Deck Deflection Research Articles

Field Monitoring and Repair of a Glass Fiber-Reinforced Polymer Bridge Deck

This paper reports on the monitoring and repair of a pilot field deployment of a glass fiber-reinforced polymer (GFRP) deck on a small steel girder bridge in the Washington State. Deck deflections were monitored periodically over a 10-month period and were found to increase significantly over that time. The GFRP deck is an adhesively bonded assembly of GFRP tubes and top and bottom plates. After 9 months of service, wearing surface cracking was observed, and upon closer inspection, the top GFRP plate was found to be delaminated from the tubes over a fairly large area. Deck deflections in the area of delamination were found to be considerably larger than those observed during previous monitoring in undamaged locations. A retrofit solution was employed where the top plate was reconnected to the tubes using screws coated with a two-part epoxy that mixed when they were driven. At the time of writing the retrofit was successful in reattaching the delaminated top plate.

In Situ Materials and Structural Assessment of Stress-Laminated Deck Bridge Treated with Chromate Copper Arsenate

A bridge consisting of three 6.7-m spans with a stress-laminated deck was constructed in 1991 in the Spirit Creek State Forest near Augusta, Georgia. The bridge was constructed by the Georgia Forestry Commission, with guidance from the U.S. Department of Agriculture, Forest Service, Forest Products Laboratory (FPL). Water-borne chromated copper arsenate lumber was used for the deck, instead of the oil-borne preservatives recommended by AASHTO. The bridge was initially monitored by FPL and remained in service from 1994 to 2001 with no maintenance, at which time the bridge was inspected and load tested and the posttensioning bars were restressed. In 2005 the bridge was again inspected and load tested, and the bars were retensioned. The results of the inspection and load tests are presented. The overall condition of the bridge is reported, along with details on the moisture condition, overall deck deflection, and timber strains under load. Details on the loss of posttensioning forces in the bars, and an investigation of the causes of this loss, are presented.

Live Load Deflection Performance of Glued Laminated Timber Girder Bridges

To demonstrate and possibly to promote the increased use of timber bridges in U.S. transportation systems, various agencies, including the United States Department of Agriculture Forest Products Laboratory and FHWA, have supported research to develop improved glued laminated timber bridges. This project is part of this research and identifies acceptable live load deflection characteristics of timber bridges. The relationship between live load deflection and the condition of the asphalt wearing surface is of particular interest. To accomplish this, eight glued laminated timber girder bridges were selected for testing. The performance of the bridges was investigated under live load tests and through bridge inspections. The structures were load tested with fully loaded tandem-axle dump trucks, and global and differential deflection data were collected. Field tests revealed that a significant amount of the asphalt wearing-surface deterioration is the result of differential deck panel deflection.

Live Load Deflection Performance of Glued Laminated Timber Girder Bridges

To demonstrate and possibly to promote the increased use of timber bridges in U.S. transportation systems, various agencies, including the United States Department of Agriculture Forest Products Laboratory and FHWA, have supported research to develop improved glued laminated timber bridges. This project is part of this research and identifies acceptable live load deflection characteristics of timber bridges. The relationship between live load deflection and the condition of the asphalt wearing surface is of particular interest. To accomplish this, eight glued laminated timber girder bridges were selected for testing. The performance of the bridges was investigated under live load tests and through bridge inspections. The structures were load tested with fully loaded tandem-axle dump trucks, and global and differential deflection data were collected. Field tests revealed that a significant amount of the asphalt wearing-surface deterioration is the result of differential deck panel deflection.

Performance Evaluation of Fiber-Reinforced Polymer Composite Deck Bridges

FHWA is committed to the strategic goals of rehabilitating the nation's bridges that are structurally deficient. Fiber-reinforced polymer (FRP) composites are among the advanced materials that appear to have great potential in bridge deck repair and replacements. In West Virginia alone, more than 30 bridges have been built or rehabilitated with FRP composite materials. Katy Truss and Market Street are two such bridges constructed with FRP bridge decks, and they are being monitored. The West Virginia University Constructed Facilities Center along with the West Virginia Department of Transportation initiated field monitoring of these bridges by performing static and dynamic load tests. The response measurements from controlled truck load tests on the two bridges included (a) deck and stringer strains and (b) deflections and deck accelerations. The following static response parameters were computed from measured data: (a) degree of composite action between deck and stringer, (b) transverse load distribution ...

Analytical and experimental study on the behavior of elastically supported reinforced concrete decks

Current design specifications prescribe that the upper and lower reinforcement mat is required in the same amount to resist negative and positive moment in bridge decks. This design concept is primarily based on the unrealistic assumption that the girder plays a role of rigid support against deck deflection. In reality, however, girders are flexible and the deflection of girders affect the behavior of deck slabs. In the present study, an analytical method was developed to take the effect of the girder flexibility on the deck behavior into account. The method was formulated based on the slope-deflection equations of plates and harmonic analysis. Unlike the conventional finite element analysis, the input and output schemes are simple and convenient. The validity of the presented study was verified by a series of comparative studies with finite element analyses and experimental tests. It was shown from the analyses that the negative transverse moments of decks were significantly reduced in many cases when the girder flexibility were appropriately taken into consideration whereas the positive moments tend to increase. This poses a strong need to improve the conventional design concept of decks on rigid girders to those on flexible girders.

