Journal of Bridge Engineering

In February 1996 the Tennessee Department of Transportation, in cooperation with the Federal Highway Administration, the American Iron and Steel Institute, the U.S. Navy, and various steel plate manufacturers, agreed to design the first bridge in the United States to use HPS 485W (70W) steel. Since that time the department has constructed a second bridge using HPS 485W (70W) and has let to contract a third bridge that uses HPS 485W (70W) in both quenched and tempered and thermomechanical controlled processing HPS 485W (70W) steel. This paper will discuss lessons learned in the process and present optimization techniques employed.

For economic reasons, manufacturers of soil-metal bridges have strived to build these structures under the shallowest possible depth of soil cover, below the one allowed by codes of practice. For such structures, special analysis is needed to circumvent or prevent the formation of failure mechanisms that may be triggered during construction or when subjected to traffic loads. Therefore, special features, such as transverse stiffeners attached to the metal shell and the use of thrust concrete beams, may be required to assist the corrugated metal shell in carrying the loads. In this paper, a novel design is proposed for such structures in which the surrounding soil is reinforced and the metal shell is tied into the soil. A finite-element analysis of long span soil-metal structures with shallow soil cover is carried out using these two designs. The analysis is verified and substantiated using field data obtained during the construction of an 18 m soil-metal bridge. Comparing the structural response from the two designs shows that the latter design can lead to a superior structure.

An innovative self-shoring staged construction method was developed to build the world’s longest reinforced composite concrete arch bridge across the Yangtze River at Wanxian, in Chongqing, China. The method uses a steel tube truss frame constructed by the conventional cantilever launching technique. This steel frame with concrete-filled tubes performs the dual role of arch falsework and arch main reinforcement for the final reinforced concrete arch bridge. An optimized schedule for concrete placement was proposed to control the stresses, deflections, and stability of the arch rib during construction. The time dependent effects of concrete, the nonlinear stress-strain relationship of steel and concrete, as well as the geometric nonlinearility were considered. Control information at various stages of construction can be provided using the model developed. A program was developed to conduct parametric studies for selection of the final construction scheme and to direct the construction progress by monitoring and comparing actual and predicted stress and deflection.

This report summarizes the comparative design of a single-span AASHTO Type III girder bridge under the AASHTO Standard Specification for Highway Bridges, 16th Edition, and the AASHTO LRFD Bridge Design Specification. The writers address the differences in design philosophy, calculation procedures, and the resulting design. Foundation design and related geotechnical considerations are not considered. The LRFD design was similar in most respects to the Standard Specification design. The significant differences were: (1) increased shear reinforcement; (2) increased reinforcement in the deck overhang; and (3) increased reinforcement in the wing wall. The comparisons would likely change if the bridge were designed purely according to LRFD Specifications rather than as a comparative design. Design procedures under the LRFD Specification tend to be more calculation-intensive. However, the added complexity of the LRFD Specification is counterbalanced by the consistency of the design philosophy and its ability to consider a variety of bridges.

The restoration of a masonry bridge pier built in 1887 was carried out using cement-based grout. Erosion of the pointing mortar of the pier core outer surface and cracks and voids in the pier core were encountered. This paper presents the methodology used to develop high-performance cement grouts for injection of deteriorated joints and cracks in the stone pier and describes the repair and monitoring operations. Portland and microfine cement-based grouts were optimized in the laboratory. An epoxy resin grout was used as a benchmark to compare the performance of the cement-based grouts. The effectiveness of the grout injection was assessed with core samples testing and nondestructive testing using the sonic tomography method to compare the quality of the medium before and after grouting. High penetrability of the grout was achieved for the high-performance mixtures. The use of high-early-strength cement with some silica fume replacement resulted in a relatively economical mixture exhibiting high performance. The results of this pilot study were later recommended for the rehabilitation of similar masonry piers.

Field tests conducted on a noncomposite steel girder bridge are described. Two separate 36.6 m (120 ft) units, each three-span continuous, were subjected to increasing static loads by means of a trailer and concrete barriers. Results show that the girders acted as partially composite sections in the positive moment region up to the onset of yield. Due to curb participation and the transverse location of the applied load, exterior girders exhibited a higher degree of partially composite action. In the negative moment region, partially composite action was evident only in the exterior girders. As a result of partially composite action and curb participation, the yield load was about 7% higher than predicted. Bearing restraint is shown not to have a significant impact on the behavior of the tested bridges. In addition, the stiffness of the interior girders, as measured under the constant weight of a dump truck, are shown to be virtually unaffected by the heavy trailer loads. More significant changes in girder stiffness were observed between different transverse load positions of the dump truck.

Elastomeric bearings have had an exemplary performance record over the past 40 years. Recently, increased testing requirements have been imposed that now make the testing of elastomeric bearings one of the major costs in constructing the supports. Currently, four low-temperature tests are required for elastomeric bearings. It is not clear whether all these tests are necessary or in fact even related to the actual performance of an elastomeric bridge bearing since some of these tests have been developed for other materials. Research was undertaken to evaluate the various tests and to determine whether they are important or even related to the performance of the bridge bearing. Tests were conducted on full-size natural rubber and neoprene bearings at low temperature subjected to compressive and shear forces, and factors such as testing speed and thermal conditioning were evaluated. As a result of the research, some test methods and performance requirements were found to have little impact on the bearing behavior, and others were overly conservative.

The dynamic responses of steel deck, tension-tied, arch bridges subjected to earthquake excitations were investigated. The 620 ft (189 m) Birmingham Bridge, located in Pittsburgh, was selected as an analytical model for the study. The bridge has a single deck tension-tied arch span and is supported by two bridge piers, which in turn are supported by the pile foundations. Due to the complex configuration of the deck system, two analytical models were considered to represent the bridge deck system. Using the normal mode method, seismic responses were calculated for two bridge models and the results were compared with each other. Three orthogonal records of the El Centro 1940 earthquake were used as input for the seismic response analysis. The modal contributions were also checked in order to obtain a reasonable representation of the response and to minimize computational cost. Displacements and stresses at the panel points of the bridge are calculated and presented in graphical form.