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36 factored sectional design forces (Vu, Mu, and Nu ). In these Example 6: Multi-Post Bent Cap examples, the critical sections used are those already avail- able from the designers who provided the case studies on This design example is for a multi-post bent cap beam 86 feet which these examples are based. wide. The beam is supported on four columns distributed at 22 ft centers below the beam. Figure J-20 shows the elevation of the multi-post bent cap beam. The design section is taken at Example 1: Precast, Pretensioned the internal face of the first pier in the first bay. Bridge details Noncomposite Box Beam were provided by the Tennessee Department of Transportation. This example demonstrates the shear design at a specific section of a 95-ft single-span AASHTO Type BIII-48 box Example 7: Type IV Girder beam bridge with no skew. The example is based on Exam- ple 9.2 of the PCI Bridge Design Manual [PCI, 1997]. Seven This example demonstrates the shear design of a section of the 29 0.5-inch diameter strands used for flexural tension of a 100-ft span AASHTO Type IV beam bridge. Bridge reinforcement in the 39-inch-deep precast box beams are details were provided by the Texas Department of Trans- debonded. portation. The bridge consists of 3 spans with each span sim- ply supported. The composite pretensioned beams are 54 inch deep and have an 8 in. thick deck. Example 2: Three-Span Continuous Precast, Pretensioned Girders Example 8: Segmental Girder This example is based on Example 9.6 of the PCI Bridge Design Manual [PCI, 1997]. The bridge uses 72-inch bulb tees This example gives the shear design calculations for a with harped (draped) pretensioned strands on 110-foot end 5-span Precast Balanced Cantilever Bridge constructed using spans and 120-foot interior span. The beams are made contin- AASHTO-PCI-ASBI segmental box girders. The design sec- uous for live load by the addition of unstressed reinforcement tion is taken from the second bay near the support. in the deck in the negative moment region. This example illus- trates the shear design in the negative moment region of a beam made continuous with nonprestressed reinforcement. 3.4 EVALUATION OF SIMPLIFIED PROVISIONS WITH SELECTED TEST DATA Example 3: Reinforced Concrete Cap Beam Appendix G presents a detailed evaluation of the two pro- This design example demonstrates the shear design of a posed changes to the LRFD shear design provisions using the section of a non-prestressed 15-ft span cap beam supported selected experimental database. The first of these is the on three circular columns of 3-ft diameter. The cap beam proposed simplified provisions which are a significant mod- supports a 3-lane superstructure consisting of six AASHTO ification to the AASHTO standard approach and which intro- Type IV beams. duces the use of a variable angle truss model. The second is the proposed modification to the LRFD Sec- tional Design in which the equations replace the tables for Example 4: Reinforced Concrete Column evaluating and and a simplified relationship is used for and Footing evaluating the strain at mid-depth, x, that eliminates the dependency on the angle . This is essentially the new CSA This design example demonstrates shear design for two approach. sections of a reinforced concrete column and footing, which The selected experimental database consists of 64 rein- are part of a pier designed by Modjeski and Masters, Inc. In forced concrete members and 83 prestressed concrete mem- the shear design of the footing, only one-way action is con- bers. All of these members contain at least the traditional sidered for a demonstration of proposals. ACI level of minimum shear reinforcement (v fy > 50 psi), have an overall height of a least 20 inches, were cast with Example 5: Two-Span Continuous Post- concretes that had cylinder compressive strengths of 4000 psi Tensioned Box Bridges in Nevada or greater, and had shear span-to-depth ratios at least 1.70 and usually considerably higher. The members were selected BERGER/ABAM designed this two-span, cast-in-place, from the larger database described in Section 2.3. post-tensioned box girder bridge. Spans are 110 and 120 feet Appendix G also presents evaluations with the selected for the 5-foot deep box girder. Shear design for positive and database of the current LRFD Specifications and AASHTO negative moment regions, and in the vicinity of the inflection standard procedures, an examination of the proposal's abil- point, are illustrated. ity to predict cracking strengths, and a more detailed discus-