Organizations operating in dynamic environments confront rapid changes in both internal and external conditions that affect their performance. Such changes produce new information that requires attention, comprehension, and integration into existing knowledge to enable individuals and organizations to adapt their performance, and that of the larger system, accordingly. Understanding the dynamics of learning, change, and adaptation to new information under uncertain operating conditions is central to managing the complex, interdependent infrastructure systems characteristic of metropolitan regions. Responsible managers of rail, air, highway, subway and waterway systems seek to reduce the level of uncertainty in interdependent environments by extensive use of information technologies. These technologies, however, produce large amounts of information that may further overwhelm personnel, especially under constraints of limited time and resources. Creating training environments that enable technical personnel to increase their ability to manage large amounts of rapidly changing information is critical to improving organizational performance in dynamic, uncertain conditions. Advanced training environments include techniques for graphic representation of knowledge, information exchange among shared knowledge bases, and intelligent reasoning by the computer. These techniques increase the ability of personnel to absorb, integrate, and act upon increasingly complex information under dynamic conditions.

Performance measures are central to managing infrastructure assets, since they provide quantitative benchmarks and express values and preferences that are important for decision making. For example, one performance measure for decisions on upgrading an electrical power line is the improvement in service reliability, measured in terms of annual customer interruption hours. This paper first presents an overall framework for developing performance measures for infrastructure decision-making. The framework is then illustrated with an example that involves a decision of whether or not to place overhead power lines underground in order to improve performance measured as service reliability, health and safety, operation and maintenance cost, and impacts on property values.

Many engineers share the concern that the constructed facilities, which serve as the backbone of our infrastructure systems, are not providing the performance expected by society in the 21st Century. A major impediment to advancing performance is a lack of associated metrics. Civil engineering design, construction and evaluation guidelines, codes, specifications and related documents describe performance of constructed facilities and entire infrastructure systems qualitatively, often in nebulous, incomplete, unrealistic or inaccurate terms. Even when quantitative limits related to performance of some structures are offered in the code commentaries, whether these limits are realistic, or whether the design and construction processes may provide assurance of satisfying such limits is uncertain.

There should be no argument that the quality of life and the economic vitality of modern civilizations are dependent on the infrastructures that support them. Of major importance is the transportation system that provides for the transport of goods and services as well as the mobility of the citizens within those civilizations. The enormous investment that Governments have made in highway systems since the 1950's has led the U.S. to be recognized as having the largest and most modern highway system in the world. Within this highway system, bridges are singly the most important link. Without bridges, highway transportation as we know it would cease to exist. In recognition of this, the California Department of Transportation continues to take aggressive actions in the protection of its bridge infrastructure as evidenced by the delivery efforts of the Seismic Retrofit Program and the creation of the Bridge Scour Mitigation Program.

The history of the Brooklyn, Williamsburg, Manhattan and Queensboro bridges across the East River in New York City is examined, seeking to determine trends and most recent developments in their management. Reconstruction and maintenance costs are summarized. Crucial federal and local decisions and policies are identified. An attempt is made to draw conclusions from the management of the East River bridges during the 20th century and make recommendations for their future.

The generation of longitudinal pavement pressures or growth of jointed-rigid pavement have been recognized by many engineers for at least a century. The manifestations of this pressure/growth phenomenon, in the form of progressive pavement and bridge damage, are vivid examples of its destructive potential. Yet, only a few researchers have attempted to measure the pressures generated by this phenomenon. None, to the author's knowledge, have attempted to periodically monitor pressure generation for the purpose of either determining and describing pressure generation characteristics or predicting the probability of its abrupt final and destructive manifestations. Because the pavement/growth phenomenon occurs over such a long period of time (a decade or more), it is generally unrecognized, or if recognized, it is poorly understood. Consequently, design and maintenance of jointed rigid pavement continues to be guided more by intuition and personal judgement rather than be replicated research and professional consensus. This paper provides a speculative description of the pavement pressure/growth phenomenon. It also contains an appeal to research professionals to develop instrumentation suitable to monitor generating pavement pressures. The results of such research should finally enable the transportation profession to establish suitable background so that future pavement design and maintenance will be guided so that pressure generation will be minimized and pavement and bridge function and durability will be improved. Otherwise, transportation systems will continue to experience progressive and substantial pavement and bridge damage, commensurate repair costs, and the traveling public will continue to be exposed to occasional but abrupt manifestations of its destructive potential.

The ND durability monitoring procedure, which measures the soundness of field concrete, is based on the fundamental relationship between ultrasonic pulse velocity (UPV) and permeability of an elastic medium. An experimental study documented adequate sensitivity between UPV and concrete permeability. The durability monitoring procedure is based on a parameter developed as part of this study and called paste quality loss (PQL) which is computed from the probability density function parameters of ultrasonic pulse velocity measurements taken from standard and field concrete. For PQL computation, measurements taken on standard concrete specimens, which are made from field concrete mixture, are compared to field measurements. The verification tests on 1000 mm x 1500 mm x 230 mm lab-deck specimens indicated that the PQL parameter computed from the UPV measurements as early as the 28th day is a good predictor of soundness. The UPV measurements made at increasing age of concrete very clearly document the rapid loss of soundness of improperly cured concrete decks. Deck replacement projects on three NHS bridges were used in the implementation of durability monitoring by PQL (paste quality loss) evaluation. The respective 56-day PQL's were calculated as 15%, 31% and 9% indicating a significant variability in the three bridges.

