This thesis presents a method which facilitates rapid determination of the cable tension in suspension bridges. A set of tables and curves is included for use in the application of the method. The method is valid for suspension bridges with stiffening girders or trusses either hinged at the supports or continuous. A modified superposition method is discussed and the use of influence lines for cable tension in non-linear suspension bridges is demonstrated. A derivation of the suspension bridge equations is included and various refinements in the theory are discussed. A computer program to analyse suspension bridges was written as an aid in the research and for the purpose of testing the manual method proposed. A description of the program is included along with Its Fortran listing. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Plenty of bridges in U.S. are suffering from prestress force loss and foundation settlements. The loss of prestress force in bridge load-carrying members such as girders may lead to the malfunction and even failure of the prestressed bridges that comprises more than 55% of all new and replaced bridges built in US between the year 2000 and 2012. Settlement of foundations supporting the bridge piers and abutments impairs the superstructure integrity and serviceability of the bridge, or even collapses the bridge if the settlement is over a certain limit. In present study, the dynamic interaction between vehicles and the bridges subjected to prestress force loss and foundation settlement has been investigated. Based on modal superposition technique and principal of virtual works, new bridge-vehicle interaction models have been created to take the effects of prestress and foundation settlement on dynamic bridge and vehicle responses into account. With the developed models, numerical simulations have been performed to show that the prestress force makes the distribution of impact factors along the bridge unbalanced and the existence of foundation settlement may couple with road surface roughness of the bridge deck to possess an aggregated overall effect amplifying the bridge responses. In general, the vehicle responses are vulnerable to the prestress force loss and foundation settlement, which harms the riding comfort of passengers. The existed direct and indirect methods used for prestress loss identification are all based on the measurement collected from sensors deployed on the outside or inside of the bridge, which is not only costly but also inconvenient. The current study proposes to detect the prestress force loss of the bridge through the analysis of vehicle responses. Through simulations, it is found that light, low-frequency vehicles moving at low speeds have a better performance in detecting the bridge prestress loss than the heavy, high-frequency vehicles with high speeds. The advantage of the proposed method is that it only needs a few sensors installed on the vehicle, and works without interrupting the ongoing traffic, which is efficient and cost-effective.

This thesis deals with the application of the Life Cycle concept to the design of bridges. Its focus is on methodology rather than on any particular application, with emphasis on the preliminary design stage. With the help of conceptual equations for the construction, maintenance, and vehicle delay costs, a procedure for making decisions at the preliminary design stage is presented. Decisions are made on the basis of minimum present equivalent total cost and include the number of lanes to be provided, the span between piers, and the design alternative (type of bridge) to be adopted for detail design. Minimization is done by a total enumeration procedure. Sensitivity of the decisions with respect to the interest rate and the study period is analyzed, and design decision reversals are noted. This includes a joint sensitivity analysis with respect to these design independent parameters. Limited analysis of errors in cost estimating equations is also performed. A FORTRAN code, implementable on mainframe and personal computers is developed to aid calculations. / Master of Science

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Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Humanities, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND HUMANITIES. / Bibliography: leaves 115-118. / by Susan Kay Jackson. / B.S.

published_or_final_version / Civil and Structural Engineering / Doctoral / Doctor of Philosophy

The design of bridge structures to resist explosive loads has become more of a concern to the engineering community. This thesis proposes a method to evaluate the effects of conventional blast loads on a two span continuous composite steel girder bridge system. The bridge design is based on AASHTO LRFD method. Resistance capacities of bridge deck and composite steel girder are calculated according to AASHTO specifications. Equivalent blast pressures on the bridge components are obtained. Response and performance of concrete deck, steel girders, and supporting piers are evaluated under typical blast loads. The blast induced force in the bridge components are computed in the static analyses for varying amounts of TNT. The blast effects in the supporting pier are determined using both static and dynamic analyses. Further research needs to be done in the dynamic analysis of the bridge system subjected to blast loads. / by Fang Zhou. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

The torsional rigidity of tub-girder makes them ideal for use in curved bridges. The use on skewed support applications by bridge designers is limited as the behavior is complex and requires the use of advanced analysis tools. In consequence, a simplified analysis method to account for the effects of skew on tub-girder twist rotations and internal torques and how these affect the internal component forces was proposed. The combined effects of skew and curvature are studied by examining the results for analysis with different levels of sophistication for 18 representative bridges. The data generated constitutes the first systematic study on a large set of curved and skewed tub-girder bridges using consistent, refined 3D FEA models to model construction forces and deformations. Comparisons of the simplified analysis method to the refined 3D FEA analysis display the limitations of the simplified analysis and present potential sources of error. Furthermore, the results from the 3D FEA helped identify interactions between components and, therefore, an improved simplified procedure was proposed to account for the effects of the resulting increased stresses. In addition, the bridge erection procedures are discussed and specific examples illustrating the calculation of the fit-up forces is presented. These findings provided additional tools for the analysis process and erection engineering to account for the effects of skew. Lastly, further research needs considering the analysis of additional loading conditions and construction procedures are described.