Editor’s Note

The March 2008 issue of the ASCE Journal of Bridge Engineering begins with a paper on construction simulations of concrete bridge decks. In “Special-Purpose Simulation Model for Balanced Cantilever Bridges,” Marzouk, Said, and El-Said present a special simulation model that can aid agencies in planning the construction of bridge decks by using cast-in-place and precast balanced cantilever techniques. Data from an actual project can be entered into the model to carry out what-if analyses.

Next are two papers on inspecting and evaluating of bridges. In “Performance Evaluation through Field Testing of a Century-Old Railroad Truss Bridge,” DelGrego, Culmo, and DeWolf provide research that was done to evaluate structural behavior and the influence of aging on a century-old steel railroad truss bridge consisting of built-up members, either multiple eyebars or laced channel sections joined with true truss pins, and an indeterminate interior panel. The study investigated the structural behavior and live-load distribution throughout the bridge, with a major component of the research being extension field monitoring. The results found that the actual live-load distribution was significantly different than expected from typical truss analysis.

The second inspection and evaluation paper is “Investigation of Damaged $12\text{-}\text{Year}$ Old Prestressed Concrete Box Beams.” In this paper Naito, Sause, and Thompson present the results of an investigation of damage to a pair of three-span continuous spread prestressed box beam bridges after $12\text{years}$ of service. Routine inspection had found cracks in the box beams near the piers and abutments. A further inspection was conducted to assess the condition of the beams in the bridges as well as their as-built properties and remaining strength. The investigation indicated that although the beams were built in accordance with the design drawings and specifications, load tests showed that the effective prestress was lower than standard design estimates. The investigation concluded that cracks in the beams were the result of a combination of conditions created by the design, detailing, and production of the beams.

The fourth paper in this issue is by Wang and Helwig and is titled “Stability Bracing Requirements for Steel Bridge Girders with Skewed Supports.” The LRFD AASHTO Specifications no longer provide specific spacing requirements for bracing and instead require that bracing be designed by a rational analysis. The paper outlines the stability bracing requirements for bridges with normal and skewed supports. The solutions developed by the method were compared with finite-element results and were found to have good agreement.

The next three papers are on seismic issues, with the first two being companion papers. “Effect of Asynchronous Earthquake Motion on Complex Bridges. Part I: Methodology and Input Motion”—by Burdette, Elnashai, Lupoi, and Sextos—studied quantifying the effect of geometric incoherence and wave arrival delay on complex straight and curved bridges by using state-of-the-art methodologies and tools. This paper presents the development of the input motion sets and the modeling and analysis approach employed. “Effect of Asynchronous Earthquake Motion on Complex Bridges. Part II: Results and Implications on Assessment,” by Burdette and Elnashai, presents detailed results and implications on seismic assessment. The study results are used to suggest an appropriate domain for considering asynchronous excitation as well as an efficient methodology for analysis.

“Seismic Testing of a Two-Span Reinforced Concrete Bridge” is the last of the seismic papers. In this paper Johnson, Ranf, Saiidi, Sanders, and Eberhard present the results of testing a quarter-scale, two-span reinforced concrete bridge on a shake-table system. The objective of the investigation was to study the effects of soil-foundation-structure interaction. The paper discusses the development and testing of the bridge model, as well as selected experimental results. The study found that motion incoherency affected the symmetric bridge response but had little effect on the symmetric bridge response, which is consistent with conclusions from numerical analyses conducted by other researchers.

The last three papers in this issue deal with the use of composite materials in bridges. “Fatigue Behavior of Composite-Reinforced Glulam Bridge Girders,” by Davids, Nagy, and Richie, presents the findings of a study on the response of full- and partial-length fiberglass composite reinforced glulam beams under fatigue cycling followed by quasi-static bending to failure. A hydrothermal cycling regime was used to replicate the effective stress history of a $50\text{-}\text{year}$ service life by using a $55\text{-}\text{day}$ period in a moisture-controlled kiln. In addition, some test pieces had initial delaminations introduced between the reinforcing and the wood, similar to delaminations observed in the field. The results of the postfatigue tests to failure compared with the expected strength. With the exception of the unconfined, partial-length reinforced beams, all specimens had a residual strength that compared favorably with the expected strength. The unconfined, partial-length reinforced beams did not perform well under fatigue loading, and the authors did not believe that they are a viable alternative for use as a reinforced glulam bridge girder.

Schnerch and Rizkalla in “Flexural Strengthening of Steel Bridges with High Modulus CFRP Strips” present the results of an experimental study that investigated the feasibility of different strengthening approaches for steel bridge girders. All the techniques that were examined were effective in using the full capacity of the CFRP material and increased the elastic stiffness and ultimate strength of the beams. The results of the experimental program were compared with an analytical model used to investigate the importance of several key parameters. The authors conclude with a proposed method for the design of a flexurally strengthened steel girder that considers the bilinear behavior of a typical strengthened beam to the elastic-plastic behavior of the same beam before strengthening.

The last paper in this issue of the Journal of Bridge Engineering is by Kim, Green, and Wight and is titled “Live Load Distributions on an Impact-Damaged Prestressed Concrete Girder Bridge Repaired Using Prestressed CFRP Sheets.” That paper describes the flexural behavior, including live load distribution, of a 4-span prestressed concrete girder bridge supported by $14\mathrm{m}$ C-shaped girders. The bridge was damaged by frequent impact by heavy trucks and was repaired by using prestressed carbon-fiber-reinforced polymer sheets. The flexural behavior of the bridge was investigated by using a calibrated finite-element analysis. It was found that the AASHTO LRFD and Canadian Highway Bridge Design Code predicted well the live load on the exterior girder but underestimated the loads in the interior girders. Consequently, the authors recommend that a refined analysis should be used for this type of bridge.