Structural terms

ACCESS FLOOR SYSTEM

is an assembly consisting of panels mounted on pedestals to provide an under-floor space for the installation of mechanical, electrical, communication or similar systems or to serve as an air-supply or return-air plenum.

AGRICULTURAL BUILDING

is a structure designed and constructed to house farm implements, hay, grain, poultry, livestock or other horticultural products. The structure shall not be a place of human habitation or a place of employment where agricultural products are processed, treated, or packaged, nor shall it be a place used by the public.

ALLOWABLE STRESS DESIGN (ASD)

is a method of proportioning and designing structural members such that elastically computed stresses produced in the members by nominal loads do not exceed specified allowable stresses (also called working stress design).

ASSEMBLY BUILDING

is a building or portion of a building for the gathering together of 50 or more persons for such purposes as deliberation, education, instruction, worship, entertainment, amusement, drinking or dining, or awaiting transportation.

AWNING

is an architectural projection that provides weather protection, identity, or decoration and is wholly supported by the building to which it is attached.

BALCONY, EXTERIOR

is an exterior floor system projecting from and supported by a structure without additional independent supports.

BASE

is the level at which the earthquake motions are considered to be imparted to the structure or the level at which the structure, as a dynamic vibrator, is supported.

BASE SHEAR

is the total design lateral force or shear at the base of a structure.

BASIC WIND SPEED

is a three-second gust speed at 10 m above the ground in Exposure C (see Section 207A.7.3) as determined in accordance with Section 207A.5.1 and associated with an annual probability of 0.02, (i.e. 50-year mean recurrence interval).

BEARING WALL SYSTEM

is a structural system that does not have a complete vertical load-carrying space frame.

BOUNDARY ELEMENT

is an element at edges of openings or at perimeters of shear walls or diaphragms.

BRACED FRAME

is essentially a vertical truss system of the concentric or eccentric type that is provided to resist lateral forces.

BUILDING FRAME SYSTEM

is essentially a complete space frame that provides support for gravity loads.

BRACED WALL LINE

is a series of braced wall panels in a single storey that meets the requirements of Section 620.10.3.

BRACED WALL PANEL

is a section of wall braced in accordance with Section 620.10.3.

BUILDING, ENCLOSED

is a building that does not comply with the requirements for open or partially enclosed buildings.

BUILDING ENVELOPE

refers to cladding, roofing, exterior wall, glazing, door assemblies, window assemblies, skylight assemblies, and other components enclosing the building.

BUILDING, FLEXIBLE

refers to slender buildings that have a fundamental natural frequency less than 1.0 Hz.

BUILDING, LOW-RISE

is an enclosed or partially enclosed building that complies with the following conditions:

1. Mean roof height, h, less than or equal to 18m, and

2. Mean roof height, h, does not exceed least horizontal dimension.

BUILDING, OPEN

refers to a building having each wall at least 80 percent open. This condition is expressed for each wall by the equation A, ≥ 0.84. See symbols and notations.

BUILDING, PARTIALLY ENCLOSED

is a building that complies with both of the following conditions:

1. the total area of openings in a wall that receives positive external pressure exceeds the sum of the areas of openings in the balance of the building envelope (walls and roof) by more than 10%

2. The total area of openings in a wall that receives positive external pressure exceeds 0.5 m2 or 1 percent of the area of that wall, whichever is smaller, and the percentage of openings in the balance of the building envelope does not exceed 20 percent. These conditions are expressed by the following equations:

3. A, > 1.10Aoi

4. A,> smaller of (0.5 m2 or 0.014)

5. Aoi/Agi ≤ 0.20

BUILDING OR OTHER STRUCTURE, REGULAR-SHAPED

refers to a building or other structure having no unusual geometrical irregularity in spatial form.

BUILDING OR OTHER STRUCTURES, RIGID

refer to a building or other structure whose fundamental frequency is greater than or equal to 1.0 Hz. BUILDING, SIMPLE DIAPHRAGM

CANTILEVERED COLUMN ELEMENT

is a column element in a lateral-force-resisting system that cantilevers from a fixed base and has minimal moment capacity at the top, with lateral forces applied essentially at the top.

