EQ Safe Engineering

EQ Safe Engineering (ESE) makes use of SAP, ETABS and SAFE: All programs are published and tested by CSI, Computers & Structures Inc. Berkeley, 1995 University Avenue, Berkeley 94704, California.

CHIARC provides the full range of services you may need for seismic strengthening your buildings for health care and educational purposes as well as for historic structures. All certificates, especially for power plant security, required by Chinese government authorities may be rendered by collaboration with our specialist partners.

SAP 2000 is approved for use in all applications, including safety-related nuclear, as governed by 10CFR50 requirements as well as other international quality assurance standards, such as ISO 9000:2000 requirements. SAP is a finite analysis program that was initially developed at the University of California-Berkeley more than 25 years ago. Since development, SAP has been used widely for structural analysis. The ongoing usage of the program coupled with continuing program upgrades are strong indicators that most program bugs have been identified and corrected.

Example screen from SAP 2000: Deformed truss shape.

The tallest building in China (Shanghai World Financial Center, 上海环球金融中心) is designed with ETABS, a sophisticated, yet easy to use, special purpose analysis and design program developed specifically for building systems. Dating back more than 30 years to the original development of TABS, the predecessor of ETABS, it was clearly recognized that buildings constituted a very special class of structures. As computers and computer interfaces evolved, ETABS added computationally complex analytical options such as dynamic nonlinear behavior and powerful CAD-like drawing tools in a graphical and object-based interface.

Cooling tower for traditional or nuclear power plants.

The SAFE program will analyze and design slabs of arbitrary geometry including drop panels, openings, edge beams and embedded beams subjected to vertical point, line or surface loads. Column supports, wall supports, or soil supports for basemats can be modeled. Discontinuities in the slab system, due to slip joints or differences in slab elevations can be included. The slab is modeled with orthotropic plate elements. The beam element allows for bending, torsion, and shear deformations.

Example screen from SAFE: Elastic deformed shape based on surface loading.

Examples for foundation and roof design.

Go on reading here about:
EQ Safe Architecture,
EQ Safe Buildings,
EQ Safe Construction,
EQ Safe Design and
→ EQ Safe Engineering.

Terms and definitions from the American Society of Civil Engineers (ASCE) and Federal Emergency Management Agency (FEMA) 356 prestandard project [PDF 8MB] (currently in the ANSI approval process):

Acceleration-sensitive nonstructural component

A nonstructural component that is sensitive to, and subject to, damage from inertial loading.

Acceptance criteria

Limiting values of properties such as drift, strength demand, and inelastic deformation used to determine the acceptability of a component at a given performance level.

Action

An internal moment, shear, torque, axial load, deformation, displacement, or rotation corresponding to a displacement due to a structural degree of freedom; designated as force- or deformation-controlled.

Active Fault

A fault for which there is an average historic slip rate of 1 mm per year or more, and evidence of seismic activity within Holocene times (past 11000 years).

Adjusted Resistance

The reference resistance adjusted to include the effects of applicable adjustment factors resulting from end use and other modifying factors excluding time-effect adjustments, which are considered separately and not included.

Aspect ratio

Ratio of height to width for shear walls and span to width for horizontal diaphragms.

Assembly

Two or more interconnected components.

Balloon framing

Continuous stud framing from sill to roof, with intervening floor joists nailed to studs and supported by a let-in ribbon.

Base

The level at which EQ effects are imparted to the building.

Beam

A structural member whose primary function is to carry loads transverse to its longitudinal axis.

Bearing wall

A wall that supports gravity loads of at least 200 pounds per lineal foot from floors and/or roofs.

Bed joint

The horizontal layer of mortar on which a masonry unit is laid.

Boundary component (boundary member)

A member at the perimeter (edge or opening) of a shear wall or horizontal diaphragm that provides tensile and/or compressive strength.

Braced frame

A vertical lateral-force-resisting element consisting of vertical, horizontal, and diagonal components joined by concentric or eccentric connections.

