Performance Verification of a Flexible Vibration Monitoring System

The performance of measurement or manufacturing systems in high-precision applications is dependent upon the dynamics of the system, as vibration can be a significant contributor to the measurement uncertainty and process variability. Technologies making use of accelerometers and laser vibrometers are available to rapidly measure and process structural dynamic data but the software infrastructure is yet to be available in an open source or standardised format to allow rapid inter-platform use. In this paper, we present a novel condition monitoring system, which uses commercially available accelerometers in combination with a control-monitoring infrastructure to allow for the appraisal of the performance of a measurement or manufacturing system. A field-programmable gate array (FPGA)-based control system is implemented for high-speed data acquisition and signal processing of six triaxial accelerometers, with a frequency range of 1 Hz to 6000 Hz, a sensitivity of 102.5 mV/ms−2 and a maximum sample rate of 12,800 samples per second per channel. The system includes two methods of operation: real-time performance monitoring and detailed measurement/manufacturing verification. A lathe condition monitoring investigation is undertaken to demonstrate the utility of this system and acquire typical machining performance parameters in order to monitor the “health” of the system

LOCAL POSITIONING SYSTEMS VERSUS STRUCTURAL MONITORING: A REVIEW

SUMMARY Structural monitoring and structural health monitoring could take advantage from different devices to record the static or dynamic response of a structure. A positioning system provides displacement information on the location of moving objects, which is assumed to be the basic support to calibrate any structural mechanics model. The global positioning system could provide satisfactory accuracy in absolute displacement measurements. But the requirements of an open area position for the antennas and a roofed room for its data storage and power supply limit its flexibility and its applications. Several efforts are done to extend its field of application. The alternative is local positioning system. Non-contact sensors can be easily installed on existing infrastructure in different locations without changing their properties: several technological approaches have been exploited: laser-based, radar-based, vision-based, etc. In this paper, a number of existing options, together with their performances, are reviewed. Copyright © 2014 John Wiley & Sons, Ltd

Live Load Effects of Railroads on Retaining Walls and Temporary Shoring

Analysis of the causes of major train derailment and its effect on accident rates shows that the second most common reason for train derailment is changes in track geometry. Excavation near railroads is a significant potential cause of changes in the track geometry. Soldier pile walls and sheet pile walls are widely used as temporary shoring systems to minimize the vertical track settlement associated with nearby excavations. Design methods for these temporary shoring systems are typically based on (1) simple limit equilibrium calculations for dead loads from the soil self-weight and (2) elastic solutions for idealized geometries for predicting the effects of live loads. Both approaches involve significant simplifications, so conservative approaches are usually adopted to offset uncertainties in the analysis methodology. The work in this dissertation focuses on the effects of live loads on temporary shoring systems. The results of this study indicate that while existing methodology is often conservative, it can be un-conservative under certain soil and site conditions. On the one hand, excessive conservatism can lead to needless costs. On the other hand, situations can arise where simplified methods are un-conservative. All of this points to the need for improved understanding of the mechanics of the response of temporary shoring systems to live loads in specific conditions. The existing analysis methods, when tempered by engineering judgment, usually lead to safe designs. Thus, the intent of the completed research is not to supplant existing analysis methods with complex numerical models. Rather, the goal is to improve understanding of shored wall system behavior to provide guidelines on (1) when existing simplified analysis methods are appropriate and (2) when the simplified methods are potentially unsafe and more rigorous analyses should be undertaken. Generally, based on the finite element results it could be concluded that Boussinesq theory predicts more deflection for stiff soil and less deflection for soft soil. It means for stiff soil, the Boussinesq theory is conservative and for soft soil, it underestimates the deflection

