• Steel and Composite Structures
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• v.28 no.3
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• pp.363-380
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• 2018

This paper presented an integral design procedure for demountable bolted composite frames with semi-rigid joints. Moment-rotation relationships of beam-to-column joints were predicted with analytical models aiming to provide accurate and reliable analytical solutions. Among this, initial stiffness of beam-to-column joints was derived on the basis of Timoshenko's plate theory, and moment capacity was derived in accordance with Eurocodes. The predictions were validated with relevant test results prior to further applications. Frame analysis was conducted by using Abaqus software with material and geometrical nonlinearity considered. Variable lateral loads incorporating wind actions and earthquake actions in accordance with Australian Standards were adopted to evaluate the flexural behaviour of the composite frames. Strength and serviceability limit state criteria were utilized to verify configurations of designed models. A wide range of frames with the varied number of storeys and bays were thereafter programmed to ascertain bending moment envelopes under various load combinations. The analytical results suggest that the proposed approach is capable of predicting the moment-rotation performance of the semi-rigid joints reasonably well. Outcomes of the frame analysis indicate that the load combination with dead loads and live loads only leads to maximum sagging and hogging moment magnitudes in beams. As for lateral loads, wind actions are more crucial to dominate the design of the demountable composite frames than earthquake actions. No hogging moment reversal is expected in the composite beams given that the frames are designed properly. The proposed analysis procedure is demonstrated to be a simple and efficient method, which can be applied into engineering practice.

• Earthquakes and Structures
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• v.12 no.5
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• pp.559-567
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• 2017

Slender structures like reinforced concrete (RC) chimneys are severely damaged or collapsed during severe wind storms or strong ground motions all over the world. Today, with the improvement in technology and industry, most factories need these slender structures with increasing height and decreasing in shell thickness causing vulnerable to winds and earthquakes. Main objectives in this study are to make structural wind and earthquake analysis of RC chimneys by using a well-known international standard CICIND 2001 and real recorded time history accelerations and to clarify weak points of these tall and slender structures against these severe natural actions. Findings of this study show that maximum tensile stress and shear stress approximately increase 103.90% and 312.77% over or near the openings on the body of the RC chimneys that cause brittle failure around this region of openings.

• Wind and Structures
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• v.2 no.3
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• pp.189-200
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• 1999

In this paper, a new algorithm for active control design of structures is proposed and investigated. The algorithm preserves the decoupling property of the modal vibration equation and eliminates the spillover problem, which is the main shortcoming in the independent modal space control(IMSC) algorithm. With linear quadratic regulator(LQR) control law, the analytical solution of algebraic Riccati equation and the optimal actuator control force are obtained, and the control design procedure is significantly simplified. A numerical example for the control design of a tall building subjected to wind loads demonstrates the effectiveness of the proposed algorithm in reducing the acceleration and displacement responses of tall buildings under wind actions.

• Wind and Structures
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• v.6 no.6
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• pp.451-470
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• 2003

The classical two-degree-of-freedom (2-d-o-f) "sectional model" is of common use to study the dynamics of suspension bridges. It takes into account the first pair of vertical and torsional modes of the bridge and describes well global oscillations caused by wind actions on the deck, yielding very useful information on the overall behaviour and the aerodynamic and aeroelastic response; however, it does not consider relative oscillations between main cables and deck. On the contrary, the 4-d-o-f model described in the two Parts of this paper includes longitudinal deformability of the hangers (assumed linear elastic in tension and unable to react in compression) and thus allows to take into account not only global oscillations, but also relative oscillations between main cables and deck. In particular, when the hangers go slack, large nonlinear oscillations are possible; if the hangers remain taut, the oscillations remain small and essentially linear: the latter behaviour has been the specific object of Part I (Sepe and Augusti 2001), while the present Part II investigates the nonlinear behaviour (coexisting large and/or small amplitude oscillations) under harmonic actions on the cables and/or on the deck, such as might be generated by vortex shedding. Because of the discontinuities and strong nonlinearity of the governing equations, the response has been investigated numerically. The results obtained for sample values of mechanical and forcing parameters seems to confirm that relative oscillations cannot a priori be excluded for very long span bridges under wind-induced loads, and they can stimulate a discussion on the actual possibility of such phenomena.

• Wind and Structures
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• v.14 no.5
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• pp.383-411
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• 2011

Roof is an integral part of building envelope. It protects occupants from environmental forces such as wind, rain, snow and others. Among those environmental forces, wind is a major factor that can cause structural roof damages. Roof due to wind actions can exhibit either flexible or rigid system responses. At present, a dynamic test procedure available is CSA A123.21-04 for the wind uplift resistance evaluation of flexible membrane-roofing systems and there is no dynamic test procedure available in North America for wind uplift resistance evaluation of rigid membrane-roofing system. In order to incorporate rigid membrane-roofing systems into the CSA A123.21-04 testing procedure, this paper presents the development of a load cycle. For this process, the present study compared the wind performance of rigid systems with the flexible systems. Analysis of the pressure time histories data using probability distribution function and power spectral density verified that these two roofs types exhibit different system responses under wind forces. Rain flow counting method was applied on the wind tunnel time histories data. Calculated wind load cycles were compared with the existing load cycle of CSA A123.21-04. With the input from the roof manufacturers and roofing associations, the developed load cycles had been generalized and extended to evaluate the ultimate wind uplift resistance capacity of rigid roofs. This new knowledge is integrated into the new edition of CSA A123.21-10 so that the standard can be used to evaluate wind uplift resistance capacity of membrane roofing systems.

