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The American Association of State Highway and Transportation Officials recently published the third edition of its “LRFD Movable Highway Bridge Design Specifications” guide. To order a copy, visit the online AASHTO Store online and search by the publication’s Item Code – LRFDMOV-3 – or click here for a direct link to the publication’s web page on the AASHTO Store site.
AASHTO Issues LRFD Movable Highway Bridge Spec Guide
Cast-in-place and post-installed anchors have been used extensively on road and bridge projects for many years. ACI 318 has had LRFD provisions for anchor designs since 2002, and now AASHTO also has incorporated these design provisions into the revamped Article 5.13 of the reorganized Section 5 of the AASHTO LRFD Bridge Design Specifications, 8th Edition. Except for the adjustment to the sustained load-reduction factor from 0.55 to 0.50, Article 5.13 is a copy of Chapter 17 which aligns these two reference codes.
Controlling breakout
The specifications in this third edition of the guide – which covers several types of movable bridges, including bascule, swing, and vertical lift – supersedes the previous 2007 second edition and its subsequent interim revisions. The other major revision to Section 5 is the new article 13 which deals with the design of cast-in-place and post-installed anchors in concrete. Prior to the 8th Edition, the LRFD Bridge Design Specifications have not contained provisions on how to design anchor connections to concrete, regardless if this was a cast-in-place or post-installed anchor. The American Association of State Highway and Transportation Officials (AASHTO) welcomes the republication in whole or in part of any original content from The AASHTO Journal with proper attribution to the association and publication. This includes a link to direct visitors to the AASHTO Journal website. The server is temporarily unable to service yourrequest due to maintenance downtime or capacityproblems.
AASHTO LRFD Bridge Design Specifications (9th Edition)
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In addition, they will review the manufacturing quality control for the anchor products to make sure that any product that has been evaluated will perform to the load level that has been published in their evaluation report. Engineers and building officials working on projects following the AASHTO regulations should become familiar with these evaluation service bodies and the product evaluation reports. ACI 318 Building Code Requirements for Structural Concrete have included provisions for designing cast-in and post-installed undercut and expansion anchors in concrete since the 2002 edition, and included post-installed adhesive anchors in 2011. From 2002 to 2011 the design provisions were contained in Appendix D - Anchoring to Concrete. In the 2014 edition of ACI 318, Appendix D became a full section and moved to Chapter 17 as part of the ACI 318 reorganization. Condition assessment and safety verification of existing bridges and decisions as to whether posting is required currently are addressed through analysis, load testing, or a combination of methods.
Bridge rating through structural analysis is by far the most common procedure for rating existing bridges. Load testing may be indicated when analysis produces an unsatisfactory result or when the analysis cannot be completed due to lack of design documentation, information, or the presence of deterioration. Gamache is manager of approvals and project engineering / anchors for Hilti North America. He is responsible for creating the technical data for the Hilti North American Product Technical Guide, Vol. 2, for Anchor Fastening, and publishing external evaluation reports such as ICC-ES ESR’s.
Third-party evaluation services such as ICC-ES and IAPMO UES are publishing technical data based on ACI 355 test criteria, and most post-installed anchor manufacturers will provide software for their products with the data taken directly from the evaluation reports. Since ACI 318 anchor designs have been around for many years and since engineers may have already been exposed to these LRFD design provisions, it will hopefully be a smooth transition for anchor designs under the new Article 5.13 of the reorganized Section 5 of the AASHTO LRFD Bridge Design Specifications, 8th Edition. Cast-in-place and post-installed anchor systems have been used extensively in highway construction projects for many years for applications such as bridge girder connections, seismic retro-fit and strengthening, precast concrete member attachments, and attachments of light poles, signs, guard rails, and pedestrian fencing. Since there were no design provisions in the LRFD Bridge Design Specifications, engineers would use design provisions from other sources such as the Portland Cement Association (PCA) design handbook for cast-in-place anchors or from manufacturer’s product technical data in the case of post-installed anchors. And since 2002, some engineers working on road and bridge projects migrated over to ACI 318 Appendix D which provided design procedures for cast-in-place anchors and some post-installed anchor systems. Both above evaluation service companies will review the test data from an independent, accredited test facility, and will issue the technical data that is in conformance with the ACI 355 test programs.
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