BSE-1

Basic Safety EQ-1, taken as the lesser of the ground shaking for a 10%/50 year EQ or two-thirds of the BSE-2 at a site.

BSE-2

Basic Safety EQ-2, taken as the ground shaking based on the MCE at a site.

BSO

Basic Safety Objective is a Rehabilitation Objective that achieves the dual rehabilitation goals of the Life Safety Building Performance Level for the BSE-1 EQ Hazard Level and the Collapse Prevention Building Performance Level for the BSE-2 EQ Hazard Level.

Building Occupancy

The purpose for which a building, or part thereof, is used, or intended to be used, designated in accordance with the applicable building code.

Building Performance Level

A limiting damage state for a building, considering structural and nonstructural components, used in the definition of Rehabilitation Objectives.

Cast Iron

A hard, brittle nonmalleable iron-carbon alloy containing 2.0 to 4.5 percent carbon. Shapes are obtained by reducing iron ore in a blast furnace, forming it into bars (or pigs), and remelting and casting it into its final form.

Cavity wall

A masonry wall with an air space between wythes.

Chord

Same like diaphragm chord: A component provided to resist tension or compression at the edges of a diaphragm.

Clay tile masonry

Masonry constructed with hollow units made of clay tile.

Clay-unit masonry

Masonry constructed with solid, cored, or hollow units made of clay; can be ungrouted or grouted.

Closed stirrups or ties

Transverse reinforcement defined in Chapter 7 of ACI 318 consisting of standard stirrups or ties with 90-degree hooks and lap splices in a pattern that encloses longitudinal reinforcement.

Code Official

The organization, political subdivision, office, or individual legally charged with responsibility for administering and enforcing the provisions of this standard.

Coefficient of variation

For a sample of data, the ratio of the standard deviation for the sample to the mean value for the sample.

Collar joint

Vertical longitudinal joint between wythes of masonry or between masonry wythe and backup construction; can be filled with mortar or grout.

Collector

Same like drag strut: A component parallel to the applied load that collects and transfers diaphragm shear forces to the vertical lateral-force-resisting elements, or other portions of the diaphragm. Also called collector, diaphragm strut, or tie.

Column (or beam) jacketing

A rehabilitation method in which a concrete column or beam is encased in a steel or concrete "jacket" to strengthen and/or repair the member by confining the concrete.

Component, flexible

A component, including attachments, having a fundamental period greater than 0.06 seconds.

Component, rigid

A component, including attachments, having a fundamental period less than or equal to 0.06 seconds.

Components

The basic structural members that constitute a building, including beams, columns, slabs, braces, walls, piers, coupling beams, and connections; designated as primary or secondary.

Composite masonry wall

Multi-wythe masonry wall acting with composite action.

Composite panel

A structural panel comprising thin wood strands or wafers bonded together with exterior adhesive.

Concentric Braced Frame

Braced frame element in which component worklines intersect at a single point or at multiple points such that the distance between intersecting components, or eccentricity, is less than or equal to the width of the smallest member connected at the joint.

Concrete masonry

Masonry constructed with solid or hollow units made of concrete; can be ungrouted or grouted.

Condition of service

The environment to which the structure will be subjected.

Connection

A link that transmits actions from one component or element to another component or element, categorized by type of action (moment, shear, or axial).

Connection hardware

Proprietary or custom fabricated body of a component that is used to link wood components.

Connectors

Nails, screws, lags, bolts, split rings, and shear plates used to link wood components to other wood or metal components.

Contents

Movable items within the building introduced by the owner or occupants, weighing 400 pounds or more.

Continuity plates

Column stiffeners at the top and bottom of a panel zone.

Control node

A node located at the center of mass at the roof of a building used in the NSP to measure the effects of EQ shaking on a building.

Corrective measure

Any modification of a component or element, or the structure as a whole, implemented to improve building performance.

Coupling beam

A component that ties or couples adjacent shear walls acting in the same plane.