COLLECTOR

is a member or element provided to transfer lateral forces from a portion of a structure to vertical elements of the lateral-force-resisting system.

COMPONENT

is a part or element of an architectural, electrical, mechanical or structural system.

COMPONENT, EQUIPMENT

is a mechanical or electrical component or element that is part of a mechanical and/or electrical system.

COMPONENT, FLEXIBLE

is a component, including its attachments, having a fundamental period greater than 0.06 s.

COMPONENT, RIGID

is a component, including its attachments, having a fundamental period less than or equal to 0.06s.

COMPONENTS AND CLADDING

refers to elements of the building envelope that do not qualify as part of the MWFRS.

CONCENTRICALLY-BRACED FRAME

is a braced frame in which the members are subjected primarily to axial forces.

CONVENTIONAL LIGHT-FRAME CONSTRUCTION

is a type of construction in which the primary structural elements are formed by a system of repetitive wood framing members.

COVERING, IMPACT-RESISTANT

is a covering designed to protect impact-resistant glazing.

CRIPPLE WALL

is a framed stud wall extending from the top of the foundation to the underside of floor framing for the lowest occupied level.

DEAD LOADS

consist of the weight of all materials and fixed equipment incorporated into the building or other structure.

DECK

is an exterior floor system supported on at least two opposing sides by an adjacent structure and/or posts, piers, or other independent supports.

DESIGN BASIS GROUND MOTION

is that ground motion that has a 10 percent chance of being exceeded in 50 years as determined by a site-specific hazard analysis or may be determined from a hazard map.

DESIGN FORCE

is the equivalent static force to be used in the determination of wind loads for open buildings and other structures.

DESIGN RESPONSE SPECTRUM

is an elastic response spectrum for 5 percent equivalent viscous damping used to represent the dynamic effects of the Design Basis Ground Motion for the design of structures in accordance with Sections 208.5 and 208.5.3.

DESIGN SEISMIC FORCE

is the minimum total strength design base shear, factored and distributed in accordance with Section 208.5.

DESIGN PRESSURE

is the equivalent static pressure to be used in the determination of wind loads for buildings.

DIAPHRAGM

is a horizontal or nearly horizontal system acting to transmit lateral forces to the vertical resisting elements. The term "diaphragm" includes horizontal bracing systems.

DIAPHRAGM, BLOCKED

is a diaphragm in which all sheathing edges not occurring on framing members are supported on and connected to blocking.

DIAPHRAGM CHORD or SHEAR WALL CHORD

is the boundary element of a diaphragm or shear wall that is assumed to take axial stresses analogous to the flanges of a beam.

DIAPHRAGM STRUT (drag strut, tie, and collector)

is the element of a diaphragm parallel to the applied load that collects and transfers diaphragm shear to the vertical resisting elements or distributes loads within the diaphragm. Such members may take axial tension or compression.

DIAPHRAGM, UNBLOCKED

is a diaphragm that has edge nailing at supporting members only. Blocking between supporting structural members at panel edges is not included.

DRIFT or STOREY DRIFT

is the lateral displacement of one level relative to the level above or below.

DUAL SYSTEM

is a combination of moment-resisting frames and shear walls or braced frames designed in accordance with the criteria of Section 208.4.6.4.

EAVE HEIGHT

is the distance from the ground surface adjacent to the building to the roof eave line at a particular wall. If the height of the eave varies along the wall, the average height shall be used.

ECCENTRICALLY BRACED FRAME (EBF)

is a steel-braced frame designed in conformance with Section 528.

EFFECTIVE WIND AREA

is the area used to determine GC. For cladding fasteners, the effective wind area shall not be greater than the area that is tributary to an individual fastener.

ELASTIC RESPONSE PARAMETERS

are forces and deformations determined from an elastic dynamic analysis using an unreduced ground motion representation, in accordance with Section 208.5.3.

