Wind Vibration Coefficient Research Articles

Wind field simulation and wind‐induced responses of large wind turbine tower‐blade coupled structure

SummaryHerein, by a case study on a 5‐MW wind turbine system developed by Nanjing University of Aeronautics and Astronautics, the wind field simulation and wind‐induced vibration characteristics of wind turbine tower‐blade coupled systems is analyzed. First, the blade‐nacelle‐tower‐basis integrated finite element model with centrifugal forces induced by rotational blades is established. Then, based on a harmony superposition method and the modified blade element‐momentum theory, the fluctuating wind field of tower‐blade coupled systems is simulated, which considers wind shear effect, tower shadow effect, rotational effect, blade‐tower dynamic and model interaction effects. Finally, the wind‐induced dynamic responses and wind vibration coefficients of the wind turbine tower‐blade coupled structure are discussed through the ‘consistent coupled method’ previously proposed by us. The results indicate that the wind‐induced responses of a large wind turbine tower‐blade coupled structure present complicated modal responses and multimode coupling effect. Additionally, the rotational effect would amplify aerodynamic loads on blades with high frequency, wind‐induced dynamic responses and wind vibration coefficients of wind turbine tower. The centrifugal force effect could also amplify natural vibration frequency of the tower‐blade coupled system and reduce the wind‐induced dynamic responses and wind vibration coefficients of wind turbine tower. The research could contribute to wind‐resistant design of structure for a large‐scale wind turbine tower‐blade system. Copyright © 2014 John Wiley & Sons, Ltd.

Investigations on the Wind Vibration Coefficient of Single Layer Lattice Barrel Vault Structures

Wind actions on the structures consist of two parts, the average action and the fluctuation action. The fluctuation action will cause the structures vibrating and enlarge the wind action of the structures. This paper investigates the wind vibration coefficient for the single layer lattice barrel vault structures. In the analysis, the simulation velocity-time curve of wind is developed and the finite element methods are used to analyze the wind-induced vibration responses of the lattice barrel vault structures. The influence of the rise to span ratio, the length to width ratio of the structure, and the different average velocity of the wind are investigated. Based on the numerical analysis results, the formula of the wind vibration coefficient for the single layer lattice barrel vault structure is suggested for the wind resistance design of the structures.

Analysis of Random Vibration Fatigue Life Based on Fluctuation Wind for Antenna Structure

Aimed at fatigue damage in the antenna structure caused by large amplitude vibration with long time fluctuating wind loads, this paper use the harmonic synthesis method to transform power spectrum of Davenport fluctuating wind to fluctuating wind speed time series based on time domain. Then comprehensively considering the surface roughness coefficient, wind pressure coefficient of variation with height, wind vibration coefficient in Beijing area ,it transforms the fluctuating wind speed into the fluctuating wind pressure curve, takes the structural dynamics simulation and is obtained the dynamic response of the antenna structure in turbulent wind Loads; By the method of rain-flow counting , the fatigue life is analyzed with the statistics for the dangerous location of the antenna structure coursed of fatigue stress with time.

Wind-induced responses of super-large cooling towers

Traditional gust load factor (GLF) method, inertial wind load (IWL) method and tri-component method (LRC+IWL) cannot accurately analyze the wind-induced responses of super-large cooling towers, so the real combination formulas of fluctuating wind-induced responses and equivalent static wind loads (ESWLSs) were derived based on structural dynamics and random vibration theory. The consistent coupled method (CCM) was presented to compensate the coupled term between background and resonant response. Taking the super-large cooling tower (H=215 m) of nuclear power plant in Jiangxi Province, China, which is the highest and largest in China, as the example, based on modified equivalent beam-net design method, the aero-elastic model for simultaneous pressure and vibration measurement of super-large cooling tower is firstly carried out. Then, combining wind tunnel test and CCM, the effects of self-excited force on the surface pressures and wind-induced responses are discussed, and the wind-induced response characteristics of background component, resonant component, coupled term between background and resonant response, fluctuating responses, and wind vibration coefficients are discussed. It can be concluded that wind-induced response mechanism must be understood to direct the wind resistant design for super-large cooling towers.

Design and Full-Scale Test for Steel Tubular Tower of UHV and EHV Quadruple-Circuit Transmission Line on the same Tower

State Grid Corporation of China has carried out research on key technology of UHV&EHV AC and DC multi-circuit transmission lines, the research on material and structure of transmission tower is the important part. The SSZT2 tower, on which 1000 kV AC double-circuit and 500 kV AC double-circuit are arranged, is the largest power transmission capacity all over the world. Q420 high-strength tubular steel, the plug-in boards and forging flanges are used in SSZT2 tower,and the forging flange with strength classification is applied for the first time. Through the monographic study on the tower structures, wind vibration coefficient, and biaxial bending of steel tube etc. The success of full-scale test verified the reliability in design and manufacture of multi-circuit steel tubular tower for UHV and EHV. Research results of this paper can be applied in UHV transmission line projects.

Study on Wind Load Performance for L Type Aerial Work Suspended Platform

Based on the wind load calculation model increases Suspended Platform vibration characteristics of wind vibration coefficient, and gets Suspended Platform natural vibration period and inherent frequency by ANSYS finite element modal analysis, then determines the wind vibration coefficient, calculates the wind load of Suspended Platform in working state and non-working state. Aiming at three different conditions, analyzes the platform structure in the wind load the stress intensity and deformation. Through analysis to finds the most dangerous positions of Suspended Platform in three different conditions, provides effective references for the L Type Suspended Platform in wind-resistant design and optimization design.

