THE CONCRETE BRIDGE MAGAZINE

SUMMER 2008

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

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52 | ASPIRE , Winter 2008 A A S H T O L R F D Agenda Item 35 is a relatively straight- forward item addressing issues regarding combined shear and torsion. It corrects errors in equation numbering in Articles 5.8.6.5 and C5.8.6.5, Nominal Shear Resistance, and adds commentary on the use of Equation 5. This equation is only used to establish concrete section dimensions for sections subjected to combined shear and torsion. Agenda Item 36 is a companion to a 2007 agenda item moved forward by Technical Committee T-5, Loads and Load Distribution, which simplified the determination of effective flange width in Article 4.6.2.6 in Section 4, Structural Analysis and Evaluation. The revision to the effective flange width determination is applicable to sections of all materials and thus is included in the general section on analysis. The revision of Article 4.6.2.6 states that in general "the effective flange width of a concrete deck slab in composite or monolithic construction may be taken as the tributary width perpendicular to the axis of the member for determining cross-section stiffnesses for analysis and for determining flexural resistances." There are exceptions to this simplification specified in Article 4.6.2.6 including girders with large skew angles. Agenda Item 36 standardizes the definition of "b" in Articles 5.3, 5.7.3.1.1, and 5.7.3.2.2, by defining it as the width of the compression face of the member, or for a member with a flange in compression, effective width of the flange as specified in Article 4.6.2.6. Agenda Item 37 clarifies Article 5.10.6.3 with regard to column ties for bundled bars. This clarification is made by modifying every reference to "bars" in the fourth paragraph of Article 5.10.6.3 to "bars or bundle." The existing specification language was not fully clear and required interpretation as to how bundled bars should be treated. Making the requirements explicit eliminates the need for designer interpretation, and provides more consistent application of the specifications to columns with bundled bars. The SCOBS met in Omaha during May and adopted changes for publication in 2009. These additions and revisions will be reviewed and discussed in future articles. 2008 interim Changes Part 2 S ix agenda items related to concrete structures were adopted by the AASHTO Subcommittee on Bridges and Structures (SCOBS) in Wilmington, Delaware, in July 2007. Agenda Items 32 through 37 were developed by Technical Committee T-10, Concrete Design, over the past several years and moved to the full subcommittee ballot last year. The agenda items represent revisions and additions to the AASHTO LRFD Bridge Design Specifications or the AASHTO LRFD Bridge Construction Specifications and appeared as the 2008 Interim Revisions published earlier this year. Agenda items 32 through 34 were discussed in the Winter 2008 issue of ASPIRE.™ The other three 2007 concrete-structures agenda items are reviewed in this article. by Dr. Dennis R. Mertz Aspire_sum08.indb 52 6/24/08 1:49:14 PM

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