abutment

The end support of a bridge, retaining the approach fill.

anchorage

The mass or rock socket that holds a suspension bridge's main cable; also the device that grips a prestressing tendon.

arch

A curved member carrying load in compression and thrusting outward at its ends.

balanced cantilever (FCM)

Building a girder outward from a pier in segments on both sides at once.

bascule

A movable bridge that tilts upward about a horizontal axis.

bearing

The device between superstructure and substructure that transfers load and allows rotation and movement.

box girder

A hollow closed-section girder, stiff in torsion.

camber

Upward curvature built into a member to offset deflection.

cantilever

A member supported at one end only.

cable-stayed

A bridge whose deck is supported by straight cables from towers.

composite

Steel and concrete acting as one section through shear connectors.

creep

Slow deformation of concrete under sustained load.

DC / DW

AASHTO dead loads of components and of wearing surface/utilities.

deck

The riding surface slab of a bridge.

development length

Embedment needed for a bar to develop its strength by bond.

distribution factor

Fraction of a lane load carried by one girder.

extradosed

A prestressed girder bridge with stays from low pylons acting as external tendons.

falsework

Temporary structure supporting a bridge during construction.

fatigue

Cracking from repeated stress cycles below yield.

form traveller

The moving formwork that casts balanced-cantilever segments.

fracture-critical (NSTM)

A steel tension member whose failure would cause collapse.

girder

A main longitudinal load-carrying beam.

hanger

A vertical tension member from a cable or arch to the deck.

HL-93

AASHTO's notional live-load model: design truck or tandem plus lane load.

incremental launching (ILM)

Casting a deck in a yard and pushing it out over the piers.

integral abutment

An abutment cast monolithically with the superstructure, with no joint or bearing.

limit state

A condition beyond which the structure no longer meets a design requirement.

load rating

Assessment of the live load an existing bridge can carry.

LRFD

Load and Resistance Factor Design.

main cable

The draped cable of a suspension bridge.

match casting

Casting each precast segment against its neighbour so joints fit.

MSS

Movable scaffolding system: self-launching span-by-span falsework.

orthotropic deck

A steel deck plate stiffened by ribs, acting with the girders.

pier

An intermediate support.

pile

A slender foundation element driven or bored into the ground.

post-tensioning

Prestressing applied after the concrete hardens, through ducts.

pretensioning

Prestressing applied before casting, against abutments in a bed.

prestress loss

Reduction of prestress from elastic shortening, creep, shrinkage, relaxation, friction and anchorage set.

pylon / tower

The vertical support of a cable-supported bridge.

reliability index β

A measure of the probability that a limit state is not exceeded; ~3.5 in AASHTO strength calibration.

scour

Erosion of the bed around foundations by flowing water.

segmental

A bridge built from precast or cast-in-place segments joined by prestressing.

shrinkage

Volume loss of concrete as it dries.

span

Distance between adjacent supports.

spandrel

The zone between an arch rib and the deck.

stay

A straight cable of a cable-stayed bridge.

stiffening girder

The deck girder of a suspension bridge that distributes load and resists deformation.

strand

A seven-wire prestressing element, usually 12.7 or 15.2 mm.

strip seal / modular joint

Expansion joint types for moderate and large movements.

substructure

Piers and abutments.

superstructure

Everything above the bearings.

tendon

A group of strands or bars acting as one prestressing unit.

tied arch

An arch whose thrust is resisted by a tie member in the deck.

truss

A framework of members in triangles carrying axial force.

voussoir

A wedge-shaped stone of a masonry arch.

weathering steel

Steel that forms a protective rust patina, needing no paint in suitable exposures.

The standards this book leans on, with their roles. Official homes are linked from the Reference library.

• AASHTO LRFD Bridge Design Specifications: 10th edition (2024), loads, limit states, materials, and design of every component. The primary reference for Chapters 4–9.
• AASHTO Manual for Bridge Evaluation (MBE), inspection, condition rating, load rating (Chapter 10).
• AASHTO Guide Specifications for seismic design, vessel collision, and temporary works.
• FHWA HEC-18 / HEC-20 / HEC-23, scour evaluation, stream stability, countermeasures.
• NBIS (23 CFR 650) and the FHWA Bridge Inspector's Reference Manual.
• ACI 318-19, concrete design where AASHTO defers to it (foundation and ancillary elements).
• Eurocodes EN 1990, EN 1991-2, EN 1992-2, EN 1993-2, EN 1994-2 with national annexes.
• IRC:6, IRC:112 (India), NZTA Bridge Manual, Abu Dhabi DMT TR-516 / TR-511, KDS 24 (Korea), JRA Specifications for Highway Bridges (Japan).
• PTI / ASBI guides for post-tensioning and segmental construction; fib Model Code and bulletins for cable and concrete durability.

Historical facts in Chapter 2 follow the standard histories of bridge engineering and the published records of the bridges named; span records in Chapter 11 are cross-checked against the site's Rankings data, which is verified against published sources. Where this book gives a number, it names the standard it came from; where it gives an opinion, it is the author's.

How to read a standard: the specification clause states the rule, the commentary alongside it explains the reason and the calibration, and the referenced research reports (NCHRP for AASHTO) hold the data. When two codes disagree, the commentary usually shows why.