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| GLOSSARY Anchorages: Devices at either end of a prestressed concrete beam that hold the prestressing steel tension elements (bars or wires). Also, the massive concrete blocks at the end of a suspension bridge that resist the inward pull of the bridge cables. Beam: A horizontal member, usually of constant depth, that carries a vertical load by bending. Bending moments: Internal forces on a structural element that cause the element to bend and thus create internal compression on one side of the element and internal tension on the other. Cable-stayed bridge: A form defined by a deck supported by diagonal stays that emanate from a tower. Concrete: Artificial stone made by mixing crushed stone or gravel, sand, cement, and water and allowing the cement to react chemically with the water to bind the mix into a solid. Deck: On a bridge, the horizontal structure consisting of a roadway slab (or deck slab), deck beams, and spandrel walls (when they are above the roadway). Deck-stiffened arch: An arch connected by vertical elements to a deck beam (or spandrel beam) that stiffens the arch in such a way that the arch carries almost no bending moments and can therefore be thin. Deflections: Changes in shape due to live loads. Formwork: The structure (usually wooden) into which fluid concrete is cast and allowed to harden. Graphic statics: A method of analyzing a structure by visual diagrams rather than algebraic formulas. Hinge: In concrete structures, a point where the element is purposely reduced in size to such an extent that it is free or nearly free to rotate at that point. In some cases, an actual steel hinge is embedded in the concrete; in other cases, the hinge may be made by creating a plane of weakness in the concrete. Hollow box: A structural element (beam, column, or arch) made up of a combination of vertical and horizontal walls that together carry the loads. The walls are usually thin and leave a substantial open space within. In a hollow-box arch, the top wall can be the roadway, and the bottom wall can be an arched slab, while the side walls connect the top and bottom elements. Loads: Weight of the bridge (dead load) plus additional weight (live load) such as traffic. Pier: The support of a bridge below the roadway. Pneumatic form: A concrete roof shape defined by inflating a bladder that gives a form defined by pressure loading, i.e., loading perpendicular everywhere to the surface. Prestressed concrete: A method of construction whereby compression forces are applied to concrete elements (usually by steel bars or wires under high tension, anchored at either end of the element) with the goal of counteracting the tension that would otherwise occur due to loads. Pylon: The tower above a bridge deck that usually carries cable stays. Reinforced concrete: Steel bars embedded in concrete and designed to take the tension that occurs on account of loads. Span: The length of a horizontal element measured horizontally between its two end supports. Stiffened suspension bridge: A suspension bridge with a stiff horizontal deck. Suspension bridge: Usually defined as a bridge where the deck load is carried vertically (or mostly vertically) by suspenders up to cables that transfer the loads by nearly horizontal forces to towers and then over them to side spans ending in heavy concrete anchorages. Thin-shell concrete structure: A curved concrete surface whose thickness is small in relation to its length and width. Three-hinged arch: A curved structure with hinges usually at each abutment and at the crown. Truss:
A structure composed of a usually horizontal top element and a usually
horizontal bottom element, the two connected by vertical and diagonal
elements to create a beamlike form. GLOSSARY
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