AISC LRFD 1.pdf

xxviiiGLOSSARYas determined by computations using specified material strengths and dimensions andformulas derived from accepted principles of structural mechanics or by field tests orlaboratory tests of scaled models, allowing for modeling effects and differencesbetween laboratory and field conditionsNoncompact section. Noncompact sections can develop the yield stress in compressionelements before local buckling occurs, but will not resist inelastic local buckling atstrain levels required for a fully plastic stress distributionP-Delta effect. Secondary effect of column axial loads and lateral deflection on themoments in membersPanel zone. The zone in a beam-to-column connection that transmits moment by a shearpanelPartially composite beam. A composite beam for which the shear strength of shear connectorsgoverns the flexural strengthPlane frame. A structural system assumed for the purpose of analysis and design to betwo-dimensionalPlastic analysis. Determination of load effects (force, moment, stress, as appropriate) onmembers and connections based on the assumption of rigid-plastic behavior, i.e., thatequilibrium is satisfied throughout the structure and yield is not exceeded anywhere.Second order effects may need to be consideredPlastic design section. The cross section of a member which can maintain a full plasticmoment through large rotations so that a mechanism can develop; the section suitablefor design by plastic analysisPlastic hinge. A yielded zone which forms in a structural member when the plasticmoment is attained. The beam is assumed to rotate as if hinged, except that it isrestrained by the plastic moment M pPlastic-limit load. The maximum load that is attained when a sufficient number of yieldzones have formed to permit the structure to deform plastically without further increasein load. It is the largest load a structure will support, when perfect plasticity is assumedand when such factors as instability, second-order effects, strain hardening, and fractureare neglectedPlastic mechanism. See MechanismPlastic modulus. The section modulus of resistance to bending of a completely yieldedcross section. It is the combined static moment about the plastic neutral axis of thecross-sectional areas above and below that axisPlastic moment. The resisting moment of a fully-yielded cross sectionPlastic strain. The difference between total strain and elastic strainPlastic zone. The yielded region of a memberPlastification. The process of successive yielding of fibers in the cross section of a memberas bending moment is increasedPlate girder. A built-up structural beamLRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION