Abstract
Structures include elements designated as load bearing and non-load bearing. While non-load bearing elements, such as facades and internal partitions, are acknowledged to add mass to the system, the structural stiffness and strength is generally attributed to load bearing elements only. This paper investigates the contribution of non-load bearing elements to the dynamic response of a new structure, the Charles Institute, in the grounds of University College Dublin (UCD) Ireland. The vertical vibration response of the first floor and the lateral response at each floor level were recorded at different construction stages. The evolution of the structural response as well as the generation of a finite element (FE) model is discussed. It was found that the addition of the non-load bearing facades increased the first floor natural frequency from 10.7 Hz to 11.4?Hz, a change of approximately +6.5%. Similarly these external facades resulted in the first sway mode having its frequency increased by 6%. The subsequent addition of internal partitions, mechanical services and furnishings resulted in the floor natural frequency reducing to 9.2 Hz. It is concluded that external facades have the net effect of adding stiffness and the effect of internal partitions and furnishings is to add mass. In the context of finite element modelling of structures there is a significant challenge to represent these non-structural elements correctly so as to enable the generation of truly predictive FE models.
Highlights
A building consists of a primary structural system which is designed to resist a variety of loads
To track the contribution of non-structural elements, as the structure evolved toward completion, vibration response data was recorded at three stages so that an accurate picture of the effect of different non-structural components could be assessed
In general terms it is concluded that facades and partitions have an effect on the modal characteristics of structures and it is recommended that where vibration response serviceability compliance tests are required, that these be only executed on a structurally complete and fully furnished system
Summary
A building consists of a primary structural system which is designed to resist a variety of loads. Su et al [5] investigated the influence of non-structural components on the lateral stiffness of three tall buildings using full-scale ambient vibration measurements It was concluded, with the aid of Finite Element (FE) models, that non-structural elements were the largest contributors to structural stiffness compared to other parameters added to the initial bare frame FE model. With the aid of Finite Element (FE) models, that non-structural elements were the largest contributors to structural stiffness compared to other parameters added to the initial bare frame FE model These other parameters included a modified Young’s Modulus for reinforced concrete, the inclusion of secondary beams and the addition of flexible floor diaphragms. The analysis of these structures highlighted the significant impact non-structural elements can have on the dynamic response of structures. To track the contribution of non-structural elements, as the structure evolved toward completion, vibration response data was recorded at three stages so that an accurate picture of the effect of different non-structural components could be assessed
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