Tuned vibration control of slender structures

In many cases slender structures are lightly damped, a condition described as ‘lively’, and can undergo large vibrations when subjected to traffic or environmental forcing. One measure against above vibrations is the application of tuned vibration control facilities in structures. The fibre members with variable prestressing forces and tuning facilities are adopted for the purpose of tuned vibration control of structures below. Theoretical backgrounds of present approaches as well as numerical and experimental studies of tuned vibration control problems in slender structures of guyed masts are submitted below. Copyright © 1999 John Wiley & Sons, Ltd.     

Behaviour control of slender composite structures

Numerical and experimental assessment of a new connecting strip for the behaviour control of modern composite structures is treated in the present paper. The wave approach of the back‐propagation neural network in micromechanical modelling is used for the numerical analysis of the problem. Some numerical and experimental results are submitted in order to demonstrate the efficiency of the connecting strip developed. Copyright © 2006 John Wiley & Sons, Ltd.     

Behaviour control of modern composite structures

Numerical and experimental assessment of modern composite structures provided with knowledge‐based joints for their behaviour control is treated in the present paper. Special connection strip, joining composite materials, is adopted. The wave approach of the back propagation neural network in micro‐ and macromechanical modelling is used for the numerical analysis of the problem. Some numerical and experimental results are given in order to demonstrate the efficiency of the control joint suggested. Copyright © 2004 John Wiley & Sons, Ltd.     

Material instability in fatigue of fibre composites

Research of the ultimate behaviour of the carbon fibre composites is treated in the present paper. The material instability on the basis of the fibre kinking theory is adopted for the treatment of the failure process in the problem. The micromechanical modelling adopting the FETM‐wave approach is used for the numerical analysis of the problem. Some numerical and experimental results obtained are submitted in order to demonstrate the efficiency of the procedures suggested. Copyright © 2004 John Wiley & Sons, Ltd.     

Load‐bearing control of slender bridges

An active control of the load‐bearing capacity of slender bridges is treated in the present paper. Interactive conditions in ultimate response are considered. A numerical treatment of the occurring/appearing non‐linear problems is made using the updated Lagrangian formulation of motion. Each step of the iteration approaches the solution of linear problem and the feasibility of the parallel processing FETM‐technique with adaptive mesh refinement and substructuring for the analysis of ultimate behaviour of bridges is established. Application to an actual bridge is submitted in order to demonstrate the efficiency of the procedures suggested. Copyright © 2004 John Wiley & Sons, Ltd.     

Neuro‐genetic algorithm for non‐linear active control of structures

In a companion paper, a new non‐linear control model was presented for active control of three‐dimensional (3D) building structures including geometrical and material non‐linearities, coupling action between lateral and torsional motions, and actuator dynamics (Int. J. Numer. Meth. Engng; DOI: 10.1002/nme.2195 ). A dynamic fuzzy wavelet neuroemulator was presented for predicting the structural response in future time steps. In this paper, a new neuro‐genetic algorithm or controller is presented for finding the optimal control forces. The control algorithm does not need the pre‐training required in a neural network‐based controller, which improves the efficiency of the general control methodology significantly. Two 3D steel building structures, a 12‐story structure with vertical setbacks and an 8‐story structure with plan irregularity, are used to validate the neuro‐genetic control algorithm under three different seismic excitations. Numerical validations demonstrate that the new control methodology significantly reduces the displacements of buildings subjected to various seismic excitations including structures with plan and elevation irregularities. Copyright © 2008 John Wiley & Sons, Ltd.     

Fatigue life estimation of non‐penetrated butt weldments in ligth metals by artificial neural network approach

This study presents a model for estimating the fatigue life of magnesium and aluminium non‐penetrated butt‐welded joints using Artificial Neural Network (ANN). The input parameters for the network are stress concentration factor K_t and nominal stress amplitude s_a,n. The output parameter is the endurable number of load cycles N. Fatigue data were collected from the literature from three different sources. The experimental tests, on which the fatigue data are based, were carried out at the Fraunhofer Institute for Structural Durability and System Reliability (LBF), Darmstadt – Germany. The results determined with use of artificial neural network for welded magnesium and aluminium joints are displayed in the same scatter bands of SN‐lines. It is observed that the trained results are in good agreement with the tested data and artificial neural network is applicable for estimating the SN‐lines for non‐penetrated welded magnesium and aluminium joints under cyclic loading.     

Time‐domain BEM for three‐dimensional site response analysis of topographic structures

This paper presents a formulation of a time‐domain three‐dimensional boundary element method for site response analysis of topographic structures. The boundary element algorithm that uses the presented time‐convoluted traction kernels is applied to site response analyses of topographic structures. The seismic responses of canyon and ridge subjected to incident P and S waves are analyzed to demonstrate the accuracy of the kernels and the applicability of the presented boundary element algorithm for site response analysis of topographic structures. Seismic response analyses of three‐dimensional Gaussian‐shaped ridges show that the three‐dimensional axisymmetric ridge has a more amplification potential compared with three‐dimensional non‐axisymmetric elongated and two‐dimensional ridges, if the ridge is impinged by incident waves with wavelength of about the ridge's width. Copyright© 2009 John Wiley & Sons, Ltd.     

Materialbeanspruchungsanalyse und ihre Anwendung auf Prüfstandsversuche zum Oberflächenausfall (Nierlich‐Schadensmodus) von Wälzlagern

Material Response Analysis and its Application to Rig Tests for the Surface Failure (Nierlich Damage Mode) of Rolling Bearings The material response analysis according to Nierlich using X‐ray diffraction represents an important physical examination technique for the evaluation of material stressing and the lifetime estimation of rolling bearings and other highly loaded machine parts. The method is presented and employed for the evaluation of automobile gearbox rig tests. The extensively described damage modes of the practically predominating surface and the classical sub‐surface failure of rolling bearings can be distinguished that way. In gearboxes, lubricating oil contaminated by metal abrasion of the cogwheels usually appears. Penetrating foreign particles produce indentations at the ring raceways and rolling elements of the rolling bearings, which promotes surface fatigue. The results of the X‐ray diffraction measurements confirm this damage mode. Evaluation of the occurred material stressing permits a more detailed characterization of the surface failure of rolling bearings.