Bridge Structures - Volume 3, issue 3, 4

Authors: Mahmoud, Khaled M.

Article Type: Other

DOI: 10.1080/15732480701567981

Citation: Bridge Structures, vol. 3, no. 3, 4, pp. 147-148, 2007

Authors: Kozy, Brian | Tunstall, Shawn

Article Type: Research Article

Abstract: Twin I-girder structural systems are often encountered in practice on pedestrian bridges, railroad bridges, and temporary conditions during multi-girder bridge erection and demolition. The current paper is based on an in-depth stability analysis and bracing design conducted on a twin I-girder pedestrian bridge recently constructed in Minnesota. This work demonstrates that the strength of non-composite twin-girder systems without lateral bracing can be controlled by the limit state of ‘system’ or ‘global’ buckling, however the existing literature and governing design specifications do not adequately address this limit state. For twin-girder systems with partially braced spans and/or non-prismatic cross-sectional properties, a complete …3-D finite element (FE) buckling analysis should be considered for quantifying buckling strength and associated bracing forces; either linearized eigenvalue analysis or complete non-linear incremental collapse analysis. These FE stability analysis models can be verified effectively by checking the vertical, lateral, and torsional stiffness against results provided by classical solution techniques. Show more

Keywords: Stability, Buckling, Bracing, Steel bridge, Girder

DOI: 10.1080/15732480701520196

Citation: Bridge Structures, vol. 3, no. 3, 4, pp. 149-163, 2007

Authors: Arici, M. | Granata, M.F.

Article Type: Research Article

Abstract: The incrementally launching technique is today widely used for the construction of continuous concrete bridges. During construction, the static scheme of these bridges varies continuously, with the advance of the deck above piers producing temporary stresses rather different from those occurring in service. An approach to analyse the construction phases of curved incrementally launched bridges is presented for concrete single box girder. A procedure based on the Transfer Matrix Method (TMM), already developed for straight launched bridges, has been extended to curved beams, allowing engineers to estimate the effects of horizontal curvature during the entire launching process. This procedure allows …engineers to carry out parametric studies for the optimization of structural design of curved concrete launched bridges. Show more

Keywords: Launched bridges, Curved bridges, Transfer matrices, Box concrete

DOI: 10.1080/15732480701510445

Citation: Bridge Structures, vol. 3, no. 3, 4, pp. 165-181, 2007

Authors: De Corte, W. | Delesie, C. | Van Bogaert, PH.

Article Type: Research Article

Abstract: A substantial number of orthotropic decks suffer from fatigue-related problems, which can be attributed to increase in traffic loads, bad detailing, or lack of understanding of the mechanisms leading to these problems. Of the various fatigue-prone locations, the rib to floorbeam joint is the most challenging, since it is subjected to a complex set of in- and out-of-plane stresses. In this paper, the case of continuous longitudinal ribs passing through the floorbeam web by an additional cope hole is addressed. In such a configuration, the first fatigue crack initiating at the joint can either grow in the floorbeam web or …in the rib walls, depending on the geometric conditions. Both situations are addressed in the paper, providing a parametric study of distortion-induced rib stresses as well as a simplified method for cutout stress calculations. Show more

Keywords: Orthotropic bridge deck, Rib to floorbeam connection, Rib distortion, Fatigue

DOI: 10.1080/15732480701508159

Citation: Bridge Structures, vol. 3, no. 3, 4, pp. 183-191, 2007

Authors: Sivakumar, Bala | Sheikh Ibrahim, Firas I.

Article Type: Research Article

Abstract: Over the past century, the American Association of State Highway and Transportation Officials (AASHTO)-specified live loads have been evolving to catch up with the ever-changing knowledge and trends of vehicular traffic. The latest loads are based on past Canadian traffic data, and may not represent modern or future traffic conditions in some US jurisdictions. Today, weigh-in-motion (WIM) systems can provide a solution to this dilemma by providing valuable site-specific traffic data for bridge design and evaluation, weight-limit enforcement, and the likelihood of illegally overloaded trucks causing premature bridge deterioration. Bridge owners have long recognized the importance of incorporating site- or …state-specific truck loads in their bridge evaluation and preservation programs. The AASHTO LRFD and LRFR Bridge Specifications have evolved to advance the trend toward information-sensitive specification formulation. When warranted, the specified live loads can be enhanced utilizing more relevant site or route data. This paper reviews the evolution of US bridge design live loads, and discusses the possible enhancement of bridge live loads and load factors using WIM data. The paper presents recent investigations for evaluating the design live loads for the State of New York, and calibrating the live load factors used in rating for the State of Oregon using WIM data. The New York investigation indicates that truck loads at two studied sites may be significantly heavier than the AASHTO-specified loads. It also indicates that WIM enhanced site-specific fatigue design loading is significantly heavier than the AASHTO LRFD fatigue design truck. In the Oregon investigation, state-specific WIM data resulted in a significant reduction in the live load factor for legal and permit trucks for the entire State of Oregon, which is attributable to the State’s regulatory and enforcement environment. Show more

Keywords: Bridge live load, Weigh-in-motion, AASHTO bridge specifications, Site-specific live loads, Calibration of live loads

DOI: 10.1080/15732480701515386

Citation: Bridge Structures, vol. 3, no. 3, 4, pp. 193-204, 2007

Authors: Wu, Haiyong | Najjar, Walid S.