Cripple studs

Short studs between a header and top plate at openings in wall framing, or studs between the base and sill of an opening.

Cripple wall

Short wall between the foundation and first floor framing.

Critical action

The component action that reaches its elastic limit at the lowest level of lateral deflection or loading of the structure.

Cross tie

A component that spans the width of the diaphragm and delivers out-of-plane wall forces over the full depth of the diaphragm.

Decay

Decomposition of wood caused by action of wood-destroying fungi. The term "dry rot" is used interchangeably with decay.

Decking

Solid sawn lumber or glue-laminated decking, nominally two to four inches thick and four inches and wider. Decking shall be tongue-and-groove or connected at longitudinal joints with nails or metal clips.

Deep foundation

Driven piles made of steel, concrete, or wood, or cast-in-place concrete piers or drilled shafts of concrete. Deformation-sensitive nonstructural component: A nonstructural component that is sensitive to deformation imposed by the drift or deformation of the structure, including deflection or deformation of diaphragms.

Demand

The amount of force or deformation imposed on an element or component.

Design displacement

The design EQ displacement of an isolation or energy dissipation system, or elements thereof, excluding additional displacement due to actual and accidental torsion.

Design EQ

A user-specified EQ for the design of an isolated building having ground shaking criteria described in Chapter 2. Design resistance (force or moment as appropriate): Resistance provided by member or connection; the product of adjusted resistance, the resistance factor, and time effect factor.

Diagonal bracing

Inclined components designed to carry axial load, enabling a structural frame to act as a truss to resist lateral forces.

Diaphragm

A horizontal (or nearly horizontal) structural element used to distribute inertial lateral forces to vertical elements of the lateral-force-resisting system.

Diaphragm chord

A component provided to resist tension or compression at the edges of a diaphragm.

Diaphragm collector

A component provided to transfer lateral forces in the diaphragm to vertical elements of the lateral-force-resisting system or to other portions of the diaphragm.

Diaphragm ratio

Same like aspect ratio: Ratio of height to width for shear walls and span to width for horizontal diaphragms.

Diaphragm strut

Same like drag strut: A component parallel to the applied load that collects and transfers diaphragm shear forces to the vertical lateral-force-resisting elements, or other portions of the diaphragm. Also called collector, diaphragm strut, or tie.

Differential compaction

An EQ- induced process in which soils become more compact and settle in a nonuniform manner across a site.

Dimensioned lumber

Lumber from nominal two through four inches thick and nominal two or more inches wide.

Displacement-dependent energy dissipation devices

Devices having mechanical properties such that the force in the device is related to the relative displacement in the device.

Displacement restraint system

Collection of structural components and elements that limit lateral displacement of seismically-isolated buildings during the BSE-2.

Dowel-bearing strength

The maximum compression strength of wood or wood-based products when subjected to bearing by a steel dowel or bolt of specific diameter.

Dowel type fasteners

Bolts, lag screws, wood screws, nails, and spikes.

Drag strut

A component parallel to the applied load that collects and transfers diaphragm shear forces to the vertical lateral-force-resisting elements, or other portions of the diaphragm. Also called collector, diaphragm strut, or tie.

Dressed size

The dimensions of lumber after surfacing with a planing machine.

Dry rot

Same like Decay: Decomposition of wood caused by action of wood-destroying fungi. The term "dry rot" is used interchangeably with decay.

Dry service

Structures wherein the maximum equilibrium moisture content does not exceed 19%.

Dual system

A structural system with the following features: 1. A space frame included to support gravity loads with or without capability of resisting lateral loads. 2. Lateral-load-resisting system included to resist at least 25% of the lateral loads provided by one or more of the following: concrete or steel shear walls, steel eccentrically braced frames (EBF), concentrically braced frames (CBF), and moment-resisting frames (Special Moment Frames, or Ordinary Moment Frames). 3. Each system designed to resist the total lateral load in proportion to relative rigidity.

