• Wind and Structures
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• 제2권1호
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• pp.25-40
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• 1999

In this paper, artificial neural networks, a new kind of intelligent method, are employed to model and predict amplitude dependent damping in buildings based on our full-scale measurements of buildings. The modelling method and procedure using neural networks to model the damping are studied. Comparative analysis of different neural network models of damping, which includes multi-layer perception network (MLP), recurrent neural network, and general regression neural network (GRNN), is performed and discussed in detail. The performances of the models are evaluated and discussed by tests and predictions including self-test, "one-lag" prediction and "multi-lag" prediction of the damping values at high amplitude levels. The established models of damping are used to predict the damping in the following three ways : (1) the model is established by part of the data measured from one building and is used to predict the another part of damping values which are always difficult to obtain from field measurements : the values at the high amplitude level. (2) The model is established by the damping data measured from one building and is used to predict the variation curve of damping for another building. And (3) the model is established by the data measured from more than one buildings and is used to predict the variation curve of damping for another building. The prediction results are discussed.

• Wind and Structures
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• 제6권3호
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• pp.221-248
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• 2003

The design of high-rise building is often influenced by wind-induced motions such as accelerations and lateral deflections. Consequently, the building's structural stiffness and dynamic (vibration periods and damping) properties become important parameters in the determination of such motions. The approximate methods and empirical expressions used to quantify these parameters at the design phase tend to yield values significantly different from each other. In view of this, there is a need to examine how actual buildings in the field respond to dynamic wind loading in order to ascertain a more realistic model for the dynamic behavior of buildings. This paper describes the findings from full-scale measurements of the wind-induced response of typical high-rise buildings in Singapore, and recommends an empirical forecast model for periods of vibration of typical buildings in Singapore, an appropriate computer model for determining the periods of vibration, and appropriate expressions which relate the wind speed to accelerations in buildings based on wind tunnel force balance model test and field results.

• Wind and Structures
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• 제2권2호
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• pp.95-104
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• 1999

The dynamic properties of one-span or multi-span reinforced concrete footbridges of catenary form (see e.g., Fig. 1) include the very low fundamental natural frequency, usually near the step-frequency of pedestrians, and the low damping of bending vibrations. The paper summarized the results of model as well as full-scale measurements with particular reference to the influence of torsional rigidity of the stress-ribbon on the magnitude of aerodynamic response, the results of measurements on footbridges of catenary form being completed by results obtained on footbridges of some other types. Additionally the influence of the local broadening of the bridge deck on the bridge response was tested. Starting from these results the criterion has been derived for the decision, whether the flutter analysis is necessary for the design of the footbridge.

• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.261-273
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• 2017

The control of the deformative behaviour of pre-stressed concrete roof elements for a satisfactory service performance is a main issue of their structural design. Slender light-weight wing-shaped roof elements, typical of the European heritage, are particularly sensitive to this problem. The paper presents the results of deformation measurements during storage and of both torsional-flexural and purely flexural load tests carried out on a full-scale 40.5 m long innovative wing-shaped roof element. An element-based simplified integral procedure that de-couples the evolution of the deflection profile with the progressive shortening of the beam is adopted to catch the experimental visco-elastic behaviour of the element and the predictions are compared with normative close-form solutions. A linear 3D fem model is developed to investigate the torsional-flexural behaviour of the member. A mechanical non-linear beam model is used to predict the purely flexural behaviour of the roof member in the pre- and post-cracking phases and to validate the loss prediction of the adopted procedure. Both experimental and numerical results highlight that the adopted analysis method is viable and sound for an accurate simulation of the service behaviour of precast roof elements.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1778-1783
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• 2000

When visual intrusion is an important factor, it is desirable to find alternative methods of improving the insertion loss of a noise barrier without increasing the height. Therefore, the primary object of the work attenuates the noise due to transport vehicle by small interference device installed at noise barrier edge. In this paper the performance of noise barriers with attached interference device, in terms of shape, absorptive material and split panel, are examined using the boundary element approach. Also, the scale models are moanted in an anechoic chamber and the frequency of the sound sources are appropriately scaled to simulate full scale site conditions. Lastly, experimental measurements of the designs are executed for a range of frequencies and receiver positions, and are compared with the results of numerical modeling.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 춘계학술대회 논문집
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• pp.537-542
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• 2000

When visual intrusion Is an Important factor, it is desirable to find alternative methods of Improving the insertion loss of a noise barrier without Increasing the height. Therefore, the primary object of the work attenuate the noise due to railway by small interference device installed at noise barrier edge. In this paper the performance of noise barriers with attached interference device, in terms of shape, absorptive material and split panel, we examined using the boundary element approach. Also, the scale models are mounted in an anechoic chamber and the frequency of the sound sources are appropriately scaled to simulate full scale site conditions. Lastly, experimental measurements of the designs are executed for a range of frequencies and receiver positions, and are compared with the results of numerical modeling.