Program for the Analysis of Wind-Induced Vibration of Steel Roof Structures

Wind loads are key considerations in the structural design of steel roof structures, especially for large span ones. The analysis of wind loads on large span steel roof structure (LSSRS) requires large amounts of calculations. Due to combined effects of horizontal and vertical winds, the wind induced vibrations of LSSRS are analyzed with the frequency domain method as the first application of the method for the analysis of wind responses of LSSRS. A program is developed to analyze the wind-induced vibrations due to a combination of wind vibration modes. The program, which predicts the wind vibration coefficient and wind pressure acting on the LSSRS, is designed with input and output interfaces to other finite element software, resulting in preferably solving the wind load analytical problem in the design of LSSRS. The effectiveness and accuracy of the proposed method and the program are verified by numerical analyses of practical projects.

Wind-Induced vibration responses of prestressed double-layered spherical latticed shells

This paper focuses on the wind-induced vibration response of prestressed double-layered spherical latticed shell (PDSLS) structures by adopting time-domain analysis method. Welch spectrum analysis method is used to make precision evaluation of power spectrum of fluctuating wind speed time history simulated by weighted amplitude wavelet superposition (WAWS) method and linear filtering method of auto-regression (AR) model. Results show that the two methods produce little precision difference, but AR method is far more efficient than WAWS and is more suitable for wind speed simulation of PDSLSs. The effect of various parameters on the wind-induced vibration response of PDSLS structures are comprehensively investigated, including rise-span ratio, span, shell thickness, elastic constraint stiffness, prestress value, with or without cables and cable layout scheme. Results show that rise-span ratio and span are the major factors that affect wind-induced vibration response of PDSLSs. When cables are set, the wind vibration coefficient of nodal vertical displacement becomes smaller and more equally distributed, which demonstrates that PDSLSs are less sensitive to fluctuating wind effect than common latticed shell structures without cables. Finally, based on the envelopment concept and with the maximum dynamic and average wind-induced displacement responses as control indicators, the calculating method for global wind vibration coefficient (GWVC) of PDSLSs is proposed and the value with usual design parameters is given. Meanwhile, when the structure is made static analysis by means of the equivalent static wind load obtained from GWVC, the obtained internal member force response is relatively accordant with the actual response got from time-history analysis, and is a little safer.

Nonlinear Analysis and Design of a Guyed Mast: Comparison of Two Design Proposals

The guyed mast structure consists of a vertical shaft supported along its height by several layers of inclined pre-tensioned guys. The central shaft is generally made of lattice steel structure, and the guys are spaced at equal angles around the mast to ensure the vertical shaft’s stability. By taking a 102 m meteorological guyed tower in Hainan as an example, this paper made two design proposals using steel pipe and round steel material for the shaft respectively. According to the requirements of the project, this paper then did non-linear static analysis and buckling analysis of the structure by finite element software SAP2000, and compared the results of the two proposals so as to find the optimal one. The results show that steel pipe material is more economical when used for the mast shaft and more reasonable for bearing forces. The choice of the number and the initial tension of guys, as well as the wind vibration coefficient, which have a great effect on a guyed mast, are also discussed in this paper.

Software Practicalization for Analysis of Wind-Induced Vibrations of Large Span Roof Structures

Wind loads are key considerations in the structural design of large-span structures since wind loads can be more important than earthquake loads, especially for large flexible structures. The analysis of wind loads on large span roof structures (LSRS) requires large amounts of calculations. Due to the combined effects of horizontal and vertical winds, the wind-induced vibrations of LSRS are analyzed in this paper with the frequency domain method as the first application of method for the analysis of the wind response of LSRS. A program is developed to analyze the wind-induced vibrations due to a combination of wind vibration modes. The program, which predicts the wind vibration coefficient and the wind pressure acting on the LSRS, interfaces with other finite element software to facilitate analysis of wind loads in the design of LSRS. The effectiveness and accuracy of the frequency domain method have been verified by numerical analyses of practical projects.

Wind Load on Integral-Lift Scaffolds for Tall Building Construction

The integral-lift scaffolds are widely used in construction of tall buildings in Asia. However, the wind load on scaffolds may be much greater than dead load and be the dominant effect as the scaffolds climb over 150 m in height. The shape coefficient and vibration coefficient are important factors in calculation of wind load. However, there is no available approach at present for determining the two coefficients for calculating the wind load on this temporary structure. In order to determine the shape coefficient of wind pressure on the typical scaffolds, wind tunnel tests have been conducted. The drag coefficients have been measured, which are proved to be identical to the wind shape coefficients. By using random vibration theory, formulae are obtained for predicting the wind vibration coefficients of the scaffolds at the two stages of climbing up and down. The useful guidelines for the safe design of integral-lift scaffolds against winds are proposed in this paper.

A New Frequency Domain Method for Wind Response Analysis of Spatial Lattice Structures with Mode Compensation

The large span spatial lattice structures have many natural frequencies in a narrow frequency range, the conventional frequency domain method is difficult to contain all significant contribution modes. Through numerical examples, it is found that some high order modes are likely to be overlooked because of their higher positions of modal order, in spite of their significance to wind response. According to the contributions of modes to strain energy of system, the paper presented an efficient method to compensate the errors owing to missing out some significant high order modes. The effectiveness of the proposed method is verified through a numerical analysis of the wind responses of a spherical dome. At last, a simplified method of wind vibration coefficient is present for design of practical projects.