Journal of Bridge Engineering

The historic Wheeling suspension bridge over the Ohio River is one of the 57 long-span suspension bridges in operation in the United States. The bridge was designed and constructed in 1849 by Charles Ellet, Jr., who rightfully may be considered the father of the modern American suspension bridge. Despite the fact that the bridge was not designed to carry today's live loads, the bridge has served as a vital link across the Ohio River for nearly a century and a half. This paper represents the first comprehensive structural analysis using modern computer techniques and in situ nondestructive testing evaluation of this bridge. Static analysis showed that deflections and stresses caused by present-day loading conditions are within allowable limits. Rating factors demonstrated that none of the structural members are overstressed by the posted live load. Seismic analysis to the American Association of State Highway and Transportation Officials loads showed little damage, which was confined to floor beams at the east tower. Analysis using historic earthquakes showed localized damage of floor beams and diagonal floor ties at the east tower and top chords of the stiffening truss at midspan. The methodology developed could be applied to a wide range of cable suspension bridges.

The effect of concrete material properties on cracking in bridge decks is evaluated based on field surveys of 40 continuous steel girder bridges, representative of construction throughout the State of Kansas. Information collected from construction documents and field books is compared with observed levels of cracking to identify correlations between cracking and the variables studied. The results of the evaluation indicate that cracking in monolithic bridge decks increases with increasing values of concrete slump, percent of concrete volume occupied by water and cement, water content, cement content, and compressive strength, and decreasing values of air content (especially below 6.0%). Bridge deck overlays placed with zero slump concrete exhibit consistently higher levels of cracking than overlays with measurable slumps.

This paper presents an energy method of analysis for the in-plane ultimate load capacity of cable-stayed bridges. The potential energy of the whole bridge, including bridge deck, stayed cables, and pylons, and the work done by external loads are considered in the development of the bridge energy equation. Both geometric and material nonlinearities are taken into account in the analysis. The method is simple to use and has a high convergence rate. The predictions of the proposed method show good agreement with experimental results.

This paper presents experimental results from large-scale red maple glued-laminated (glulam) double t-beam testing for application in hardwood glulam bridge design. Experimental results indicate that glulam t-beams assembled with gaps between glulam deck panels experience a 5.8% increase in bending stiffness above that of a beam with no deck panel. The 5.8% stiffness increase is independent of beam depth. T-beams assembled with top abutted deck panels experience a 14.6% stiffness increase for 737 mm deep beams and a 10.1% stiffness increase for 1,143 mm deep beams. Additional testing results indicate that a common construction practice (roofing felt between deck panels and beams) does not influence glulam t-beam bending stiffness.

The study described here investigates the nonlinear static and ultimate behavior of a long-span cable-stayed bridge up to failure and evaluates the overall safety of the bridge. Both geometric and material nonlinearities are involved in the analysis. The geometric nonlinearities come from the cable sag effect, axial force-bending interaction effect, and large displacement effect. Material nonlinearities arise when one or more bridge elements exceed their individual elastic limits. The example bridge is a long-span cable-stayed bridge of a 605 m central span length with steel box girder and reinforced concrete towers under construction in China. Based on the limit point instability concept, the ultimate load-carrying capacity analysis is done starting from the deformed equilibrium configuration due to bridge dead loads. The effects of the steel girder hardening and the girder support conditions on the ultimate load-carrying capacity of the bridge have been studied. The results show that the geometric nonlinearity has a much smaller effect on the bridge behavior than material nonlinearity. The overall safety of a long-span cable-stayed bridge depends primarily on the material nonlinear behavior of individual bridge elements. The critical load analysis based on the bifurcation point instability concept greatly overestimated the safety factor of the bridge. The ultimate load-carrying capacity analysis and overall safety evaluation of a long-span cable-stayed bridge should be based on the limit point instability concept and must trace the load-deformation path of the bridge from applied loads to failure.

