Non-Contact Air-Coupled Sensing for Rapid Evaluation of Bridge Decks

Elastic wave-based non-destructive testing (NDT) methods are commonly used for evaluation of civil engineering infrastructure, including bridges, dams and buildings. However, most of these methods require coupling (direct contact) between sensors and the test surface, which significantly restricts the testing speed and consistency, especially for large scale concrete structures in civil engineering. The air-coupled sensing technology was developed by Dr. Jinying Zhu as a solution for rapid scanning of concrete infrastructure. In this webinar, Dr. Zhu will review the development of air-coupled sensing technique for civil engineering applications, including fundamental theory and field application of air-coupled sensing on concrete structures. She will also present a recently developed automated acoustic scanning system for quick bridge deck evaluation and imaging

Community Grid Management Under the View of Griders: Problems and Countermeasures- Based on the Study of Grid Management in Haikou

The urban community grid management is a kind of social management innovation and represents the future development of China's urban management. It put forward in the background of the increasingly complicated urban management and the increasingly diversity of public demand. This paper takes the grid management of Haikou as a sample, using a combination of methods which included literature, questionnaires, and interviews. The grider as a "street bureaucratic", they have a unique feeling for grid management. Therefore, this paper chooses the griders' feelings of Haikou City's grid management as an analytical perspective. Through the investigation, the author finds that the community grid management in Haikou has some problems such as work cognitive bias, legal status embarrassment, poor management system, overload management matters and public participation consciousness. In the end, the author gives targeted countermeasures and suggestions. Keywords: Grider; Community; Grid management; Haiko

Applications of Stretching Technique and Time Window Effects on Ultrasonic Velocity Monitoring in Concrete

Coda wave interferometry (CWI) has been used to measure the relative wave-velocity change (dV/V) caused by small changes in materials. This study uses the stretching processing technique which has been used for CWI analysis to investigate velocity changes of direct longitudinal (P) wave, direct shear (S) wave, and coda wave in concrete by choosing different time windows of ultrasonic signals. It is found that the obtained wave-velocity change depends on the time window position, because the relative contribution of P wave and S wave is different in each signal window. This paper presents three experimental scenarios of velocity change in concrete: early-age hydration, temperature change, and uniaxial loading. In early-age concrete, the S wave has a larger relative velocity change than the P wave, which is consistent with the microstructure development due to the hydration process. Temperature change causes a larger dV/V on the P wave than on the S wave, and the difference between P and S wave-velocity changes may be used to determine nonlinear elastic constants of materials. In the uniaxial loading experiment, analysis of the direct P wave can distinguish the acoustoelastic effects in the stress direction and the non-stress direction, which may potentially be used for stress evaluation in prestressed structures. However, the coda wave does not show this directional property to stress due to multiple scattering in the medium

Applications of Stretching Technique and Time Window Effects on Ultrasonic Velocity Monitoring in Concrete

Coda wave interferometry (CWI) has been used to measure the relative wave-velocity change (dV/V) caused by small changes in materials. This study uses the stretching processing technique which has been used for CWI analysis to investigate velocity changes of direct longitudinal (P) wave, direct shear (S) wave, and coda wave in concrete by choosing different time windows of ultrasonic signals. It is found that the obtained wave-velocity change depends on the time window position, because the relative contribution of P wave and S wave is different in each signal window. This paper presents three experimental scenarios of velocity change in concrete: early-age hydration, temperature change, and uniaxial loading. In early-age concrete, the S wave has a larger relative velocity change than the P wave, which is consistent with the microstructure development due to the hydration process. Temperature change causes a larger dV/V on the P wave than on the S wave, and the difference between P and S wave-velocity changes may be used to determine nonlinear elastic constants of materials. In the uniaxial loading experiment, analysis of the direct P wave can distinguish the acoustoelastic effects in the stress direction and the non-stress direction, which may potentially be used for stress evaluation in prestressed structures. However, the coda wave does not show this directional property to stress due to multiple scattering in the medium

Development of an NDT Tool for in-Situ Assessment of Prestress Loss

The research objective is to develop a non-destructive testing (NDT) method to evaluate the prestress loss in prestressed concrete bridge girders using ultrasonic waves. The work principle is based on acoustoelastic effect - ultrasonic wave velocity varies with stress level in prestressed concrete. A self-reference test setup was proposed to measure wave velocity in two orthogonal directions (prestress and unstressed directions) in the girder. This setup will be able to reduce effects of material variation and temperature change. The concept was first validated on small concrete specimens (cylinders and beams) in laboratory. A signal analysis algorithm was developed to reliably measure P wave velocity change with stress, i.e. the acoustoelastic coefficient. Then the proposed technique was applied to a full-scale prestressed concrete bridge girder (131 ft long) to monitor the stress release process. The stress change monitored by the ultrasonic test showed good agreement with the result from the strain measurement. In both the small beam test and the large girder test, the measured acoustoelastic coefficients were in the range of 0.7%/ksi. The temperature effects on acoustoelastic coefficient were investigated on two prestressed concrete members. Experimental results showed a slight difference between temperature induced velocity changes in the prestress and unstressed directions. Although temperature variation can cause large change of velocity, the self-reference setup will be able to correct about 80% of temperature effect. The relationship between relative wave velocity changes and stress changes in two orthogonal directions after temperature correction can be used to predict the stress level in concrete and reduce environmental influences

Devices, systems, and methods for non-destructive testing of materials and structures

Provided are devices, systems, and methods for the testing of materials and structures. For example, the devices, systems, and methods are optionally used for the non-destructive testing of a material or structure. Furthermore, the devices, systems, and methods may optionally use a high-amplitude, air-coupled acoustic source for non-destructive testing of materials and structures.Board of Regents, University of Texas Syste

Gene and Pathway-Based Analysis: Second Wave of Genome-wide Association Studies

Despite great success of GWAS in identification of common genetic variants associated with complex diseases, the current GWAS have focused on single SNP analysis. However, single SNP analysis often identifies a number of the most significant SNPs that account for only a small proportion of the genetic variants and offers limited understanding of complex diseases. To overcome these limitations, we propose gene and pathway-based association analysis as a new paradigm for GWAS. As a proof of concept, we performed a comprehensive gene and pathway-based association analysis for thirteen published GWAS. Our results showed that the proposed new paradigm for GWAS not only identified the genes that include significant SNPs found by single SNP analysis, but also detected new genes in which each single SNP conferred small disease risk, but their joint actions were implicated in the development of diseases. The results also demonstrated that the new paradigm for GWAS was able to identify biologically meaningful pathways associated with the diseases which were confirmed by gene-set rich analysis using gene expression data