These are just a few explanations of some of the technical terms used by civil and mechanical engineers.

ABUTMENT – A substructure element supporting each end of a single span or the extreme ends of a multi-span superstructure and, in general, retaining or supporting the approach embankment.

AASHTO (American Association of State Highway and Transportation Officials) – A standards setting body which publishes specifications, test protocols and guidelines used in highway design and construction throughout the U.S. AASHTO advocates transportation-related policies and provides technical services to support states in their efforts to efficiently and safely move people and goods. Although most of its activities are specific to highways, it also represents air, rail, water and public transportation.

APPROACH SPAN – The span or spans connecting the abutment with the main span or spans.

BEAM – A linear structural member designed to span from one support to another.

BENT – A substructure unit supporting each end of a bridge span; also called a pier; made up of two or more columns or column-like members connected at their top most ends by a cap, strut, or other member holding them in their correct positions.

CAST-IN-PLACE – Concrete poured within form work on site to create a structural element in its final position.

CATWALKS – Temporary foot bridges, used by bridge workers to spin the main cables (several feet above each catwalk), and to attach the suspender cables that connect the main cables to the deck.

CHORD – A horizontal member of a truss.

COFFERDAM – A temporary structure designed to keep water and/or soil out of an excavation in which a bridge pier or other structure is to be built. It provides a safe environment in which to work and allows excavation and construction of structures in an otherwise poor environment. Materials used to construct cofferdams can typically be reused on other projects

CONTRACT SPECIFICATIONS – The requirements which are to be followed in the construction of the highway. The standard specifications, supplemental specifications, special provisions, and all written or printed agreements and instructions that pertain to the method and manner of performing the work, or to the quantity and quality of the material to be furnished under the contract.

DEAD LOAD – A static load due to the weight of the structure itself.

DECK – The roadway portion of a bridge that directly supports vehicular and pedestrian traffic.

DECK BRIDGE – A bridge in which the supporting members are all beneath the roadway.

DECK TRUSS – A bridge whose roadway is supported from beneath by a truss.

DIAGONAL – A sloping structural member of a truss or bracing system.

EXPANSION JOINT – A joint designed to provide means for expansion and contraction movements produced by temperature changes, load, or other forces.

FATIGUE – Cause of structural deficiencies, usually due to repetitive loading over time.

GUSSET PLATE – Thick sheets of steel that are used to connect beams and girders to columns or to connect truss members. A gusset plate can be fastened to a permanent member either by bolts, rivets or welding or a combination of the three. Gusset plates not only serve as a method of joining steel members together but they also strengthen the joint.

JOINT – In masonry, the space between individual stone; in concrete, a division in continuity of the concrete; in a truss, the point at which members of a truss frame are joined.

LIVE LOAD – Vehicular traffic, wind, water, and/or earthquakes.

LOWER CHORD – The bottom horizontal member of a truss.

MAIN BEAM – A beam supporting the spans and bearing directly onto a column or wall.

MEMBER – An individual angle, beam, plate, or built piece intended to become an integral part of an assembled frame or structure.

PIER – A vertical support or substructure unit that supports the spans of a multi-span superstructure at an intermediate location between its abutments.

PILE – A vertical shaft driven into the ground that carries loads through weak layers of soil to those capable of supporting such loads.

PLATE GIRDER – A large, solid web plate with flange plates attached to the web plate by flange angles or fillet welds, typically fabricated from steel.

PORTAL – The clear, unobstructed space of a bridge forming the entrance to the structure.

RAMP – A connecting roadway between two intersecting roads.

REINFORCED CONCRETE – Concrete with steel reinforcing bars bonded within it to supply increased tensile strength and durability.

RESONANCE – The regular vibration of an object as it responds in step (at the same frequency) with an external force.

RIGID FRAME BRIDGE – A bridge with moment-resistant connections between the superstructure and the substructure to produce an integral, elastic structure.

RIGHT-OF-WAY – Land acquired by purchase, gift, or eminent domain in order to build and maintain a public road or to install another public utility.

RIVETED CONNECTION – A rigid connection of metal bridge members that is assembled with rivets. Riveted connections increase the strength of the structure.

SHAFT – A vertical load bearing structure that uses end bearing and friction to support loads.

SPAN – The distance between piers, towers, or abutments.

STEEL – A very hard and strong alloy of iron and carbon.

STRINGER – A longitudinal beam supporting the bridge deck.

SUBSTRUCTURE – The parts of a bridge that are below the bottom of the girders. Pilings, shafts, spread footings, and columns may be part of the substructure.

SUPERSTRUCTURE – The parts of a bridge that are above the bottom of the girders. Girders, bridge deck, and bridge railing are parts of the superstructure.

TENSION – A force that pulls or stretches.

TIE – A member carrying tension.

TORSION – A twisting force or action.

TRUSS – A rigid, jointed structure made up of individual straight pieces arranged and connected, usually in a triangular pattern, so as to support longer spans.

TRUSS BRIDGE – A bridge having a pair of trusses for the superstructure.

UPPER CHORD – The top longitudinal member of a truss.