This study proposes a method to utilize remotely sensed pre- and post-disaster (bi-temporal) imagery data in order to detect the change specifically associated with structural and major regional damage caused by natural disasters such as a strong earthquake. The input is a pair of coregistered remotely sensed images of the same scene acquired at different times and the output is a binary image in which 'changed' pixels are separated from 'not-changed' ones. Correlation analysis generally fails to detect structural change, especially if images are acquired under different illumination conditions. In fact, automated detection in such a case becomes problematic since making distinction of change due to structural damage from that associated with the difference in the illumination condition is difficult. To overcome this problem, a method of principal component analysis (PCA) is employed. The approach produced promising results on the model images and currently under further study to be extended for near real-time damage assessment purposes.

Besides the severe ground shaking, fires induced by earthquakes are usually the major causes of human casualties and properties losses. This paper presents a newly developed intelligent system, which can prevent ignition of fires and promptly report fires following earthquakes. The system consists of three key components: (1) a remote-controlled off/on valve for gas pipes to prevent the ignition of fires following earthquakes, (2) a cell-phone based wireless information unit to promptly report the fires if fires do occur, and (3) a central signal processing unit to analyze the fire data transferred and send the commands such as shut-off/reset-on of the valves through the wireless information unit.

The purpose of this study is to demonstrate and evaluate the feasibility of change and damage detection in urban environments after a disastrous earthquake using SAR data. Marmara earthquake occurred on August 17, 1999 with a magnitude of 7.4 and caused extensive urban damage in the northwestern region of Turkey. In a reconnaissance mission1, observation and ground truth of several locations in that area were made about fifty days after this earthquake. In this paper, town of Seymen (40 degree(s) 42' N latitude and 29 degree(s) 54' E longitude) is being focused. The city extensively suffered building damage with dominant mode of pancaking failure. The area of interest basically consisted of residential apartment buildings situated in large, open areas. Typically buildings are 6 stories moment resisting concrete frame structures with inclined roofs. Pancaking modes of failure were observed involving collapses ranging from one to three stories in most of the buildings. ERS SAR data (for before and after earthquake), Landsat images of the area and GPS readings of building corners are used in this research. Image processing and change detection algorithms, especially correlation and coherence maps are obtained from before and after SAR complex images. Implemented algorithms show valuable means for change detection and can indicate the location of building damages.

A reliable, robust monitoring system can improve the maintenance of and provide safety protection for civil structures and therefore prolong their service lives. A built-in, active sensing diagnostic technique for civil structures has been under investigation. In this technique, piezoelectric materials are used as sensors/actuators to receive and generate signals. The transducers are embedded in reinforced concrete (RC) beams and are designed to detect damage, particularly debonding damage between the reinforcing bars and concrete. This paper presents preliminary results from a feasibility study of the technology. Laboratory experiments performed on RC beams, with piezo-electric sensors and actuators mounted on reinforced steel bars, have clearly demonstrated that the proposed technique could detect debonding damage. Analytical work, using a special purpose finite-element software, PZFlex, was also conducted to interpret the relationship between the measured data and actual debonding damage. Effectiveness of the proposed technique for detecting debonding damage in civil structures has been demonstrated.

This paper presents the research which is carried out in the field of adaptive structures at the Institute for Lightweight Structures at the University of Stuttgart. The application of adaptive systems in the field of architecture and structural engineering creates new chances to design lightweight structures. Different concepts of active control can be used to manipulate the forces, the deflections and the vibration of structures. These concepts are categorised into two groups: control of external loads and control of internal forces. Active shape control can be used to reduce the external wind load by changing the shape of the cross-section of wide-span bridges or high-rise towers. Alternatively active force and/ or stiffness control can be used to manipulate the internal flow of forces and stresses in structures. Systems with active force control superimpose the actively generated forces with the already existing forces, while systems with active stiffness control redistribute the forces according to their varying stiffness distribution. The authors use active elements with variable length and/ or stiffness in static indeterminate structures to control the deflections and redistribute the forces. A bridge with actively controlled elements is presented, where the stress peaks can be reduced and a homogenisation of the force distribution can be obtained.

Polyvinylidene fluoride (PVDF) is a semicrystalline polymer exhibiting piezoelectric and pyroelectric properties which has been used for sensing infrared energy and the measurement of high frequency stress and strain, such as shocks. Despite the low material cost, durability, high sensitivity, and fast response, PVDF-based sensors have not been successfully used for infrastructure monitoring, where these benefits would seem appropriate. One reason is that the low frequency response of the sensor and integrated charge amplifier (the hybrid characteristic of the sensor) has not been adequately measured and modeled. In this paper we report on the development of a PVDF displacement sensor designed for infrastructure monitoring.