• Wind and Structures
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• 제4권6호
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• pp.481-494
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• 2001

Wind tunnel pressure tests were conducted on a 1:100 scale model of a large industrial building with solar panels mounted parallel to the flat roof. The model form was chosen to have the same aspect ratio as the Texas Tech University test building. Pressures were simultaneously measured on the roof, and on the topside and underside of the solar panel, the latter two combining to produce a nett panel pressure. For the configurations tested, varying both the lateral spacing between the panels and the height of the panels above the roof surface had little influence on the measured pressures, except at the leading edge. The orientation of the panels with respect to the wind flow and the proximity of the panels to the leading edge had a greater effect on the measured pressure distributions. The pressure coefficients are compared against the results for the roof with no panels attached. The model results with no panels attached agreed well with full-scale results from the Texas Tech test building.

• Structural Engineering and Mechanics
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• 제29권2호
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• pp.171-186
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• 2008

The seismic response analysis of an existing bridge needs a mathematical model that can be calibrated with measured dynamic characteristics. These characteristics are the periods and the associated mode shapes of vibration and the modal damping coefficients. This paper deals with the measurements and the interpretation of the results of ambient vibration tests done on a newly erected cable stayed bridge across the Oued Dib River at Mila city in Algeria. The signal analysis of ambient vibration records will permit to determine the dynamic characteristics of the bridge. On the other hand, a 3-D model of the bridge is developed in order to assess the frequencies and the associated modes of vibration. This information will be necessary in the planning of the test on the site (locations of the sensors, frequencies to be measured and the associated mode shapes of vibration). The frequencies predicted by the finite element model are compared with those measured during full-scale ambient vibration measurements of the bridge. In the same way, the modal damping coefficients obtained by the random decrement method are compared to those of similar bridges.

• Wind and Structures
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• 제10권5호
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• pp.401-420
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• 2007

Field measurements of the wind-induced response of two residential reinforced concrete buildings, among the tallest in the world, have been performed during two typhoons. Natural periods and damping values have been determined and compared with other field measurements and empirical predictors. Suitable and common empirical predictors of natural period and structural damping have been obtained that describe the trend of tall, reinforced concrete buildings whose structural vibrations have been measured in the collection of studies in Hong Kong compiled by the authors. This data is especially important as the amount of information known about the dynamic parameters of buildings of these heights is limited. Effects of the variation of the natural period and damping values on the alongwind response of a tall building for serviceability-level wind conditions have been profiled using the gust response factor approach. When using this approach on these two buildings, the often overestimated natural periods and structural damping values suggested by empirical predictors tended to offset each other. Gust response factors calculated using the natural periods and structural damping values measured in the field were smaller than if calculated using design-stage values.

• 국제초고층학회논문집
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• 제4권1호
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• pp.9-25
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• 2015

Field measurements of various structures have been conducted for many purposes. Measurement data obtained by field measurement is very useful to determine vibration characteristics including dynamic characteristics such as the damping ratio, natural frequency, and mode shape of a structure. In addition, results of field measurements and modal identification can be used for modal updating of FEM analysis, for checking the efficiency of damping devices and so on. This paper shows some examples of field measurements and modal identification for structural health monitoring. As the first example, changes of dynamic characteristics of a 15-story office building in four construction stages from the foundation stage to completion are described. The dynamic characteristics of each construction stage were modeled as accurately as possible by FEM, and the stiffness of the main structural frame was evaluated and the FEM results were compared with measurements performed on non-load-bearing elements. Simple FEM modal updating was also applied. As the next example, full-scale measurements were also carried out on a high-rise chimney, and the efficiency of the tuned mass damper was investigated by using two kinds of modal identification techniques. Good correspondence was shown with vibration characteristics obtained by the 2DOF-RD technique and the Frequency Domain Decomposition method. As the last example, the wind-induced response using RTK-GPS and the feasibility of hybrid use of FEM analysis and RTK-GPS for confirming the integrity of structures during strong typhoons were shown. The member stresses obtained by hybrid use of FEM analysis and RTK-GPS were close to the member stresses measured by strain gauges.