BRIDGE TERMS - D |
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dead
load |
dead load - a static load due to the weight of the structure itself debris - any material including floating wood trash, suspended sediment, or bed load, moved by a flowing stream deck - that portion of a bridge which provides direct support for vehicular and pedestrian traffic deck bridge - a bridge in which the supporting members are all beneath the roadway decking - a term specifically applied to bridges having wooden floors and used to designate the flooring only; it does not include the members serving to support the flooring deficiency - see BRIDGE DEFICIENCY deflection - elastic movement of a structural member under a load deformation - distortion of a loaded structural member; includes plastic, non-recoverable movement deformed bars - concrete reinforcement consisting of steel bars with projections or indentations to increase the mechanical bond between the steel and concrete degradation - general progressive lowering of the channel stream bed by erosion delamination - subsurface separation of concrete into layers design load - the force for which a structure is designed; the worst possible combination of loads deterioration - decline in quality over a period of time due to chemical or physical action of the environment diagonal - a sloping structural member of a truss or bracing system diagonal stay - a cable support in a suspension bridge extending diagonally from the tower to the roadway system to add stiffness to the structure and diminish the deformations and undulations resulting from traffic service diagonal tension - the principal tensile force due to horizontal and vertical shear in a beam diaphragm - a member placed within a member or superstructure system to distribute stresses and improve strength and rigidity; see BRACING diaphragm wall - a wall built transversely to the longitudinal centerline of a spandrel arch serving to tie together and reinforce the spandrel walls, together with providing a support for the floor system in conjunction with the spandrel walls; also known as cross wall differential settlement - uneven settlement of individual or independent elements of a substructure dike - an earthen embankment constructed to retain floodwater; when used in conjunction with a bridge, it prevents stream erosion and localized scour and/or so directs the stream current such that debris does not accumulate; also known as dyke; see SPUR DIKE discharge - the volume of fluid per unit of time flowing along a pipe or channel displacement induced stress - stresses caused by differential deflection of adjacent parts distributed load - a load uniformly applied along the length of an element or component of a bridge ditch - a trough-like excavation made to collect water diver - a specially trained individual who inspects the underwater portion of a bridge substructure and the surrounding channel dolphin - a group of piles driven close together and placed to protect portions of a bridge exposed to possible damage by collision with river or marine traffic double movable bridge - a bridge in which the clear span for navigation is produced by joining the arms of two adjacent swing spans or the leaves of two adjacent bascule spans at or near the center of the navigable channel; see MOVABLE BRIDGE dowel - a short length of bar embedded in two parts of a structure to hold the parts in place and to transfer stress drainage - a system designed to remove water from a structure drainage area - an area in which surface run-off collects and from which it is carried by a drainage system; also known as catchment area drain hole - hole in a box shaped member or a wall to provide means for the exit of accumulated water or other liquid matter; also known as drip hole; see WEEP HOLE drain pipes - pipes below the ground that remove rainwater drawbridge - a general term applied to a bridge over a navigable body of water having a movable superstructure span of any type permitting the channel to be freed of its obstruction to navigation; popular but imprecise term drift bolt - a short length of metal bar used to connect and hold in position wooden members placed in contact; similar to a dowel drip notch - a recess cast on the underside of a parapet which prevents water from following the concrete into the supporting beams and causing deterioration of the members drop inlet - a type of inlet structure which conveys the water from a higher elevation to a lower outlet elevation smoothly without a free fall at the discharge ductile - capable of being molded or shaped without breaking; plastic ductile fracture - a fracture characterized by plastic deformation ductility - the ability to withstand non-elastic deformation without rupture dumbbell pier - a pier consisting of two cylindrical or rectangular shaped piers joined by a web constructed integral with them |
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