Wind Effects on Structures

Simiu, Emil; Yeo, Dong Hun

doi:10.1002/9781119375890

Cited by 164 publications

(141 citation statements)

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“…The along‐wind load is simulated from the power spectral density function (PSDF) of longitudinal wind velocity fluctuations defined by Kaimal et al, Simiu, Simiu and Scanlan, which is given as

S_{rr} ((),, H, {normalω}_{normalf}) = \frac{1}{2} \frac{200}{2 π} u_{*}^{2} \frac{H}{U ((), H)} \frac{1}{{([], 1 + 50 \frac{ω_{f} H}{2 italicπU ((), H)})}^{5 / 3}},

where H is the height of the structure, and ω f , u * , and U ( H ) are, respectively, the angular/circular frequency (rad/s), friction velocity, and the mean wind speed at height, H .…”

Section: Wind Force Simulationmentioning

confidence: 99%

Along-wind response control of chimneys with distributed multiple tuned mass dampers

Elias

Matsagar

Datta

2018

Struct Control Health Monit

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The effectiveness of distributed multiple tuned mass dampers (d-MTMDs) for multimode control of chimney for along-wind response is presented. A concrete chimney considered herein is an assemblage of two-dimensional (2D) beam elements, each assumed to have constant diameter over the element length. Along-wind forces are simulated using the Kaimal wind spectrum.The response of the chimney is to be controlled by installing tuned mass dampers (TMDs). Suitable locations of the TMDs are identified along height of the chimney based on its uncontrolled (NC) mode shapes. A TMD unit is placed where the mode shape amplitude of the chimney is the largest or larger in a particular mode to be controlled and is tuned with the corresponding modal frequency-the approach is called multimode vibration response control. The number of modes to be controlled is decided according to desired total modal mass participation. The coupled differential equations of motion for the system are derived and solved using Newmark's step-by-step iteration method. The displacement and acceleration responses of the chimney under the alongwind forces are computed to study the effectiveness of the d-MTMDs as compared with single tuned mass damper (STMD) and with arbitrarily installed d-MTMDs (ad-MTMDs). In addition, suitable mass and damping ratios for the STMD, ad-MTMDs, and d-MTMDs are obtained to achieve improved dynamic response control. It is observed that the d-MTMDs are effective controllers being designed as per vibration mode to be controlled.

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S_{rr} ((),, H, {normalω}_{normalf}) = \frac{1}{2} \frac{200}{2 π} u_{*}^{2} \frac{H}{U ((), H)} \frac{1}{{([], 1 + 50 \frac{ω_{f} H}{2 italicπU ((), H)})}^{5 / 3}},

where H is the height of the structure, and ω f , u * , and U ( H ) are, respectively, the angular/circular frequency (rad/s), friction velocity, and the mean wind speed at height, H .…”

Section: Wind Force Simulationmentioning

confidence: 99%

Along-wind response control of chimneys with distributed multiple tuned mass dampers

Elias

Matsagar

Datta

2018

Struct Control Health Monit

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“…In the book of "Wind Effects on Structures", 34 wind can be regarded as an alternating force with different cycles. In general, the wind with a cycle of 10 min or above is called a long period wind which can produce a static effect, while the wind with a cycle of a few seconds or dozens of seconds is called a shortperiod wind which can generate an alternating effect.…”

Section: Feasibility Analysis Of the Ideas Used In This Studymentioning

confidence: 99%

“…Essentially this process is the fragmentation and relative slippage of macromolecule chain. In the book of "Wind Effects on Structures", 34 wind can be regarded as an alternating force with different cycles, which will make the sand-fixing polymer materials fatigue and fracture, reducing of the sand-fixing durability of polymers. Then, what kind of materials can limit the damage caused by the alternating force?…”

Section: Introductionmentioning

confidence: 99%

“…The answer is the polymer damping materials, which can turn the external periodic force into heat through the internal friction of its own molecular chains, resulting in a self-protection through the dissipation of heat. 34 Therefore, we introduce the concept of damping materials into the design of sand-fixing material for the first time, expecting to improve the sand-fixing durability of materials by strengthening its own anti-wind erosion property.…”

Section: Introductionmentioning

confidence: 99%

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Inner relationship between the damping property and the sand‐fixing durability of polymer materials

