Editor’s Note

The May 2008 issue of the Journal of Bridge Engineering begins with three papers on existing bridges. In “Chloride Ion Transport in Bridge Deck Concrete under Different Curing Durations,” Ghanem, Phelan, Senadheera, and Pruski present the results from a broader research study exploring the possibility of opening bridge decks earlier to highway traffic by decreasing the number of wet-mat curing days. Seven concrete mixtures typically used in Texas were evaluated for chloride permeability. The results indicated that the curing duration may be decreased for some of the concrete mixtures.

Tapan and Aboutaha, in their paper, “Strength Evaluation of Deteriorated RC Bridge Columns,” present a bridge pier column strength evaluation method that can be adapted for current bridge condition evaluation methods. Their proposed method uses damaged material properties and accounts for the amount of corrosion and exposed bar length for each reinforcement, concrete loss, bond failure, and type of stresses in corroding reinforcement. The proposed method provides a good estimate of the condition and load-carrying capacity of bridge columns that cannot be obtained by visual surveys. As a consequence, the method will aid in reducing costs, avoid overconservative condition ratings, and result in a more uniform level of safety for concrete bridge substructures.

The last of the papers on existing bridges deals with fatigue in railway bridges. Imam, Righiniotis, and Chryssanthopoulos, in “Probabilistic Fatigue Evaluation of Riveted Railway Bridges,” present a probabilistic fatigue assessment methodology for riveted railway bridges applied to a typical short-span, riveted U.K. railway bridge under historical and present-day train loading. Randomized dynamic amplification and traffic volumes are used for the loadings, while for resistance, the S–N curves and cumulative damage models are treated probabilistically. Model uncertainty is based on the ratio of actual to calculated stresses, and Monte Carlo simulation is used to develop the annual response spectra for a fatigue-critical connection. S–N curves proposed in U.S. and U.K. codes are used in combination with Miner’s rule to estimate the remaining fatigue life of the connection. Parametric studies determined that fatigue-life estimates exhibit the highest sensitivity to detail classification, to S–N predictions in the region of high endurances, and to model uncertainty. The article highlights the importance of field monitoring of older bridges as they approach the end of their service life.

The fourth paper in this issue of the Journal of Bridge Engineering, “Computerized Database for Maintenance and Management of Highway Bridges in Vietnam” by Hai, describes the development of a computerized database for highway bridges in Vietnam. First the existing bridges were reviewed for current physical condition and maintenance management practices to identify current problems. Advanced techniques were then introduced into the system to manage and maintain the highway bridges in the most suitable manner. The author concludes with recommendations for determining if any further modifications are necessary.

Frangopol, Strauss, and Kim, in “Bridge Reliability Assessment Based on Monitoring,” discuss the need for the efficient use of structural monitoring data in reliability assessment and prediction models. Their paper has two main objectives: first, to present an approach for the efficient inclusion of monitoring data in the structural reliability assessment process, and second, to demonstrate the use of monitored data for the development of prediction models. Their approach is illustrated using an existing bridge in Pennsylvania.

“Structural Testing of a Vehicular Carbon Fiber Bridge: Quasi-Static and Short-Term Behavior” by Gutiérrez, Primi, Mieres, and Calvo presents their work using carbon-fiber-reinforced polymers as the primary load-carrying material in new bridge designs. The paper includes results from laboratory quasistatic tests conducted on a full-scale section of a $46\text{-}\mathrm{m}$ long vehicular bridge. Their work found satisfactory performance of the structure and includes stress distribution and failure results for the structure.

The seventh paper, by Kunnath, Erduran, Chai, and Yashinsky, “Effect of Near-Fault Vertical Ground Motions on Seismic Response of Highway Overcrossings,” presents the results of a comprehensive nonlinear response history analysis of typical highway overcrossings subjected to the effects of vertical and horizontal components of near-fault ground motions. Results from numerical simulations indicate that the vertical components of ground motions cause significant amplification in the axial force demand in columns and moment demands in girders at both the midspan and at the face of the bent cap. Their work concludes that seismic demand analysis of ordinary highway bridges in general and overcrossings in particular should include provisions for adverse vertical effects of near-fault ground motions.

The final paper is a historical piece by W. N. Marianos, “George Shattuck Morison and the Development of Bridge Engineering,” which reviews the contributions to the practice of bridge engineering by this famous engineer.

This issue of the Journal of Bridge Engineering contains one technical note, “Combined Damping Effect of Two Dampers on a Stay Cable,” by Hoang and Fujino, which presents the analytic study of the combined effect of two dampers, either on the same end or opposite ends of a stay cable. They found that when two dampers are installed at opposite ends of a cable, the total damping effect is asymptotically the sum of the contributions from single dampers, while if two dampers are at the same end, no advantage is gained from increasing the maximum modal damping in the cable over the use of a single damper.