Article Type: Research Article

Abstract: Curved steel box-girder bridges are aesthetically pleasing and functionally effective, particularly at highway interchanges with curved alignments. A parametric analytical study of the seismic behavior of this type of bridges is performed. The study should be useful to the bridge industry, because of the need to construct these bridges in urban areas with tight right-of way restrictions, including earthquake-prone regions, and the fact that current specifications for horizontally curved highway bridges and other available information do not address sufficiently the seismic behavior of these bridges. A three-dimensional finite element model of an existing two-span continuous bridge with curved steel box-girders …is analyzed for site-specific earthquake loads. Multiple parameters of the model are evaluated, including girder curvature, bearing condition, diaphragm spacing and free vibration characteristics. Results of the study with potential design recommendations are outlined. Seismic criteria by local and national specifications are contrasted and discussed in light of the analysis results. Show more

Keywords: Seismic response, Curved box-girders, Steel, Highway bridge, Finite element analysis

DOI: 10.1080/15732480701511989

Citation: Bridge Structures, vol. 3, no. 3, 4, pp. 205-213, 2007

Authors: Hewes, J.T.

Article Type: Research Article

Abstract: Four unbonded post-tensioned precast segmental concrete columns were subjected to pseudostatic simulated lateral seismic loading in the Charles Lee Powell Structural Research Laboratories at the University of California at San Diego. The influence of parameters including steel jacket confinement, prestress level, and column aspect ratio on column force – deformation characteristics, energy dissipation, damage level, and failure mode was studied. To investigate prestress influence and damage repairability, each column was tested twice: the first test with a given prestress level and a second test, subsequent to column repair, with higher initial prestressing. Shear keys were not provided at segment interfaces, …and thus shear was transferred by a friction mechanism. Ductile flexural response was observed in all tests, and maximum column drift levels of 4 – 6% were achieved. Damage included minor concrete crushing at the interface of column and footing, steel jacket inelastic straining, and residual drift on the order of one-half per cent. Key test results are compared to those predicted by a simple analytical model and good agreement is observed. It is concluded that this structural system can be designed to resist severe seismic demands while offering the benefit of reduced post-earthquake damage and the associated economic loss. Show more

Keywords: Precast concrete, Segmental concrete, Bridges, Unbonded post-tensioning, Prestressed concrete, Seismic response

DOI: 10.1080/15732480701520352

Citation: Bridge Structures, vol. 3, no. 3, 4, pp. 215-227, 2007

Authors: Stoyanoff, S. | Haskett, T. | Pridham, B. | Hunter, M. | Zoli, T.

Article Type: Research Article

Abstract: Pedestrian-induced vibrations (PIV) on footbridges, overpasses, and floors are attracting more attention to the designers and are becoming as important dynamic excitation to consider as wind and earthquake. A key reason for this trend is the public awareness and higher performance standards set on new projects where better comfort is sought and lively structures are less tolerated. At the same time, more efficient material utilization and new construction methods are producing more efficient structures with less capability to dissipate the energy input (low damping) and as a result, are more sensitive to dynamic excitations. In addition, recent research has led …to an improved understanding of the pedestrian vibration problem and with the advances in both practical and refined analytical methods, designers may better determine what vibration control measures are appropriate for an optimized design. This paper presents the basics of the PIV problem and a new method for direct time domain simulations of PIVs that allows rather realistic evaluation of a bridge’s dynamic performance and evaluation of comfort to its users. Based on statistical distributions of key parameters such as gait frequency, phase and length, personal weight and type of activity, a wide variety of loading scenarios may be readily evaluated. Most importantly, the hypothesis of ‘lock-in’ can be verified, which allows less conservative response estimates derived from methods based on formulae that assume post lock-in conditions. A brief discussion on vibration control is also included. Show more

Keywords: Footbridges, Pedestrian bridges, Pedestrian-induced vibrations, Pedestrian lock-in, Pedestrian excitation phenomenon, Controlling parameters, Response analysis to pedestrian excitations, Comfort criteria, Response estimation at lock-in, Direct simulations in time domain, Vibration control

DOI: 10.1080/15732480701515196

Citation: Bridge Structures, vol. 3, no. 3, 4, pp. 229-245, 2007