Journal of Bridge Engineering

The addition of vertically oriented shear spikes (fiberglass reinforced polymer rods) was shown to increase the effective stiffness of the stringers of a full-scale timber bridge chord specimen. Results found from the flexural load testing of a full-scale timber bridge chord laboratory specimen are presented. Reinforcement was provided with $19\mathrm{mm}$ diameter shear spikes bonded to the wood by an epoxy resin. The bridge chord specimen was intentionally damaged to simulate degradation. Shear spikes were then installed from the top of the member into predrilled holes to provide horizontal shear resistance and to improve the flexural effective stiffness. 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%.

Stochastic response of bridges seismically isolated by the friction pendulum system (FPS) is investigated. The earthquake excitation is modeled by a nonstationary random process (i.e., uniformly modulated broadband excitation). The stochastic response of the isolated bridge is obtained using the time dependent equivalent linearization technique due to nonlinear force-deformation behavior of the FPS. The nonstationary response of the isolated bridge is compared with the corresponding stationary response in order to study the influence of nonstationary characteristics of earthquake excitation. An optimum value of the friction coefficient of FPS for which the root mean square absolute acceleration of the bridge deck attains a minimum value was observed. The influence of system parameters such as isolation period of the FPS, frequency content, and intensity of an earthquake on the optimum friction coefficient of FPS is investigated. It was observed that the above parameters have significant effects on the optimum friction coefficient of FPS. A closed form expression for the optimum friction coefficient of FPS and corresponding response of the isolated bridge system are proposed. These expressions were derived based on the model of the bridge with rigid deck and pier conditions subjected to stationary white-noise excitation. It was concluded that there is a good comparison between the proposed closed form expressions and actual optimum parameters and the response of the isolated bridge system. The maximum difference observed was about 10–15% percent and these expressions may be used for initial optimal design of the FPS for bridges.

This study evaluates the shear behavior and capacity of the precast concrete box culverts subjected to HS 20 truck wheel load. The most critical culvert behavior was considered by studying culverts subjected to zero depth of the fill and placed on a rigid bedding material. Full-scale experimental tests, with wheel load placed at the distance $d$ from the tip of the haunch to the edge of the load plate, were conducted on 24 typical precast concrete box culverts designated as per ASTM C1433-05. The test results further indicated that flexure governed the behavior up to and beyond AASHTO 2005 factored load. Three-dimensional nonlinear finite-element models (FEMs) of the test specimens were developed and verified with the experimental results. The three-dimensional volumetric shear force distributions on the top slab of the 42 ASTM C1433-05 boxes were obtained by using the FEM from which the distribution width for each box was calculated. This was used to obtain the critical factored shear force for all the boxes which were then compared with the American Concrete Institute shear capacity equations. It was shown that the shear capacity exceeded the factored critical shear force for all the ASTM C1433-05 boxes. This study shows that the AASHTO 2005 provision with regard to the shear transfer device across the joint is unsupported.

The LRFR Manual, within commentary Article C6.4.4.2.3, contains provisions for development of site-specific live load factors. In Oregon, truck weigh-in-motion (WIM) data were used to develop live load factors for use on state-owned bridges. The factors were calibrated using the same statistical methods that were used in the original development of LRFR. This procedure maintains the nationally accepted structural reliability index for evaluation, even though the resulting state-specific live load factors were smaller than the national standard. This paper describes the jurisdictional and enforcement characteristics in the state, the modifications used to described the alongside truck population based on the unique truck permitting conditions in the state, the WIM data filtering, sorting, and quality control, as well as the calibration process, and the computed live load factors. Large WIM data sets from four sites were used in the calibration and included different truck volumes, seasonal and directional variations, and WIM data collection windows. Finally policy implementation for actual use of the factors and future provisions for maintenance of the factors are described.

Many reinforced concrete bridges are posted or restricted to traffic, and repair or replacement decisions for these bridges involves both economical and safety considerations. To avoid the high costs of unnecessary replacement or repair, safety evaluation should be done with the most accurate methods available. Due to variability in material properties, geometrical properties, and methods of analysis, load carrying capacity evaluation may lead to uncertain outcomes. This paper presents a statistical model for combined shear-moment resistance of conventionally reinforced concrete bridge girders with common vintage design details and properties. 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. The model offers bias factor and coefficient of variation for combined moment and shear carrying capacity per modified compression field theory. AASHTO-LRFD and ACI-318 were utilized to calculate capacity of the selected sections and strength reduction factors in AASHTO-LRFD and ACI-318 were compared using the obtained statistical parameters.

