State Bridge Load Posting Processes and Practices (2014)

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54 DEFINITIONS, ABBREVIATIONS, AND ACRONYMS DEFINITIONS Allowable Stress Rating (ASR) [from (5)]—“A traditional specification to provide structural safety (in which) actual loadings are combined to produce a maximum stress in a member, which is not to exceed the allowable or working stress. The latter is found by taking the limiting stress of the material and applying an appropriate factor of safety.” Annual permit (overweight)—A routine overweight permit that is valid for a period of one year. Axle group—A set of consecutive axles that are compared with limits on load to determine whether vehicles conform to legal loads or to permittable overweight loads. Axle load—The total load on one axle. Base highway network [from (3)]—“The base highway net- work includes the through lane (mainline) portions of the NHS, rural/urban principal arterial system, and rural minor arterial system.” Blanket permit (overweight)—A routine overweight permit. Bridge [from (87)]—“A structure including supports erected over a depression or an obstruction, such as water, high- way, or railway, and having a track or passageway for car- rying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contigu- ous opening.” Note that this definition admits culverts. Complex bridge [from (87)]—“Movable, suspension, cable stayed, and other bridges with unusual characteristics.” Continuous trip permit (overweight)—A routine overweight permit. Critical finding [from (87)]—“A structural or safety related deficiency that requires immediate follow-up inspection or action.” Culvert [from (201)]—“A culvert is a structure designed hydraulically to take advantage of submergence to increase hydraulic capacity. Culverts, as distinguished from bridges, are usually covered with embankment and are composed of structural material around the entire perimeter, although some are supported on spread footings with the streambed serving as the bottom of the culvert. Culverts may qualify to be considered “bridge” length.” Deck [from (201)]—“The deck is that component of a bridge to which the live load is directly applied.” Design load rating vehicle—A numerical specification of a group of axles intended to produce load effects simi- lar to actual traffic that is used in design of bridges and culverts. Designated national network for trucks—A network of routes for large vehicles that includes interstate highways plus U.S. routes and state routes designated in USC Title 23 (35). Diagnostic load test—A controlled-load test of a structure to “confirm the precise nature of load distribution to the main load carrying members of a bridge and to the individual components of a multi-component member” (5). Exempt load—A class of vehicles defined by owner, use, or load, that is not subject to one or more statutory limits on weight. Exempt vehicle—see Exempt load. Extended permit (overweight)—A routine overweight permit. Federal Information Processing Standards (FIPS)—Standards for federal computer systems to support data security and system interoperability. FIPS codes that identify U.S. states are used in the national bridge inventory. Field Evaluation and Engineering Judgment (FE/EJ)— A method of load rating that combines field observed conditions of in-service bridges with knowledge of the traffic carried by bridges to determine whether bridges have adequate safe load capacity. FE/EJ is used for bridges that lack as-built plans and cannot be load rated by a compu- tational method. Fracture critical member (FCM) [from (87)]—“A steel mem- ber in tension, or with a tension element, whose failure would probably cause a portion of or the entire bridge to collapse.” Functionally obsolete [from (20)]—“Functional obsolescence is a function of the geometrics of the bridge in relation to the geometrics required by current design standards.” Gross vehicle weight (GVW)—The total weight of a vehicle plus its load. H15—A single-unit truck with GVW equal to 15 tons defined by AASHTO as a design live load for load factor design and allowable stress design of highway bridges (5). H20—A single-unit truck with GVW equal to 20 tons defined by AASHTO as a design live load for load factor design and allowable stress design of highway bridges (5). HS20—A tractor plus semi-trailer combination vehicle with GVW equal to 36 tons defined by AASHTO as a design live load for load factor design and allowable stress design of highway bridges (5). HL93—A design live load having simultaneous uniform lane load and loads from axle groups. The design live load defined by AASHTO for use in load and resistance factor design of bridges. Load and resistance factor rating (LRFR)—A basis for load rating that compares effects of factored loads to reduced failure capacities of bridge components. The basis pro- vides “a methodology for load rating a bridge consistent with the load and resistance factor design philosophy of the AASHTO LRFD Bridge Design Specifications” (5). Load zoned (Texas)—Limits on axle weight and GVW for some routes, usually county roads, to preserve pavements and structures that were designed for loads less than state legal loads (52).