ESCARPMENT

also known as scarp, with respect to topographic effect in Section 207A.8, is a cliff or steep slope generally separating two levels or gently sloping areas (see Figure 207A-8-1).

ESSENTIAL FACILITIES

are buildings, towers and other vertical structures that are intended to remain operational in the event of extreme environmental loading from wind or earthquakes.

FACTORED LOAD

is the product of a load specified in Sections 204 through 208 and a load factor. See Section 203.3 for combinations of factored loads.

FIBERBOARD

is a fibrous, homogeneous panel made from lignocellulosic fibers (usually wood or sugar cane bagasse) and having a density of less than 50 kg/m3 but more than 160 kg/m3.

FLEXIBLE ELEMENT or SYSTEM

is one whose deformation under lateral load is significantly larger than adjoining parts of the system. Limiting ratios for defining specific flexible elements are set forth in Section 208.5.1.3.

FOREST PRODUCTS RESEARCH AND DEVELOPMENT INSTITUTE (FPRDI)

is the Department of Science and Technology's (DOST's) research and development arm on forest products utilization. It is mandated to conduct basic and applied research to help the wood-using industries disseminate information and technologies on forest products to end users.

FREE ROOF

is a roof with a configuration generally conforming to those shown in Figures 207B.4-4 through 207B.4-6 (monoslope, pitched, or troughed) in an open building with no enclosing walls underneath the roof surface.

GARAGE

is a building or portion thereof in which motor vehicle containing flammable or combustible liquids or gas in its tank is stored, repaired or kept.

GARAGE, PRIVATE

is a building or a portion of a building, not more than 90m2 in area, in which only motor vehicles used by the tenants of the building or buildings on the premises are kept or stored.

GLAZING

is a glass or transparent or translucent plastic sheet used in windows, doors, skylights, or curtain walls.

GLAZING, IMPACT-RESISTANT

is a glazing that has been tested in accordance with ASTM E1886 and ASTM E1996 or other approved test methods to withstand the impact of wind-borne missiles likely to be generated in wind-borne debris regions during design winds.

GLUED BUILT-UP MEMBERS

are structural elements, the section of which is composed of built-up lumber, wood structural panels or wood structural panels in combination with lumber, all parts bonded together with structural adhesives.

GRADE (LUMBER)

is the classification of lumber in regard to strength and utility in accordance with the grading rules of an approved lumber grading agency.

HARDBOARD

is a fibrous-felted, homogeneous panel made from lignocellulosic fibers consolidated under heat and pressure in a hot press to a density not less than 50kg/m3.

HILL

is a land surface characterized by strong relief in any horizontal direction

HORIZONTAL BRACING SYSTEM

is a horizontal truss system that serves the same function as a diaphragm.

IMPACT-RESISTANT COVERING

is a covering designed to protect glazing, which has been shown by testing in accordance with ASTM E1886 and ASTM E1996 of other approved test methods to withstand the impact or wind-borne debris missiles likely to be generated in wind-borne debris regions during design winds.

IMPORTANCE FACTOR

is a factor that accounts for the degree of hazard to human life and damage to property.

INTERMEDIATE MOMENT RESISTING FRAME (IMRF)

is a concrete frame designed in accordance with Section 412.

LATERAL-FORCE-RESISTING SYSTEM

is that part of the structural system designed to resist the Design Seismic Forces.

LIMIT STATE

is a condition beyond which a structure or member becomes unfit for service and is judged to be no longer useful for its intended function (serviceability limit state) or to be unsafe (strength limit state).

LIVE LOADS

are those loads produced by the use and occupancy of the building or other structure and do not include dead load, construction load, or environmental loads.

LOADS

are forces or other actions that result from the weight of all building materials, occupants and their possessions, environmental effects, differential movements, and restrained dimensional changes. Permanent loads are those loads in which variations over time are rare or of small magnitude. All other loads are variable loads.

