Full Bridge Model Research Articles

Health monitoring of bonded composite repair in bridge rehabilitation

Structural rehabilitation with carbon fiber reinforced composite materials has proven to bean excellent way to enhance/repair steel reinforced concrete structures and prolongtheir service lives. However, disbonds between composite repair patches and hoststructures continue to be a great concern of this technology. In this paper, a built-inpiezoelectric sensor network based structural health monitoring system is introduced formonitoring the disbonds between composite repair patches and the host structures.This diagnostic system combines the sensor network, diagnostic hardware anddata analysis software allowing for real-time monitoring of the integrity of thebonded repair. The effectiveness of detecting disbonds using the system has beendemonstrated on a full scale bridge model in a laboratory setting. The bridge model wasloaded incrementally to failure, and disbond monitoring was carried out during theloading intervals. Test results showed that the system could detect the disbondsbefore they have a noticeable effect on the global stiffness of the bridge model.

Bai Chay Bridge, Vietnam

The Bai Chay Bridge, spanning a strait within sight of Ha Long Bay, Vietnam's premier World Heritage site, has the world's longest center span length of 435 m, as a single plane cable-stayed prestressed concrete bridge, with a bridge length of 903 m. The foundations for the main piers were constructed by the pneumatic caisson method. Form travelers were used for the cast-in-situ box girder erection by the balanced cantilever method. The main pylons, which extend 91,5 m in height above the deck level and which incorporate 28 stay cables and anchorages each side, were constructed using a climbing formwork system. The design wind speed for the bridge is 50 m/s over a ten-minute averaging period at 50 m above sea level. Wind tunnel tests, using a three-dimensional (3D) full bridge model, were conducted to examine the structural stability against strong winds. The box girder is lightweight with internal steel pipe bracing and prestressing tendons. Technologically advanced vibration control devices, such as reduced-section high-density polyethylene (HDPE) ducts and internal radial dampers for the stay cables together with tuned liquid dampers for the pylons, were incorporated into the construction.

Determination of flutter derivatives by a taut strip model

The taut strip model is a kind of aeroelastic model, which can be regarded as an in-between model between the sectional model and the full aeroelastic bridge model. Determination of flutter derivatives by taut strip models has rarely been studied. In this paper, a theory of determination of flutter derivatives using the taut strip model is established based on the eigensystem realization algorithm. Considering the restriction of measuring points, modal coordinate expansion technique is introduced to get the information of unknown measuring points. Generalized inverse matrix theory is employed to obtain the stiffness matrix and damping matrix of taut strip models. Then, the flutter derivatives can be extracted by the subtraction of stiffness and damping matrixes. A method of identifying of flutter derivatives in turbulence flow is also proposed through the random decrement technique. Experimental study of determination of flutter derivatives by taut strip model is carried out based on the theory discussed in the paper. A taut strip model of a thin plate is designed, and it is used in smooth flow to determine flutter derivatives as well as in turbulence flow in TJ-2 wind tunnel of Tongji University. In the end, comparisons with theoretical flutter derivatives of a thin-plate section are undertaken to validate the reliability of the theory.

Frequency- and time-domain methods for the numerical modeling of full-bridge aeroelasticity

A numerical framework for full-bridge aeroelasticity is presented, based on unsteady cross-sectional load models and on the finite-element modeling of the structure. A frequency-domain approach based on aeroelastic derivatives and nonlinear complex eigenvalue analysis is compared to its equivalent time-domain counterpart based on indicial functions and direct integration of the equations of motion. A version of the time-domain load model consistent with the quasi-steady limit behavior is developed and a procedure for the numerical identification of the indicial functions from measured aeroelastic derivatives is presented. The aeroelastic stability analysis is chosen as benchmark. A numerical example is offered where the equivalency of the two approaches is proved for a full-bridge model. Advantages and disadvantages of the two techniques are discussed.