EQ Hazard Level

Ground shaking demands of specified severity, developed on either a probabilistic or deterministic basis.

Eccentric Braced Frame

Braced frame element in which component worklines do not intersect at a single point and the distance between the intersecting components, or eccentricity, exceeds the width of the smallest member connecting at the joint.

Edge distance

The distance from the edge of the member to the center of the nearest fastener.

Effective damping

The value of equivalent viscous damping corresponding to the energy dissipated by the building, or element thereof, during a cycle of response.

Effective stiffness

The value of the lateral force in the building, or an element thereof, divided by the corresponding lateral displacement.

Effective Void Ratio

Ratio of collar joint area without mortar to the total area of the collar joint.

Element

An assembly of structural components that act together in resisting forces, including gravity frames, moment-resisting frames, braced frames, shear walls, and diaphragms.

Energy dissipation device

Non-gravity-load-supporting element designed to dissipate energy in a stable manner during repeated cycles of EQ demand.

Energy dissipation system

Complete collection of all energy dissipation devices, their supporting framing, and connections.

Expected Strength

The mean value of resistance of a component at the deformation level anticipated for a population of similar components, including consideration of the variability in yield strength as well as strain hardening and plastic section development.

Fair Condition

Masonry found during condition assessment to have mortar and units intact but with minor cracking.

Fault

Plane or zone along which earth materials on opposite sides have moved differentially in response to tectonic forces.

Flexible connection

A link between components that permits rotational and/or translational movement without degradation of performance, including universal joints, bellows expansion joints, and flexible metal hose.

Flexible diaphragm

A diaphragm with horizontal deformation along its length more than twice the average interstory drift.

Foundation system

An assembly of structural components, located at the soil-structure interface, that transfer loads from the superstructure into the supporting soil.

Fundamental period

The highest natural period of the building in the direction under consideration.

Gauge or row spacing

The center-to-center distance between fastener rows or gauge lines.

Glulam beam

Shortened term for glue-laminated beam, which is a wood-based component made up of layers of wood bonded with adhesive.

Good Condition

Masonry found during condition assessment to have mortar and units intact and no visible cracking.

Grade

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

Grading rules

Systematic and standardized criteria for rating the quality of wood products.

Gypsum wallboard or drywall

An interior wall surface sheathing material; can sometimes be considered for resisting lateral forces.

Head joint

Vertical mortar joint placed between masonry units in the same wythe.

Hold-down

Hardware used to anchor vertical chord forces in a shear wall to the foundation or framing of the structure in order to resist the effects of overturning.

Load path

A path through which seismic forces are delivered from the point at which inertial forces are generated in the structure to the foundation and, ultimately, the supporting soil.

Load sharing

The load redistribution mechanism among parallel components constrained to deflect together.

Load/slip constant

The ratio of the applied load to a connection and the resulting lateral deformation of the connection in the direction of the applied load.

Lumber

The product of the sawmill and planing mill, usually not further manufactured other than by sawing, resawing, passing lengthwise through a standard planing machine, crosscutting to length, and matching.

Masonry

The assemblage of masonry units, mortar, and possibly grout and/or reinforcement; classified with respect to the type of masonry unit, including clay-unit masonry, concrete masonry, or hollow-clay tile masonry.

Mat-formed panel

A structural panel manufactured in a mat-formed process including oriented strand board and waferboard.

Maximum Considered EQ (MCE)

An extreme EQ hazard level defined by MCE maps which are a combination of mean 2%/50 year probabilistic spectra and 150% of median deterministic spectra at a given site.

Maximum displacement

The maximum EQ displacement of an isolation or energy dissipation system, or elements thereof, excluding additional displacement due to actual or accidental torsion.

Mean Return Period

The average period of time, in years, between the expected occurrences of an EQ of specified severity.

Model Building Type

One of the common building types listed and described in Table 10-2.

Moisture content

The weight of the water in wood expressed as a percentage of the weight of the ovendried wood.