The propagation and scattering of high-frequency ultrasound in concrete is discussed. Frequencies above 100 kHz have wavelengths short enough for sensitivity to microcracking. However, the heterogeneous composition of concrete causes the ultrasound at such frequencies to scatter considerably. Theoretical descriptions of the scattering attenuations based on a stochastic wave equation are discussed. These expressions require information about the two-point spatial correlation function. The form for this function is proposed and confirmed experimentally. Finally, ultrasound diffusion experiments are discussed. In the limit of many scattering events, the ultrasonic energy density in circular cylinders of concrete is shown to evolve in accordance with a one-dimensional diffusion equation. The ultrasonic diffusivity was measured experimentally over the frequency range of 100-900 kHz. Theoretical descriptions of the diffusivity are in accord with the experimental values. Such frequencies are well above typical frequencies used for concrete inspection. Thus, it is anticipated that the use of these higher frequencies will result in new techniques for characterizing material properties and damage in concrete structures.

A method is presented for detecting damage in a clamped-clamped beam based on redistribution of dead load in the member. The approach is based on measuring static strains due to dead load only, at three locations on the beam. In the event of damage (modeled as a local reduction in flexural stiffness at a single location in the beam) the bending moment in the beam redistributes and is no longer symmetric. Using the measured strains, a genetic optimization algorithm is used to determine the location and severity of damage in the beam. Four different damage scenarios are tested, these include: no damage (to test for false positive results); varying levels of damage near mid-span; equal levels of damage near the support, quarter point and mid-span; and damage near the support with 'noisy' measurement data. The technique is found to work well under a broad range of circumstances: the accuracy and success of the method depends on the damage location and the level of measurement noise in the data. Damage near the support and center of the beam can be identified with good accuracy. As one might expect, damage at or near to the point of inflection in the beam is more difficult to identify because the dead load strain in this vicinity is small. The technique is found to work well even with measurement noise on the order of 3 to 5%.

Colombia's topography, climatic conditions, intense seismic activity and acute social problems place high demands on the nations deteriorating civil infrastructure. Resources that are available for maintenance of the road and railway networks are often misdirected and actual inspection methods are limited to a visual examination. New techniques for inspection and evaluation of safety and serviceability of civil infrastructure, especially bridges, must be developed. Two cases of civil structures with health monitoring systems in Colombia are presented in this paper. Construction of the Pereria-Dos Quebradas Viaduct was completed in 1997 with a total cost of 58 million dollars, including 1.5 million dollars in health monitoring instrumentation provided and installed by foreign companies. This health monitoring system is not yet fully operational due to the lack of training of national personnel in system operation and extremely limited technical documentation. In contrast to the Pereria-Dos Quebradas Viaduct monitoring system, the authors have proposed a relatively low cost health monitoring system via telemetry. This system has been implemented for real-time monitoring of accelerations of El Hormiguero Bridge spanning the Cauca River using the Colombian Southwest Earthquake Observatory telemetry systems. This two span metallic bridge, located along a critical road between the cities of Puerto Tejada and Cali in the Cauca Valley, was constructed approximately 50 years ago. Experiences with this system demonstrate how effective low cost systems can be used to remotely monitor the structural integrity of deteriorating structures that are continuously subject to high loading conditions.

Despite the increasing popularity of cable-stayed bridges there is no convenient and accurate means available to measure the forces in the cable stays. The measurement of the forces is important for monitoring excessive wind or traffic loadings, to gage the redistribution forces which may occur after seismic events, and for detecting corrosion via loss of the cross-section. Although magnetoelastic stress sensors have been extensively tested on many types of prestressing cables, and have demonstrated accuracies of < 1%, to-date they have been based upon a solenoid geometry, which is not practical for cable force measurements in existing bridges having hundreds of cables. In order to address this problem a magnetoelastic sensor for the direct measurement of stress in steel cables is currently under development. The sensor differs from previous magnetoelastic sensors in that the cable is magnetized by a removable C- shaped circuit, rather than by a solenoid. We report preliminary results on measurement of the initial permeability curve indicating adequate sensitivity to stress with this geometry, but further work is necessary to understand the influence of the more complicated field geometry on data reduction and calibration procedures.

