H. Felix Wu

Evaluating road surface conditions using dynamic tire pressure sensor

In order to best prioritize road maintenance, the level of deterioration must be known for all roads in a city’s network. Pavement Condition Index (PCI) and International Roughness Index (IRI) are two standard methods for obtaining this information. However, IRI is substantially easier to measure. Significant time and money could be saved if a method were developed to estimate PCI from IRI. This research introduces a new method to estimate IRI and correlate IRI with PCI. A vehicle-mounted dynamic tire pressure sensor (DTPS) system is used. The DTPS measures the signals generated from the tire/road interaction while driving. The tire/road interaction excites surface waves that travel through the road. DTPS, which is mounted on the tire’s valve stem, measures tire/road interaction by analyzing the pressure change inside the tire due to the road vibration, road geometry and tire wall vibration. The road conditions are sensible to sensors in a similar way to human beings in a car. When driving on a smooth road, tire pressure stays almost constant and there are minimal changes in the DTPS data. When driving on a rough road, DTPS data changes drastically. IRI is estimated from the reconstructed road profile using DTPS data. In order to correlate IRI with PCI, field tests were conducted on roads with known PCI values in the city of Brockton, MA. Results show a high correlation between the estimated IRI values and the known PCI values, which suggests that DTPS-based IRI can provide accurate predictions of PCI.

Preliminary study of matching pursuit for extracting GPR rebar reflections

Ground penetrating radar (GPR) has developed into a primary investigation tool for the non-destructive evaluation of reinforced concrete bridge deck. The collected GPR signals are generally composed of direct wave, rebar reflections, bottom reflection and noise. Before making GPR-based predictions, rebar reflections need to be extracted first. One obstacle is that the first rebar layer is in the shallow subsurface in some cases and the target signals may be overlapped with the direct waves. Another problem associated is that the testing surfaces may be rough in real field testing environments, which lead to strong uneven direct waves in the collected signals. This kind of direct wave cannot be removed by the commonly adopted average removing method. In this paper, Matching pursuits equipped with a customized dictionary are applied to deal with the above mentioned two problems. The dictionary is built based on the excitation function and the electromagnetic scattering mechanisms. Compared to the commonly used Gabor dictionary, the proposed dictionary is more adapted to the GPR wavefronts and each target signal can be reconstructed by just one atom. In addition, there is no need for a reference signal that is not always available. The performance of the proposed method is evaluated by simulation data in this paper.

Evaluating road surface conditions using tire generated noise

Classifications of road conditions are crucial because officials prioritize road maintenance decisions based on them. Pavement condition index (PCI) surveys are performed manually and used by many cities in the U.S. to evaluate road surface conditions. In this research, a more efficient method is used to detect road surface conditions. This method applies a probabilistic analysis to acoustic pressure data collected from a vehicle-mounted microphone. The data is collected while the driving and processed in real time. Acoustic pressure data contains information on road surface conditions because acoustic pressures change when the tire impacts different road surfaces. This change is audible to human ears, for example, a driver transitions from a normal road to a bridge. The acoustic pressure data used in this research was collected from roads with known PCI values that are used as a reference. To reveal the dominant common features and neglect trivial differences within a certain length of road, a probabilistic method is used to evaluate road surface conditions. This approach uses the Weibull probability density function (PDF) to evaluate road surface conditions. This distribution was chosen because it is closest to the actual PDF among other distributions such as the normal distribution and lognormal distribution. A key finding of this paper is that the Weibull PDF shows the largest change between roads with different PCI values. Another finding is that the Weibull pdf changes when the van hits road defects such as cracks and patches.

