Editor’s Note

Three papers based on experimental work lead off this issue of the Journal of Bridge Engineering. “Experimental Evaluation of Compressive Behavior of Orthotropic Steel Plates for the New San Francisco-Oakland Bay Bridge” by Chou, Uang, and Seible, presents the findings from compression tests which were conducted on two reduced-scale orthotropic plates for the New San Francisco-Oakland Bay Bridge. The purpose of the work was to verify the design strength of the steel box girders. The experimental tests found that the first specimen failed in global buckling followed by local buckling in the deck plate and ribs, while the second specimen experienced global buckling as well as local buckling in the ribs and deck plate. The ultimate strength and failure mode of the two specimens were evaluated by the 1998 AASHTO-LRFD and the 2002 Japanese JRA specifications. This evaluation determined that sufficient flexural rigidity of the ribs was provided by both specimens, that the JRA specification slightly over-estimated the ultimate strength of the specimens, and that neither specification predicted the observed buckling sequence that occurred in Specimen No. 2. Following a finite-element analysis, it was determined that the ultimate strength and postbuckling behavior of the specimens could be reliably predicted when both the effects of residual stresses and initial geometric imperfections were considered in the model.

The second experimental paper by Xiao, Wu, Yaprak, Martin, and Mander titled “Experimental Studies on Seismic Behavior of Steel Pile-to-Pile-Cap Connections” investigates the seismic behavior of bridge pile-to-pile-cap connections. Five full-scale, H-shaped steel pile-to-pile-cap connection subassemblies were used for the study. Two were subjected to vertical cyclic load simulating axial forces in the pile due to footing overturning. Two other specimens were loaded with cyclic lateral force and constant vertical load. The fifth specimen was tested under proportionally varied vertical and horizontal forces. It was determined that although designed as a pinned connection, the pile-to-pile-cap connection was capable of supporting a significant amount of moment. Test results also showed that the anchorage details using two V-shaped bars could not develop the full design ultimate tensile capacity.

The final experimental paper also leads off a series of three papers on the subject of steel bridges. In “Examination of Level of Analysis Accuracy for Curved I-Girder Bridges through Comparisons to Field Data” by Nevling, Linzell, and Laman, an evaluation of the accuracy of different levels of analysis used to predict horizontally curved, steel, I-girder bridge response was performed on a three-span structure. Strain information was used to develop the girder vertical and lateral moments, and these experimental moments were compared to numerical moments obtained from three commonly employed levels of analysis. The results showed that the Level 2 (grillage models) and Level 3 (three-dimensional finite-element models) analyses predicted the girder vertical bending moment distributions more accurately than the Level 1 analysis and that the Level 3 methods offered no appreciable increase in accuracy over the Level 2 methods. Finally the study found that both the Level 1 (manual calculation methods) and Level 3 analyses provided bottom flange lateral bending moment distributions that do not correlate well with field test results for the bridge used in the study.

The second steel bridge paper is by Berglund and Schultz and is titled “Girder Differential Deflection and Distortion-Induced Fatigue in Skewed Steel Bridges.” Out-of-plane web distortion results in fatigue cracking in steel bridges. In a previous study, the frequency and magnitude of distortional stresses on a typical skewed steel bridge with staggered bent-plate diaphragms were assessed. The results found that a diaphragm deformation mechanism that causes distortional fatigue in the girder web gap can be used to accurately and easily determine the fatigue stress if the bridge properties and differential vertical deflection between the girders are known. This study uses linear finite-element models to represent composite steel bridges and to identify the bridge parameters that influence the relative deflection of adjacent girders. The parameters that were found to be the most significant were girder spacing, angle of skew, span length, and deck thickness. The results were incorporated into a simple procedure that is intended to be used in management schemes for this type of bridge.

The third and final steel bridge paper is “Influence of Secondary Elements and Deck Cracking on the Lateral Load Distribution of Girder Bridges” by Chung, Liu, and Sotelino. This paper presents the results of research to investigate the effect of secondary elements and deck cracking on the lateral load distribution to bridge girders. Using nonlinear finite-element modeling, the investigation established that the presence of secondary elements may produce load distribution factors up to 40% lower than those based on the AASHTO LRFD specification. Longitudinal cracking was found to increase the load distribution by as much as 17%, while transverse cracking had little effect on the transverse distribution of moment.