The advantages of fiber-reinforced polymer (FRP) composite include excellent corrosion resistance, high specific strength and stiffness, as well as outstanding fatigue behavior. The University of California San Diego's I- 5/Gilman Advanced Technology Bridge Project will help demonstrating the use of such materials in civil infrastructures. This paper presents an acoustic emission (AE) study performed during laboratory proof tests of carbon fiber-reinforced polymer stay-cables of possible use in the I-5/Gilman bridge. Three types of cables, both braided and single strand, were tested to failure at lengths ranging from 5500 mm to 5870 mm. AE allowed to monitor damage initiation and progression in the test pieces more accurately than the conventional load versus displacement curve. All of the cables exhibited acoustic activities revealing some degree of damage well before reaching final collapse, which is expected in FRP's. It was also shown that such cables are excellent acoustic waveguides exhibiting very low acoustic attenuation, which makes them an ideal application for an AE-based health monitoring approach.

As the state of the art in bridge design is advancing toward the performance-based design, it becomes increasingly important to monitor and evaluate the long-term structural performance of bridges, including strains in critical structural members, soil pressures on the abutment back walls and footings, accelerations on the decks and bents, etc. Such information is essential in developing new performance criteria for design. In this research, sensor systems for long-term structural performance monitoring have been installed on two new highway bridges on Orange County, California: the Jamboree Road Overcrossing and the West Street On-Ramp.

The inspection of structures by humans is often hampered by safety and accessibility concerns. One method of reducing human inspection activities is to use remotely located sensors, such as strain gages and accelerometers. Running cables to power the sensors and transmit data can be expensive and inconvenient. This paper describes a development effort in which a robot is used to power and interrogate remotely placed sensors. The sensors are powered by a noncontact inductive system, which eliminates the need for batteries or interconnecting lead wires. The data are sent by a wireless connection back to a central data logger and processor. The power demands of telemetering data are decreased by close proximity of robot. The system utilizes existing microminiature, multichannel, wireless programmable Addressable Sensing Modules (ASM's) to sample data from a wide variety of sensors. Demonstration style robots are built and tested with ASMs in simple tabletop design, and a more robust task specific I-beam crawler robot for structural application.

A prototype of an interactive support system for visual inspection of bridges has been developed. The aims of this system are to complement a technical knowledge of skilled inspectors and to suggest several alternatives concerned with decision-making to inspectors who are carrying out their tasks on a bridge site. A client/server architecture has been adopted in order to reduce the client-terminals' load, to compute at high speed, and to store and centralize a great amount of information on bridge inspection. Open- source software packages were installed in the server and a Web application tied-up with a database system containing past records of bridge visual inspections and technical information on bridge inspection was constructed. By using a wearable computer and a mobile communication device, a hands-free operation and a seamless communication between the client and the server are implemented so that the system will not spoil the performance of an inspector. Regarding the support information, the system can offer the possible causes of defects which an inspector finds during the inspection and the criteria of fatal defects which need urgent measures.

In order to rationalize structural maintenance, this paper focuses on vibration characteristics as indices to detect damage, and addresses advanced vibration measurement system and damage detection method based on changes in vibration characteristics. First of all, vibration measurement system using Laser Doppler Vibrometer, which can scan the objective structural surface, is developed and an identification method from laser ambient vibration measurement is proposed. Next, a damage detection method, which calculates mass and stiffness changes in reverse based on changes in mode shapes, is also constructed. These methods show their validity experimentally through vibration measurement for a steel plate before/after damage. Furthermore, to be applied for real civil structures which possess low laser reflection, the laser vibration measurement system is advanced with adding a function which can automatically search the maximum points of laser reflection. By means of this advanced laser vibration measurement system, vibration measurement on a reinforced concrete deck is carried out and its local mode shapes are identified.

In Germany a research group from four universities has developed an advanced experimental supported objective condition assessment method for concrete bridges, called 'EXTRA'. This method is useable preferably in cases, where conventional assessment methods cannot be applied successfully. In the past more than 200 bridges and buildings were evaluated regarding their real actual load bearing capacity using this method. An authorized guideline for the practical use at concrete structures is available. Until now the process of mounting and dismantling the loading structure was the most time-consuming part of such a test and influenced testing costs and duration of traffic interruption decisive. This background and the technical conception for development and testing the truck prototype with a maximum total loading capacity of 150 t will be introduced. Main subjects are a brief characterization of EXTRA method, the truck structure, the hydraulic loading system, measurement equipment and control facilities as well as the loading regime and belonging on-line information controlling the structure response as main parts of the testing process. The concept of the future employment of such trucks and ideas for a co-operation of consulting offices, owners and authorities will be short discussed. First testing experiences and an outlook on further activities will be given. Acknowledgments finalize the contribution.

The Structure Monitoring System SMS 2001 (applied for patent) represents a modular structured multi-component measurement devise for use under outdoor conditions. Besides usual continuously (static) measurements of e.g. environmental parameters and structure related responses the SMS is able to register also short term dynamic events automatically with measurement frequencies up to 1 kHz. A larger range of electrical sensors is able to be used. On demand a solar based power supply can be realized. The SMS 2001 is adaptable in a wide range, it is space-saving in its geometric structure and can meet very various demands of the users. The system is applicable preferably for small and medium sized concrete and steel structures (besides buildings and bridges also for special cases). It is suitable to support the efficient concept of a controlled life time extension especially in the case of pre-damaged structures. The interactive communication between SMS and the central office is completely remote controlled. Two point or multi-point connections using the internet can be realized. The measurement data are stored in a central data bank. A safe access supported by software modules can be organized in different levels, e.g. for scientific evaluation, service reasons or needs of authorities.

