Editor’s Note

The September 2007 issue of the ASCE Journal of Bridge Engineering begins with a paper on hybrid plate girders. In “Shear Capacity of Hybrid Plate Girders,” Azizinamini, Hash, Yakel and Farimani present the results of an experimental investigation to address the limitation on the consideration of tension field action in hybrid girders. Eight girders were tested and were found to be capable of supporting loads greater than those predicted considering tension field action. In part because of this work, modifications appeared in the 2004 version of the AASHTO LRFD Bridge Design Specifications.

The next two papers are companion papers by Wang, Swanson, Helmicki, and Hunt. In “Development of Static-Response- Based Objective Functions for Finite-Element Modeling of Bridges” and “Development of Dynamic-Response-Based Objective Functions for Finite-Element Modeling of Bridges,” the authors discuss the use of static and dynamic response-based objective functions. These are used to improve the convergence of the finite-element models and show that automatic calibration of models is practical.

In “Behavior of RCC T-Beam Bridges with Cross Diaphragms in Nonlinear Range” by Kayal, the behavior of reinforced cement concrete T-beam bridges with cross diaphragms is studied for a realistic range of values of three parameters: span, type of loading, and type of bridge deck layout. Grillage idealization was used for the study, and material nonlinearity was considered through elastoplastic idealization of moment curvature and torque-twist relationships of the cross section. Geometric nonlinearity was neglected. The study found that behavior of the T-beam bridges could be broadly placed in two categories, depending on the type and location of the formation of the first plastic hinge. The first was the formation of the first plastic hinge, a torsional hinge, in the mid-outer cross girder. The second was the formation of the first plastic hinge, a flexural hinge, in the exterior longitudinal girder under maximum loading.

Shah, Sennah, Kianoush, Tu, and Lam—in “Experimental Study of Prefabricated Concrete Bridge Girder-to-Girder Intermittent Bolted Connections System”—report on a new bridge deck slab flange-to-flange connection system for precast deck bulb $T$ -girders. Rather than casting the deck onto the girders, the study investigated the development of an intermittent bolted connection through the flanges of the girders to make it continuous for live load distribution. The objective of the study was to develop the connection and to obtain experimental data on its ultimate capacity. The study found that the location of the wheel load at the deck slab joint affected the ultimate load-carrying capacity of the connections, with failure of the joint coming from either excessive deformation and yield of the connecting steel plates or debonding of the studs embedded in the concrete.

The sixth paper in this issue of the Journal of Bridge Engineering is by Khaloo and Kafimosavi and is titled “Enhancement of Flexural Design of Horizontally Curved Prestressed Bridges.” The flexural behavior of horizontally curved prestressed (posttensioned) box girders was studied by using 3D and refined finite-element modeling analysis. The study kept the bridge length, section geometry, and material properties the same in all the models, with the only variable being the angle of curvature. The results indicated that the stress distribution in curved bridges is significantly different from that in straight bridges, with the level of stresses considerably higher in some locations of the section. The authors propose to vary the distribution of prestressing tendons across the section to optimize the bridge’s capacity.

The next three papers deal with seismic issues. In “Seismic Behavior and Retrofit of Outrigger Knee Joints,” Shattarat and McLean present the results of experimental tests conducted on six 1/3-scale models to identify the vulnerabilities of existing outrigger bents under in-plane and out-of-plane seismic loading and then to develop retrofit measures. The test specimens failed at low ductility levels as a result of shear distress, low torsional strength of the outrigger beam, and reinforcement bond failures within the joint. Circular steel jackets were used for the retrofit solution for these types of bents and proved to perform satisfactorily.

The next seismic paper is “Seismic Retrofit of Bridge Steel Truss Piers Using a Controlled Rocking Approach.” Pollino and Bruneau investigated a seismic retrofitting technique that allows the bridge piers for steel trusses to uplift and rock on their foundations. To do this, displacement-based passive energy dissipation devices are used at the uplifting location to control the rocking response while providing additional energy dissipation. The authors present a capacity-based design procedure for sizing the energy dissipation devices and provide a design example to illustrate the key steps.

The ninth and final seismic paper is by Nielson and DesRoches. In “Seismic Performance Assessment of Simply Supported and Continuous Multispan Concrete Girder Highway Bridges,” seismic evaluation of typical concrete girder bridges is conducted for both multispan simply supported and continuous girder bridges common to the central and southeastern United States. The results indicated significant vulnerabilities in the reinforced concrete columns, the abutments, and in the unseating of the girders, with the longitudinal loading of the bridges representing a greater demand on the structure than the transverse loading. For a simply supported span, both the transverse and longitudinal loads were significant demands on the structure. The results suggest that both longitudinal and transverse loading are significant and should be considered when performing seismic hazard analyses of these types of bridges.

“Tests of RC Deck Girders with 1950s Vintage Details”—by Higgins, Potisuk, Farrow, Robelo, McAuliffe, and Nicholas—describes the work performed in a research program that investigated the behavior and capacity of conventionally reinforced concrete bridge girders with vintage details. Laboratory tests were conducted on large-size girders typically used in the 1950s, along with various reinforcing steel configurations and loading conditions. The results of the tests were used to provide information for comparison of analysis methods and repair strategies. In addition, the tests showed that anchorage of flexural steel was significant to developing higher ultimate capacity, that initial crack damage does not necessarily contribute to the final failure mode, and that crack width alone may not indicate the level of damage to the beam.

The eleventh paper in this issue of the Journal of Bridge Engineering is by Benmokrane, El-Salakawy, El-Gamal, and Goulet. In “Construction and Testing of an Innovative Concrete Bridge Deck Totally Reinforced with Glass FRP Bars: Val-Alain Bridge on Highway 20 East,” the authors describe the first concrete bridge deck constructed in Canada using high-performance concrete and totally reinforced with GFRP reinforcing bars. The bridge is instrumented and has been tested with calibrated loads. The paper presents the design concepts used for the bridge, the construction details, and the results of the first series of live load tests.

The first of two papers dealing with cracking in reinforced concrete is by Muttoni and Ruiz. “Concrete Cracking in Tension Members and Application to Deck Slabs of Bridges” presents an investigation into the influence of loading history on cracks and presents a physical model to describe it. An analytical model is developed, and its results are compared with various tests with favorable agreement. The authors conclude with the development of a simple design formula, along with proposed recommendations on its application to practical cases.

“Crack Condition Evaluation Approach for the Deteriorated Girder of an RC Bridge” by Chen, Huang, and Wang is the last of the two papers dealing with cracking in reinforced concrete, as well as the final paper for this issue of the Journal of Bridge Engineering. This paper proposes a crack-condition evaluation method that identifies the damaged state of deteriorated reinforced concrete girders in situ. This nondestructive testing approach is based on stress wave propagation theory and can identify the profile of flexural crack tips inside reinforced concrete girders. A damage index is determined by comparing the measured crack tip and the theoretical neutral axis of a girder. The index is used to analyze the current loading capacity of deteriorated reinforced concrete girders on the basis of AASHTO-LRFR.

Finally, a technical note by Brencich and Sabia is titled “Tanaro Bridge: Dynamic Tests on a Couple of Spans.” The demolition of the Tanaro Bridge presented an opportunity for dynamic tests to be performed on the bridge during two stages of demolition: with fill removed and then with fill and internal spandrels removed. The results of this work can be useful for safety assessment procedures.