Fiber optic Bragg gratings packaged in long gage configurations are being used to measure static and dynamic macro-strains in structures and structural models to monitor structural health and detect and identify macro-damage incurred from a seismic event. These long gage sensors are being used to experimentally verify analytical models of small-scale structural models in their pre- and post-damage states using system identification techniques. This fiber optic deformation measurement system could play a significant role in monitoring/recording with a higher level of completeness the actual seismic response of structures and in non-destructive seismic damage assessment techniques based on dynamic signature analysis. This new sensor technology will enable field measurements of the response of real structures to real earthquakes with the same or higher level of detail/resolution as currently in structural testing under controlled laboratory conditions.

Determining the health of concrete structural members, such as bridge columns and retaining walls is often difficult because a large portion of the interesting features, including damage are buried underneath the surface. This paper describes a development effort in which high-frequency electromagnetic waves (0.5 to 6 GHz) are used to interrogate reinforced concrete bridge columns, retaining walls and roadways. This technology, often known as ground penetrating radar (GPR), has previously been used to examine roadways and geological formations, primarily with lower frequencies. Rebar locations, concrete degradation and some cracks can be identified. However, most of the presently available GPR systems are bulky and specifically designed for examining horizontal surfaces. It is envisioned to use GPR technology to also examine non-horizontal surfaces, such as columns and walls. A prototype handheld system has been developed and tested on columns and retaining walls in the field as well as in the laboratory. The design of the system, field data compared with visual and historical information, as well as design concepts for an improved system will be presented.

The final purpose of our study is development of the structural health-monitoring technique for the real existing buildings. In this paper, the results of the analytical studies are shown as the first step of our health-monitoring scenario. One of the purposes of the first step is to make the analytical models for evaluating the structural performance.

A system realization algorithm is used to identify a structural model directly from input and response measurement data. The algorithm starts with computing the information matrix to derive a special correlation matrix that in turn produces the system observability matrix. A system model can then be identified from the observability matrix. Finally an algorithm was developed which produced a modal model, including stiffness matrix and damping matrix, from this state space system realization. Verification of the method through both numerical simulation and experimental data from shaking table test is carried out in this study.

Emerging image processing techniques demonstrate their potential applications in earthquake engineering, particularly in the area of system identification. In this respect, the objectives of this research are to demonstrate the underlying principle that permits system identification, non-intrusively and remotely, with the aid of video camera and, for the purpose of the proof-of-concept, to apply the principle to a system identification problem involving relative motion, on the basis of the images. In structural control, accelerations at different stories of a building are usually measured and fed back for processing and control. As an alternative, this study attempts to identify the relative motion between different stories of a building for the purpose of on-line structural control by digitizing the images taken by video camera. For this purpose, the video image of the vibration of a structure base-isolated by a friction device under shaking-table was used successfully to observe relative displacement between the isolated structure and the shaking-table. This proof-of-concept experiment demonstrates that the proposed identification method based on digital image processing can be used with appropriate modifications to identify many other engineering-wise significant quantities remotely. In addition to the system identification study in the structural dynamics mentioned above, a result of preliminary study is described involving the video imaging of state of crack damage of road and highway pavement.

The primary objective of novelty detection is to examine a system's dynamic response to determine if the system significantly deviates from an initial baseline condition. In reality, the system is often subject to changing environmental and operation conditions that affect its dynamic characteristics. Such variations include changes in loading, boundary conditions, temperature, and moisture. Most damage diagnosis techniques, however, generally neglect the effects of these changing ambient conditions. Here, a novelty detection technique is developed explicitly taking into account these natural variations of the system in order to minimize false positive indications of true system changes. Auto-associative neural networks are employed to discriminate system changes of interest such as structural deterioration and damage from the natural variations of the system.

This paper uses a damage detection approach based on dereverberated transfer functions. In 1D structures, conventional reverberated transfer functions are formed because of the interactions between incident and reflected waves in structures. By applying virtual controllers to eliminate wave reflections, dereverberated transfer functions can be obtained. Dereverberated transfer functions provide good representation of a structure's local dynamics. Because local dynamics are more sensitive to parameter changes, the dereverberated transfer function appears to be suitable to infer structural damage. In this study, a three- story building model is tested under seismic wave excitation. Experimental results show that this approach can be used to locate damage, determine damage type, and quantify damage extent.

