Determination of brace forces caused by construction loads and wind loads during bridge construction.

PDFTech ReportBDK75-977-70UF Project Nos. 101350 and 102056Bridge constructionBracingGirdersPrecast concreteLoad testsAerodynamic forceBridge designFinite element methodStructural analysisScale modelsWind tunnelsFloridaUniversity of Florida. Dept. of Civil and Coastal EngineeringConsolazio, Gary R.Edwards, Samuel T.University of Florida. Dept. of Civil and Coastal EngineeringFlorida. Dept. of Transportation. Research Management CenterUS Transportation CollectionThe first objective of this study was to develop procedures for determining bracing forces during bridge construction.Numerical finite element models and analysis techniques were developed for evaluating brace forces induced by construction loads actingon precast concrete girders (Florida-I Beams) in systems of multiple girders braced together. A large-scale parametric study was performedwith both un-factored (service) and factored (strength) construction loads (in total, more than 600,000 separate three-dimensional (3-D)structural analyses were conducted). The parametric study included consideration of different Florida-I Beam cross-sections, span lengths,girder spacing, deck overhang widths, skew angles, number of girders, number of braces, and bracing configurations (K-brace and Xbrace). Additionally, partial coverage of wet (non-structural) concrete load and variable placement of deck finishing machine loads wereconsidered. A MathCad calculation program was developed for quantifying brace forces using a database approach that employs multiple dimensional linear interpolation. The accuracy of the database program was assessed by using it to predict end-span and intermediate-spanbrace forces for parameter selections not directly contained within the database, and then comparing the interpolated predictions to resultsobtained from finite element analyses of corresponding verification models. In a majority of cases, the database-predicted brace forceswere found to be less than ten percent (10%) in error.The second objective of this study was to experimentally determine wind load coefficients (drag, torque, and lift) for commonbridge girder shapes with stay-in-place (SIP) formwork and overhang formwork in place, and then to develop recommended global(system) pressure coefficients (e.g., for strength design of substructures). Wind tunnel tests were performed on reduced-scale models ofFlorida-I Beam (FIB), plate girder, and box girder cross-sectional shapes to measure aerodynamic forces acting on individual girders in thebridge cross-section. Tests were conducted at multiple wind angles, and corresponding tests with and without overhang formwork wereconducted. Data from the wind tunnel tests were used to develop conservative procedures for calculating global pressure coefficientssuitable for use in bridge design