Editor’s Note

This issue of the Journal begins with a paper on the calibration procedure and background data for the development of the load and resistance factor design (LRFD) code provisions for timber bridges. “LRFD Calibration For Wood Bridges,” by Nowak and Eamon, details the work done to develop recommended load and resistance factors for use when designing timber bridges.

Bennett, Wood, Drumm, and Rainwater, in “Vertical Loads on Concrete Box Culverts Under High Embankments,” report the results of an investigation into the loads and resulting forces in an instrumented concrete box culvert. The work found that the measured roof pressures averaged 1.5 times greater than the pressure from the soil overburden. A simplified reliability analysis by the authors suggests that culverts designed using the soil-structure interaction factor recommended by the AASHTO Specifications provides a sufficient level of safety.

In “Correction of Errors in Simplified Transverse Bending Analysis of Concrete Box-Girder Bridges,” Kurian and Menon studied analyzing the transverse bending moments of concrete box girders using both simple frame analysis (SFA) and three-dimensional finite-element analysis for different load conditions and wheel contact areas. With these results the errors from the SFA analysis were studied. A set of correction factors are proposed by the authors and two illustrative examples are provided to demonstrate their use.

“Design and Experimental Study of a Harp-Shaped Single-Span Cable-Stayed Bridge,” by Shao, Zhao, Li, Peng, Liu, and Yan presents the issues of the design, analysis, and test results of a harp-shaped single-span cable-stayed bridge. The authors present the design approach that was used for the main components of the structure.

Fennema, Laman, and Linzell, in “Predicted and Measured Response of an Integral Abutment Bridge,” give the results of a project that examined several uncertainties of integral abutment design and analysis. The authors used field modeling of an integral abutment bridge and three levels of numerical models that were used to predict the behavior of other integral abutment bridges of similar construction. The project yielded several conclusions. The results of the work confirmed that the inclusion of multilinear soil springs created from $p\text{-}y$ curves is a valid approach for modeling soil-pile interaction and that the primary accommodation of superstructure expansion and contraction is through rotation of the abutment about its base rather than longitudinal translation. It was also determined that girder axial forces are influenced by creep and shrinkage effects in the bridge superstructure, and pile strains are well below the strains corresponding to the pile plastic moment.

Next are two papers on the topic of curved box girder bridges. The first, “Distribution Factors for Curved Continuous Composite Box-Girder Bridges,” by Samaan, Sennah, and Kennedy, present the results of an extensive parametric study of 240 two-equal-span continuous curved box-girder bridges of various geometries. The authors investigated the following parameters: span-to-radius of curvature ratio, span length, number of lanes, number of boxes, web slope, number of bracings, and truck-loading type. Based on the results, empirical formulas for load distribution factors for maximum longitudinal flexural stresses and maximum deflection due to dead load as well as AASHTO live loading were developed. Finally, an illustrative design example is presented to demonstrate the use of the formulas.

Recent incidents of problems in curved steel box-girder erection have demonstrated problems during construction ranging from buckling of individual bracing members to complete failure of a trapezoidal box-girder. In the second curved box-girder paper, “Evaluation of Top Flange Bracing Systems For Curved Box Girders,” Topkaya, Widianto, and Williamson present the results of analytic studies which evaluated the performance of different girder-bracing configurations with different deck-placing sequences, and based on the results design recommendations are provided.

The remainder of this issue of the ASCE Journal of Bridge Engineering consists of six papers related to the use of composites for bridge structures. The first three papers are on the subject of bridge decks. In “Critical Evaluation of Strain Measurements in GFRP Bridge Decks,” Coogler, Harries, Wan, Rizos, and Petrou present the results of an experimental study of the principal strains and deflections of a glass-fiber-reinforced-polymer (GFRP) composite bridge deck. In the study, experimental results are compared and shown to correlate well with those from an analytic model. The results of the work suggest that the performance of this type of structure should be assessed under fatigue loading conditions. The authors provide recommendations for accurately assessing the longitudinal strain in GFRP bridge decks.

The second composite bridge deck paper, by Gostautas, Ramirez, Peterman, and Meggers, titled “Acoustic Emission Monitoring and Analysis of GFRP Bridge Decks,” present the performance results, based on acoustic emission, of six full-scale GFRP bridge deck panels with deck thicknesses varying from 152 mm (6 in.) to 800 mm (30 in.). The objective of the study was to develop an acoustic emission monitoring strategy for use during field inspections that would provide a determination of the structural performance of the deck.

The last composite bridge deck paper, “Dynamic Response of Three Fiber-Reinforced-Polymer Composite Bridges,” by Aluri, Jinka, and GangaRao, describes dynamic tests performed on three FRP bridge decks. The dynamic response parameters evaluated for these decks include dynamic load allowance factors, natural frequencies, damping ratios, and deck accelerations cause by moving test trucks. The results of the tests are presented and compared.

The fourth paper on composites is by Quattlebaum, Harries, and Petrou and is titled “Comparison of Three Flexural Retrofit Systems under Monotonic and Fatigue Loads.” With the majority of experimental work in flexural retrofitting of concrete bridge girders based on beam specimens having an adhesive-applied, soffit-mounted fiber-reinforced-polymer composite system where the performance can be controlled by the quality of the bond between the composite and the concrete, this paper presents the results of an investigation of two additional soffit-mounted retrofit schemes. These two additional schemes are near-surface mounted and powder-actuated fastener-applied. The authors made a comparative study of the static and fatigue performance of retrofitted concrete using these two methods and compared the results with specimens retrofitted using the conventional adhesive-application method. The results of the study found that while all three methods realized a significant increase in strength under monotonic loading conditions, the conventional adhesive-application method of retrofitting outperformed the two other methods under cyclical loading conditions.

The last of the papers on composites and the last two papers for this issue of the Journal of Bridge Engineering are companion papers by Haroun and Elsanadedy: “Behavior of Cyclically Loaded Squat Reinforced Concrete Bridge Columns Upgraded with Advanced Composite-Material Jackets” and “Fiber-Reinforced Plastic Jackets for Ductility Enhancement of Reinforced Concrete Columns with Poor Lap-Splice Detailing.” The first paper summarizes the experimental studies of squat model-scale bridge columns that are repaired and retrofitted with jackets consisting of composite materials. Fourteen circular and rectangular repaired columns were compared against three as-built columns. In addition, another 10 column samples were tested after being repaired with a different composite jacket system. The repair process included both crack injection as well as the addition of a carbon/epoxy composite jacket. The experimental results showed that the common failure mode for retrofitted columns was due to flexure with an improvement in the column ductility, and repaired columns demonstrated an improvement in ductility over the as-built control column.

Finally, the second of the companion papers presents the results of a test program of scale reinforced-concrete bridge columns that are constructed with insufficient reinforcing bar lap splice lengths. Thirteen half-scale circular and square columns were tested and compared with three as-built control columns as well as 10 samples that were retrofitted with a different composite jacket system. The jacketed circular columns were found to have significant improvements in their performance under cyclical loadings. The square jacket columns showed a very limited improvement in the clamping of the lap-splice region and for enhancing the ductility of the column.

This issue of the Journal of Bridge Engineering concludes with a discussion and closure on “Warping Stresses in Curved Box Girder Bridges: Case Study” by Okeil et al. In the discussion, Mr. Dongzhou Huang provides clarification on the issue of warping stresses and their effect on shear and normal stresses. In their closure, the authors respond to Mr. Huang’s comments and observations, providing additional clarification on the scope and intent of their study.