Current AASHTO specifications pertaining to the analysis and design of horizontally curved bridges are based upon research work conducted prior to 1978. Since then a significant amount of work has been conducted to further advance analysis methods and to better understand the behavior of these complex structural systems. Unfortunately, the results of these various research efforts are scattered and, in some cases, unevaluated. This paper complements and updates survey articles published in 1968 and 1978 and presents highlights of the analytical work conducted on horizontally curved steel I-girder bridges.

In this paper, serviceability limit states of prestressed concrete bridges are examined. Allowable compressive and tensile stresses in concrete under service loads are first used to determine the upper and lower limits of the longitudinal prestressing force. The same allowable stresses are used to define allowable shear stresses that prevent excessive tensile stresses in the principal tensile stress direction and that prevent excessive compressive stresses in the principal compressive stress direction. In some cases where the shear stresses due to service loads exceed the allowable shear stress, shear cracking may be controlled by transverse prestressing of the webs. Equations are presented to determine the required transverse prestressing force. An example concludes the paper.

In seeking an efficient arrangement for the bearing cables of a cable-stayed bridge, inspiration is drawn from the natural wrinkling behavior of in-plane stressed triangular membranes. The bridge deck is thought of as being sustained by such a membrane, rather than stays, and the wrinkle pattern is studied as vertical loads act on the deck. Since it can be shown that the resulting wrinkles are straight and develop in such a way as to offer maximum stiffness towards impinging actions, the idea is to place cables according to their layout. The examined cases consider various ratios between the height of the towers and the main span of the bridge, reproducing as well the scheme of significant existing bridges and the possible presence of notches in the membrane. In all the cases, the patterns assumed by the wrinkles show evident resemblance to the traditional harp, half-fan, and fan schemes, and reveal surprising similarities with the disposal of the stays really adopted in existing bridges.

Many multigirder steel bridges built before 1985 are experiencing distortion-induced fatigue cracking at diaphragm-girder connections. A means of eliminating the cyclic stresses that cause those fatigue problems is to remove the interior diaphragms (diaphragms not at the girder supports). The effects of removing interior channel diaphragms from an existing three-span bridge with rolled steel girders are reported in this paper. The effects of removing the diaphragms are evaluated using field measurements of girder stresses and deflections made before and after the diaphragms were taken out. Results from tests with trucks of known weight indicate that removing the diaphragms results in increases up to 15% in the maximum bottom flange stresses at the most heavily loaded girder. Comparisons of measured and calculated stresses show that the conservatism of common design practice is not significantly reduced by removing diaphragms, and the effects of removing interior diaphragms are judged insignificant.

Composite steel-concrete multicell box girder bridges combine excellent torsional stiffness with elegance. While the current design practices in North America recommend few analytical methods for the design of composite multicell box girder bridges, practical requirements in the design process necessitate a need for a simpler design method. This paper presents an extensive parametric study—using the finite-element method—in which 120 bridges of various geometries were analyzed. The parameters considered are: number of cells, number of lanes, span length, and cross bracings. Results from testing a simply supported three-cell bridge model is used to substantiate the analytical modeling. Based on the parametric study, moment and shear distribution factors are deduced for such bridges subjected to AASHTO truck loadings as well as dead load. Saint-Venant torsional stiffness for composite cellular cross sections used in this study is also investigated. Recommendations to enhance the torsional stiffness are formulated. An illustrative design example is presented.

The objective of this project is to evaluate the cumulative damage caused by vehicle loading to bridge concrete deck slabs. As part of this study, an existing analytical model has been implemented to evaluate the effect of user loads on a statistical sample of bridge deck slabs. In addition, an extensive literature review was conducted to determine the state of the art for cumulative deck slab damage evaluation. This review forms the basis for the deck slab FORTRAN program developed for this study. Results of the bridge deck study indicate the influence of a very large exponent used for bridge decks. The relationship between environmental and mechanical factors in bridge deck deterioration is particularly important. The very high number of cycles to failure implies that the damage to bridge decks due to mechanical loading is insignificant compared to environmental factors, a conclusion that seems to be supported by the literature review.