Laboratory and Field Testing of Composite Bridge Superstructure

Bridge rehabilitation utilizing a hybrid fiber-reinforced polymeric composite has recently been completed in Blacksburg, Va. This project involved replacing the superstructure in the Tom's Creek Bridge, a rural short-span traffic bridge with a timber deck and corroded steel girders, with a glue-laminated timber deck on composite girders. To verify the bridge design and to address construction issues prior to the rehabilitation, a full-scale mock-up of the bridge was built and tested in the laboratory. This setup utilized the actual composite beams, glue-laminated timber deck panels, and the skewed geometry implemented in the rehabilitation. Following rehabilitation, the bridge was field tested under controlled conditions (vehicle load and position). Both tests examined service load deflections, girder strains, load distribution, degree of composite action, interpanel deck deflections, and impact factor. The field test results indicate a service load deflection of L/400 under moving loads and a high factor of safety in the composite members against material failure. The data from the field test serve as a baseline reference for future field durability assessments as part of a long-term performance and durability study.

Field Performance of Three Stress-Laminated Southern Pine Timber Bridges

Three southern pine stress-laminated deck bridges were constructed in late 1991 in Leon County, Fla. The bridges consisted of approximately 7.32 m (24 ft) simple spans and were 10.97 m (36 ft) wide. They were constructed with #2 and better lumber treated with chromated copper arsenate and redried to moisture contents of <12%. A monitoring program for the bridges was undertaken to investigate the use of southern pine lumber treated with waterborne preservatives in stress-laminated bridges. The program began with static load testing in January 1992. The performance monitoring involved gathering data on the moisture content of the decks, force levels in stressing bars, deck deflection, and the behavior of the bridges under static load conditions. In addition, comprehensive visual inspections were conducted to assess the overall condition of the bridges. Based on almost 3 years of field evaluations, the bridges performed well with no major structural or serviceability deficiencies.

Fatigue Response of Concrete Decks Reinforced with FRP Rebars

The fatigue response of concrete decks reinforced with fiber-reinforced plastic (FRP) bars is critical to the long-term endurance of this type of innovative structure. To evaluate the degradation of FRP reinforced bridge decks, fatigue tests were conducted on four concrete deck steel stringers. An initial stress range of 2.27 MPa (0.33 ksi) (tension) in the main FRP reinforcement, 3.1 MPa (0.45 ksi) (compressive) in the concrete deck top, and 24.8 MPa (3.6 ksi) (tension) at the bottom flange of a steel stringer was applied for all specimens. The stringer stiffness, composite versus noncomposite casting, and transverse posttensioning using high-strength Dywidag steel rods were varied during this research. The fatigue test results showed no loss of bond between FRP rebars and concrete in any of the test specimens. The major crack patterns were in the direction parallel to the stringers, i.e., flexural cracks in the concrete deck spanning the steel stringers. Effective central deck deflections could be set as a measure of global deck degradation during fatigue, and this rate of degradation in decks reinforced with FRP rebars was found comparable to decks reinforced with steel rebars.

INITIAL THOUGHTS ON THE DESIGN OF A CABLE-STAYED BRIDGE.

Keywords GIFFORDS, GIFFORD GRAHAM BRIDGES, CABLE STAYED, DESIGN, RIVERS, PROCESS, STRUCTURES, CABLES, STEEL, STIFFNESS, TOWERS, LOADS, LIVE, CONCRETE, CREEP, DECKS, DEFLECTION, EFFECT, SECONDARY, TROUGHS, AESTHETICS RIVER DEE, WALES UK... Show All

Punching Shear Failure in Concrete Decks As Snap-Through Instability

This paper presents part of an investigation on the failure modes in reinforced concrete bridge decks subjected to monotonic static concentrated wheel-loads. The punching shear deck failure appears to be interrelated with a snap-through instability of an “arching” action mechanism activated in the deck. The predicted critical deflection of about 25% of the deck thickness at instability of a two-dimensional laterally restrained three-hinge compressive strut mechanism correlates well with the measured static ultimate deck deflection values of bridge decks that failed primarily in punching. There is also good agreement between the predicted critical applied static concentrated load at instability of the proposed three-hinge truss and the experimental static deck ultimate strength values.

Cross‐Bracing Effects in Curved Stringer Bridges

A finite element bridge model of cross section reflecting interstate quality was analyzed for varying curvatures, lengths, and bracing intervals. Results from this parametric study were analyzed by linear and nonlinear regression techniques to predict the ratio of: (1) Maximum bending stress; (2) maximum warping stress; and (3) maximum deck deflection for a curved bridge to corresponding quantities of a straight bridge of equal length. In addition, an empirical equation was developed to provide a guideline for setting the maximum bracing spacing.