Aashto Lrfd Bridge Design Specifications 2020 Pdf
Sophie Reynolds
This publication provides guidelines for the maintenance actions to address fatigue cracking, as well as details at risk of constraint-induced fracture (CIF) in steel bridges. It is a synthesis of best practices from published literature, project reports, and past and on-going research projects, as well as input from industry professionals. Intended to be a practical reference text for a wide range of audiences, including maintenance contractors, asset managers, and design engineers, this publication provides detailed descriptions of the driving causes of fatigue cracking and CIF in steel bridges and accepted methods for repair or retrofit.
These guidelines offer guidance on bridge design for human-induced extreme events. It provides information on the response of concrete bridge columns subjected to blast loads, as well as blast-resistant design and detailing guidelines and analytical models of blast load distribution. The guidelines include discussion on how to potentially reduce risk of other structural bridge components (e.g., bridge towers, cable stays, suspender ropes), as well as other intentional hazards to consider for threat vulnerability risk assessments (nonexplosive cutting devices, collisions or impacts, and fire). This second edition includes additional resources for identifying potential solutions to mitigate risk from other intentional hazards. This 2022 2nd edition supersedes the first edition, published in 2011.
These guide specifications address the design of bridges subjected to light rail transit (LRT) loadings, or both LRT and conventional highway traffic loadings. This second edition provides additional definitions common to the rail industry and clarifies the application of live loading and derailment loading. It also revises language to improve consistency with the AASHTO LRFD Bridge Design Specifications, 9th Edition, with which they are designed to be used.
Recent years have seen devastating tsunami events in Asia, and the likelihood of such an event happening on the West Coast of North America is growing. The Guide Specifications for Bridges Subject to Tsunami Effects, 1st Edition, provides methods for estimating the risk posed by tsunamis in new bridge design, and identify accepted methodologies and details to mitigate that risk in design. With the introduction of these guide specifications, bridge designers now have a means to quantify forces associated with a tsunami event and a systematic method of applying these loads to bridge structures. For states with bridges exposed to tsunami hazard, the implementation of these guide specifications will result in more robust structures that are better able to survive a tsunami event and participate in the recovery of affected areas. These guide specifications were developed by the AASHTO Committee on Bridges and Structures, Technical Committee on Loads and Load Distribution.
This document is the introduction to the 2020 American Association of State Highway and Transportation Officials Load and Resistance Factor Design Bridge Design Specifications. It discusses the history of bridge design standards in the United States dating back to 1931. It notes that the current specifications needed to be updated to incorporate advances in engineering knowledge, new materials, and the load and resistance factor design philosophy which better accounts for variability in loads and structural resistance. The introduction provides background on different design philosophies including working stress design, load factor design, and load and resistance factor design.Read less
These guide specifications offer a description of the unique material properties of glass fiber reinforced polymer (GFRP) composite materials, as well as provisions for the design and construction of concrete bridge decks and railings reinforced with GFRP reinforcing bars. This revised edition includes information on the advancements in material specifications, and new knowledge and field experiences beyond bridge decks and traffic railings. Some of the major updates in this new edition include a title change from the 2009 first edition, AASHTO LRFD Bridge Design Guide Specification for GFRP-Reinforced Concrete Bridge Decks and Traffic Railings, to acknowledge the inclusion of information beyond bridge decks and traffic railings; greater consistency with the AASHTO LRFD Bridge Design Specifications, 8th Edition; consideration of flexural members, such as girders and bent caps, not included in first edition; consideration of substructure and foundation elements along with compression members; differentiation between the fatigue and creep limit states; and revised shear design methodology.
