Editor’s Note

The September 2008 issue of the Journal of Bridge Engineering begins with a paper on modeling concrete bridges. In “Modeling Early-Age Bridge Restraint Moments: Creep, Shrinkage, and Temperature Effects,” Newhouse, Roberts-Wollmann, Cousins, and Davis present the results from an experimental study that was performed to monitor the early-age restraint moments that develop in two-span continuous systems constructed from full-depth PCBT girders. The observed restraint moments were compared to predicted restraint moments and were found to be significantly lower than the predicted values. The study found that expansion of the deck during curing, which is generally not considered in the predictions, significantly influenced the early-age restraint moments. The authors concluded the paper by proposing a simplified model to predict the restraint moments by considering thermal effects.

Li, Wekezer, and Kwasniewski, in “Dynamic Response of a Highway Bridge Subjected to Moving Vehicles,” present the results of full-scale load tests performed on a Florida highway bridge. The bridge was dynamically excited by two fully loaded trucks. The strain, acceleration, and displacement at selected points were recorded as part of the investigation, and these values were compared with simplified vehicle and bridge finite-element models. The authors found that the numerical analysis matched well with the experimental data, and this was used to successfully explain critical dynamic phenomena observed during testing.

The next two papers are on the subject of strengthening existing bridges. In the first, “Design of Prestressing Tendons for Strengthening Steel Truss Bridges,” Albrecht and Lenwari introduce a design space for the design of prestressing tendons concentric with members for strengthening steel truss bridges. The design space contains all feasible solutions for the cross-sectional area of the tendon and the level of prestressing that satisfies criteria for tendon yielding, member buckling, and member fracture and yielding.

The second strengthening paper, by Petrou, Parler, Harries, and Rizos, “Strengthening of Reinforced Concrete Bridge Decks Using Carbon Fiber-Reinforced Polymer Composite Materials,” presents the results of an investigation of the monotonic and fatigue behavior of one-way and two-way reinforced concrete slabs strengthened with carbon fiber-reinforced polymer (CFRP) materials. Five one-way slab specimens were removed from a decommissioned bridge in South Carolina. Three of the slabs were strengthened with CFRP, and two were left as control specimens. In addition, six half-scale, two-way slab specimens were constructed to represent a full-scale prototype of a highway bridge deck designed using the empirical requirements of the AASHTO LRFD Bridge Design Manual. Of these six slabs, two were left as control specimens, two were retrofitted using CFRP strips bonded to their soffits in a grid pattern, and two were retrofitted with a preformed CFRP grid material bonded to their soffits. The results of testing these specimens monotonically until failure and under cyclic (fatigue) loading until failure are presented.

The fifth paper in this issue of the Journal of Bridge Engineering is on a bridge constructed by using high-performance concrete. Barr, Kukay, and Halling, in “Comparison of Prestress Losses for a Prestress Concrete Bridge Made with High-Performance Concrete,” instrumented five prestressed concrete girders made with high-performance concrete using vibrating-wire strain gauges and monitored their behavior for $3\text{years}$ from the time of casting. The concrete strain at the centroid of the prestressing strands was used to evaluate the changes in the prestressing force. The total measured prestress loss was as large as 28% of the total jacking stress. The observed values of prestress loss were compared with values calculated by using the recommended AASHTO LRFD and NCHRP 18-07 procedures. It was found that the AASHTO LRFD method overpredicted the averagejprestress losses, while the NCHRP method underpredicted the average losses for the same girder. The authors found that the NCHRP method was more inclusive and adaptable to regional construction.

The next paper, by Baxter and Balan, “Design of the Fulton Road Bridge Precast Segmental Concrete Arches,” describes the design of the segmental concrete arches for the Fulton Road Bridge. The posttensioning concept, superstructure-arch interaction, effective $k$ -factor for moment magnification, and construction sequence analysis methods used for the design are discussed.

The next two papers are based on the results of full-scale tests. “Full-Scale Tests of Bridge Steel Pedestals,” by Hite, DesRoches, and Leon, describes the results of cyclic tests conducted on steel pedestals to evaluate their seismic response. These steel pedestals have been used by the Georgia Department of Transportation to elevate highway bridges to reduce the likelihood of impact damage as a result of limited vertical clearance. While cost efficient, the pedestals were not detailed to provide end fixity, and consequently considerable flexibility to the superstructure supports is provided. The tests found that the steel pedestals undergo kinematic rigid body motion, dissipate energy, and demonstrate reasonable deformation and strength capacities when subjected to quasistatic reversed cyclic loads.

The second full-scale test paper, by Huang, “Full-Scale Test and Analysis of a Curved Steel-Box Girder Bridge,” presents the results of field tests conducted on the Veterans’ Memorial Bridge, a curved steel-box girder bridge. The tests and analytic work found that the current AASHTO guide specifications regarding the first transverse stiffener spacing at the simple end support may be too conservative for bridge load capacity ratings. It was also determined that the current guide specifications may greatly overestimate the dynamic loadings of curved box girder bridges with long spans. Finally, a plane grid finite-element model of about 20 elements per span in the longitudinal direction can be used to analyze curved multigirder bridges with external bracing located only over the supports.

The ninth paper in this issue is also about horizontally curved steel bridges. “Evaluation of Live-Load Lateral Flange Bending Distribution for a Horizontally Curved I-Girder Bridge” by DePolo and Linzell focuses on live-load lateral bending moment distribution in a horizontally curved steel I-girder bridge. The paper presents results from experimental and numerical studies.

The tenth and eleventh papers in this issue of the Journal of Bridge Engineering are on integral abutment bridges. “Parametric Study of Concrete Integral Abutment Bridges” by Huang, Shield, and French presents the work from a parametric study conducted to extend the results of an experimental program on a concrete integral abutment bridge in Rochester, Minnesota: the numerical results indicated that bridge length and soil types surrounding the piles have a significant impact on the behavior of integral abutment bridges.

Dicleli and Erhan in “Effect of Soil and Substructure Properties on Live-Load Distribution in Integral Abutment Bridges” investigated the effect of soil-structure interaction and substructure properties at the abutments on the distribution of live-load effects in integral abutment bridge components. The analyses results revealed that soil-structure interaction had a significant effect on the live-load distribution factors for the abutment, but had negligible effects on those for the girders and piles. It was further found that the abutment height had a considerable effect on the live-load distribution factors calculated for the abutment and pile moments, while the wingwalls had a negligible effect on all of the components making up the integral abutment bridge.

The final two papers are on timber and their use in bridges. Nowak and Eamon in “Reliability Analysis of Plank Decks” present the results of a study to summarize the load and resistance criteria for highway bridge plank decks and to estimate the reliability of plank decks designed by the AASHTO code. Both transverse and longitudinal planks for a variety of typical stringer spacings and plank sizes were considered. The paper presents reliability indices for both the AASHTO standard and the AASHTO LRFD code. The results indicate that there are considerable differences in plank reliability indices, and the causes of the inconsistencies in safety are identified in the paper.

The final paper, “Composite Effect of Bolt-Laminated Sweetgum and Mixed Hardwood Billets” by Shmulsky, Saucier, and Howard, investigates the performance of industrial hardwood laminated billets and mats. These are used for heavy equipment ground support and as temporary bridges for logging, road building, utility line construction, etc. The results of their study found that bolt laminating contributes significantly to mechanical performance as compared with that of individual billets.

In the discussion and closure for “Evolution of the Continuous Truss Bridge” by Griggs, Wortman and Wortman, provide additional information on the evolution of continuous truss design. In his closure, Griggs comments on and thanks the discussers for the additional information provided in their discussion.