Recently proposed methodologies in the field of vibration- based structural health monitoring have focused on the incorporation of statistical-based analysis. The structure in question is dynamically excited, some feature is identified for extraction from a measured data set, and that feature is classified as coming from a damaged or undamaged structure by means of some statistical approach. Perhaps the most important aspect of this new paradigm is the selection of a `feature' which accurately details the appearance, and possibly the location and scope, of the damage. In this paper we propose a feature derived from the field of nonlinear time-series analysis. Specifically, system response is classified according to the geometry of its dynamical attractor.

Intelligent reinforced concrete structures with transformation-induced-plasticity (TRIP) steel rebars that have self-diagnosis function are proposed. TRIP steel is special steel with Fe-Cr based formulation. It undergoes a permanent change in crystal structure in proportion to peak strain. This changes from non-magnetic to magnetic steel. By using the TRIP steel rebars, the seismic damage level of reinforced concrete structures can be easily recognized by measuring the residual magnetic level of the TRIP rebars, that is directly related to the peak strain during a seismic event. This information will be most helpful for repairing the damaged structures. In this paper, the feasibility of the proposed intelligent reinforced concrete structure for seismic damage sensing is experimentally studied. The relation among the damage level, peak strain of rebars, and residual magnetic level of rebars of reinforced concrete beams implemented with TRIP steel bars was experimentally studied. As the result of this study, this intelligent structure can diagnose accumulated strain/damage anticipated during seismic event.

A smart composite bridge is described that features an all-composite design and an integral sensor network. This short-span structure is nine meters in length and is designed for an AASHTO H20 highway load rating. The prototype bridge, the first full-composite bridge in Missouri, was installed on the University of Missouri-Rolla campus as a field laboratory for smart structures courses and a demonstration of composite technology. It was designed, analyzed, and manufactured as a cooperative product development among university, industry, and government partners. It has a modular construction based on a pultruded 76-mm-square composite tube. The cross section of the overall structural element is an I-beam formed by seven layers of bonded tubes. The top and bottom layers are carbon/vinyl-ester tubes for strength and the other layers are glass/vinyl-ester tubes for economy. Extrinsic Fabry-Perot interferometric fiber-optic sensors were embedded throughout to measure temperature, flexure strain, and shear strain. Also, radio-frequency identification tags were co-located with sensors to aid in determining load placement during field tests. This paper gives an overview of the project emphasizing the smart instrumentation. In particular, the installation of the integral sensors, the plan for the sensor network, and preliminary strain results for vehicle loading are discussed.

The CCD measuring technique is effectively applicable to structures which are not physically accessible or contain the radioactive waste material or other harmful materials to man. Unlike other measuring systems with numerous sensors attached to the structure, it simplifies the complicated problems in transferring the signal and thereby makes it possible to work more effectively. Such a non-contact type of CCD measuring technique is suggested to measure some structural characteristics of civil infrastructures. Calibration of this system is performed based on the DLT theory. And based on the calibration, 3D coordinates for changing displacement of a structure are measured. This measuring system also compares the result of trigonometrical leveling in terms of its exactitude.

Structural identification (St-Id) of constructed systems is of interest to researchers as well as civil infrastructure systems owners and operators. St-Id offers an objective, quantitative evaluation of constructed systems through effective and integrated utilization of state-of-the-art experimental and analytical technologies. During the past five years two test beds were created at the University of Cincinnati and Drexel University for the exploration of analytical and experimental barriers obstructing successful St-Id applications. The two physical models are plane-grid structures with different controlled mechanisms of uncertainty. The objective of this paper is to present the St-Id studies to the two physical models. The principal mechanisms of uncertainty that governed the global structure behavior of the first physical model were nonlinear visco- elastic boundaries. The second model incorporated a fiber- reinforced polymer composite deck and its connection details to the grid. The impact of these different mechanisms of uncertainty on the success of St-Id will be addressed.

In a cylindrical configuration, ER devices can be created by forming multiple flow paths with a set of concentric annular ducts. These ducts can be connected in parallel to maximize the range of adjustable forces or in series to maximize the absolute force levels. A synergistic result is obtained when groups of ducts are interconnected in parallel and in series within a single device. This paper presents the details of the design, construction, testing, and modeling of ER dampers designed in this fashion. These ER dampers feature multiple concentric electrodes which are electrically in parallel, but may be hydraulically inter-connected through multiple paths. The number of possible interconnection of N concentric ducts is 2^(N-1). Each configuration has distinctly different properties.

