Uniform TitleLive-load models for design and fatigue evaluation of highway bridges
NameDavis, Joseph (author), Nassif, Hani (chair), Nawy, Edward (internal member), Najm, Husam (internal member), Tsakalakos, Thomas (outside member), Rutgers University, Graduate School - New Brunswick,
SubjectCivil and Environmental Engineering,
Bridges--Design and construction
DescriptionNew load design factors and models are introduced to account for site-specific live-load demands in the state of New Jersey. Live-load for highway bridges is highly site specific. The current AASHTO LRFD design specifications provide a notional design truck to which load factors are applied. These strength design factors were calibrated using reliability theory to provide a consistent level of safety for various spans and bridge types. The original calibration was done using a small sample of data from decades ago. Truck weights and volumes have significantly increased, reducing the level of safety of highway bridges designed today.
Live-load is quantified using an extensive weigh-in-motion (WIM) database for the state of New Jersey as well as instrumentation at a bridge located in the heart of Port Newark, NJ. An integrated system combines a WIM system to measure truck loads and a data logger to capture the strains and deflections. This, first of its kind, system provides a complete picture of bridge behavior. The WIM data collected include all of the parameters needed to quantify truck loading: gross and axle weights, axle spacings, classification, counts, speeds, lane, etc. The bridge response includes parameters such as: strains and deflections.
Information on truck loads are used to develop load effect envelopes for various span lengths. The load effects are then extrapolated using Normal probability paper to predict the maximum expected levels for the full service life of 75 years. The effect of other distributions, various measurement durations, and truck multiple presence is also studied. Based on the analysis of moment and shear envelops for various spans, it was found that the current load factors must be increased to maintain the level of safety that the code dictates. A new load model is proposed to provide a more uniform bias for New Jersey trucks.
Fatigue load effects are studied in terms of effective truck weights, truck dimensions, and multiple presence in comparison with current evaluation procedures. Experimental load and response data from the instrumented bridge along with computer models is used to study the effect of truck weight, volume, and multiple presence of the fatigue life. Statistical techniques developed by the automotive industry are applied to short experimental measurements to predict a fatigue load profile that would be expected if measurement extended to a much longer duration. The rainflow extrapolation techniques utilize Extreme Value Theory and non-parametric smoothing methods to render a future prediction of the rainflow counted stress cycle matrix. The effect of measurement duration, seasonality, and truck multiple presence on fatigue life prediction is studied.
NoteIncludes bibliographical references (p. 315-316).
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.