55 Redundant bridge—In Maine statute, a bridge is redundant if the product of average daily traffic and detour length is less than 200 (83). Route segment—A portion of highway route designated by route number, starting milepost, and ending milepost. Routine inspection [from (87)]—“Regularly scheduled inspec- tion consisting of observations and/or measurements needed to determine the physical and functional condition of the bridge, to identify any changes from initial or previously recorded conditions, and to ensure that the structure con- tinues to satisfy present service requirements.” Also called safety inspection. Routine permit load [from (87)]—“A live load, which has a gross weight, axle weight, or distance between axles not conforming with state statutes for legally configured vehi- cles, authorized for unlimited trips over an extended period of time to move alongside other heavy vehicles on a regular basis.” Strategic Highway Network (STRAHNET)—A designated net- work of highways that link domestic U.S. military installa- tions and ports. Structurally deficient (SD)—[from (202)]—“Bridges are con- sidered structurally deficient if significant load-carrying elements are found to be in poor or worse condition due to deterioration and/or damage, or the adequacy of the water- way opening provided by the bridge is determined to be extremely insufficient to the point of causing intolerable traffic interruptions.” Substructure [from (202)]—“The substructure is that com- ponent of a bridge which includes all the elements which support the superstructure.” Superstructure [from (202)]—“The superstructure is that component of the bridge which supports the deck or rid- ing surface of the bridge, as well as the loads applied to the deck.” Survey—When capitalized, refers to the Survey used for NCHRP Project 20-05/Topic 44-15—State Bridge Load Posting Processes and Practices, distributed to U.S. state DOTs in year 2013. SU4—A legal load rating vehicle defined by AASHTO having four axles and GVW equal to 54 kips (5). SU5—A legal load rating vehicle defined by AASHTO hav- ing five axles and GVW equal to 62 kips (5). SU6—A legal load rating vehicle defined by AASHTO having six axles and GVW equal to 69.5 kips (5). SU7—A legal load rating vehicle defined by AASHTO hav- ing seven axles and GVW equal to 77.5 kips (5). Tandem axle—A pair of single axles with center-to-center spacing not more than 96 inches. Type 3—A legal load rating vehicle defined by AASHTO having three axles and GVW equal to 50 kips (5). Type 3S2—A legal load rating vehicle defined by AASHTO having five axles and GVW equal to 72 kips (5). Type 3-3—A legal load rating vehicle defined by AASHTO having six axles and GVW equal to 80 kips (5). Weight-restricted bridge—A bridge that is open to legal loads, but not open to overweight permit loads. Legal load [from (87)] “The maximum legal load for each vehicle configuration permitted by law for the state in which the bridge is located.” Legal load rating vehicle—A rating vehicle intended to impose load effects similar to actual traffic on bridges and cul- verts. AASHTO legal load rating vehicles include Type 3, Type 3S2, Type 3-3, a notional rating load and the single- unit special hauling vehicles SU4, SU5, SU6, and SU7. Load factor rating (LFD) [from (5)]—(a load rating method) “based on analyzing a structure subject to multiples of the actual loads (factored loads). Different factors are applied to each type of load, which reflect the uncertainty inher- ent in the load calculations. The rating is determined such that the effect of the factored loads does not exceed the strength of the member.” Load rating [from (87)]—“The determination of the live load carrying capacity of a bridge using bridge plans and supple- mented by information gathered from a field inspection.” Low volume road—Roads with average daily traffic fewer than 400 vehicles. National Bridge Inspection Standards—United States Code Title 23 Part 650 Subpart C (35)—Federal regulation for the execution and reporting of periodic safety inspec- tions of bridges and culverts on public roads in the United States. National Highway System [from (4)]—“The National High- way System shall consist of interconnected urban and rural principal arterials and highways (including toll facilities) which serve major population centers, international border crossings, ports, airports, public transportation facilities, other intermodal transportation facilities, and other major travel destinations; meet national defense requirements; and serve interstate and interregional travel. All routes on the Interstate System are a part of the National Highway System.” Notional rating load—A legal load rating vehicle, defined by AASHTO, having eight axles and GVW equal to 80,000 pounds. Off-system bridges—Bridges carrying routes that are not part of the National Highway System (3). On-system bridges—Bridges carrying routes that are part of the National Highway System (3). Operating rating [from (87)]—“The maximum permissible live load to which the structure may be subjected for the load configuration used in the rating.” Overweight load rating vehicle—A rating vehicle having GVW, axle weights, and axle spacings that produce load effects similar to an overweight permit vehicle. Proof load test—A direct demonstration of load capacity of a structure for a maximum “proof” level. When used in load rating, the safe load capacity is set to a value less than the proof load. Rating vehicle—A numerical specification of an axle group defined by axle count, axle spacings, and axle weights used in load rating computations for bridges and culverts. Rating vehicles are specified for design live loads, legal live loads, and overweight live loads.

56 ABBREVIATIONS AND ACRONYMS ASD Allowable stress design ASR Allowable stress rating C-1 Caution crossing sign type 1 (New Hampshire) C-2 Caution crossing sign type 2 (New Hampshire) C-3 Caution crossing sign type 3 (New Hampshire) DOT Department of transportation E-1 Excluded crossing sign type 1 (New Hampshire) E-2 Excluded crossing sign type 2 (New Hampshire) FE/EJ Field evaluation and engineering judgment FIPS Federal information processing standards GCR General condition rating GVW Gross vehicle weight HIS Highway information system (Wisconsin) L The length in feet between the first axle and last axle of a vehicle or group of consecutive axles, used in a bridge formula to compute limits on loads LCV Longer combination vehicle LFD Load factor design LFR Load factor rating LRFD Load and resistance factor design LRFR Load and resistance factor rating MAP-21 Informal name for Moving Ahead for Progress in the 21st Century Act, Public Law 112–141 112th Congress MBE Manual of Bridge Evaluation N The count of axles for a vehicle or group of consecutive axles, usually used in a bridge formula to compute limits on loads NBI National bridge inventory NBIS National Bridge Inspection Standards NHS National Highway System PIR Physical inspection rating (Minnesota) RF Rating factor QA Quality assurance QC Quality control SCOBS AASHTO’s Subcommittee on Bridges and Structures STRAHNET Strategic highway network U.S.DOT United States Department of Transportation W Limit on gross weight of a vehicle or group of consecutive axles from a bridge formula WIM Weigh-in-motion