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CONTENTS
Volume 6, Number 3, September 2019
 

Abstract
Steel-confined reinforced concrete (SCRC) columns feature highly complex and invisible mechanisms that make damage evaluation and pattern recognition difficult. In the present article, the prevailing acoustic emission (AE) technique was applied to monitor and evaluate the damage process of steel-confined RC columns in a quasi-static test. AE energy-based indicators, such as index of damage and relax ratio, were proposed to trace the damage progress and quantitatively evaluate the damage state. The fuzzy C–means algorithm successfully discriminated the AE data of different patterns, validity analysis guaranteed cluster accuracy, and principal component analysis simplified the datasets. A detailed statistical investigation on typical AE features was conducted to relate the clustered AE signals to micro mechanisms and the observed damage patterns, and differences between steel-confined and unconfined RC columns were compared and illustrated.

Key Words
steel-confined RC structure; acoustic emission; damage evaluation; cluster analysis; pattern recognition

Address
Fangzhu Du and Dongsheng Li: School of Civil Engineering, Dalian University of Technology, China

Abstract
The aim of the present investigation is to examine the propagation of plane waves in transversely isotropic homogeneous magneto thermoelastic rotating medium with fractional order heat transfer. It is found that, for two dimensional assumed model, there exist three types of coupled longitudinal waves (quasi-longitudinal, quasi-transverse and quasi-thermal waves). The wave characteristics such as phase velocity, attenuation coefficients, specific loss, penetration depths, energy ratios and amplitude ratios of various reflected and transmitted waves are computed and depicted graphically. The conservation of energy at the free surface is verified. The effects of rotation and fractional order parameter by varying different values are represented graphically.

Key Words
thermoelastic; transversely isotropic; magneto-thermoelastic rotating medium; fractional-order heat transfer; plane wave propagation

Address
Parveen Lata and Iqbal Kaur: Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India

Abstract
Scheduled inspections of common crossings are one of the main cost drivers of railway maintenance. Prognostics and health management (PHM) approach and modern monitoring means offer many possibilities in the optimization of inspections and maintenance. The present paper deals with data driven prognosis of the common crossing remaining useful life (RUL) that is based on an inertial monitoring system. The problem of scheduled inspections system for common crossings is outlined and analysed. The proposed analysis of inertial signals with the maximal overlap discrete wavelet packet transform (MODWPT) and Shannon entropy (SE) estimates enable to extract the spectral features. The relevant features for the acceleration components are selected with application of Lasso (Least absolute shrinkage and selection operator) regularization. The features are fused with time domain information about the longitudinal position of wheels impact and train velocities by multivariate regression. The fused structural health (SH) indicator has a significant correlation to the lifetime of crossing. The RUL prognosis is performed on the linear degradation stochastic model with recursive Bayesian update. Prognosis testing metrics show the promising results for common crossing inspection scheduling improvement.

Key Words
railway common crossing; track-side monitoring; structural health indicator; MODWPT; Lasso regularization; RUL

Address
Mykola Sysyn and Dimitri Gruen: Institute of Railway Systems and Public Transport, Technical University of Dresden, Dresden 01069, Germany
Olga Nabochenko and Vitalii Kovalchuk: Department of the rolling stock and track, Lviv branch of Dnipro National University of Railway Transport,
Lviv 79052, Ukraine
Andriy Pentsak: Department of Construction industry, Lviv Polytechnic National University, Lviv 79013, Ukraine


Abstract
This paper presents an improved time series based damage detection approach with experimental verifications for detection, localization, and quantification of damage in shear-type structures under varying mass effects using output-only vibration data. The proposed method can be very effective for automated monitoring of buildings to develop proactive maintenance strategies. In this method, Auto-Regressive Moving Average models with eXogenous inputs (ARMAX) are built to represent the dynamic relationship of different sensor clusters. The damage features are extracted based on the relative difference of the ARMAX model coefficients to identify the existence, location and severity of damage of stiffness and mass separately. The results from a laboratory-scale shear type structure show that different damage scenarios are revealed successfully using the approach. At the end of this paper, the methodology limitations are also discussed, especially when simultaneous occurrence of mass and stiffness damage at multiple locations.

Key Words
structural health monitoring; damage detection; time series analysis; structural dynamics

Address
Ngoan T. Do, Qipei Mei and Mustafa Gul: Department of Civil and Environmental Engineering, University of Alberta, 9211 116 St NW Edmonton,
Alberta, Canada T6G 1H9


Abstract
Civil infrastructures, such as bridges and tunnels are most important assets and their failure during service will have significant economic and social impact in any country. Behavior of a bridge can be evaluated only through actual monitoring/measurements of bridge members under the loads of interest. Theoretical analysis alone is not a good predictor of the ability of a bridge. In some cases, theoretical analyses can give less effect than actual since theoretical analyses do not consider the actual condition of the bridge, support conditions, level of corrosion and damage in members and connections etc. Hence actual measurements of bridge response should be considered in making decisions on structural integrity, especially in cases of high value bridges (large spans and major crossings). This paper describes in detail the experimental investigations carried out on an open web type steel railway bridge. Strain gages and displacement transducers were installed at critical locations and responses were measured during passage of locomotives. Stresses were evaluated and extrapolated to maximum design loading. The responses measured from the bridge were within the permissible limits. The methodology adopted shall be used for assessing the structural integrity of the bridge for the design loads.

Key Words
open web girders; railway bridges; stress; strain; performance evaluation

Address
B. Arun Sundaram, K. Kesavan and S. Parivallal: Structural Health Monitoring Laboratory, CSIR-Structural Engineering Research Centre, CSIR Campus, Chennai, India


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