In this study, a bridge management strategy based on minimization of the total cost during considered years is discussed. As an example, a 50-years old steel railway plate girder bridge in Japan is selected. For this bridge, the following three strategies are considered: A. to demolish the bridge and to build a new one as a replacement and, B. to continue ordinary maintenance work with no major rehabilitation work, C. to make a diagnosis of the existing bridge and to rehabilitate it. It is shown that the management strategy C in which the existing bridge continues to be used after the appropriate reinforcement based upon the detailed diagnosis is the most effective when the annual social discount ratio is less than 5%. Furthermore, sensitivity analysis is carried out to understand the effect of uncertainties of various parameters on the total cost. Bootstrap analysis where the discount ratio is treated as a randomly fluctuating variable indicates that the total cost based on Strategy C is least influenced among three strategies because of small potential investment in the future.

This paper presents an overview of ISIS Canada's development and application of fiber optic sensing systems in a variety of civil infrastructure projects. Three types of fiber optic sensors have been utilized in ISIS projects-to-date: fiber Bragg gratings (FBGs), Fabry-Perot sensors, based on measuring displacement between two fibers; and a new sensor called a `long gauge (LG)', which employs a low coherence interferometry technique to measure deformations over gauge lengths ranging from 10 cm to 40 m. Details on the operation of the LG system are described below. Applications of the FBG and LG sensors are given for several ISIS projects that also involved the rehabilitation and strengthening of concrete structures using advanced composite materials.

The concept of steel-free deck slab is discussed along with six field applications in Canada. In particular, the phenomenon of cracking in deck slabs is discussed with reference to laboratory studies as well as field observations, both of which have shown that, notwithstanding the presence of cracks, the fatigue resistance of the steel- free deck slab is very high. The provision of a layer of nominal tensile reinforcement within the thickness of the steel-free deck slab, however, eliminates the unaesthetic wide cracks. Laboratory studies, currently underway, have shown that the technique of acoustic attenuation is very effective in tracking the growth of cracks in concrete deck slabs. The conventional sensors were not successful in this respect.

This paper has demonstrated the structural strain measurement of the steel beam with the distributed fiber optical sensor system based on Brillouin scattering. The experiments were conducted both in the lab and in outdoor conditions. When it is in outdoor environment, the temperature compensation must be taken into account for the sunlight radiation effects. The compressive strain can be measured without need of the pre-tension on the fiber. The spatial resolution of the strain measurement is 0.5 m. The strain measurement accuracy is 10 (mu) (epsilon) for the lab environment.

The Hall's Harbour wharf in Nova Scotia is the first Canadian project to demonstrate the application of fibre reinforced polymer reinforcement, the steel-free concrete deck slab concept and fibre optic monitoring systems to structures in the marine environment. The extreme environmental exposure conditions make the site an excellent location for testing both material performance and sensing system durability. The early results of the monitoring program indicate that the innovative structure is meeting service level performance requirements. Long-term durability assessment is continuing and being complemented by controlled field and laboratory testing programs. Continuous remote monitoring of the fibre optic sensors is producing valuable reinforcement strain information for tracking structural response to ambient conditions. The fibre optic sensors themselves were found to be rugged enough to withstand the construction process and exposure environment; however, further work is required to achieve feasible field units for some types of fibre optic sensing instruments and associated equipment.

Under the auspices of the Canadian Network of the Centers of Excellence on Intelligent Sensing of Innovative Structures ( ISIS) a number of bridges incorporating innovative materials and/or innovative structural concepts have been instrumented with a view to monitoring their health. ISIS has initiated a project to create a central archive for the long-term collection and maintenance of the data obtained from the instrumented bridges. Typical instrumentation consists of sensors of various kinds (temperature, strain, displacement and acceleration). Data may be collected at regular intervals under normal traffic conditions using an automated or semi-automated data acquisition system. As well, static and dynamic load tests may be scheduled and performed from time to time. The data received from the various sources will be converted to a common format and will reside in a central relational database. A world-wide-web interface to the archive has been provided. The interface will allow authorized bridge managers to submit data to the archive. It will also allow other researchers to explore the archive, and to extract data from it, using many common formats.

This paper describes the proposed new Benicia Martinez Bridge of the State of California's transportation system and highlights the factors that led to health monitoring of this important structure. The instrumentation plan includes monitoring the structure for short term and long term structural behavior and monitoring the behavior of the structure during a seismic event. A brief overview of the instrumentation plan for the structure will be presented. As part of the health monitoring, the bridge will be instrumented during construction. A joint effort involving several agencies will be responsible for the instrumentation, data collection and data interpretation. The information collected will be used to periodically evaluate the performance of the bridge and to validate/enhance current design practice.

