Journal of Bridge Engineering

An increasing number of bridges are being designed with continuous spans instead of simple spans. By reducing the number of joints in a bridge, the traveling public receives a better riding surface and corrosion caused by leaking joints can be reduced. Also, redundancy is created when the system is made continuous, producing a tougher structure. However, a continuous system is more complicated to design and secondary restraint moments due to creep, shrinkage, and thermal effects can develop at the connection. This paper presents results from an experimental study done to monitor the early age restraint moments that develop in a two-span continuous system made of full-depth precast concrete bulb tee girders. The restraint moments observed were compared to the predicted restraint moments using the RMCalc program . The observed restraint moments were significantly lower than predicted by the program. Expansion of the deck during curing, which is generally not considered in the predictions, significantly influenced the early age restraint moments. A simplified model to predict the restraint moments considering thermal effects is proposed.

Several full-scale load tests were performed on a selected Florida highway bridge. The bridge was dynamically excited by two fully loaded trucks, and the strain, acceleration, and displacement at selected points were recorded for the investigation of the bridge’s dynamic response. Experimental data were compared with simplified vehicle and bridge finite-element models. The vehicle was represented as a three-dimensional mass–spring–damper system with $11\text{degrees}$ of freedom, and the bridge was modeled as a combination of plate and beam elements that characterize the slab and girders, respectively. The equations of motion were formulated with physical components for the vehicle and modal components for the bridge. The coupled equations were solved using a central difference method. It was found that the numerical analysis matched well with the experimental data and was used to successfully explain critical dynamic phenomena observed during the testing. Impact factors for this tested bridge were thoroughly investigated by using these models.

The paper introduces a design space for the design of prestressing tendons concentric with members for strengthening steel truss bridges. The design space contains all feasible solutions for the cross-sectional area of the tendon and the level of prestressing that satisfy the following criteria: (1) tendon yielding; (2) member buckling; and (3) member fracture and yielding. In the tendon design, two options for the degree of prestressing and backup are available. The prestressing option controls the amount of fatigue crack propagation under cyclic loadings, while the backup option provides the tendon area capable of replacing or backing up the member.

This paper presents the results of an investigation of the monotonic and fatigue behavior of one-way and two-way reinforced concrete slabs strengthened with carbon fiber-reinforced polymer (CFRP) materials. The five one-way slab specimens were removed from a decommissioned bridge in South Carolina. Three of the slabs were retrofitted with CFRP strips bonded to their soffits and the other two served as unretrofit, control specimens. Of the five one-way slab specimens, one unretrofit and two retrofit slabs were tested monotonically until failure. The remaining two specimens, one unretrofit and one retrofit, were tested under cyclic (fatigue) loading until failure. In addition, six half-scale, two-way slab specimens were constructed to represent a full-scale prototype of a highway bridge deck designed using the empirical requirements of the AASHTO LRFD Bridge Design Manual. Of the six square slabs, two were unretrofitted and served as the control specimens, two were retrofitted using CFRP strips bonded to their soffits making a grid pattern, and two were retrofitted with a preformed CFRP grid material bonded to their soffit. Three slabs, one unretrofit, one CFRP strip, and one CFRP grid retrofitted, were tested monotonically until failure and the remaining three slabs were tested under cyclic (fatigue) loading until failure.

Five prestressed concrete girders made with high-performance concrete were instrumented using vibrating-wire strain gages. Their behavior was monitored for three years from the time of casting. The measured change in concrete strain at the centroid of the prestressing strands was used to evaluate changes in prestress. The total measured prestress loss was as large as 28% of the total jacking stress. Due to the higher stresses, this loss is larger than would be expected for a girder made with conventional-strength concrete. The observed values of prestress losses were compared with values calculated using the recommended AASHTO LRFD and NCHRP 18-07 procedures. The AASHTO LRFD method overpredicted the average prestress losses for the highly stressed Span 2 girders by 20% while the NCHRP method underpredicted the average losses by 16%. The NCHRP method was found to be more inclusive and adaptable to regional construction. The calculated NCHRP Span 2 losses were found to be within 10% of the average measured losses when the elastic shortening losses were calculated based on measured data and differential shrinkage was calculated based on continuous beams.

This paper describes the design of the Fulton Road Bridge segmental concrete arches. The posttensioning concept, superstructure–arch interaction considerations, effective length $k$ factor for moment magnification, and construction sequence analysis methods used for design are discussed.

Overheight vehicle collisions can cause major damage to bridges. To address the issue of limited vertical clearance heights and reduce the likelihood of impact damage, the Georgia Department of Transportation has implemented a program to elevate major highway bridges using very short columns referred to as steel pedestals. The process to elevate the bridges and install the steel pedestals is cost effective and efficient, resulting in minimum disruption to highway traffic. However, in practice, these pedestals are not detailed to provide end fixity, so they add considerable flexibility to the superstructure supports and potentially make the bridge more susceptible to instability and damage from seismic loads. Therefore, there is a need to evaluate how these steel pedestals will perform under the low-to-moderate earthquakes expected in this region. A full-scale $12.2\mathrm{m}$ $\left(40\mathrm{ft}\right)$ dual steel girder simply supported bridge elevated with $500\mathrm{mm}$ $\left(19\mathrm{in.}\right)$ and $850\mathrm{mm}$ $(331∕2\mathrm{in.})$ steel pedestals is constructed based on typical field procedures. The full-scale bridge specimen is subjected to quasistatic unidirectional reversed cyclic loads to determine the strength and deformation capacity of the steel pedestals and overall system performance. The kinematics, mechanisms, and load–displacement hysteretic relationships of the bridge steel pedestals and its components are presented. Results show that the steel pedestals undergo kinematic rigid body motion, dissipate energy, and demonstrate reasonable deformation and strength capacities when subjected to quasistatic, reversed cyclic loads.

