Kirk A. Grimmelsman

Analysis of Data Quality for Ambient Vibration Testing of the Henry Hudson Bridge

The quality of test data is an important consideration in conducting field experiments on civil infrastructure. In addition to possible errors due to the experimental setup, the uncertainties due to incomplete knowledge of a structures behavior and its interactions with the natural environment greatly affect the reliability of the final results. This study discusses the uncertainty related to ambient vibration testing of a long-span steel arch bridge. The consistency of the identified parameters is examined through statistical analyses, and the effects of bandwidth and stationarity on the identified parameters are discussed.

Structural identification of Commodore Barry Bridge

The Commodore Barry Bridge is a major long-span bridge across the Delaware River connecting the cities of Bridgeport, New Jersey and Chester, Pennsylvania. A Structural Identification (St-Id) study of Commodore Barry Bridge is presented. The objective of this structural identification approach is to characterize the as-is structural condition and the loading environment of the bridge through experimental information and analytical modeling. The attributes that make long-span bridges different for utilization of experimental and analytical applications as compared to short-span bridges are presented. Some of the experimental, analytical and information tools which are utilized for this research are discussed. The details of constructing a preliminary analytical model after conceptualization of the structural characteristics are presented. Development of the 3D analytical model, and the model characteristics such as elements used, boundary and continuity representations are summarized. The experimental techniques that are necessary for the structural identification of a long span bridge are defined and application examples are provided from the Commodore Barry Bridge. Experiences gained during the applications of different forms of dynamic tests, instrumented monitoring and controlled static and crawl speed load tests are presented with example experimental data. Correlation of experimental results and analytical simulations are presented. Immediate and possible future uses of information generated are summarized.

Instrumented monitoring of the Commodore Barry Bridge

The Drexel Intelligent Infrastructure and Transportation Safety Institute, working in partnership with the Delaware River Port Authority (DRPA), has been investigating the application of various health monitoring techniques to long span bridges. Specifically, the researchers efforts have focused on the Commodore Barry Bridge, a major cantilevered through truss bridge owned by the DRPA. Health monitoring, in the case of civil infrastructure systems, may be considered as measuring and tracking the operating and loading environment of a structure and corresponding structural responses in order to detect and evaluate operational anomalies and deterioration or damage that may impact service or safety reliability. This paper describes the development and implementation of the health monitoring system that has been installed on the Commodore Barry Bridge. Issues that should be considered when conducting health monitoring of long span bridges are also discussed. The health monitoring system takes advantage of in excess of 100 data channels to continuously track the loading environment and numerous structural responses of the bridge. The major attributes of the health monitoring system for this bridge, many of which are applicable for use on other long span bridges, are also presented and described.

Health monitoring for effective management of infrastructure

Significance of effectively managing civil infrastructure systems (CIS) throughout CIS life-cycles, and especially during and after natural or man-made disasters is well recognized. Disaster mitigation includes preparedness for hazards to avoid casualties and human suffering, as well as to ensure that critical CIS components can become operational within a short amount of time following a disaster. It follows that mitigating risk due to disasters and CIS managementare intersecting and interacting societal concerns. A coordinated, multi-disciplinary approach that integrates field, theoretical and laboratory research is necessary for innovating both hazard mitigation and infrastructure management. Health monitoring (HM) of CIS is an emerging paradigm for effective management, including emergency response and recovery management. Challenges and opportunities in health monitoring enabled by recent advances in information technology are discussed in this paper. An example of HM research on an actual CIS test-bed is presented.

Evaluation of Economical Dynamic Exciters for Vibration Testing of Bridges

Quantitative data describing condition and performance is essential for evaluating the structural health of bridges. Dynamic testing is a common approach for globally characterizing bridges in a quantitative sense. Dynamic testing is most commonly accomplished for full-scale bridge structures through either forced vibration testing or ambient vibration testing methods. Forced vibration testing offers many advantages, but is generally not a practical or economical approach for many bridges due to the high cost of providing controlled excitation, limits to the excitation that can be supplied, and interference with the normal operation of the bridge. The writers have been investigating the feasibility of using low-cost, small-scale dynamic exciters for forced vibration testing of short to medium span bridges. The exciters being evaluated have a unit cost that is comparable to a typical accelerometer, and could be deployed in numbers using a spatially distributed setup for forced vibration testing. This paper presents and describes the results of a laboratory evaluation program conducted for these devices. Their capabilities and operating characteristics are compared with a more conventional linear mass shaker. The preliminary results of a vibration test using these devices on an in-service highway bridge are also discussed.