Fatigue Analysis and Design of Steel Orthotropic Deck for Bronx-Whitestone Bridge, New York City

A description is given of the parametric study done to evaluate the structural behavior of the replacement steel orthotropic deck planned for the Bronx—Whitestone Bridge in New York City. A principal objective was to analyze the deck details for stress ranges that indicated sensitivity to fatigue cracking. On the basis of the analysis findings, important modifications were made to the preliminary deck design. These changes were primarily to reduce the maximum stresses in the diaphragms and ribs around the diaphragm cutouts—locations that traditionally have been prone to cracking, as observed on orthotropic decks on other bridges. After the completion of the deck design, a full-scale prototype deck measuring 48 by 37 ft was fabricated and subjected to a series of laboratorycontrolled fatigue tests. Proper boundary conditions and loading procedures were created to produce stress ranges similar to those in the full bridge model. Laboratory test results correlated well with the computed stress ranges and demonstrated that the deck had outstanding fatigue resistance and could readily provide the 75-year design service life specified for the orthotropic deck.

Study of Passive Deck-Flaps Flutter Control System on Full Bridge Model. II: Results

A passive aerodynamic control method for suppression of the wind-induced instabilities of a very long span bridge is presented in this paper. The control system consists of additional control flaps attached to the edges of the bridge deck. Control flap rotations are governed by prestressed springs and additional cables spanned between the control flaps and an auxiliary transverse beam supported by the main cables of the bridge. The rotational movement of the flaps is used to modify the aerodynamic forces acting on the deck and provides aerodynamic forces on the flaps used to stabilize the bridge. A time-domain formulation of self-excited forces for the whole three-dimensional suspension bridge model is obtained through a rational function approximation of the generalized Theodorsen function and implemented in the FEM formulation. This paper lays the theoretical groundwork for the one that follows.

Study of Passive Deck-Flaps Flutter Control System on Full Bridge Model. I: Theory

Study of Passive Deck-Flaps Flutter Control System on Full Bridge Model. I: Theory

Flutter and buffeting responses of the Shantou Bay Bridge

Shantou Bay Bridge is the first long-span suspension bridge in China. Because of its location near the Shantou Seaport and its exposure to high typhoon winds, wind-resistant studies are necessary to be made. In this paper, critical flutter wind speeds and buffeting responses of this bridge at its operation and main construction stages are investigated. The Buffeting Response Spectrum method is first briefly presented. Then the sectional model test is carried out to directly obtain the critical flutter wind speed and to identify the flutter derivatives, which are adopted for the later analysis of the buffeting responses using the Buffeting Response Spectrum method. Finally the aeroelastic full bridge model is tested to further investigate the dynamic effects of the bridge. The results from the tests and the computations indicate that the flutter and buffeting behaviors of the Shantou Bay Bridge are satisfied.

Theory and Full-Bridge Modeling of Wind Response of Cable-Supported Bridges

As is well known, long, suspended bridge spans require, in the design stage, careful study of their resistance and response to site winds. This has driven, on the one hand, detailed quantitative observation of bridge models in the wind tunnel and, on the other, a steady development and refinement of parallel theory. Currently, both aspects have arrived at good stages of sophistication, although with continued room for improvement. Successes in the extension of bridge spans to record-breaking lengths are mainly due to progress in wind-resistant design, a primary component in the design of long-span bridges. Recently, multimode flutter and buffeting analysis procedures have been developed. These procedures, which were based centrally on frequency-domain methods, take into account the fully coupled aeroelastic and aerodynamic response of long-span bridges to wind excitation. This paper briefly reviews the current state of the art in long-span bridge wind analysis, emphasizing the analytical infrastructure. The focus then turns to exhibit an example of application of the theory to the stability (flutter) and serviceability (buffeting) analyses of a new long-span bridge in North America. This example not only demonstrates the application of the theory to a real structure but also serves to highlight some insights into the versatility that is gained by this analytically based approach. The results demonstrate that the analytical method with appropriate inputs and a complementary full-bridge model agree even for relatively unusual incoming turbulence in the flow caused by the presence of structures upstream of the bridge. This paper seeks to exhibit recent developments in the field to the interested structural/bridge engineer, outline alternative procedures available for assessment of wind effects on cable-supported bridges, and provide an overview of the basic steps in the process of a typical aerodynamic analysis and design.