In 2020, the American Association of State Highway and Transportation Officials (AASHTO) Committee on Bridges and Structures (COBS) completed a project to investigate the use and effectiveness of the current AASHTO LRFD Bridge Construction Specifications (BCS). The project included a questionnaire to each state to determine the use of the document, a review of the document contents, the development of a prioritized approach for reorganizing and maintaining the document, and the development of prioritized recommendations for updating the document. The study concluded that the AASHTO LRFD BCS is being used by many state transportation agencies (STAs) on a regular basis, justifying future updates and maintenance. The study recommended (1) converting the document to a guide specification, (2) adding commentary similar to the AASHTO LRFD Bridge Design Specifications, and (3) updating existing content and adding new content as needed to be consistent with current industry standards and STA specifications. The study provided options for reorganizing the AASHTO LRFD BCS.Research is needed to develop recommendations for updating the bridge construction requirements to be considered by the AASHTO COBS in its next update to the AASHTO LRFD BCS.The objective of this research is to develop recommendations for effective bridge construction requirements that align with current bridge design and construction methods to provide clear expectations and minimize ambiguity.
The AASHTO Load Resistance Factor (LRFD) Bridge Design Specifications are intended for use in the design, evaluation, and rehabilitation of bridges, and are mandated by the Federal Highway Administration (FHWA) for use on all bridges using federal funding. The Technical Committee for Structural Steel Design (T14) recently passed changes to Section 6 (Steel Structures) of the document and the revised language will appear in the 8th revision to be published Fall 2017.
The revised language of Section 6 reflects the need within the industry to re-define the available surface condition classes and associated values for slip coefficients used to calculate the nominal slip resistance of a high-strength bolt in slip-critical connections.
Class definitions within the 11th paragraph of Article C6.13.2.8 were updated to revise the class for hot-dip galvanized faying surfaces, and include options for metallized faying surfaces and blast-cleaned surfaces coated with zinc-rich paints:
Eventually, specifications related to structural connections used in other industries may be similarly revised. Meanwhile, for the galvanizer involved in any federal highway and transportation projects, wire brushing of the HDG faying surface is no longer required. Doing so will only lead to increased cost, as industry research determined wire brushing does not increase slip properties.
For the FHWA/bridge customer, the revisions allow a greater variety of coating systems that can be used for the design of high-strength slip-critical connections. Specifically, it will become easier and cheaper for the specifier to select hot-dip galvanizing and metallizing for corrosion protection. Although the slip coefficient for hot-dip galvanized surfaces is reduced from 0.33 to 0.30 in this revision based on the results of industry research, it is anticipated the new value will have minimal impact on design. However, there is a potential for a small increase in the number of bolts used in connections with HDG fasteners. Regardless, customers will benefit from the removal of additional labor previously required to roughen HDG faying surfaces. For the new Class D surface condition, a slightly lower slip coefficient value is provided than for Class B, but the value will not cause a significant impact in the overall number of bolts required for most high-strength bolted connections. Therefore, the addition of Class D simply provides a greater variety of coating options to the specifier/designer, including the use of HDG surfaces with zinc-rich paints.
2024 American Galvanizers Association. The material provided herein has been developed to provide accurate and authoritative information about after-fabrication hot-dip galvanized steel. This material provides general information only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability. The information provided herein is not intended as a representation or warranty on the part of the AGA. Anyone making use of this information assumes all liability arising from such use.
- The objectives of this research are to (1) propose modification to the AASHTO LRFD Bridge Design Specifications related to loading requirements of the AASHTO Manual for Assessing Safety Hardware (MASH) for bridge deck overhang and (2) develop examples to demonstrate the application of the proposed modifications. The research includes analysis in LS-DYNA and surrogate vehicle impact tests on bridge deck overhangs supporting solid concrete parapets, concrete posts-on-deck, steel posts-on-deck, and steel posts-on-curbs.
- Historically, roadside safety features have been subjected to crashworthiness evaluations using a variety of impact test specifications and/or guidelines. The implementation of American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) has left state departments of transportation (DOTs) and manufacturers in a situation where a significant number of breakaway poles, sign supports, and work zone traffic control devices need to be evaluated for MASH compliance. The development of robust surrogate test vehicles, with an ability to largely capture vehicle deformation and penetrations as well as accurate system behavior, would reduce crash-testing costs and promote greater innovation for new products for manufacturers and DOTs. The objective of this research is to develop a guide for the implementation of surrogate test vehicles, including pendulums and bogie vehicles, for evaluation of Systems for MASH compliance and propose modifications to the AASHTO MASH for sign supports, breakaway poles, and work zone traffic control devices.
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