Structural Identification of a Long-Span Truss Bridge

An ongoing research project involving structural identification of the Commodore Barry Bridge, a major long-span truss bridge over the Delaware River, is described. Structural identification is an approach in which a constructed facility and its loading environment are objectively characterized by field observations, measurements, and controlled experiments in conjunction with an analytical model. This process is a necessary precursor to performing health monitoring of the bridge. Long-span bridges have attributes that make utilization of experimental and analytical techniques on them quite different than for short-span bridges. The concept of structural identification and the methods used in applying it to a long-span bridge are presented and discussed. The structural characteristics of the bridge are described and conceptualized. Development of the three-dimensional analytical model and the model characteristics are summarized. Static and dynamic analyses are conducted to help locate anomalies and errors in the model. The experimental techniques necessary for structural identification of a long-span bridge are defined. A limited-scale health-monitoring system, which integrates operational data with structural performance and loading environment data, was designed and installed on the bridge. Mechanical and electrical characteristics of the monitor system and issues related to management of the data from this system are discussed. The monitoring system currently has over 80 channels of different sensor types collecting various data from the bridge. In addition, data from the system can be viewed from a remote location in real time.

Dynamic Characterization of a Truss Bridge by Falling Weight Deflectometer

Several full-scale testing methods can be used to characterize and evaluate the global performance and condition of a bridge. These global methods consist of mainly static load tests and dynamic tests that use controlled or uncontrolled dynamic excitation. Each approach has advantages and disadvantages for experimental and logistical considerations, data analysis requirements, and scope and utility of the characterization results obtained. This paper presents a global dynamic characterization program based on controlled impact dynamic testing that was applied to a truss bridge. The impact testing was performed with a hand-held impact hammer and a falling weight deflectometer (FWD) as dynamic excitation sources. The objective of the project was to evaluate whether the FWD, which could produce a broadband dynamic force, could be an effective tool for the quantitative characterization of bridge performance and condition. Many transportation agencies already use FWD devices for their pavement evaluation programs, and it follows that if the device is suitable for the impact dynamic testing of bridges, then agencies also can use FWDs to evaluate bridges quantitatively. Dynamic testing approaches are discussed, and an impact dynamic testing program executed for the truss bridge is presented. The results obtained with the two dynamic excitation devices are presented and compared with each other and with the results from an analytical model of the bridge. Finally, several observations and conclusions related to the efficacy of FWD devices for the impact dynamic testing of bridges are presented and discussed.

Critical issues, condition assessment and monitoring of heavy movable structures: emphasis on movable bridges

In this paper, a relatively less studied class of structures is presented based on the research conducted on Floridas movable bridges over the last several years. Movable bridges consist of complex structural, mechanical and electrical systems that provide versatility to these bridges, but at the same time, create intermittent operational and maintenance challenges. Movable bridges have been designed and constructed for some time; however, there are fewer studies in the literature on movable bridges as compared to other bridge types. In addition, none of these studies provide a comprehensive documentation of issues related to the condition of movable bridge populations in conjunction with possible monitoring applications specific to these bridges. This paper characterises and documents these issues related to movable bridges considering both the mechanical and structural components. Considerations for designing a monitoring system for movable bridges are also presented based on inspection reports and expert opinions. The design and implementation of a monitoring system for a representative bascule bridge are presented along with long-term monitoring data. Various movable bridge characteristics such as opening/closing torque, bridge balance and friction are shown since these are critical for maintenance applications on mechanical components. Finally, the impact of environmental effects (such as wind and temperature) on bridge mechanical characteristics is demonstrated by analysing monitoring data for more than 1000 opening/closing events.

Static and Dynamic Testing of a Concrete T-Beam Bridge Before and After Carbon Fiber–Reinforced Polymer Retrofit

This paper summarizes the design and execution of field studies to improve the performance of a deteriorated bridge through the use of carbon fiber-reinforced polymer (CFRP) material. The objective of the CFRP retrofit was to extend the life of Bridge 2028 in Cayey, Puerto Rico, by increasing its load rating. Field testing before and after the retrofit was performed to evaluate objectively improvement in load capacity and stiffness. The field testing program included both static load tests and dynamic tests. The first set of field tests was conducted in November 2002 to capture baseline bridge performance characteristics before the retrofit. The CFRP retrofit was installed in October 2003, and a second set of nearly identical field tests was performed in August 2004. The test results indicated that the retrofit increased the bending stiffness of the bridge by 15% and decreased the tensile strains in the bottom rebars of the concrete T-beams by about 13%. Furthermore, the maximum rebar strains under a heav...

Evaluating the reliability of highway bridges following hazards in real-time by structural health monitoring (RT-SHM-D+P)

Health monitoring of infrastructure systems for their proactive management to make the best use of limited resources for their optimum life-cycle performance, protection and preservation is a promising paradigm. Structural health monitoring (SHM) technologies have sufficiently evolved to accomplish real-time post-hazard evaluation of highway bridges. Solution of the pressing and critical problem of post-hazard bridge condition evaluation is possible by problem-focused, coordinated cross-disciplinary research. A newly initiated research program, which has been formulated for creating knowledge to construct an intelligent bridge SHM system, is presented in this paper. An overview of the state-of-the-art research in SHM is outlined.