The California Department of Transportation (Caltrans) Engineering Service Center, Division of Structure Maintenance and Investigations is responsible for bridge maintenance and investigation activities for over 24,000 bridge structures in California. This Division is also the Department lead for bridge damage assessment activities. This paper provides an overview of the bridge damage assessment efforts that were conducted following the 1994 Northridge earthquake near Los Angeles, California.

The University of Nevada, Reno is currently developing a study on the seismic behavior of two-column bents with drop cap beams built prior to the 70's. Three 1/4 scale models were built with typical geometric and reinforcement properties and using the same construction details used at the time. One specimen was tested as built under the Sylmar record (Northridge 1994). The other two identical specimens were retrofitted, using carbon fibers wraps and longitudinal fibers on one bent, and an infill wall between the columns in the other. Both retrofitted specimens were tested under the same conditions as those of the as built. The fragile shear failure mode of the as built specimen was successfully modified with the retrofits, enhancing the performance and ductility. Overall performance and the effectiveness of the retrofit methods implemented used are discussed. The results indicate that the retrofits used are effective, however there are some concerns on the failure modes and excessive increase of strength.

The temperature monitoring of Tsing Ma Bridge is performed by the Wind and Structural Health Monitoring System on the Lantau Link as one of its functions. The system consists of over 90 platinum resistance type detectors on Tsing Ma Bridge installed at 4 selected cross-sections. Since May 1997, temperature measurements have been continuously recorded. The University of Hong Kong has been assisting in the analysis of these field measurements. This paper describes the instrumentation and data analysis related to the study. In parallel with this, experimental segmental steel sections under the influence of solar radiation have been set up on the university campus and temperature measurements have been recorded since 1993. Correlation results of observed data have shown that the temperature of steel sections mainly depends on the solar intensity and shade air temperature. Based on the theory of heat transfer, finite element models for different structural components of the bridge deck have been developed for prediction of temperature distribution. Good agreement with field data was observed. Comparison of positive temperature gradients among different structures has shown that they can generally be classified into two categories depending on the number of web faces exposed to the environment.

Structural health monitoring for the three cable-supported bridges located in the West of Hong Kong or the Tsing Ma Control Area has been carried out since the opening of these bridges to public traffic. The three cable-supported bridges are referred to as the Tsing Ma (suspension) Bridge, the Kap Shui Mun (cable-stayed) Bridge and the Ting Kau (cable-stayed) Bridge. The structural health monitoring works involved are classified as six monitoring categories, namely, wind load and response, temperature load and response, traffic load and response, geometrical configuration monitoring, strains and stresses/forces monitoring and global dynamic characteristics monitoring. As wind loads and responses had been a major concern in the design and construction stages, this paper therefore outlines the work of wind load and response monitoring on Tsing Ma, Kap Shui Mun and Ting Kau Bridges. The paper starts with a brief description of the sensory systems. The description includes the layout and performance requirements of sensory systems for wind load and responses monitoring. Typical results of wind load and response monitoring in graphical forms are then presented. These graphical forms include the plots of wind rose diagrams, wind incidences vs wind speeds, wind turbulence intensities, wind power spectra, gust wind factors, coefficient of terrain roughness, extreme wind analyses, deck deflections/rotations vs wind speeds, acceleration spectra, acceleration/displacement contours, and stress demand ratios. Finally conclusions on wind load and response monitoring on the three cable-supported bridges are drawn.

A field measurement to validate a moving force identification method was carried out on an existing prestressed concrete highway bridge with a span length of 28 m. The test bridge is located at Ma Tau Wai, Kowloon, Hong Kong. A heavy 2-axle truck with known axle loads was used as a control vehicle. Besides the control vehicle, axle load data of in-service vehicles were also collected. The bridge responses acquired for the identification were indirectly measured using strain gauges. Results show that dynamic axle loads induced from both control and in-service vehicles can be identified indicating the method is valid for identification of moving forces.

GIS can be used to integrate and to manage various sources of spatial and attribute data on bridge health monitoring. In this study, an integrated GIS and Bridge Health Monitoring system is developed for Ting Kau Bridge in Hong Kong. The developed system manages information of a bridge at three levels. At the region level, the GIS combines and offers spatial analysis to various types of information corresponding to the surrounding environment of the bridge, for instances, road network, typhoon, seismic attack and traffic impact. At the bridge level, the GIS maintain topological, graphical and textual information of the bridge. User can retrieve location-related information of the bridge. GIS can also connect to a spectral analysis software which generates damage indices for the bridge. Then, users can examine the distribution of health indicator at different locations of the bridge. The level of sensors provides detail information for on-line monitoring. Different types of sensors are mounted on the critical points of the bridge to collect on-line information of the bridge. Users can examine if there is any abnormal readings found from the sensors on the bridge. The developed GIS is proven to be a potential tool for providing a complete picture of the health status of the bridge at different scales.