Investigations of Structural Damage Caused by the Fertilizer Plant Explosion at West, Texas. I: Air-Blast Incident Overpressure

AbstractAn explosion occurred at a fertilizer plant in the town of West, Texas, on Wednesday, April 17, 2013, devastating a populated neighborhood. A total of 15 people were killed, and approximately 160 people were injured. Approximately 150 buildings were damaged in the explosion. The damage to affected homes and businesses was estimated to exceed

Investigations of structural damage caused by the fertilizer plant explosion at West, Texas. II: ground shock

100 million. The purpose of this study was to collect on-site technical data of the explosion and gain knowledge of blast loadings and structural responses from this unprecedented explosion. Specifically, this research documented the building damages caused by the West Fertilizer plant explosion and the affected buildings’ construction and materials and evaluated the technical information for the explosion, including the blast loadings, i.e.,xa0the air-blast incident overpressures and ground shocks, on different buildings with respect to the standoff distances. A total of two technical papers have been prepared. The Part I paper (this manuscript) focused on the...

Simulated Transient Electromagnetic Response for the Inspection of GFRP-Wrapped Concrete Cylinders Using Radar NDE

AbstractAn explosion occurred at a fertilizer plant in the town of West, Texas, on Wednesday, April 17, 2013, devastating a populated neighborhood. A total of 15 people were killed, and approximately 160 more people were injured. Approximately 150 buildings were damaged in the explosion, and the damage to affected homes and businesses was estimated to exceed

Optimal sensor placement for structural health monitoring: a comparative study between the control engineering and civil engineering approaches

100xa0million. This research documents the building damages caused by the unprecedented explosion and evaluates the technical information for the explosion. The Part I paper of this research focused on the building damage documentation and air-blast incident overpressure calculations. As a companion paper, this manuscript (Part II) primarily focuses on the study of blast-induced ground-shock effects. The ground shock–induced building damages and ground vibration peak particle velocities (PPVs) are analyzed. With a combined consideration of these two types of blast loadings, the air-blast incident overpressures and ground shocks, the field investigated ...

Wideband subsurface radar for bridge structural health monitoring and nondestructive evaluation

Assessing the subsurface condition of glass fiber reinforced polymer (GFRP)-retrofitted concrete structures is an important inspection problem for the maintenance of reinforced concrete structures retrofitted with high performance composites like GFRP. The objective of this paper is to investigate the radar response of GFRP-concrete cylinders through a parametric study, using the finite difference time domain (FDTD) method. Intact and artificially damaged GFRP-wrapped concrete cylinders were modeled in a two dimensional domain. Considered parameters include the thickness of GFRP wrap/layer, width and depth of artificial defects, and the incident frequency. Modulated Gaussian signals with a carrier frequency ranging from 8 GHz to 18 GHz were used as the incident wave. Field and power responses in both time and frequency domains were investigated. A nonlinear effect due to the variation of defect dimensions is found in both time and frequency responses, indicating the multiple, interlayer scattering effect in the system.

In-situ health monitoring on steel bridges with dual mode piezoelectric sensors

We conduct a comparative study of approaches for optimal sensor placement from the fields of control engineering and civil engineering. The widely used civil engineering approaches such as EI and MAC have limitations due to the negligence of damping parameters. On the other hand, control engineering approaches do not consider the key parameters of interest in civil structures. We study the maximization of estimation performance of key structural characteristics from impulse response data, using approaches from both fields to unveil the pros and cons of each.

Design and implementation of a remote UAV-based mobile health monitoring system

The nondestructive evaluation (NDE) inspection for building and bridge structures has attracted a lot of attentions for the fundamental research and the sensor system development. In this paper, development of a distant subsurface imaging radar is reported. Theoretical background of subsurface radar imaging is first provided. Experimental laboratory measurements using radar signals in the frequency range of 1-18 GHz were conducted. From the theoretical analysis and the initial experimental results on a laboratory reinforced concrete specimens, it is proved that the proposed subsurface imaging radar system can detect the location of steel reinforcement inside a concrete cylinder and identify the material property of panel specimens. Range-dependent attenuation of radar signals is experimentally studied using different materials. Findings are reported in the summary.