Live Load Effects of Railroads on Retaining Walls and Temporary Shoring

Analysis of the causes of major train derailment and its effect on accident rates shows that the second most common reason for train derailment is changes in track geometry. Excavation near railroads is a significant potential cause of changes in the track geometry. Soldier pile walls and sheet pile walls are widely used as temporary shoring systems to minimize the vertical track settlement associated with nearby excavations. Design methods for these temporary shoring systems are typically based on (1) simple limit equilibrium calculations for dead loads from the soil self-weight and (2) elastic solutions for idealized geometries for predicting the effects of live loads. Both approaches involve significant simplifications, so conservative approaches are usually adopted to offset uncertainties in the analysis methodology. The work in this dissertation focuses on the effects of live loads on temporary shoring systems. The results of this study indicate that while existing methodology is often conservative, it can be un-conservative under certain soil and site conditions. On the one hand, excessive conservatism can lead to needless costs. On the other hand, situations can arise where simplified methods are un-conservative. All of this points to the need for improved understanding of the mechanics of the response of temporary shoring systems to live loads in specific conditions. The existing analysis methods, when tempered by engineering judgment, usually lead to safe designs. Thus, the intent of the completed research is not to supplant existing analysis methods with complex numerical models. Rather, the goal is to improve understanding of shored wall system behavior to provide guidelines on (1) when existing simplified analysis methods are appropriate and (2) when the simplified methods are potentially unsafe and more rigorous analyses should be undertaken. Generally, based on the finite element results it could be concluded that Boussinesq theory predicts more deflection for stiff soil and less deflection for soft soil. It means for stiff soil, the Boussinesq theory is conservative and for soft soil, it underestimates the deflection

Structural health monitoring of in-service tunnels

This work presents an overview of some of the most promising technologies for the structural health monitoring (SHM) of in-service tunnels. The common goal of damage or unusual behaviour detection is best pursued by an integrated approach based on the concurrent deployment of multiple technologies. Typically, traditional SHM systems are installed in problematic or special areas of the tunnels, giving information on conditions and helping manage maintenance. However, these methodologies often have the drawbacks of forcing the interruption of traffic for SHM system installation and monitoring only selected portions. Alternative solutions that would make it possible to keep the tunnel in normal operation and/or to analyse the entire infrastructure development through successive and continuous scanning stages, would be beneficial. In this paper, the authors will briefly review some traditional monitoring technologies for tunnels. Furthermore, the work is aimed at identifying alternative solutions, limiting or avoiding traffic interruptions

Displacement filed calculation of large-scale structures using computer vision with physical constrains

Because of the advantages of easy deployment, low cost and non-contact, computer vision-based structural displacement acquisition technique has received wide attention and research in recent years. However, the displacement field acquisition of large-scale structures is a challenging topic due to the contradiction of camera field of view and resolution. This paper presents a large-scale structural displacement field calculation framework with integrated computer vision and physical constraints using only one camera. Firstly, the full-field image of the large-scale structure is obtained by processing the multi-view image using image stitching technique; secondly, the full-field image is meshed and the node displacements are calculated using an improved template matching method; and finally, the non-node displacements are described using shape functions considering physical constraints. The developed framework was validated using a scaled bridge model and evaluated by the proposed evaluation index for displacement field calculation accuracy. This paper can provide an effective way to obtain displacement fields of large-scale structures efficiently and cost-effectively

Design and Testing of a Structural Monitoring System in an Almería-Type Tensioned Structure Greenhouse

Greenhouse cultivation has gained a special importance in recent years and become the basis of the economy in south-eastern Spain. The structures used are light and, due to weather events, often collapse completely or partially, which has generated interest in the study of these unique buildings. This study presents a load and displacement monitoring system that was designed, and full scale tested, in an Almería-type greenhouse with a tensioned wire structure. The loads and displacements measured under real load conditions were recorded for multiple time periods. The traction force on the roof cables decreased up to 22% for a temperature increase of 30 °C, and the compression force decreased up to 16.1% on the columns or pillars for a temperature and wind speed increase of 25.8 °C and 1.9 m/s respectively. The results show that the structure is susceptible to daily temperature changes and, to a lesser extent, wind throughout the test. The monitoring system, which uses load cells to measure loads and machine vision techniques to measure displacements, is appropriate for use in different types of greenhouses