Since the first edition of the AASHTO Guide Specifications for Horizontally Curved Steel Girder Highway Bridges was published in 1980, there have been two more editions including many revisions to the specifications. Some changes were based on valid research results and others were based on limited or uncertain research results and information. The current edition of the specifications contains provisions that may result in unreasonably conservative load capacity ratings. In this paper, the results of field tests and analyses conducted on the Veterans’ Memorial curved steel-box girder bridge are discussed. Test and analytical results show: (1) current AASHTO guide specifications regarding the first transverse stiffener spacing at the simple end support of a curved girder may be too conservative for bridge load capacity ratings; (2) current AASHTO guide specifications may greatly overestimate the dynamic loadings of curved box girder bridges with long span lengths; and (3) a plane grid finite-element model of about 20 elements per span in the longitudinal direction can be used to analyze curved multigirder bridges with external bracings located only over supports. The research results are instructive and applicable to bridge design and bridge load-rating activities.

This paper focuses on levels of live-load lateral bending moment (bimoment) distribution in a horizontally curved steel I-girder bridge. Work centered primarily on the examination of (1) data from field testing of an in-service horizontally curved steel I-girder bridge and (2) results from a three-dimensional numerical model. Experimental data sets were used for calibration of the numerical model and the calibrated model was then used to examine the accuracy of lateral bending distribution factor equations presented in the 1993 Edition of the (AASHTO) Guide Specifications for Horizontally Curved Bridges. It is of interest to examine these equations for potential use in preliminary design even though they have been eliminated during recent AASHTO specification modifications that addressed curved bridge analysis, the 2005 Interims to the AASHTO LRFD Bridge Design Specifications. In addition, they were developed using idealized computer models and small-scale laboratory testing with very few field tests of in-service full-scale curved steel bridges conducted to support or refute their use. Results from such experimental and numerical studies are presented and discussed herein.

A parametric study was conducted to extend the results of an experimental program on a concrete integral abutment (IA) bridge in Rochester, MN to other integral abutment bridges with different design variables including pile type, size, orientation, depth of fixity, and type of surrounding soil, fixity of the connection between the abutment pile cap and abutment diaphragm, bridge span and length, and size and orientation of the wingwalls. The numerical results indicated that bridge length and soil types surrounding the piles had a significant impact on the behavior of IA bridges. To select pile type and orientation, there is a need to balance the stresses in the piles with the stresses in the superstructure for long IA bridges or IA bridges in stiff soils. Plastic hinge formation is possible at the pile section near the pile head for combined critical variables, such as long span, compliant piles in weak axis bending, deep girders, and stiff soils. Because large pile curvatures or stresses may be caused due to the rotation of the pile cap during temperature increases, hinged connections between the abutment pile cap and diaphragm are not recommended for the practice of IA bridges. Cast-in-place piles are recommended only for short-span IA bridges because their relatively large bending stiffness can cause large superstructure concrete stresses during temperature changes.

This study is aimed at investigating the effect of soil–structure interaction and substructure properties at the abutments on the distribution of live-load effects in integral abutment bridge (IAB) components. For this purpose, numerous 3D and corresponding 2D structural models of typical IABs are built and analyzed under AASHTO live-load. In the analyses, the effect of various geotechnical and substructure properties such as foundation soil stiffness, considering and neglecting the effect of backfill, backfill compaction level, considering and neglecting the effect of wingwalls, abutment height and thickness, as well as number, size, and orientation of the piles are considered. The results from the 2D and 3D analyses are then used to calculate the live-load distribution factors (LLDFs) for the components of IABs as a function of the above-mentioned properties. The analyses results revealed that soil–structure interaction has a significant effect on the LLDFs for the abutment, but negligible effects on those for the girders and piles. Furthermore, the abutment height is observed to have a considerable effect on the LLDFs calculated for the abutment and pile moments. Moreover, the wingwalls are observed to have only a negligible effect on the LLDFs for all the IAB components.

The objective of this study is to summarize the load and resistance criteria for highway bridge plank decks, and to estimate the reliability of plank decks designed by the AASHTO Code. Both transverse and longitudinal planks for a variety of typical stringer spacings and plank sizes are considered. Truck traffic load data are based on the model used to calibrate the 1994 AASHTO LRFD Code. However, for plank decks, wheel load rather than whole vehicle weight is most important, and these statistics are developed for this study. For wood planks, dead load and dynamic load are not significant. The limit state considered is flexural strength, and resistance statistics are presented for wood planks in terms of modulus of rupture. Special flat-wise use data are presented to account for section aspect ratio as well as edge of load application. The reliability analysis is carried out using the procedure developed for calibration of AASHTO LRFD. Reliability indices for both the AASHTO Standard and AASHTO LRFD Code are presented for plank decks. The results indicate that there are considerable differences in plank reliability indices. Causes of inconsistencies in safety are identified.

Industrial hardwood laminated billets and mats were proposed, manufactured, and tested. The raw material for the mats was structural composite lumber billets manufactured from sweetgum and mixed hardwood lumber. Each mat consisted of three bolt-laminated billets. Both billets and mats were tested in third-point bending across a 1.87-m span. The span-to-depth ratio was 21. Results showed that bolt laminating contributes significantly to mechanical performance as compared to that of individual billets.