First part of this paper covers experimental studies on mechanical properties of two types of magneto-rheological fluid (MRF) dampers. One is a commercial built-in-pass type damper and the other an original by-pass type damper. In the test, they are subject to cyclic sinusoidal displacements with different amplitudes, velocities and intensities of magnetic field. Not only their hysteretic properties but also their quickness to respond to the applied magnetic field are examined. In the second part, two analytical methods to represent the mechanical properties of the dampers are presented. One is a semi-empirical method making use of a Bingham Model to simulate the hysteretic properties of the damper. The other one, an analytical method based on the theory of non-Newtonian fluid. A design formula to predict the resistance of the damper is so obtained as to take into consideration the damper's dimensions, the properties of the fluid and the intensity of the magnet field applied.

CHIME is a research project, funded by the European Union, which investigates the adoption of innovative structural control techniques in view of the seismic rehabilitation of the wide monumental cultural heritage in Mediterranean countries as Egypt, Tunisia and Cyprus. The structural control devices are mainly of the semi-active type. In this particular paper one reports the first results achieved within a case study. It considers an Egyptian large size monolithic monument. Alternative solutions for its seismic rehabilitation are eventually conceived and discussed.

The potential of smart fluids (both electrorheological, and magnetorheological) in damping devices is now well-known. Whilst both types of fluid can suffer from drawbacks such as sedimentation, fluid degradation, and problems with containment or sealing, these issues are not insurmountable and solutions have been engineered such that practical damping devices are now commercially available. However, one drawback is that the free-velocity characteristics of a smart fluid device are inherently non-linear, possessing the general form associated with a Bingham plate. This means that while practical devices have the potential to modify rapidly their behavior, it can be difficult automatically to adjust the device's response.

The application of Nitinol shape memory alloys (SMA) in steel connections is evaluated using connections incorporating SMA tendons. Shape memory alloys are a class of alloys that exhibit thermo-mechanical characteristics that are ideally suited for seismic applications. They have the ability to dissipate significant energy with little permanent deformation, and possess highly reliable energy dissipation based on a repeatable solid state phase transformation. To assess the validity of using SMA in real structures, two full-scale connections are tested. The tests are conducted on exterior joint specimens and tested according to the SAC testing protocol. The beams are W24 x 94 and the columns W14 x 159, all of A572 Grade 50 steel. Companion regular steel connections are tested for comparison. The connections are of a T-stub type, with four 11/2 inch diameter SMA rods providing the tensile resistance to the column. The specimens are re-tested several times to determine the ability of the SMA rods to regain their original configuration. The tests will lead to the development of an innovative beam-column connection that can be used for both retrofit and new construction that exhibits performance which is superior to existing designs.

Two similar full scale seismic isolation SMA prototype devices, with 600 KN maximum force and 200 KN supplemental recentering force were the final product of the MANSIDE (Memory Alloys for New Seismic Isolation DEvices) project funded by the European Commission. Exploiting the superelastic behaviour of NiTi wires, they have full recentering and some energy dissipation capabilities, as well as high resistance to large strain cycle fatigue and great durability. They can be used for both bridges and building structures. Their applicability is demonstrated by an experimental application made on a small building in Italy. The building was subjected to a release test, by moving it 150 mm and then suddenly releasing it to measure free oscillations. A description of the devices, their applicability and the relevant experimental tests is provided in the paper.

A wide ranging R&D Project (ISTECH) on validation and application of the Innovative Antiseismic Techniques (IATs) for the restoration of Cultural Heritage Structures (CUHESs), especially masonry buildings, based on the Shape Memory Alloys (SMAs), has been funded by the European Commission (EC), in the framework of the Environment and Climate RTD Programme. Because Traditional Restoration Techniques (TRTs) have sometimes proved inadequate in avoiding collapses and often too invasive, the use of superelastic SMA Devices (SMADs) has been developed. Theoretical and numerical studies, as well as intensive testing of material specimens, devices, structural models and in situ campaigns, show that SMADs can substantially increase the stability of masonry CUHESs exposed to an earthquake. Different SMAD types have been investigated to fulfil different structural needs and they can be custom designed taking into account each monument's characteristics. The successful results of the research and its exploitation led to important applications in Italy: the S. Giorgio Church Bell-Tower, located at Trignano, S. Martino in Rio, Reggio Emilia, damaged by the 15th October 1996 earthquake, the transept tympana of the S. Francesco Basilica in Assisi and the S. Feliciano Cathedral façade in Foligno, both heavily damaged by the September 1997 earthquake. In addition, further studies and applications of SMAD technology are foreseen in Italy in the next future, in the framework of Italian and European research projects and proposals.