LOAD AND RESISTANCE FACTOR DESIGN (LRFD) METHOD

is a method of proportioning and designing structural elements using load and resistance factors such that no applicable limit state is reached when the structure is subjected to all appropriate load combinations. The term "LRFD" is used in the design of steel structures.

MACHINE-GRADED LUMBER (MGL)

is a lumber evaluated by a machine using a non-destructive test and sorted into different stress grades.

MAIN WIND-FORCE RESISTING SYSTEM (MWFRS)

is an assemblage of structural elements assigned to provide support and stability for the overall structure. The system generally receives wind loading from more than one surface.

MARQUEE

is a permanent roofed structure attached to and supported by the building and projecting over public right-of-way.

MEAN ROOF HEIGHT

is the average of the roof eave height and the height to the highest point on the roof surface, except that, for roof angles of less than or equal to 10°, the mean roof height shall be the roof eave height.

MOISTURE CONTENT (MC)

is the amount of moisture in wood, usually measured as the percentage of water to the oven dry weight of the wood.

MOMENT-RESISTING FRAME

is a frame in which members and joints are capable of resisting forces primarily by flexure.

MOMENT-RESISTING WALL FRAME (MRWF)

is a masonry wall frame especially detailed to provide ductile behavior and designed in conformance with Section 708.2.6.

NOMINAL LOADING

is a design load that stresses a member or fastening to the full allowable stress tabulated in this chapter. This loading may be applied for approximately 10 years, either continuously or cumulatively, and 90 percent of this load may be applied for the remainder of the life of the member or fastening.

NOMINAL SIZE (Lumber)

refers to the commercial size designation of width and depth, in standard sawn lumber and glued laminated lumber grades somewhat larger than the standard net size of dressed lumber.

OPENINGS

are apertures or holes in the building envelope that allow air to flow through the building envelope and that are designed as "open" during design winds as defined by these provisions.

ORDINARY BRACED FRAME (OBF)

is a steel-braced frame designed in accordance with the provisions of Section 527 or 528 or concrete-braced frame designed in accordance with Section 421.

ORDINARY MOMENT-RESISTING FRAME (OMRF)

is a moment-resisting frame not meeting special detailing requirements for ductile behavior.

ORTHOGONAL EFFECTS

are the earthquake load effects on structural elements simultaneously occurring to the lateral-force-resisting systems along two orthogonal axes.

OVERSTRENGTH

is a characteristic of structures where the actual strength is larger than the design strength. The degree of over-strength is material-and system-dependent.

PARTICLEBOARD

is a manufactured panel product consisting of particles of wood or combinations of wood particles and wood fibers bonded together with synthetic resins or other suitable bonding system by a bonding process, in accordance with approved nationally recognized standard.

PLYWOOD

is a panel of laminated veneers conforming to Philippine National Standards (PNS 196) "Plywood Specifications".

PA EFFECT

is the secondary effect on shears, axial forces and moments of frame members induced by the horizontal displacement of vertical loads from various loading, when a structure is subjected to lateral forces.

RECOGNIZED LITERATURE

are published research findings and technical papers that are approved.

RIDGE

with respect to topographic effects in Section 207A.8, is an elongated crest of a hill characterized by strong relief in two directions (see Figure 207A.8-1).

ROTATION

is the torsional movement of a diaphragm about a vertical axis.

SHEAR WALL

is a wall designed to resist lateral forces parallel to the plane of the wall (sometimes referred to as vertical diaphragm or structural wall).

SHEAR WALL-FRAME INTERACTIVE SYSTEM

uses combinations of shear walls and frames designed to resist lateral forces in proportion to their relative rigidities, considering interaction between shear walls and frames on all levels.

SHEATHING

is a layer of boards or of other wood or fiber materials applied to the outer studs, joists, and rafters of a building to strengthen structures and serve as a base for an exterior weatherproof cladding.

SHEATHING, WALL

is a layer of boards or of other wood or fiber materials used to cover the wall studding.