A long suspension bridge is usually located in a unique wind environment and accordingly strong winds at the site seldom attack the bridge at a right angle to its longitudinal axis. However, the buffeting response prediction often assumes that the wind approaches the bridge at a right angle to its longitudinal axis. This paper thus intends to investigate this subject to some extent. The conventional buffeting analysis method in the frequency domain is refined first to take into account the effects of wind inclination and yaw angle. The field measurement data, which were recorded during Typhoon Sam in 1999 by the `Wind And Structural Health Monitoring System' (WASHMS) installed on the Tsing Ma Bridge, are then analyzed to obtain both wind characteristics and structural responses. Finally, the aerodynamic and aeroelastic coefficients of the Tsing Ma bridge deck under yawed and inclined winds, which are required in the analytical prediction, are measured through wind tunnel tests and reported in this paper. The detailed comparison of the field measurement data with the analytical results, however, is still under the way, which cannot be reported in this paper.

Fatigue assessment for the Tsing Ma Bridge (TMB) are presented based on the British standard BS5400 and the real-time structural health monitoring data under railway loading. TMB, as an essential portion of transport network for the Hong Kong airport, is the longest suspension bridge in the world carrying both highway and railway traffic. The bridge design has been mainly based on BS5400. A structural health monitoring system - Wind and Structural Health Monitoring System (WASHMS) for TMB has been operated since the bridge commissioning in May 1997. In order to assess the fatigue behavior of TMB under railway loading, strain gauges were installed on the bridge deck to measure the strain-time histories as soon as the bridge is loaded by a standard railway loading due to the service of an actual train. The strain-time history data at the critical members are then used to determine the stress spectrum, of which the rainflow method recommended for railway bridges by BS5400 is applied to count cycles of stress range. Miner's law is employed to evaluate fatigue damage and remaining service life of the bridge. The evaluated results of fatigue damage and remaining service life would help us to well understand about the fatigue design of the bridge and status in fatigue accumulation.

Since the probabilistic neural network (PNN) describes measurement data in a Bayesian probabilistic approach, it shows great promise for structural damage detection in noisy conditions. In the traditional PNN, the smoothing parameter is unique to all pattern classes and is specified artificially, which may result in inaccuracy of identification results and computational inefficiency. In this study, we explore the damage localization of the Tsing Ma suspension bridge by use of an adaptive PNN that optimally determines different smoothing parameters for different pattern classes through an iteration scheme. A series of pattern classes are defined for the Tsing Ma Bridge to depict different damage locations.

Wavelets analysis is a mathematical tool that can represent a signal in terms of a set of basis functions and thus can describe the signal on various levels of resolutions or scales corresponding to different frequency bands. They have advantages over traditional Fourier methods in analyzing nonstationary signal. In this study, a method based on wavelet packet decomposition (WPD) is proposed to process vibration signals of a structure that undergoes characteristic changes due to damage. The method decomposes the vibration signals into a data set with various levels of resolutions, hence small changes caused by structural damage become visible in some levels. The wavelet packets are used since they can produce narrower and more improved frequency resolutions as compared to the original wavelet. Based on this decomposition, component energy indices are chosen as indicators for structure health condition assessment. For illustration, a numerical simulation is performed on a three-span continuous bridge deck with different characteristic changes under impact loads. The case study shows that the component energy indices obtained from the WPD are excellent indicators for structure health condition assessment. When they are fed into well-trained neural network classifiers, structural conditions such as damage occurrence, location and severity can be identified quite accurately.

This paper presents a study in an effort to develop a remote visualized health monitoring system for three cable- supported bridges in Hong Kong in accordance with the existing on-structure instrumentation system. The envisaged system remotely delivers the measurement data to the user's deck top and processes the data in a visualized form and in an on-line way. The raw data acquired from typical sensors are first transmitted, pre-processed and reorganized into a general-purpose database that can be updated dynamically. Then the data are analyzed and presented to the end user on screen and automatically processed for the monitoring purpose.

This paper presents a comparative study of using the modal curvature index and the modal flexibility index for damage localization in the cable-stayed Kap Shui Mun Bridge from the bridge global modal data before and after damage. Based on a precise and validated 3D finite element model of the bridge, a series of damage cases associated with the deck are introduced in the simulation study. They are the damage occurring at the members within deck segments and the damage occurring at the support and bearing system of the deck. The damage indices are applied to determine the specific deck segment that contains damaged member(s).

In order to improve the efficiency and accuracy of the existing Wind and Structural Health Monitoring System (WASHMS) for the three cable-supported bridges, namely, the Tsing Ma (Suspension) Bridge, the Kap Shui Mun (Cable-Stayed) Bridge and the Ting Kau (Cable-Stayed) Bridge, Global Positioning System (GPS) is introduced to monitor the displacements of the cables (main suspension cables only), the stiffening decks and the bridge-towers. The measured displacement values will be used to calculate relevant motions at center-lines of the stiffening decks and bridge-towers, which will then be used to derive relevant stress status acting on the major bridge components. The GPS here refers to the `NAVSTAR GPS or NAVigation System with Time And Ranging Global Positioning System' which is a satellite-based system that uses a constellation of 24 (currently 27) satellites to determine the accurate coordinates or position of a user/receiver. The GPS applied to monitor the displacements of three cable-supported bridges is known as `Global Positioning System--On-Structure Instrumentation System or GPS-OSIS'. This GPS-OSIS is a real-time monitoring system and made up of five sub-systems, namely, the GPS Sensory System, the Local Data Acquisition System, the Global Data Acquisition System, the GPS Computer System and the Optical Fiber Network System. This paper first introduces the system layout and technical performance requirements of the GPS-OSIS, then briefly discusses the applications of GPS results in structural health monitoring of cable-supported bridges, e.g. the correlation of bridge responses to the effects of wind, temperature and traffic loads and the significance of monitoring geometrical variations and dynamic characteristics.