This paper describes the rehabilitation of the S. Giorgio Church Bell-Tower (Trignano, Municipality of S. Martino in Rio, Reggio Emilia, Italy), completed in September 1999. This masonry building, seriously damaged by the earthquake of October 15th 1996 which struck the Reggio Emilia and Modena Districts (Italy), was investigated by the authors immediately after the seismic event, as other ancient Cultural Heritage Structures (CUHESs) in the same area. In the past, seismic events have visited substantial destruction that translates into a significant loss of architectural heritage. The most common solution traditionally used to enhance the CUHESs seismic behaviour is the introduction of localized reinforcements, usually Traditional Steel Ties (TSTs), increasing stability and ductility. Anyway, in many cases said reinforcement techniques, often too invasive, proved to be inadequate to prevent collapse. For these reasons, the Bell-Tower intervention applies Innovative Antiseismic Techniques (IATs) by the use of superelastic Shape Memory Alloy (SMA) Devices (SMADs), a technology developed after a large amount of theoretical studies, numerical analyses and test campaigns. The SMADs, which can be considered a powerful tool with respect to the traditional methods, provide acceleration reduction, force limitation and energy dissipation. Furthermore, they are characterized by low invasivity and complete reversibility. When another earthquake occurred on June 18th 2000, with the same epicenter and a comparable Richter Magnitudo, the Bell-Tower, subjected to a new investigation, showed no damage of any type. Thus, the new seismic event has been the best verification of the retrofit intervention.

This paper presents a formulation for the optimal design of MR dampers. MR materials are suspensions of magnetically soft particles in a hydraulic medium. The application of intense magnetic flux to these materials gives rise to a fibrated microstructure which, when sheared, resists flow with yielding and viscous mechanisms. The yield stress is controllable by the magnetic field and is completely and immediately reversible when the field is removed. Controllable MR dampers utilizing MR materials entails a magnetic circuit consisting of a coil and low-permeability magnetic material to contain and guides the magnetic field.

The present study attempts to develop a stochastic optimal coupling-control strategy for the seismic response mitigation of adjacent structures coupled with active control devices. The proposed control strategy is based on the combined use of the stochastic dynamical programming principle and the stochastic averaging method. The seismic response mitigation is achieved through the total energy control of modal vibration based on stochastic averaged equations, and thus the dimension of control system is reduced. The seismic excitation spectrum is taken into account by use of the stochastic optimal dynamical programming principle. Following this approach, the derived optimal feedback control force is a nonlinear generalized damping force, which means dissipating energy control. The developed control method is applicable to coupled structures with an arbitrary number of stories and with connecting controllers at any stories. Numerical examples are given to demonstrate the control efficacy of the proposed control strategy for adjacent tall buildings.

Development smart systems for damage detection and health monitoring of highway bridges using measured response data has been an important research focus. However, difficulty often exists when bridges exhibit significant nonlinear behavior due to aging degradation of structural properties, inelastic deformation and fracture damage, as well as uncertain boundary, environmental and dynamic loading conditions. This paper presents an analysis of system invariant spectrum applied to smart systems in structural health monitoring of general highway bridge systems. In particular, the spatial distribution feature of the system invariant is used to explore changes in a general nonlinear highway bridge structure due to damages.

In this paper, we present two control strategies for applications to civil engineering structures, referred to as the generalized H₂ control and L₁ control, respectively. Both control strategies are capable of addressing the performance-based design of structures, in the sense that the design requirements for the peak response quantities, such as peak interstory drifts, peak shear forces, peak floor accelerations, etc., can be satisfied. Likewise, these two controllers minimize the upper bound of the peak response of the controlled output vector. The design procedures for these two controllers are formulated in the framework of linear matrix inequalities (LMIs) so that the LMI toolbox in MATLAB can be used effectively and conveniently for the controller design. These control strategies are applied herein to the wind-excited benchmark problem to demonstrate their applicability to practical problems as well as their control performances. Simulation results illustrate that the performances of both the generalized H₂ controller and the L₁ controller are very plausible in comparison with the LQG control method.