• Wind and Structures
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• v.20 no.6
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• pp.763-791
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• 2015

"Wind and Ports" is a European project that has been carried out since 2009 to handle wind forecast in port areas through an integrated system made up of an extensive in-situ wind monitoring network, the numerical simulation of wind fields, the statistical analysis of wind climate, and algorithms for medium-term (1-3 days) and short term (0.5-2 hours) wind forecasting. The in-situ wind monitoring network, currently made up of 22 ultrasonic anemometers, provides a unique opportunity for detecting high resolution thunderstorm records and studying their dominant characteristics relevant to wind engineering with special concern for wind actions on structures. In such a framework, the wind velocity of thunderstorms is firstly decomposed into the sum of a slowly-varying mean part plus a residual fluctuation dealt with as a non-stationary random process. The fluctuation, in turn, is expressed as the product of its slowly-varying standard deviation by a reduced turbulence component dealt with as a rapidly-varying stationary Gaussian random process with zero mean and unit standard deviation. The extraction of the mean part of the wind velocity is carried out through a moving average filter, and the effect of the moving average period on the statistical properties of the decomposed signals is evaluated. Among other aspects, special attention is given to the thunderstorm duration, the turbulence intensity, the power spectral density and the integral length scale. Some noteworthy wind velocity ratios that play a crucial role in the thunderstorm loading and response of structures are also analyzed.

• Wind and Structures
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• v.37 no.6
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• pp.413-423
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• 2023

Wind turbines are usually steel hollow structures that can be vulnerable to dramatic failures due to high-intensity wind (HIW) events, which are classified as a category of localized windstorms that includes tornadoes and downbursts. Analyzing Wind Turbines (WT) under tornadoes is a challenging-to-achieve task because tornadoes are much more complicated wind fields compared with the synoptic boundary layer wind fields, considering that the tornado's 3-D velocity components vary largely in space. As a result, the supporting tower of the wind turbine and the blades will experience different velocities depending on the location of the event. Wind farms also extend over a large area so that the probability of a localized windstorm event impacting one or more towers is relatively high. Therefore, the built-in-house numerical code "HIW-WT" has been developed to predict the straining actions on the blades considering the variability of the tornado's location and the blades' pitch angle. The developed HIWWT numerical model incorporates different wind fields that were generated from developed CFD models. The developed numerical model was applied on an actual wind turbine under three different tornadoes that have different tornadic structure. It is found that F2 tornado wind fields present significant hazard for the wind turbine blades and have to be taken into account if the hazardous impact of this type of unexpected load is to be avoided.

• Wind and Structures
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• v.23 no.4
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• pp.313-350
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• 2016

Taipei 101 Tower, which has 101 stories with height of 508 m, is located in Taipei where typhoons and earthquakes commonly occur. It is currently the second tallest building in the world. Therefore, the dynamic performance of the super-tall building under strong wind actions requires particular attentions. In this study, Large Eddy Simulation (LES) integrated with a new inflow turbulence generator and a new sub-grid scale (SGS) model was conducted to simulate the wind loads on the super-tall building. Three-dimensional finite element model of Taipei 101 Tower was established and used to evaluate the wind-induced responses of the high-rise structure based on the simulated wind forces. The numerical results were found to be consistent with those measured from a vibration monitoring system installed in the building. Furthermore, the equivalent static wind loads on the building, which were computed by the time-domain and frequency-domain analysis, respectively, were in satisfactory agreement with available wind tunnel testing results. It has been demonstrated through the validation studies that the numerical framework presented in this paper, including the recommended SGS model, the inflow turbulence generation technique and associated numerical treatments, is a useful tool for evaluation of the wind loads and wind-induced responses of tall buildings.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.4
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• pp.457-466
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• 2013

Wind energy is rapidly becoming significant generating technologies in electricity markets. As probabilistic nature of wind energy creates many uncertainties in the short-term scheduling, additional actions for reliable market operation should be taken. This paper presents a novel approach to evaluate ramping capability requirement for changes in imbalance energy between day-ahead market and real-time market due to uncertainty of wind generation as well as system load. Dynamic ramp rate model has been applied for realistic solution in unit commitment problem, which is implemented in day-ahead market. Probabilistic optimal power flow has been used to verify ramping capability determined by the proposed method is reasonable in economic and reliable aspects. This approach was tested on six-bus system and IEEE 118-bus system with a wind farm. The results show that the proposed approach provides ramping capability information to meet both forecasted variability and desired confidence level of anticipated uncertainty.

• Wind and Structures
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• v.25 no.2
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• pp.177-193
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• 2017

The accelerated development of new materials, technologies and construction processes, in parallel with advances in computational algorithms and ever growing computational power, is leading to more daring and innovative architectural and structural designs. The search for non-regular building shapes and slender structures, as alternative to the traditional architectural forms that have been prevailing in the building sector, poses important engineering challenges in the assessment of the strength and mechanical stability of non-conventional structures and systems, namely against highly variable actions as wind and seismic forces. In case of complex structures, laboratory experiments are a widely used methodology for strength assessment and loading characterization. Nevertheless, powerful numerical tools providing reliable results are also available today and able to compete with the experimental approach. In this paper the wind action on a free-form complex thin shell is investigated through 3D-CFD simulation in terms of the pressure coefficients and global forces generated. All the modelling aspects and calibrating process are described. The results obtained showed that the CFD technique is effective in the study of the wind effects on complex-shaped structures.