This describes a research program to apply nonlinear analysis and chaos theory to structural health monitoring. Earlier approaches based on linear modal analysis typically examined fundamental frequencies of the structure. However, significant changes in the fundamental frequency were usually not detected until the structure was severely damaged. In chaos theory, the fundamental frequencies are not assumed to be fixed, instead they wander time in a characteristic pattern around a central value, called an attractor. In a chaotic system, a set of parameters called Lyapunov exponents play the role of fundamental frequencies in linear system analysis. The current FHWA research program involves the development of algorithms to extract these exponents from structural monitoring data. These algorithms are being evaluated against simulated data sets produced by an advanced 3D nonlinear dynamics finite element code using synthesized ambient traffic loadings. Chaotic behavior was observed in the modeled bridge.

Aging highway structures can display complicated nonlinear dynamics behavior due to degradation of structural properties or crack damage, as well as to variations in environmental and dynamic loading conditions. This paper explores the feasibility of utilizing the spatial distribution of the Lyapunov exponents for damage detection in nonlinear bridge structures. In particular, this approach considers the chaotic nature of the response of general nonlinear highway bridges due to ambient traffic loadings in the analysis of the observed bridge response data for each monitoring locations. A novel algorithm, based on the average mutual information from observed data and a stochastic orthogonalization using polynomial chaoses, is used to efficiently extract the nonlinear bridge system invariants consisting of a set of Lyapunov exponents.

Bridge dynamics data are usually collected as a function of excitations by ambient traffic loads. However, the stochastic aspects of the multi-lane, continuous traffic flows significantly complicate the loading conditions in dynamics analysis of highway bridges. Such ambient traffic loadings often cause incremental changes of structural shear or bending stresses in bridge structures and therefore result in fatigue damage. Most current approaches for modeling traffic loading rely on simple load spectra approximations and address only the maximum effect of the loading. Therefore, they have limited ability to take into account the effect of such multi-lane ambient traffic flow loadings. This paper presents a stochastic modeling and simulation approach to describe ambient traffic flows over the highway bridges.

As part of a program to apply stochastic system analysis to structural heath monitoring of highway structures, a detailed Finite Element (FE) model of a typical highway bridge has been developed. The model was created for use with the nonlinear explicit FE code, LS-DYNA, and consists of 144 parts and approximately 40,000 elements. The model represents a standard two-lane bridge with a span length of 40 meters. It consists of 4 girders and 21 cross frame sections. This paper discusses some important practical aspects involved in the modeling of such highway bridges including connections, material properties, boundary and dynamic loading conditions. Extensive simulations were conducted using a SGI supercomputer at the FHWA sponsored National Crash Analysis Center at the George Washington University to determine the bridge structural response under dynamic loadings. The resulting data sets from these simulations are used as the basis for chaotic system invariant spectrum analysis described in related papers in this conference.

This study chronicles the first stages of an ongoing research initiative to monitor several tall buildings in Chicago under the action of wind. From these measurements, comparisons with predicted analytical values and wind tunnel tests will provide valuable insights into the accuracy of current design strategies, highlighting areas for improvement to advance the state-of-the-art in tall building design. This paper overviews the entire project with detailed treatment of the current phase: the instrumentation of the four buildings.

Development in sensing technologies and data acquisition systems is making it possible for engineers to acquire the actual state of strains and stresses in structures at construction stage and during their service life. The knowledge of actual internal forces in a structure is key to identification of parameters such as stiffness and support conditions enabling the structural performance to be accurately estimated. This paper reports on the theoretical and experimental work carried out using fibre Bragg gating (FBG) strain sensors, embedded into and attached onto the concrete beam, to obtain the strain distribution of the concrete beam, therefore deduce the information of the applied load.

In the framework of a large-scale monitoring program conducted by the Port Authority of Genoa, the east quay wall of the San Giorgio pier has been equipped with an array of more than 60 SOFO fiber optic sensors for continuous monitoring. These sensors allow the measurement of the pier displacements during the dredging works, ship docking and in the long term. The sensors measure the curvature changes in the horizontal and vertical planes and allow a localization of settlements with a spatial resolution of 10 m over a total length of 400 m. The system is in operation since fall 1999, and data has been collected automatically and continuously since then. This paper is intended to present the first analyses and interpretations performed on the monitoring data. Correlation of raw data and curvature analysis to environmental conditions is also presented.