This study was conducted to investigate the application of a magnetorheological (MR) damper in the semi-active control of bridge response. A series of cyclic loading tests was carried out on a MR damper under various loading frequencies, loading amplitudes, and current levels. The damping force of the MR damper was idealized by the model composed of friction and viscous elements in parallel. Two algorithms to change damping force according to displacement or velocity were investigated. It is found that the commanded damping force can be realized by the MR damper. However, discrepancy of damping force is observed, especially when the rate of change of the damping force is high. The shaking table test was conducted on a model bridge with the MR damper to investigate the effectiveness of the control algorithms.

In this study, the seismic response of a base-isolated three-story test structure is investigated. At the isolation level, the structure is equipped with a fluid damper having adaptive characteristics. Since the isolation system is strongly nonlinear, a nonlinear feedback control algorithm is utilized to determine the appropriate level of damping in the isolation system. This paper focuses on the development of an intelligent controller that can effectively suppress vibrations of the nonlinear structural system due to various excitations. Specifically, numerical simulations are performed using several historical earthquakes to evaluate the dynamic response of the test structure and isolation system when different damping mechanisms (passive, semi-active (variable), or active) are incorporated within the isolation system. The numerical simulations demonstrate that variable damping is effective in simultaneously controlling the response of the structure and the isolation system. Such control is particularly important for structures subjected to disparate ground motions such as frequent, weak earthquakes versus rare, strong earthquakes or far-field versus near-field earthquakes.

This paper presents a new and innovative semi-active variable stiffness tuned mass damper (SAIVS-TMD). The system has the distinct advantage of retuning in real time thus making the system robust to changes in building stiffness and damping, whereas the passive tuned mass damper (TMD) can only be tuned to a fixed frequency. The SAIVS-TMD is based on a novel semi-active variable stiffness control (SAIVS) device. SAIVS system requires nominal power for operation as compared to active tuned mass dampers. The SAIVS-TMD is retuned using a new control algorithm based on instantaneous frequency estimation using Hilbert transform and short-time Fourier transform (STFT). An analytical model of a three-story structure with SAIVS-TMD is developed. Numerical simulations are performed using the analytical model. The system is implemented in a 1:10 scale three-story scale model in real time using a digital signal processing system and controller. Shake table test results of the system with the SAIVS-TMD are presented. It is shown that the SAIVS-TMD is very effective in reducing the response and providing retuning capability when the building stiffness changes, whereas the TMD is mistuned and loses its effectiveness. Analytical modeling and comparisons between analytical and experimental results are also presented.

This study presents a semi-active vibration control of a scaled two-span bridge structure. Magneto-rheological fluid dampers are utilized as the semi-active energy absorbing devices, and a bridge vibration control system is developed. Closed-loop control system based on fuzzy logic is used to suppress the bridge deck motion under random excitation. It is demonstrated that this fuzzy logic control system can significantly reduce the relative deck displacement using about 60% less power compared to passive on state, while the absolute deck acceleration remains practically unchanged.

Recent theoretical studies indicated that semi-active control using magnetorheological (MR) fluid dampers could provide better damping capability than viscous dampers for cable vibration mitigation. However, some challenging problems still remain in implementation of this smart damping technique to real engineering structures, e.g. how does the nonlinearity of MR dampers affect the system response? what are criteria of selecting MR damper size for an actual cable in design stage? which control strategies are cost effective and efficient for semi-active implementation? This paper tries to address these issues.

The stay cables in cable-stayed bridges are prone to exhibiting oscillation of large amplitude due to their large flexibility, small mass, and small damping. Continued oscillation of the cables may seriously influence the safety and durability of cable-stayed bridges. Apart from the rain- wind-induced cable vibration, large-amplitude oscillation of cables caused by parametric excitation due to support motion was recently observed in cable-stayed bridges. This kind of cable oscillation is produced by the deck and/or tower motion induced either by moving traffic or by buffeting response of gust wind. The oscillation mechanisms and control methods of stay cables excited by the deck and/or tower motion are less studied than the rain-wind-induced vibration. In this paper, a nonlinear dynamic model for the simulation and analysis of a kind of parametrically excited vibration of stay cables caused by support motion in cable- stayed bridges has been proposed.

This paper describes a study on semi-active vibration control of stay cables by using electro/magneto-rheological dampers and adopting neural network control technique. An improved neuro-controller, which is derived without need of a reduced-order system model, is first developed for implementing the semi-active control. The neuro-controller is devised following three steps.

This paper presents a feasibility study of active seismic response control of cable-stayed bridges with reference to the Ting Kau Bridge (TKB). The TKB is a selected as a representative modern cable-stayed bridge for this vibration control study due to its unique features. Two issues explored pertaining to the development of an active structural control system for the TKB: (1) control-oriented modeling of cable-stayed bridges, and (2) control strategy development.