Xie

Liu

Chen

et al. 2018

J of Applied Polymer Sci

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This article for the first time reveals the impact of the damping property of materials on its sand‐fixing durability. Based on the turbulence of wind, it could be regarded as a kind of periodic mechanical force. So, when polymers are used to fix sand, they would constantly perceive a periodic force of wind. And, this force would give rise to yielding fracture and fatigue of polymer, so that the sand‐fixing durability of material could be weakened significantly. To impair the periodic force of wind and extend the durability of sand‐fixation polymer materials, we, for the first time, introduce the designing principle of macromolecular damping material, that can transform external mechanical force into own thermal energy, into the preparation of sand‐fixing materials. In this work, poly(vinyl acetate) (PVAc) emulsions with different dangling chain have been synthesized successfully in order to improve their damping properties. The effects of the prepared PVAc with gradually growing dangling chain length have been investigated on their damping properties, on the sand stabilization strengths and sand‐fixing durability. And the relationship between the damping property and the sand‐fixing property of PVAc was built by simulating wind tunnel test. The experimental results show that, introducing the dangling chain could significantly improve the damping temperature range and extend the anti‐wind erosion time of PVAc. It has to be noticed that, introducing the dangling chain, will provide a double effects for the sand stabilization strength of materials, i.e., it can improve both the flexibility of the side‐chain and the internal friction of the molecular chains. Wind tunnel test verified that introducing the dangling chain can raise the damping performance of material and convert more periodic force of wind into the friction heat of molecular chain, and thus impair the damage of wind on the materials and improve their anti‐wind erosion properties. These findings suggest that the damping material applied in sand fixation is a bright idea and successful method for improving the sand‐fixing durability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47208.

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“…Most models are heuristic, with only a limited range of applicability. Different types exist, the most noteworthy can be classified as force decomposition models [3], single degree-of-freedom (sdof) models [4] or wake oscillator models, where the wake oscillation is generally formulated as a Van der Pol equation [5,6,7]. cylinder.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear state-space modelling of the kinematics of an oscillating circular cylinder in a fluid flow

Decuyper

Troyer

Runacres

et al. 2018

Mechanical Systems and Signal Processing

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The flow-induced vibration of bluff bodies is an important problem of many marine, civil, or mechanical engineers. In the design phase of such structures, it is vital to obtain good predictions of the fluid forces acting on the structure. Current methods rely on computational fluid dynamic simulations (CFD), with a too high computational cost to be effectively used in the design phase or for control applications. Alternative methods use heuristic mathematical models of the fluid forces, but these lack the accuracy (they often assume the system to be linear) or flexibility to be useful over a wide operating range.In this work we show that it is possible to build an accurate, flexible and low-computational-cost mathematical model using nonlinear system identification techniques. This model is data driven: it is trained over a user-defined region of interest using data obtained from experiments or simulations, or both. Here we use a Van der Pol oscillator as well as CFD simulations of an oscillating circular cylinder to generate the training data. Then a discrete-time polynomial nonlinear state-space model is fit to the data. This model relates the oscillation of the cylinder to the force that the fluid exerts on the cylinder. The model is finally validated over a wide range of oscillation frequencies and amplitudes, both inside and outside the so-called lock-in region. We show that forces simulated by the model are in good agreement with the data obtained from CFD.Although capable of qualitatively describing the characteristic behaviour of VIV, an efficient and powerful model, flexible enough to span a wide domain in parameter space with a single set of parameters has yet to be obtained. To identify such a model, system identification can be a very powerful tool. In recent years, the application of linear system identification techniques has already shown some promising results, e.g. the best linear approximation in least squares sense [8] or building an input-output relationship using delayed values of the input and the output (ARX model) [9].Nevertheless, the challenges in modelling the system at hand are substantial. Fluid-structure interactions are, for one, inherently nonlinear [10]. This is strongly pronounced by the fact that VIV is a selfexcited yet self-limited oscillation, resulting in a stable limit cycle [11]. In addition, it has been shown that the vortex shedding behaviour is hysteretic [12]. Nonlinear modelling of VIV is currently a very active research topic. In [13], the auto-regressive moving averaging (ARMA) technique is combined with the modal analysis method. A nonlinear force representation is obtained by including higher harmonic terms resulting from the fluid-structure coupling. The coefficients in the model are determined to provide a best fit to the measured time series in maximum-likelihood sense. Reasonable predictions in terms of maximum amplitude are found, although only a limited amount of validation cases were investigated. In recent work [14], local linear models are used as a surro...

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Wind Effects on Structures

Cited by 164 publications

References 0 publications

Along-wind response control of chimneys with distributed multiple tuned mass dampers

Along-wind response control of chimneys with distributed multiple tuned mass dampers

Inner relationship between the damping property and the sand‐fixing durability of polymer materials

Nonlinear state-space modelling of the kinematics of an oscillating circular cylinder in a fluid flow

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