Bridge Flutter Derivatives at Vortex Lock-In

Many structures with extended spans undergo the flow-induced oscillation commonly called vortex shedding. In the case of long-span bridges, Ehsan and Scanlan, employing basic data from deck section wind tunnel model tests, offered a nonlinear theoretical framework for predicting maximum vortex-induced amplitude under the lock-in condition. The present paper replaces the Ehsan-Scanlan model with a linearized form that brings it into conformity with the familiar flutter derivative expressions now commonly used in bridge wind-stability analyses. The essential new addition is an active sinusoidal lift term. Converting some of the Ehsan-Scanlan experimental section data to the new form, the suggested replacement model successfully reidentifies the range of original Tacoma Narrows vortex-induced response amplitudes that were experimentally obtained by Farquharson on a full-bridge model. Either vertical or torsional motions at vortex lock-in can be assayed by the method discussed.

Wind Tunnel Test of the Akashi Kaikyo Bridge using Full Bridge Model

The Akashi Kaikyo Bridge is a suspension bridge under construction whose center span is 1, 990m. The bridge will be the longest suspension bridge in the world. Since the bridge is much longer than the present longest bridge, the aerodynamic characteristics of the bridge was evaluated through wind tunnel test using full bridge model as well as section model. This report outlines a study concerning the wind tunnel study using full bridge model in smooth flow and turbulent flow. The characteristics of flutter and gust responses observed in the wind tunnel test were shown and discussed.

Interpretation of the sectional model experiments for the wind induced response of full elastic bridge structures

The wind resistant design against the wind induced vibration has based on the sectional model wind test, while some examples of the full bridge model wind tests have been carried out in order to verify safety of the target structure and its sectional model test result. In this process main topics in the testing technique are always the relationships or interpretation among these two methods. In this paper this discussion will be summarized and the re cent coupled flutter analysis will be introduced from a viewpoint of the method interpretation.

Aerodynamics of wind effects on the Akashi Kaikyo Bridge

The Akashi Kaikyo Bridge, which will cross the Akashi Kaikyo Straits with a shore-to-shore distance of about 4 km, is a very long-span truss-stiffened suspension bridge for six road lanes with a main span of 1,990 m and two side spans of 960 m. Its extremely flexible features, caused by the span length never experienced, increase importance of careful detailed considerations on static as well as dynamic effects in the aerodynamics of the superstructure. The paper describes some design considerations of wind effects and the outlines of full aeroelastic bridge model wind tunnel tests, together with primary test results analyzed so far, which have been conducted in order to carry out final verification of the wind resistance safety of this bridge at an especially constructed boundary layer wind tunnel of 41 m width.

Aerodynamic study on a proposed cable-stayed bridge in Shanghai, China

This paper deals with the aerodynamic study on a proposed composite deck cable-stayed bridge alternative over the Huangpu River in Shanghai, China. The non-steady aerodynamic model is identified directly by taking the coupled vibration response (CVR method) records under initial impulse as basic information obtained from section model wind tunnel test. The 3-D flutter analysis in full-process (from construction stage to completion stage) is carried out by using the state-space method. The analysis indicates that the alternative proposed has enough wind-resistant aerodynamic stability at completion stage, but it is necessary to add some ties or guys to raise the wind-resistant capability at the construction stage. The result of 3-D flutter analysis is also verified by the full-bridge model wind tunnel test, a first attempt of such test in China.

On predicting the performance under wind of full bridges from section model wind tunnel results

This paper describes a theory which has been developed to examine the relationship between the wind-induced response of a two-dimensional section model and that of a three-dimensional full-bridge model. Particular attention is paid to the effect of the mass parameter. Tests on simple taut-strip and sectional models were carried out to verify the theory that response of a three-dimensional model can be predicted from the results of tests on a two-dimensional one.

Parametric study on the behaviour of a full aeroelastic

A full aeroelastic cable-stayed bridge model, at a geometric scale of 1: 75, was studied in the 9m × 9m Wind Tunnel of the National Research Council of Canada. The basic structure simulates a composite cable stayed bridge over the Mississippi River at Quincy, Illinois, U.S.A. The prototype was chosen as a medium size cablestayed bridge typical of current practice. Nine deck section configurations were examined in three different flow regimes that represented scale atmospheric boundary layers . The project was carried out collaborately by the Yokohama National University, the University of Ottawa and the National Research Council of Canada.

Calculation of the wind buffeting of the lions' gate bridge and comparison with model studies

Calculations predicting the buffeting response of a suspension bridge to wind are made and compared to experimental results obtained with a full-bridge model.