Moment frame

A building frame system in which seismic shear forces are resisted by shear and flexure in members and joints of the frame.

Narrow wood shear wall

Wood shear walls with an aspect ratio (height-to-width) greater than two-to-one.

Nominal size

The approximate rough-sawn commercial size by which lumber products are known and sold in the market. Actual rough-sawn sizes vary from nominal. Reference to standards or grade rules is required to determine nominal to actual finished size relationships, which have changed over time.

Nominal strength

The capacity of a structure or component to resist the effects of loads, as determined by (1) computations using specified material strengths and dimensions, and formulas derived from accepted principles of structural mechanics; or (2) field tests or laboratory tests of scaled models, allowing for modeling effects and differences between laboratory and field conditions.

Nonbearing wall

A wall that supports gravity loads less than 200 pounds per lineal foot.

Noncompact member

A steel section that has width-to-thickness ratios exceeding the limiting values for compactness specified in AISC (1993) LRFD Specifications.

Noncomposite masonry wall

Multi-wythe masonry wall acting without composite action.

Nonstructural component

Architectural, mechanical or electrical components of a building that are permanently installed in, or are an integral part of, a building system.

Nonstructural Performance Level

A limiting damage state for nonstructural building components used to define Rehabilitation Objectives.

Ordinary Moment Frame

A moment frame system that meets the requirements for Ordinary Moment Frames as defined in seismic provisions for new construction in AISC (1997) Seismic Provisions, Chapter 5.

P-ΔG effect

The secondary effect of column axial loads and lateral deflection on the shears and moments in various components of a structure.

Redundancy

The quality of having alternative paths in the structure by which the lateral forces can be transferred, which allows the structure to remain stable following the failure of any single element.

Re-entrant corner

Plan irregularity in a diaphragm, such as an extending wing, plan inset, or E-, T-, X-, or L-shaped configuration, where large tensile and compressive forces can develop.

Rehabilitation Measures

Modifications to existing components, or installation of new components, that correct deficiencies identified in a seismic evaluation as part of a scheme to rehabilitate a building to achieve a selected Rehabilitation Objective.

Rehabilitation Method

For the purpose of this standard, a rehabilitation method is one or more procedures and strategies for improving the seismic performance of existing buildings.

Rehabilitation Objective

A Rehabilitation Objective consists of one or more rehabilitation goals, each goal consisting of the selection of a target Building Performance Level and an EQ Hazard Level.

Rehabilitation Strategy

A technical approach for developing rehabilitation measures for a building to improve seismic performance.

Reinforced masonry wall

A masonry wall with the following minimum amounts of vertical and horizontal reinforcement: vertical reinforcement of at least 0.20 in2 in cross section at each corner or end, at each side of each opening, and at a maximum spacing of at least 4 feet throughout. Horizontal reinforcement of at least 0.20 in2 in cross section at the top of the wall, at the top and bottom of wall openings, at structurally connected roof and floor openings, and at a maximum spacing of 10 feet.

Repointing

A method of repairing cracked or deteriorating mortar joints in which the damaged or deteriorated mortar is removed and the joints are refilled with new mortar.

Required member resistance (or required strength)

Load effect acting on an element or connection, determined by structural analysis, resulting from the factored loads and the critical load combinations.

Resistance

The capacity of a structure, component, or connection to resist the effects of loads.

Resistance factor

A reduction factor applied to member resistance that accounts for unavoidable deviations of the actual strength from the nominal value, and the manner and consequences of failure.

Rigid diaphragm

A diaphragm with horizontal deformation along its length less than half the average interstory drift as specified in Section 3.2.4.

Rough lumber

Lumber as it comes from the saw prior to any dressing operation.

Row of fasteners

Two or more fasteners aligned with the direction of load.

Running bond

A pattern of masonry where the head joints are staggered between adjacent courses by more than a third of the length of a masonry unit. Also refers to the placement of masonry units such that head joints in successive courses are horizontally offset at least onequarter the unit length.

