Damping For floor vibrations, it is the rate of decay of amplitude. Dead Load Loads due to the weight of the components making up the structure and that are intended to remain permanently in place. Deck A floor or roof covering made out of gage metal attached by welding or mechanical means to joists, beams, purlins, or other structural members and can be galvanized, painted, or unpainted. Deck Type The specific type of deck to be specified, such as Type B Wide Rib, Type F Intermediate, Type N Deep Rib, Type A Narrow Rib, Composite, Cellular, etc. Deflection The displacement of a structural member or system under load. Deformation The act of distorting or changing the shape or dimensions of a structural element or body resulting from forces or stresses. Depth of Joist The out-to-out distance from the top of the top chord to the bottom of the bottom chord taken a some reference location, usually at the midspan of the joist or joist girder. Design Documents The plans, details, sections, specifications, etc. prepared by the building designer. Design Length The span of a joist or joist girder in feet minus 0.3333 feet. Design Loads The loads specified in the contract drawings or specifications which a building is to be designed for. Design Strength The resistance provided by a structure, member, or connection to the forces imposed on it. Diagonal Bracing Structural members which are inclined and are usually carrying axial load which enable a structural frame to behave as a truss to resist horizontal loads. Diagonal Bridging Two angles or other structural shapes connected from the top chord of one joist to the bottom chord of the next joist to form an X shape whose l/r ratio cannot exceed 200. The bridging members are almost always connected at their point of intersection. Diaphragm Roof panel or decking, metal wall, or floor slab which provides a larger in-plane shear stiffness and strength adequate to transmit horizontal forces to the resisting structural system. Diaphragm Action The resistance to a racking affect or in-plane shear forces offered by roof deck, panels, or other structural members when properly attached to a structural frame. Double Curvature When end moments on a structural member produce a bending effect which cause the member to form an S shape or has a reversal in curvature. Downstanding Leg The leg of a structural angle which is projecting down from you when viewing. Drift The lateral movement or deflection of a structure. Drift Index The ratio of the lateral deflection to the height of the building. Drift Pin A tapered pin used during the erection process to align holes in steel members which are to be connected by bolting. Duct Any tube, pipe or other conduit by which air or fluid is transfered. Duct Opening The round or square opening required through the web system of a joist or joist girder to allow passage of a duct. Ductility Is the ability of a material to withstand large inelastic deformations without fracture. Structural steel has considerable ductility. Ductility Factor The ratio of the total deformation at maximum load to the elastic-limit deformation. Dynamic Load A load that varies with time which includes repeative loads, seismic loads, and other loads created by rapid movement.
Posted on: Mon, 02 Dec 2013 17:19:36 +0000