OBC Building Structural key terms

A design approach that verifies a structure will not become unfit for use, checking both safety under extreme loads and serviceability under normal loads using factored loads and resistances.

A condition involving collapse, loss of equilibrium, or structural failure that threatens safety of occupants, checked using factored load effects against factored resistance.

A condition limiting normal use, such as excessive deflection, vibration, or cracking, checked with unfactored service loads against specified performance criteria.

A multiplier applied to nominal loads to account for variability and uncertainty, producing factored load effects for comparison with factored resistance in limit states design.

A multiplier less than one applied to nominal material resistance to account for variability in material strength, dimensions, and workmanship in limit states design.

A prescribed arrangement of simultaneous loads, each with its own factor, used to determine the most unfavorable effect on a member or structure.

The nominal or unfactored load value given in a building code, representing the expected maximum load for a defined return period or occupancy condition.

The permanent, gravity load from the self-weight of structural members, finishes, partitions, and fixed service equipment that remains essentially constant over the structure's life.

The portion of dead load from non-structural items such as floor finishes, ceilings, partitions, and mechanical systems, added to member self-weight in design calculations.

A variable gravity load produced by occupancy and use, including people, furniture, and movable equipment, assigned by occupancy category in the building code.

A permitted decrease in design live load for members supporting large tributary areas, reflecting the low probability that the full design load covers the entire area simultaneously.

The portion of floor or roof area whose loads are assumed carried by a particular member, determined by the geometry of surrounding framing and support conditions.

The snow load on the ground at a site for a specified return period, used with exposure, thermal, and shape factors to derive roof snow load.

The design snow load on a roof surface, derived from ground snow load adjusted for exposure, thermal conditions, importance, and roof slope and geometry.

Additional snow accumulation on a roof caused by snow sliding from a higher roof or being trapped by a parapet, adjacent building, or other obstruction.

A reference pressure derived from basic wind speed and air density, used with exposure, gust, topographic, and pressure coefficients to compute design wind pressures.

The dynamic pressure of wind at a specified height, accounting for terrain exposure, gust effects, and topography, used to calculate design pressures on building surfaces.

A coefficient accounting for the dynamic amplification of wind pressure from turbulence and structural flexibility, applied in wind load calculations for buildings and structures.

The total design lateral force at the base of a structure due to earthquake, computed from seismic weight, a response coefficient, and a structural behavior factor.

The portion of total dead load plus specified fractions of other loads used in earthquake analysis to represent the effective mass resisting ground motion.

The ability of a structure or member to undergo large inelastic deformation without losing strength, allowing energy dissipation during strong earthquakes.

The condition in which the sum of forces and moments acting on a structure or free body equals zero, forming the basis for determining reactions and internal forces.

A sketch isolating a structural element or joint showing all applied loads and support reactions, used to apply equilibrium equations and solve for unknown forces.

A structure whose support reactions and internal forces can be found entirely from equilibrium equations, without needing compatibility of deformations.

A structure with more unknown reactions than equilibrium equations, requiring compatibility and deformation relationships in addition to statics for analysis.

A successive-approximation technique for analyzing indeterminate frames and continuous beams by distributing unbalanced fixed-end moments among connected members according to their stiffness.

A diagram showing how a particular response quantity, such as a reaction or bending moment, varies as a unit load moves across the structure.

The maximum pressure a soil or rock can sustain beneath a foundation without shear failure or excessive settlement, used to size footings and determine allowable soil pressure.

The downward movement of a foundation or structure caused by compression of underlying soil, which must be limited to prevent damage to the structure and its finishes.

Unequal settlement between different parts of a foundation, which induces distortion, cracking, and additional internal forces in the supported structure.

The horizontal pressure exerted by retained soil on a wall, varying with soil properties, wall movement, drainage, and whether conditions are at-rest, active, or passive.

The ratio of tension steel area to the effective concrete area of a section, governing flexural behavior and ductility of reinforced concrete members.

A reinforced concrete cross section in which concrete crushing and steel yielding occur simultaneously, defining a reference condition for ductility requirements.

The minimum embedment length required to transfer bar force to concrete through bond, ensuring reinforcement can reach its yield strength without pulling out.

A connection in which two reinforcing bars overlap over a specified length so force transfers through bond between the bars and surrounding concrete.

The compressive strength of a masonry assemblage of units and mortar, determined by prism testing and used as the basis for design compressive resistance.

A cementitious mixture placed in masonry cells and collar joints to bond units, fill voids, and embed reinforcement in reinforced masonry construction.

A measure of a compression member's susceptibility to buckling, relating its effective length to its least radius of gyration or, for walls, its thickness.

Sudden lateral instability of a compression member or plate when applied load reaches a critical value dependent on stiffness, length, and end restraint.

A failure mode of slender steel beams in which the compression flange buckles sideways while the section twists, reducing the beam's bending resistance.

A design stress for lumber obtained by applying modification factors for moisture, duration of load, size, and other conditions to a reference strength value.

A modification factor increasing allowable wood stress for short-duration loads, reflecting the time-dependent strength of wood under sustained versus brief loading.

A manufactured structural wood composite such as glued-laminated timber, laminated veneer lumber, or plywood, with properties controlled by the manufacturer.

A bolt installed with controlled tension to clamp connected plies, transferring load by friction or bearing and used in structural steel connections.

A bolted connection designed so that friction between clamped plies prevents slip under service loads, required where joint slip would be unacceptable.

The period, in minutes or hours, a building assembly resists fire exposure under standardized testing, used to satisfy code separation and structural protection requirements.

A thin applied coating that swells into an insulating char when heated, protecting steel members and raising their fire resistance without bulky encasement.