The strain distribution in a 1.65m long reinforced concrete beam was measured using the distributed fiber optic sensing system developed by Dr. Bao's Fiber Optic Group at the University of New Brunswick (UNB) with center point and two point loading pattern. A spatial resolution of 0.5m was used. Past experience has shown that the bare optical fiber is too fragile to act as a sensor in a reinforced concrete structure. Therefore, in this experiment, two methods of protecting the fibers were incorporated into the concrete beam to increase the fibers' resistance to mechanical damages and prevent chemical reaction from occurring between the fibers and the concrete. The fibers were either embedded in pultruded glass fiber reinforced vinyl ester (GFRP) rods or bonded to the steel reinforcing bars with an epoxy adhesive. The strain at midspan of the beam as measured by the distributed sensing system was compared with the readings of electrical resistance strain (ERS) and mechanical strain (MS) gauges. The experimental results showed that the pultruded GFRP rods effectively protected the fibers, but the strain readings from the GFRP rods did not agree with the strain measurement of the ERS on the steel reinforcing bars due to the possible slippage of the rods in the concrete. However, the fiber bonded to steel reinforcing bars produced more accurate results and confirmed the potential of this technology to accurately measure strain in a reinforced concrete structure. As expected, the fiber with direct contact to the concrete and steel reinforcing bar, can effectively measured the strain under center point or two point loading.

Experimental studies have been carried out to employ GPS to measure the vibrations of the 384 m tall Di Wang building in Shenzhen, China. Two GPS receivers were employed in the experiment with one set on the top of the building and the other on a reference station on the ground near-by. The GPS data were collected at a rate of 4 sets per second. The experiment was conducted under different weather conditions over two 24-hour periods. This paper describes the GPS equipment used, the field operations, the data processing and analysis strategies, and the results obtained from the study. It is shown from the study that GPS can be successfully applied for monitoring structural vibrations. However cautions have to be exercised in analyzing GPS data to remove biases such as the so-called GPS multi-path errors. Besides, some practical issues still need resolved before GPS can be applied routinely for this type of applications.

This paper discusses a data quality control, handling, and assurance process for real-time on-line monitoring. It further displays the processing steps during a typical data quality assurance. Data process design and utilization varies with type of data and information to be presented. Design of a data-flow process that would lead to real-time visualization, engineering analysis, storage, and archival of data is quite challenging for real-time on-line monitoring applications. An existing system for continuous health monitoring of a ling-span bridge is described and the design of the data quality assurance (DQA) steps is discussed. Wind that is monitored at various stations at the bridge is processed using the DQA steps. This paper further illustrates the identification of stationary wind segments on the attempt to correlate this with the various responses obtained from the critical components of the bridge.

The importance of rational decision-making for optimum resource distribution of civil infrastructure systems management is well recognized. Bridges, serving as node points of the highway transportation system, are critical components of the nation's infrastructure. As the nation's bridge population is aging, management decisions must be based on an objective, complete, accurate and compatible information for maximum reliable bridge lifecycle. For bridges sharing common materials, similar geometric design attributes and behavior mechanisms, fleet-strategies for health monitoring would offer significant advantages. Improvements from fleet health monitoring would lead to objective engineering knowledge for optimal decision making. This paper provides an overview of fleet health monitoring concept, then summarizes an on-going research on re- qualification of reinforced concrete T-beam bridge population in Pennsylvania.

Blue Road Research has designed, built, and installed fiber grating sensor systems onto bridges, and most recently into an asphalt and concrete highway test pad. The sensitivity levels of the fiber grating sensors are sufficiently high to enable detection of people standing on the bridge or highway. This paper briefly overviews the usage of these sensors for traffic monitoring.

Health monitoring has been one of particular concerns of the engineering community in Japan. Effective monitoring, reliable data analysis, rational data interpretation and correct decision making are challenging problems for engineers who specialized in bridge monitoring field. In this paper, the status of health monitoring of long-span bridges in Japan is briefly reviewed. The monitoring system was developed to be a reliable device to observe the bridge in earthquake and/or typhoon accurately, besides have a self-check function to sense the disorder of the system itself. Current practices in health monitoring of bridges are represented by the example of Akashi Kaikyo Bridge monitoring system. The reliability of the current monitoring system is confirmed by comparing the analyzed simulation results and field-measured results. Furthermore, a newly developed monitoring system is proposed to provide information for structural health maintenance, so called Monitoring Based Maintenance (MBM). This monitoring system is easily accessible, economically feasible and durable through efforts in development of innovative sensors and new generation of automated remote monitoring technology.

Reliable health monitoring, including nondestructive evaluation, is an essential part of the feedback and monitoring system for infrastructures. The goal of this paper is to provide a summary of recent research activities that will act as a catalyst to expand interest in the development of new health monitoring technologies. The paper describes the motivation for developing innovative tools for monitoring the health of the nation's infrastructure. An overview of initiatives sponsored by the National Science Foundation to develop new technologies is presented. The paper includes a review of state-of-the-art stress-wave methods for the evaluation of structural materials and pavements at National Institute of Standards and Technology. Finally, efforts at the Federal Highway Administration to develop new technologies for the assessment of the nearly 500,000 bridges along the nation's roads and highways are described.