Bridge dampers conceived as passive devices present a significant inconvenience in their need of requiring the definition of a reference ground motion for their design. They are conceived to serve as high stiffness components below a force threshold and to undergo large hysteretic cycles when the threshold is crossed. However, lower the threshold is to contrast the extreme excitation, higher the probability that the bridge devices undergo permanent deformation, under the serviceability excitation, becomes. Shifting from serviceability to ultimate conditions is only possible by adopting semi-active devices. The problem is then to select a reliable, standalone controller to be coupled with the semi-active device. This paper discusses the characteristics of a fuzzy-chip controller. It should be implemented in an electro-magnetic damper of industrial production.

A piezoelectric friction damper was designed and fabricated to control the 1/4-scale, three-story frame structure in the Structures Laboratory at the University of Missouri-Rolla. In this paper, the damper is characterized in terms of energy dissipation, frequency and temperature dependence, and long-term durability under harmonic loading.

Induced strain actuator (ISA) can change their own shapes according to external electric/magnetic fields, and vice versa. Recently these materials have been widely used for the small/precision. The objectives in this study are to develop smart members for building and to realize the smart, comfortable and safe structures. The research items are 1) Semi-active isolation of structures using piezoelectric actuator, 2) Using ISA as sensor materials and 3) Improvement of Acoustic Environment. Semi-active base isolation system with controllable friction damper using piezoelectric actuators is proposed. Simulation study was carried out, and by semi-active isolation, it could be realized to reduce response displacement of the structure to 50% of values of the passive isolation. ISA materials can act as sensors because they cause change of electric or magnetic fields under deformation. PVDF sensors are suitable for membrane structures. We evaluate performance of PVDF sensors for membrane structures by experiment. Polymer based ISA films or distributed ISA devices can control vibration mode of plane members. Applications to music halls or dwelling partition walls are expected. Results of experimental studies of noise control are discussed.

Authors propose a method to identify the mass matrix of a large building structure by using a small active dynamic damper, or equivalently, an active tuned mass damper. We modify the acceleration feedback algorithm, which was once developed for improving the dynamic damper's performance, with a different objective. The advantage of the dynamic damper is its size: it is so small that there is a possibility that we could create an extra-small device for measuring the mass of a large structure. We review the physical meaning of the acceleration feedback, and then we use a single-degree-of-freedom model to explain how to operate the device to examine the weight of a primary structure. Then, we extend this method to a multi-degree-of- freedom model so that we can measure its effective modal mass with respect to the location where this device is placed. The identification of the mass matrix of a large structure can be completed as we shift the observing points and determine the associated effective mass. Several numerical studies are also carried out to certify the proposed method.

In order to achieve more perfect vibration-free environment in precision manufacturing facilities such as semiconductor manufacturing factories, and apply steel frame structures to semiconductor manufacturing factories of the next generation, a smart structure was tested for active microvibration control of a 2-story steel frame building model of a 5 X 3 X 4^H m outer size and a 2,500 kg total weight which was excited by ambient ground vibration. In the structure, piezoelectric actuators attached to the columns and the beams were used for the microvibration control by bending moment control of them. The controller was designed using the H-infinity control theory. The tests showed that the smart structure could effectively reduce the 3D microvibration of the building model, and its applicability to floors and even entire buildings of semiconductor manufacturing factories having steel frame structures.

Three mass-spring dampers were designed and fabricated to control the seismic responses of a 1/4-scale steel frame structure. The frequencies and damping ratios of the dampers and the structure were identified with free and forced vibration tests. The dampers with different combinations of springs and masses were installed on the structure for seismic response control. Parameters studied include the weight, frequency, and placement of the dampers. The sequential procedure developed in previous studies was applied to determine the sub-optimal locations of the dampers.

A series of FBG sensor modules for the building structure are developed. And the health monitoring system using FBG-based sensor modules were installed. Which was used for the 12th floor steel frame building of the damage tolerant built. There are 64 FBG-based sensors in the building structure. A detailed experiment was done about the FBG-based displacement sensor module, the FBG-based strain sensor module, and the FBG-based temperature modules.

A fiber Bragg grating accelerometer was developed for building and civil infrastructures. The accelerometer has a high sensitivity in low frequency range to cover the most important spectrum components of the structural response. The mechanism employed for the accelerometer ensures uniform strain distribution in the Bragg grating element so that the Bragg reflection peak will not be deteriorated. A shake table test was conducted to show good performance of a prototype accelerometer. The lifetime of the accelerometer was also probabilistically evaluated.

