The Wind-Induced Vibration Response for Tower Crane Based on Virtual Excitation Method
The Dynamics characteristic of Tower Crane is complicated under the wind excitation which complicates the wind-induced vibration response analysis. The random wind-induced response analysis of tower crane is presented based on finite element method and Virtual Excitation Method. The pulsating wind loads are changed into multiple-point correlation stationary excitation. This papers uses Davenport's wind speed spectrum which does not change with height, and considers multiple-point correlation of wind-induction. The Tower Crane is employed as a numerical example, the response spectra and Mean Square Root (RMS) of the tower crane is obtained by wind-induced vibration. The results indicate that the vibration of the tower crane has a large response in low frequency and the One-third Octave acceleration RMS is lower, the influences of the wind-induced vibration on comfort are analyzed.
A Smart Tower Crane to Mitigate Turbulent Wind Loads
Abstract Tower cranes have, in general, low structural damping, leading to challenges with respect to vibrations induced by natural hazards. Crane failures due to wind excitations are very common around the world. In the present research work, a smart tower crane equipped with pairs of collocated sensors and actuators is proposed to mitigate turbulent wind. A three-dimensional finite element model of the crane is created using MATLAB®/Structural Dynamics Toolbox. Modal analysis is performed to calculate natural frequencies and corresponding mode shapes. Dynamic analysis of the crane is carried out under turbulent wind excitation. A decentralized active vibration control method is then used to prevent collapse of the crane. Active damping is added to the tower crane using pairs of force actuators–displacement sensors collocated on selected elements. A robust control strategy based on decentralized direct velocity feedback is implemented. The vibrations of the tower crane in all directions are significantly damped. It is concluded that the proposed smart tower crane model is highly efficient in mitigating the turbulent wind loads.
THE APPLICATION OF STATISTICAL CONCEPTS TO THE WIND LOADING OF STRUCTURES.
In the Paper the statistical concepts of the stationary time series are used to determine the response of a simple structure to a turbulent, gusty wind. This enables the peak stresses, accelerations, deflexions, etc., to be expressed in terms of the mean wind velocity, the spectrum of gustiness, and the mechanical and aerodynamic properties of the structure. In this connexion it is pointed out that the resistance in fluctuating flow may be significantly greater than that in steady flow, such as that prevailing in most wind-tunnel tests. An expression for the spectrum of gustiness near the ground is given, which takes into account its variation with mean wind velocity, roughness of the terrain, and the height above ground level. The statistical distribution of peak values over a large number of years is related to the statistical distribution of mean values by means of a so-called “gust factor”. A map defining the climate of extreme hourly wind speeds over the British Isles is provided. In association with the gust factor, this enables predictions of extreme peak wind loads with any given return period to be made. As an illustrative example, the wind loads which might arise on a flexible arc-lamp standard and a rigid water tower are compared. This emphasizes the considerable differences which may arise in the effective wind loads owing to differences in the local ground roughness and the dynamic characteristics of the structure.