation of old buildings in general. Whereas the load bearing behavior of TCC slabs was investigated in many research projects, the vibration resistance less often was considered. The paper introduces the TCC construction method including its advantages and disadvantages. The authors discuss the requirements to the application of TCC and analyze the request on vibration resistance while applying TCC from the technical and the legal point of view. Based on a parametric study, the paper provides information about influence parameters on vibration resistance and draws conclusions for the appropriate design of TCC slabs. This paper only refers to slabs in residential buildings. For labs in industrial buildings, shopping malls, or sports facilities, other requirements exist.
Vibrações excessivas em estruturas têm sido investigadas durante décadas. Desde o
século XIX até a contemporaneidade, ocorrências de tal fenômeno têm surpreendido tanto profissionais da engenharia quanto usuários de estruturas afetadas (pontes, passarelas, arquibancadas). Tal fenômeno pode resultar em várias consequências negativas, como: insatisfação dos usuários; sentimento de insegurança nas pessoas; prejuízos econômicos; perda de produtividade num ambiente de trabalho; etc. A partir das décadas de 1950 e 1960, situações de vibrações excessivas em lajes começaram a ser relatadas com regularidade e, até o momento, estudos de caso continuam a ser publicados na literatura científica. O comportamento dinâmico de Lajes de Ambientes de Trabalho (LATs) é um tema significativo devido ao fato destas estruturas estarem, diariamente, suscetíveis a vibrações devido à atuação de cargas de caminhada. Atualmente, critérios normativos para o projeto de lajes recomendam a hipótese na qual uma única pessoa caminha sobre a estrutura, enquanto verificação deste Estado Limite de Serviço de Vibrações Excessivas (ELS-VE). Entretanto, o recorrente número de registros de vibrações excessivas em LATs coloca em dúvida a eficiência de tal recomendação. Nesse contexto, este trabalho apresenta investigações sobre o comportamento dinâmico de um modelo numérico (via método dos elementos finitos) de uma LAT submetida a cargas de caminhada em diferentes cenários de movimentação de pessoas. Nas simulações, foi utilizado o modelo de carga expresso pela Série de Fourier, com recomendações da ISO 10137. Foram realizadas simulações considerando cenários com uma pessoa, com duas pessoas caminhando numa mesma trajetória e com duas pessoas caminhando em trajetórias distintas, em situação de ressonância. Graus diversos de sincronização entre os passos das pessoas e diferenças de tempo entre o início da trajetórias de um e outro indivíduo foram incluídos. Resultados indicam que valores RMS de aceleração (medidos no centro da laje) dos cenários com duas pessoas excedem, na maior parte dos cenários, acelerações em cenários com uma pessoa, possuindo significativos variações percentuais. Tal fato sugere a necessidade da consideração de diferentes números de pessoas em recomendações normativas afins,
visando contribuir para a elaboração de critérios mais eficientes para projetos de LATs, no
que concerne à prevenção de vibrações excessivas por ação de cargas de caminhada.