This paper deals with a new arch road bridge made from structural corrugated plates, over the Plawna Stream on a local road between Bystrzyca Klodzka and Ladek Zdroj in Stary Waliszow, Poland. The bridge replaced the old stone arch bridge destroyed during the flood of 1997. The steel bridge is founded on two continuous footings made of reinforced concrete. Its effective span is $10.00\mathrm{m}$ and clear height is $4.02\mathrm{m}$ . The results of tests carried out on the bridge under three static load schemes after $4\text{years}$ of service are presented. The average values of the measured displacements and strains in selected points and elements of the steel shell structure were found to be considerably lower than the ones calculated for the same load. Since designs of this type are now commonly used for small and medium-size bridges, the conclusions drawn from the presented tests can be generalized to the whole class of such bridge structures.

This paper reports on a survey effort of damaged bridges conducted by the writers in the aftermath of Hurricane Katrina of August 2005. As with Hurricane Ivan in 2004, low-lying coastal bridges suffered severe damage due to hydrodynamic forces caused by storm surge. Consequently, transportation networks in the affected areas were disrupted. Since coastal bridges are considered lifelines for the communities they serve, their loss resulted in hindering rescue and recovery efforts. The purpose of this paper is to present related data as observed by the writers. Data collection and documentation of perishable data after natural disasters and before recovery and reconstruction efforts is of great importance. In the case of coastal bridges, they can help in improving future designs and rehabilitating existing ones. The majority of the surveyed bridges collapsed due to unseating. Hydrodynamic forces due to wave impact and water current on the superstructure proved to exceed the capacity of common connections between the superstructure and the substructure for short- and medium-span bridges.

A continued desire for increased mobility in the aftermath of natural disasters, or on the battlefield, has lead to the need for improved light-weight bridging solutions. Currently within the United States military there is a need for a light weight bridging system for crossing short-span gaps up to $4\mathrm{m}$ $\left(13.1\mathrm{ft}\right)$ in length. The bridge must be capable of supporting up to Military Load Class 30 (MLC 30) vehicles including palletized load system (PLS) truck vehicles under extreme temperatures and loading conditions. This paper describes the design and analysis of a carbon/epoxy composite sandwich bridging system to satisfy the United States Army’s short-span gap crossing needs. The paper also includes a description of the fabrication of the bridge treadways, full scale proof testing of the treadways, and field testing using a fully loaded PLS truck. The study shows the bridging system to satisfy the design requirements and to have sufficient strength to support MLC 30 and PLS truck vehicles.

This paper examines the role of shear keys at bridge abutments in the seismic behavior of “ordinary” bridges. The seismic responses of bridges subjected to spatially uniform and spatially varying ground motions for three shear-key conditions—nonlinear shear keys that break off and cease to provide transverse restraint if deformed beyond a certain limit; elastic shear keys that do not break off and continue to provide transverse restraint throughout the ground shaking; and no shear keys—are examined. Results show that seismic demands for a bridge with nonlinear shear keys can generally be bounded by the demands of a bridge with elastic shear keys and a bridge with no shear keys for both types of ground motions. While ignoring shear keys provides conservative estimates of seismic demands in bridges subjected to spatially uniform ground motion, such a practice may lead to underestimation of some seismic demands in bridges in fault-rupture zones that are subjected to spatially varying ground motion. Therefore, estimating the upper bounds of seismic demands in bridges crossing fault-rupture zones requires analysis for two shear-key conditions: no shear keys and elastic shear keys.

Composite steel-concrete bridges constitute a major portion of the national bridge inventory. Many of these structures are approaching or have passed their service lives and are in need of repair and rehabilitation. External prestressing by means of high-strength bars or cables attached to the steel beams has been used as an effective technique for upgrading the load carrying capacity of composite steel-concrete girders. While several researchers have investigated the static behavior of prestressed composite beams, few have reported on the fatigue strength of this structural system. The writers present the results of the experimental and analytical study of ten composite girders that were prestressed with seven-wire strands and then fatigue tested to failure. Three methods of extending the fatigue life of cracks were then explored: (1) drilling a hole at the crack tip and installing a high-strength bolt; (2) splicing the web at the cracked section; and (3) increasing the prestressing force of the tendon. The efficacy of the three methods is compared.

A study has been undertaken to investigate different solver and shell element performances for curved bridge finite-element analysis. Three sparse solvers were implemented into a bridge finite-element analysis code, and the solution times and memory requirements for typical bridges were compared. In addition, the use of four-node and nine-node shell elements in modeling was investigated for different mesh densities. Based on the comparative studies performed, modeling guidelines for practicing engineers have been developed and are presented herein.