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3 Factored Applied Moment Mu Moment on Composite Horizontal Bending Section MLL+IM, MDC2, MDW Shear Transfer Stress fb (Stiffness Attracts Load in VQ Continuous Spans) I Moment Compressive of Inertia Stress in Web I First Moment for fcw Horizontal Shear Q (a) Plastic Effective Depth of Moment Width Compressive Mp beff Portion of Web Dc Limiting Web Stress Fcrw Compactness Nominal Dc Flexural of Web tw Resistance Mn, Fn Figure 2. Design parameters influenced by effective width. Conduct experimental investigations of scale-model slab- on-girder bridge structures to complement the finite element-based parametric study, (b) (c) Conduct several analysis cases of cable-stayed bridges, Figure 1. Effective width for the positive moment section. Explore impacts of proposed changes to effective width code provisions ("Process 12-50"), Analyze additional cases required by the DOE (Design of Experiments) approach that were not contained in the Considering both conventionally reinforced and pre- original scope of work, stressed decks. Analyze a few prestressed concrete girder cases to investigate whether changes proposed for effective slab In accordance with the NCHRP 12-58 Project Statement, width in composite steel bridge members could reason- the objectives of the research undertaken were to investigate ably be applied to bridges supported by prestressed con- both new and existing approaches for effective slab width crete girders, and Revise the MathCad worksheets developed for use in and to develop and validate the most promising of these. The research products consist of criteria, recommended specifi- presenting illustrative design examples to reflect the substantive changes to S6.10 and S6.11 in the 3rd Edi- cations and commentary, and worked examples addressing tion AASHTO LRFD code, published in 2004. applicable AASHTO LRFD limit states in AASHTO LRFD format. The resulting amended task descriptions were as follows: Task 1. Review domestic and foreign field and laboratory 1.2 RESEARCH TASKS test results, analytical studies, and specifications regarding the effective slab widths for all types of steel and concrete The set of research tasks in the original solicitation for the composite structures. NCHRP Project 12-58 investigation was augmented to incor- Task 2. Using the findings from Task 1, summarize applic- porate the following: able methodologies for determining the effective slab width