Editor’s Note

The July 2008 issue of the Journal of Bridge Engineering begins with “Repair of Full-Scale Timber Bridge Chord Members by Shear Spiking” by Burgers, Gutkowski, Balogh, and Radford, which presents the results of adding vertically oriented shear spikes to increase the effective stiffness of the stringers of a full-scale timber chord test specimen. The results from the testing showed that with the insertion of five sets of shear spikes, the average flexural effective stiffness recovered in the four stringers of the chord was 91.6%.

In “Stochastic Response of Bridges Seismically Isolated by Friction Pendulum System” by Jangid, earthquake excitation is modeled by a nonstationary random process, and the stochastic response from the isolated bridge is obtained by using the time-dependent equivalent linearization technique due to the nonlinear force-deformation behavior of the friction pendulum system. To study the influence of the nonstationary characteristics of earthquake isolation, the nonstationary response of the isolated bridge is compared with the corresponding stationary response. The conclusion was that there is good comparison between the proposed closed-form expressions and actual optimum parameters and the response of the isolated bridge system.

The third paper in this issue is Abolmaali and Garg’s “Shear Behavior and Mode of Failure for ASTM C1433 Precast Box Culverts,” which presents the results of a study that evaluated the shear behavior and capacity of precast concrete box culverts subjected to HS20 truck wheel loads. Full-scale experimental tests were conducted of the most critical culvert behavior and the condition of zero depth of fill placed on a rigid bedding material. These tests determined that flexure governed the behavior up to and beyond the AASHTO 2005 factored load. Then three-dimensional (3D) nonlinear finite-element models were developed and used to verify the experimental results. The study showed that the AASHTO 2005 provision with regard to the shear transfer device across the joint is unsupported.

The next paper is Pelphrey et al.’s “State-Specific LRFR Live-Load Factors Using Weigh-in-Motion Data,” which shows how weigh-in-motion data for the state of Oregon were used to develop live-load factors for LRFR for use on state-owned bridges. The factors were calibrated with the same statistical methods used in the original development of LRFR, and thus the procedure maintains the nationally accepted structural reliability index for evaluation, even though the resulting live-load factors are state specific and smaller than the national standard. Policy implementation for actual use of the factors and future provisions of maintenance of the factors are described.

“Statistical Modeling of Coupled Shear-Moment Resistance for RC Bridge Girders” by Turan, Higgins, and Rosowsky presents a statistical model for combined shear-moment resistance in conventionally reinforced concrete bridge girders for use in load-carrying capacity evaluations. New statistical data on stirrup spacing variability were developed from field measurements on in-service deck-girder bridges, and these were combined with available data in the literature to model resistance uncertainty. AASHTO-LRFD and ACI-318 were used to calculate capacity of the selected sections. Strength-reduction factors in AASHTO-LRFD and ACI-318 were compared using the obtained statistical parameters.

The sixth paper in this issue of the Journal of Bridge Engineering is “Static Load Tests of Corrugated Steel Plate Arch with Relieving Slab” by Beben and Manko, who present the results of tests carried out on a bridge under three static load schemes after 4 years of service. Their work reveals that the average values of the measured displacements and strains in selected points and elements of the steel shell are significantly lower than the values calculated for the same load.

Okeil and Cai’s timely paper, “Survey of Short- and Medium-Span Bridge Damage Induced by Hurricane Katrina,” reports on the author’s survey of damaged bridges in the aftermath of Hurricane Katrina. Low-lying coastal bridges suffered severe damage as a result of hydrodynamic forces from the storm surge. The loss of these bridges significantly affected rescue and recovery efforts after the event. The survey found that most of the surveyed bridges collapsed due to unseating of the superstructure from the substructure.

“Development of a Short-Span Fiber-Reinforced Composite Bridge for Emergency Response and Military Applications” by Robinson and Kosmatka describes the design and analysis of a carbon/epoxy composite sandwich bridging system for use by the U.S. Army for short-span crossings. The paper also describes the fabrication of the bridge treadways, full-scale proof testing of the treadways, and field testing using military trucks for which the spans were designed.

Goel and Chopra in “Role of Shear Keys in Seismic Behavior of Bridges Crossing Fault-Rupture Zones” examines the role of shear keys at bridge abutments in seismic behavior of typical bridges. The results of their work found that while ignoring shear keys provides conservative estimates of seismic demands subjected to spatially-uniform ground motion, this practice may lead to underestimation of some seismic demands in bridges in fault-rupture zones that are subjected to spatially-varying ground motion. Their conclusion was that estimating the upper bounds of seismic demands in bridge crossing fault-rupture zones requires analysis of two shear-key conditions, no shear keys and elastic shear keys.

The final paper in this issue is Albrecht and Lenwari’s “Fatigue Strength of Repaired Prestressed Composite Beams,” which presents the results of an experimental and analytical study of 10 composite girders that were prestressed with seven-wire stands and then fatigue tested to failure. The authors investigated three methods of extending the fatigue life of cracks, and the efficacy of the three methods are compared.

One technical note in this issue, Topkaya, Kalayci, and Williamson’s “Solver and Shell Element Performances for CurvedBridge Analysis,” describes the investigation of different solver and shell element performances for curved-bridge finite-element analysis. Based on the comparative studies they performed, modeling guidelines for practicing engineers were developed and presented.

S. Chen presents his discussion on “Effective Slab Width Definition for Negative Moment Regions of Composite Bridges,” and the authors Aref, Chiewanichakorn, Chen, and Ahn offer their response and closure.