A. Emin Aktan

Structural identification of constructed systems : approaches, methods, and technologies for effective practice of St-Id

Structural Identification of Constructed Systems: Approaches, Methods, and Technologies for Effective Practice of St-Id offers an overview of nearly 20 years of research directed at bridging the gap in structural engineering between models and real structural systems. Structural identification, known as St-Id, can be defined as the process of creating and updating a model of a structure (for instance, a finite element model) using experimental observations and data. By developing reliable estimates of the performance and vulnerability of structural systems, St-Id produces improved simulations that, in turn, assist in decision making and the transition to performance-based civil engineering. Drawing upon contributions from experts in the field, this report focuses on defining the most critical considerations of St-Id, which include: modelling, both analytical and numerical experimentation, including observations, sensing, and monitoring data processing, including error screening and feature extraction model calibration, including comparisons of models and experimental data, model updating, and model selection decision support, such as scenario analyses and risk assessment Two appendixes present case studies demonstrating the St-Id of buildings and of bridges. Structural engineers, educators, and researchers working in the areas of structural modelling, health monitoring, assessment, forensics, performance evaluation, predictive analysis, and decision making will find this book useful in covering critical and practical aspects of these concepts.

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.

Temperature-Based Structural Identification of Long-Span Bridges

AbstractTemperature-based structural identification (TBSI) is a quantitative structural evaluation approach that relies on responses resulting from temperature fluctuations. Through this approach, the transfer function that defines how thermal induced strains give rise to global displacements and restrained member forces can be captured. This input-output relationship is highly sensitive to mechanisms that pose modeling challenges, such as boundary and continuity conditions, and thus is quite valuable within the model updating process. The method follows the traditional structural identification (St-Id) framework with a priori modeling, experimentation, and model calibration steps appropriately modified to allow for the measurement and simulation of temperature-induced responses. TBSI was evaluated through the use of simulations and laboratory experiments and then implemented to identify an arch bridge. In addition, a comparative study was performed with an independent evaluation of the same bridge using ...

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.

Governing issues and alternate resolutions for a highway transportation agency's transition to asset management

Whether the increasingly poor performance of transportation infrastructure, the budget shortfalls many owners are facing, or the increased demand for more accountability are considered, it is clear that a revolution related to the management of transportation infrastructure is long overdue. There is a broad consensus that this revolution will take shape through adapting and transitioning to the paradigm of asset management (AM). This paper firstly reviews the concept of AM applied to transportation infrastructure, identifies key attributes, and provides a brief overview of the on-going and planned transition to AM by two transportation agencies. Secondly, this paper provides an overview of the related paradigms of performance-based engineering, lifecycle cost analysis, and structural health monitoring, and their role within an integrated AM system. Finally, this paper identifies and discusses relevant issues that transportation infrastructure owners face when they embark on a transition to AM, and proposes an outline for a roadmap to guide this transition.

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.

Advanced Visualization and Accessibility to Heterogeneous Monitoring Data

The proper management and visualization of data is crucial for the success of structural health monitoring (SHM). The article discusses how SHM is a promising tool for the better management of infrastructure. General principles for SHM data management are researched, established, and proposed by the authors, and an original solution for data management based on these principles is presented. The article discusses how data management is especially challenging when heterogeneous data are involved and combined with camera images. Various sensors based on different technologies can measure many parameters such as strain, tilt, weather, etc., whereas live cameras can visualize traffic response and all of the data streams can be registered both statically and dynamically. Data management is even more complex if multiple users access the data and have diverse backgrounds and interests (e.g., the owner/manager of the structure, operator, responsible engineer, and academic). The proposed principles were implemented in novel data management software and applied to a signature bridge for validation purposes. The article discusses how feedback from interested groups including managers, operators, engineers of record, and academics are used for validation.

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.

Impacts of Epistemic Uncertainty in Operational Modal Analysis

AbstractField experimentation on constructed systems demands consideration of many mechanisms of epistemic and aleatory uncertainties as well as human errors and subjectivity. This is especially true in operational modal analysis (OMA) applications that aim to identify the dynamic properties of a structure. Although statistics and probability theory are sufficient for quantifying aleatory uncertainty and bounding the resulting errors in OMA results, there is much debate as to whether the same tools may also be used to quantify epistemic uncertainty. This study explored a framework for better understanding the distinctions and impacts of these two types of uncertainties in OMA and how human errors and subjectivity may be classified. A physical laboratory model was designed to simulate four key sources of epistemic uncertainty that represented the primary test variables: structural complexity (changing boundary conditions, nonlinearity), ambient excitation characteristics (magnitude, directionality, and ban...

Information technology and data management issues for health monitoring of the Commodore Barry Bridge

Information technology issues for the continuous health monitoring of the Commodore Barry Bridge will be presented in two parts in this paper. The first part describes data acquisition design and the second part discusses issues related to a proposed database. Currently, the health monitor consists of more than one hundred channels of information. These channels are made up of slow speed strain gages (measuring intrinsic strains due to environmental effects, temperature changes and wind loads), high-speed strain gages (measuring strains and accelerations related to traffic effects) and one camera (recording images of the traffic pattern at the bridge). These gages are hard-wired to a central data acquisition station in which three slow speed data acquisition systems, one high-speed data acquisition system and a data acquisition computer are located. All data acquisition systems are integrated under the LabVIEW platform. It was necessary to utilize various appropriate sampling frequencies for each system due to the differing nature of the phenomena being measured by each system. The data is post- processed subsequent to acquisition and finally the data is stored and archived. Post-processing algorithms are implemented to eliminate any noise component from the data, complete any necessary signal re-sampling, and to synchronize the collection times of the different data collection systems. Once the data is transferred and archived data analysis can begin. The creation of a database for storage of all pertinent information is envisioned as a future add-on to this project. Two possible versions of the database system are currently being investigated. In the end, the database would allow users to retrieve information according to customized query criteria. It would also allow users to navigate raw data, preview data graphs, extract specified information (such as analytical data, reports, images, video clips and CBB CAD models), save the retrieved data to a local computer hard-disk and modify information for authorized users. One of the system designs being investigated would not be Internet based and thus would provide local users efficient means of access. In this design, the database would perform complex computational work without coming into contact with Internet traffic. The second proposed system design would provide flexible and robust access through the Internet. This system would allow the retrieval of information from the database through a conventional Browser. This database design would provide fast service and the rich display capabilities of highly dynamic web pages and would allow multimedia capabilities.