This paper discusses structural health monitoring data obtained using an optical fiber Bragg grating (FBG) sensor system consisting of sensors embedded in the filament-wound composite marine pile. A composite marine pile is a tube containing a cement core that is used to support bridges, piers, and other structures. This system has applications for structural health monitoring of these structures. This paper presents the results of tests that retrofit two existing composite piles with 30 Bragg grating sensors. Each pile was retrofitted with three arrays, two arrays consisting of 6 gratings and one consisting of 3 gratings for strain and temperature measurements, respectively. Grooves were cut in the piles to allow for adhesive installation of the sensor arrays, and fiberglass cloth tape was laminated over the arrays to protect the optical fiber during the pile driving process. Data were collected prior to and during the pile driving process using a commercial off-the-shelf FBG interrogation system. The purposes of these tests were to (1) determine the survivability of the sensor arrays during the pile driving process, (2) measure residual strains on the filament wound composite tube following the pile driving process, and (3) determine whether structural integrity issues are observed from the strain data.

A test was recently conducted on August 1, 2000 at the FHwA Non-Destructive Evaluation Validation Center, sponsored by The New York State DOT, to evaluate a graphite composite laminate as an effective form of retrofit for reinforced concrete bridge beam. One portion of this testing utilized Acoustic Emission Monitoring for Evaluation of the beam under test. Loading was applied to this beam using a two-point loading scheme at FHwA's facility. This load was applied in several incremental loadings until the failure of the graphite composite laminate took place. Each loading culminated by either visual crack location or large audible emissions from the beam. Between tests external cracks were located visually and highlighted and the graphite epoxy was checked for delamination. Acoustic Emission data was collected to locate cracking areas of the structure during the loading cycles. To collect this Acoustic Emission data, FHwA and NYSDOT utilized a Local Area Monitor, an Acoustic Emission instrument developed in a cooperative effort between FHwA and Physical Acoustics Corporation. Eight Acoustic Emission sensors were attached to the structure, with four on each side, in a symmetrical fashion. As testing progressed and culminated with beam failure, Acoustic Emission data was gathered and correlated against time and test load. This paper will discuss the analysis of this test data.

The effect of dowel bar looseness on the joint load transfer efficiency using Falling Weight Deflectometer is the subject of this paper. The mechanism of dynamic load transfer at transverse joints of Jointed Plain Concrete Pavement is examined using nonlinear 3D finite element analysis.

Advanced composite materials are widely recognized to be an effective material for the strengthening of structures subjected to seismic events. These materials are also being investigated as a potential rehabilitation technique to increase the live-load capacity of a bridge. While there are benefits to this technique, there are limitations as well, such as a lack of long-term performance data. Performance is taken here to include serviceability, reliability and durability. This paper will demonstrate how a structural health monitoring system can be utilized to determine measures of performance for a bridge rehabilitated using advanced composite materials. First, the theoretical framework of the health monitoring system will be developed. Next, the philosophy and design of the composite rehabilitation will be described. As part of the monitoring process, the bridge will be tested prior to beginning the rehabilitation work to verify the base line condition. After the rehabilitation work is completed, data will be collected on a periodic basis and the results evaluated to determine the performance of the bridge was improved.

For the purpose of developing a precise parameter identification procedure for bridge cables using measured multiple-mode parameters, a systematic investigation on the modal properties of cables is first carried out by using a 3D finite element formulation taking into account the cable flexural rigidity, sag-extensibility, and non-constant dynamic tension force. The dimensionless frequencies were evaluated for free vibration of cables with their parameters lying in a wide range covering most of the cables in existing cable-supported bridges. The relation surfaces between the dimensionless frequencies and structural parameters are obtained for both lower and higher modes.

This paper explores a novel approach in developing auto- adaptive, High-Performance Fiber Reinforced Concrete (HPFRC)-based composite structures. This is achieved through the selective use of hybrid, self-actuating, Shape Memory Alloy-HPFRC composites (SMA-HPFRCCs). Previous use of `passive' HPFRCs in seismic retrofit and new construction resulted in excellent seismic performance. By combining `passive' FRC fibers with continuous or discontinuous SMA fibers, self-actuating SMA-HPFRCCs that can change their stress-strain response during loading, were recently developed. The paper presents results of a numerical investigation on the use of such SMA-HPFRCCs to develop highly energy absorbing, replaceable, `fuse' zones that adjust their response to the level of overload, and thus optimize overall system response to the different levels of seismic excitations.