An Innovative GB-INSAR System for Deformation Monitoring and Disaster Management

Disaster management is a critical issue, needs timely reaction to mitigate the risks and to re-establish a safety condition. For that reason, remote monitoring solution play a crucial role to measure structure healthy and slope stability keeping operators and equipment in the safe zones. A clear understanding of displacement and stability of the target is vital to define proper remediation actions, prioritizing the most critical ones. IDS GeoRadar is a provider of radar remote monitoring technology for complex structures and natural hazards, that recently developed an ArcSAR interferometric radar system for deformation monitoring and disaster management. The innovative solution has been designed to have a portable, easy-to-use solution able to monitor the structures and area after few minutes of its deployment. The radar system detects structure displacement and slope fall precursors, triggering early warning to increase safety for emergency operations and to evacuate people and machinery at risk. The new radar system provides sub-millimeter displacement accuracy at a spatial resolution of tens of centimetres, with updated displacement information every 30 seconds. In this paper, the system is described, along with emergency monitoring experiences.

Thermoelastic Stress Analysis and Dissipated Energy Evaluation Using Infrared-Optical Synchronous Measurement

On the infrared thermography image, a false temperature change caused by the relative displacement between moving object and infrared camera is obtained. This paper shows the motion compensation system with the infrared-optical synchronous measurement. Displacement information of the specimen is calculated from the series of visible light image using the digital image correlation method (DIC). The displacement information on the visible image is reflected to the infrared image by the homography transformation. The random white pattern which can’t be detected by the infrared camera was drawn on the measured surface for DIC process. The developed motion compensation system was applied to the thermoelastic stress analysis and dissipated energy measurement. It was confirmed that a false temperature change and edge effect can be removed by using developed motion compensation system.

The Eigenfunction Method for Determining Displacement Time History in Structural Dynamic Analysis

In condition monitoring of structures, acceleration time histories are usually recorded due to ease of instrumentation. In cases where the information about a displacement time history is required, the acceleration data needs to be integrated to obtain the velocity and then the velocity needs to be integrated to obtain the displacements. However, the numerical integration of the acceleration data usually introduces an unrealistic drift component to the velocity as well as displacement. This paper presents an eigenfunction method to derive velocity and displacement time histories from a given acceleration time history. The paper analyzes displacements in two case studies using the numerical integration as well as the proposed eigenfunction method. It is concluded that the eigenfunction method is a viable approach to derive the displacement information from the acceleration data.

Load Normalization Method Accounting for Elastic and Elastic-Plastic Crack Growth

A single specimen technique to estimate crack length, standardized in ASTM E1820, is the so called load-normalization technique, also known as the Key-curve technique. The method is based on the separability between deformation and crack length. This means that if the load is normalized by a suitable function of crack length, the result will be a single crack length independent load-displacement curve. If this “Key”-curve is known, then based only on load and displacement information it is possible to estimate the corresponding crack length. The load normalizing method assumes a plastic response of the specimen during crack growth. If there is crack growth already in the elastic regime, non-linearity in the load-displacement record is not due to plasticity, but due to the crack growth. In this case the standard load-normalization method does not work since it assumes that the non-linearity is due to plasticity or crack tip blunting. Such materials require a modified approach. Here, a modified load normalization method accounting for possible elastic crack growth is presented. The method is shown to produce realistic crack growth estimates regardless of plasticity level of the specimen. The method applies an improved load normalization equation compared to the one presently used in ASTM E1820.

Determination of Displacement Fields at the Sub-Nanometric Scale

Macroscopic behavior of materials depends on interactions of atoms and molecules at nanometer/sub-nanometer scale. Experimental mechanics (EM) can be used for assessing relationships between the macro world and the atomic realm. Theoretical models developed at nanometric and sub-nanometric scales may be verified using EM techniques with the final goal of deriving comprehensive but manageable models. Recently, the authors have carried out studies on EM determination of displacements and their derivatives at the macro and microscopic scales. Here, these techniques were applied to the analysis of high-resolution transmission electron microscopy patterns of a crystalline array containing dislocations. Utilizing atomic positions as carriers of information and comparing undeformed and deformed configurations of observed area, displacements and their derivatives, as well as stresses, have been obtained in the Eulerian description of deformed crystal. Two approaches are introduced. The first establishes an analogy between the basic crystalline structure and a 120° strain gage rosette. The other relies on the fact that, if displacement information along three directions is available, it is possible to reconstruct the displacement field; all necessary equations are provided in the paper. Remarkably, the validity of the Cauchy-Born conjecture is proven to be correct within the range of observed deformations.