Editor’s Note

The January 2008 issue of the Journal of Bridge Engineering begins with a very timely paper on the effects of Hurricane Katrina on the bridges in the U.S. Gulf Coast region. In “Bridge Damage and Repair Costs from Hurricane Katrina,” Padgett, DesRoches, Nielson, Yashinsky, Kwon, Burdette, and Tavera describe the damage patterns to bridges from storm surge, wind, debris impact, scour, and water. In addition, they provide examples of the repair measures that were used to quickly restore the functionality of the bridges and transportation system.

“Repair of Bridge Girder Damaged by Impact Loads with Prestressed CFRP Sheets” by Kim, Green, and Fallis is the first of two papers on the application of carbon fiber-reinforced polymer (CFRP) in the repair of damaged concrete bridges. This paper presents an innovative strengthening method using prestressed carbon fiber reinforced polymer sheets. An adequate repair design was performed based on the U.S. American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) and Canadian Highway Bridge Design Code. Using tests as well as finite element analysis to investigate the flexural behavior of the bridge in the undamaged, damaged, and repaired states, the results of the work indicate that the repaired bridge has been fully recovered to its undamaged state.

The second CFRP paper is by Williams and Higgins and is titled “Fatigue of Diagonally Cracked RC Girders Repaired with CFRP.” This paper presents the results of field and laboratory tests of fiber-reinforced polymer (FRP) repaired reinforced concrete deck girders in order to determine the anticipated life of FRP repairs for shear strengthening of bridge girders. The results indicated relatively small in-situ FRP strains. The laboratory fatigue loading produced localized debonding along the FRP termination locations at the stem-deck interface, and the fatigue loading did not significantly alter the ultimate shear capacity of the test specimens.

Ji and Chang in “Nontarget Image-Based Technique for Small Cable Vibration Measurement” propose an image based technique for measuring small cable vibration. The technique analyzes an image sequence of a vibrating cable segment captured using a camera. Using an optical flow method, the variation of optical intensity is calculated for a selected region of interest and the obtained optical flow vector provides the direction of vibration which can then be used to estimate the displacement. The technique can be easily implemented using one camera and can be done without calibration of the camera. There is no need to attach any targets to the cable.

The fifth paper in this issue of the Journal of Bridge Engineering is titled “Condition Assessment of Shear Connectors in Slab-Girder Bridges via Vibration Measurements.” In this paper Xia, Hao, Deeks, and Zhu present a field study on condition assessment of the shear connectors of a full slab-girder bridge using vibration measurements. A model updating technique is first used to assess the condition of the whole structure from the accelerations on the slab measured in vibration testing. Then, a new damage index is developed to evaluate the condition of the shear connectors. The advantage of the method is in that it does not need any reference data (undamaged information) for the structure.

Akinci, Liu, and Bowman, in “Parapet Strength and Contribution to Live-Load Response for Superload Passages,” discuss the results of their study to evaluate the effects of parapets on the live load response of slab-on-girder steel bridges subjected to superload vehicles and the effects of these loads on the parapets. The authors found that the presence of the parapets can result in reduced girder distribution factors for critical girders, as much as 30%, depending on the stiffness of the girders and the transverse truck position, if the parapets are included in the analysis.

In some parts of the United States and the world, timber bridges are common structures. “Development of Novel Industrial Laminated Planks from Sweetgum Lumber” by Shmulsky and Shi presents their work determining the bending design values for laminated beams using this material. The results of this research will be used to determine if it can be used as a material for bolt-laminating in construction bridges and mats.

There are many older bridges that are still in service. In “Fatigue Strength of Trolley Bridge Stringers Made of ASTM A7 Steel,” Albrecht and Lenwari present the results of constant-amplitude fatigue tests performed on S15x42 ASTM A7 steel stringers from a trolley bridge built in 1900. The test results found that uniform corrosion and pitting reduced the fatigue strength of the stingers from Category A to Category D. The fatigue strength was reduced more from pitting than from the effects of corrosion.

Parameswaran, Kumar, and Sahu in “Effect of Carbonation on Concrete Bridge Service Life” discuss the results of a parametric study that was carried out to understand the deterioration of concrete bridges due to carbonation. The effect of carbonation on the initiation and propagation time of corrosion was also included in the study. As a result of the study, modifications were suggested in the clauses of the Indian concrete bridge design standard to enhance the service life of its bridges.

The tenth paper in this issue of the Journal is on vehicle induced dynamic effects on bridge structures. In “Vehicle Induced Dynamic Behavior of Short-Span Slab Bridges Considering Effect of Approach Slab Condition” by Shi, Cai, and Chen, a parametric study was conducted to analyze the effects of different truck speeds and different road conditions on the dynamic behavior of short slab bridges and their approach slabs. Critical truck speeds that resulted in peaks of dynamic response were found to follow the role that describes the resonant vibration of bridges due to train loading. The approach slab condition that includes faulting at the ends is included. The authors conclude that faulting of the approach slab caused significant large dynamic responses in short span slab bridges.

While box culverts may not be what the lay person thinks of when the word bridge is used, these structures are considered as bridges, and are designed and maintained by bridge engineers. Abolmaali and Garg in “Effect of Wheel Live Load on Shear Behavior of Precast Reinforced Concrete Box Culverts” report on part of a comprehensive study evaluating the shear capacity of precast reinforced concrete box culverts. The study found that shear was not the governing behavior mode for concrete box culverts and the live load distribution width equations along with the provisions for shear transfer devices for box culverts reported in the current standards should be revisited.

The final paper in this issue is by Lüthi, Diephuis, Icaza, Breen, and Kreger. “Effects of Duct Types and Emulsifiable Oils on Bond and Friction Losses in Posttensioned Concrete” discusses the effects of two emulsifiable oils and three duct types on bond and friction losses. The bond test results found that corrugated galvanized steel ducts provided better anchorage than corrugated high-density polyethylene (HDPE) ducts and rigid steel pipes performed poorly. The ultimate strength of posttensioned specimens with oiled tendons is similar to or better than those with unoiled tendons. The friction test results indicated that the recommended design values for the coefficient of friction for steel pipes and galvanized ducts are accurate, however, the measured coefficient for HDPE ducts was significantly less than the AASHTO recommended value.

This issue of the Journal includes a technical note by Huo and Zhang titled, “Effect of Skewness on the Distribution of Live Load Reaction at Piers of Skewed Continuous Bridges.” In this note, the results of a study of the skewness effect on live load reaction at the piers of continuous bridges is presented. A comparison of the distribution factors of live load reactions and shear revealed that the distribution factor of reaction at piers was higher than that of shear at the beam ends near the same support. The increase in reaction distribution factor was more significant than that of the shear distribution factor for interior beams when the skew angle was greater than 30°. The authors recommend that more research be performed.

Finally this issue of the Journal of Bridge Engineering concludes with a list of the reviewers that assisted the Journal and its Associate Editors in the past year with the review of all the papers and manuscripts that were submitted for peer review. The reviewers are one of the cornerstones of any journal and it is their review of the papers that determines the quality of the final product published. The Associate Editors of the ASCE Journal of Bridge Engineering along with myself would like to extend our thanks and appreciation to these reviewers for their assistance and valued contribution. Without their help this Journal would not be possible.