Page 36 - Bridge and Highway Structure Rehabilitation and Repair
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CHAPTER 1                                         OVERVIEW OF BRIDGE ENGINEERING             11



        1.3.5 Girder Shapes
            The most commonly used girder shapes are (Table 1.2):
            •  I-shaped girders
            •   Adjacent or spread box beams
            •  Composite beams
            •  Through girders.
        1.3.6  Typical Tasks Associated with Rehabilitation (see Section 1.7)

        1. Site surveying and in-depth inspection.
        2. Geotechnical investigation.
        3. Redesign criteria/application of LRFD method
            •  Live load analysis
            •  Hydraulic and scour analysis
            • Seismic analysis
            •  Structural calculations for sizing and connections.
        1.3.7  Expected Life of a Bridge

            Some bridges in the U.S. have survived for over 150 years with proper maintenance. New
        design techniques assume a shorter life of a bridge or just the superstructure of 75 to 80 years.
        With changes in demographics and urban congestion, intersections may need to be re-planned
        or widened.
            Planning considerations and design philosophy about performance of construction materials
        and joints, etc. have changed since the time when older bridges were designed.
            Some bridges may become functionally obsolete sooner and extreme events, accidents, or
        fatigue may increase the life cycle costs and cause them to be replaced even before the stipulated
        75 years.

        1.3.8  Published References and Resource Applications
            An approximate allocation of design time needed is as follows:
        1. AASHTO Code                                               25 percent
        2. State design codes (text)                                 15 percent
        3. State and in-house standard details                       15 percent
        4. Textbooks, handbooks, and HEC-18, HEC-23, etc.            10 percent
        5. Computer software/math CAD and Excel spread sheets        20 percent
        6. Technical specifi cations                                  10 percent
        7. Construction specifi cations                                 5 percent
                                                                   ___________
                                                                    100 percent
            AASHTO Codes consist of important subjects covering bridge design specifi cations, sign

        support structures, and design specifications for curved girder bridges.
        1.3.9  Contract and Bid Documents
            Comprehensive bid documents for plans, specifications, and estimates (PSE) are required:

        1. Construction plans.
        2. Specifi cations.
        3. Estimates.
        4. Construction schedule.
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