The fifth paper in this issue of the Journal is on the same topic as the previously mentioned paper. Conner and Huo in “Influence of Parapets and Aspect Ratio on Live-Load Distribution” also note the differences that occur between the girder distribution factors based on actual field conditions and those predicted by the AASHTO code. The authors indicate that secondary elements such as parapets are the source of the difference and present the results of an investigation of the effects of parapets and bridge aspect ratio on the live load moment distribution for bridge girders. These authors found that the presence of parapets reduced the distribution factors by as much as 36% for exterior girders and 13% for interior girders. The aspect ratio has little effect on the distribution factors until the ratio exceeds 1:8.

The next paper is similar to the previous two, except it focuses on the distribution factors used for shear instead of moment. In Barr and Amin’s “Shear Live-Load Distribution Factors For I-Girder Bridges,” a full-scale single-lane test bridge was used to evaluate a typical slab on girder bridge’s response to shear. A shear load test was used to determine the level of detail of a finite-element model that would be required to accurately replicate the behavior of bridges subjected to shear loads. The finite-element shear distribution factors were compared with those calculated using the AASHTO LRFD specification. It was determined that the AASHTO LRFD procedure accurately calculated the shear distribution factors for changes in girder spacing and span length, but the LRFD shear distribution factor for the exterior girder was not conservative for certain overhang distances and overly conservative for the interior girders for higher skew angles.

In the first of two papers on composites, Reay and Pantelides in “Long-Term Durability of State Street Bridge on Interstate 80” used destructive and nondestructive techniques to evaluate the long-term durability of CFRP composite and externally CFRP-reinforced concrete of the State Street Bridge. The investigation revealed that while environmental conditions have an effect on the durability of the CFRP composite and CFRP reinforced concrete substrate, no evidence of steel reinforcement corrosion was observed. The CFRP composite retrofit was still effective after $3\text{years}$ .

The second composite paper, “Designing and Testing of Concrete Bridge Decks Reinforced With Glass FRP Bars” by Benmokrane, El-Salakawy, El-Ragaby, and Lackey, presents the results of an evaluation of a concrete bridge deck reinforced with glass FRP bars in lieu of traditional steel reinforcing bars in order to eliminate the problems of long-term corrosion of the reinforcing bars. The bridge was tested for service performance using standard truck loads. The field test results under actual service conditions revealed that GFRP rebar provides satisfactory and promising performance.

“History and Esthetics of the Bronx-Whitestone Bridge” by Barelli, White, and Billington reviews the changes over time of the Bronx-Whitestone Bridge. With strong similarities to the Tacoma Narrows Bridge, it also shares noticeable oscillations and consequently has been retrofitted over the years. Each retrofit was consistent with the current state of the art of suspension bridge technology, and as a result, the bridge has recorded and preserved these advances. The paper places these retrofits in context and evaluates them on technical qualities and aesthetics.

The final two papers in this issue are companion papers. The first is titled “Effect of Vehicle Velocity on the Dynamic Amplification of a Vehicle Crossing a Simply Supported Bridge” by Brady, OBrien, and Žnidarič, and the second “The Effect of Vehicle Velocity on the Dynamic Amplification of Two Vehicles Crossing a Simply Supported Bridge” is by Brady and OBrien. The papers investigate the effect of vehicle velocity on a bridge’s dynamic amplification.

Finally, there is a discussion and closure of “Assessment of Multispan Masonry Arch Bridges I: Simplified Approach” by Brencich and Francesco. The discussion by Gilbert, Melborne, and Smith, presents several significant points regarding the original paper and its findings. In the closure, Brencich and Francesco respond to the discussion authors’ points and amend the loading conditions of the first benchmark test. In addition, the authors acknowledge that the discussion shows that there are some issues that still need to be resolved in the area of masonry bridge assessment.