Scragging

The process of subjecting an elastomeric bearing to one or more cycles of large amplitude displacement.

Seasoned lumber

Lumber that has been dried either by open air drying within the limits of moisture contents attainable by this method, or by controlled air drying.

Secondary elements or components

Those elements or components not designated as primary but affect the lateral stiffness of the structure, the distribution of the stresses in the building, or are loaded as a result of lateral deformation of the building. In nonlinear analyses, secondary elements or components can resist lateral forces at residual strength levels.

Seismic demand

Seismic hazard expressed in the form of a ground shaking response spectrum or accelogram with or without an estimate of permanent ground deformation.

Seismic evaluation

An approved process or methodology of evaluating deficiencies in a building which prevent the building from achieving a selected Rehabilitation Objective.

Shallow foundation

Isolated or continuous spread footings or mats.

Shear wall

A wall that resists lateral forces applied parallel with its plane. Also known as an in-plane wall.

Sheathing

Lumber or panel products that are attached to parallel framing members, typically forming wall, floor, ceiling, or roof surfaces.

Short captive column

Columns with height-todepth ratios less than 75% of the nominal height-todepth ratios of the typical columns at that level.

Shrinkage

Reduction in the dimensions of wood due to a decrease of moisture content.

Simplified NSP Analysis

A nonlinear static analysis in which only primary lateral-force-resisting elements are modeled, and component degradation is not explicitly modeled.

Simplified Rehabilitation Method

An approach applicable to certain types of buildings and Rehabilitation Objectives in which an analysis of the response of the entire building to EQ hazards is not required.

Slip-critical joint

A bolted joint in which slip resistance of the connection is required.

Solid masonry unit

A masonry unit with net crosssectional area in every plane parallel to the bearing surface equal to 75% or more of the gross cross-sectional area in the same plane.

Solid wall or solid infill panel

A wall or infill panel with openings not exceeding 5% of the wall surface area. The maximum length or height of an opening in a solid wall must not exceed 10% of the wall width or story height. Openings in a solid wall or infill panel must be located within the middle 50% of a wall length and story height, and must not be contiguous with adjacent openings.

Special Moment Frame (SMF)

A moment frame system that meets the special requirements for frames as defined in seismic provisions for new construction.

Stack bond

A placement of masonry units such that the head joints in successive courses are aligned vertically.

Stiff diaphragm

A diaphragm that is neither flexible nor rigid.

Storage racks

Industrial pallet racks, movable shelf racks, and stacker racks made of cold-formed or hotrolled structural members. Does not include other types of racks such as drive-in and drive-through racks, cantilever wall-hung racks, portable racks, or racks made of materials other than steel.

Strength

The maximum axial force, shear force, or moment that can be resisted by a component.

Stress resultant

The net axial force, shear, or bending moment imposed on a cross section of a structural component.

Strong back system

A secondary system, such as a frame, commonly used to provide out-of-plane support for an unreinforced or under-reinforced masonry wall.

Strong column-weak beam

A connection required to localize damage and control drift; the capacity of the column in any moment frame joint must be greater than that of the beams, to ensure inelastic action in the beams.

Structural components

Components of a building that provide gravity and lateral load resistance as part of a continuous load path to the foundation.

Structural Performance Level

A limiting structural damage state; used in the definition of Rehabilitation Objectives.

Structural Performance Range

A range of structural damage states; used in the definition of Rehabilitation Objectives.

Structural system

An assemblage of load-carrying components that are joined together to provide regular interaction or interdependence.

Stud

Vertical framing member in interior or exterior walls of a building.

Subassembly

A portion of an assembly.

Sub-diaphragm

A portion of a larger diaphragm used to distribute loads between members.

Systematic Rehabilitation Method

An approach to rehabilitation in which complete analysis of the response of the building to EQ hazards is performed.

Target displacement

An estimate of the maximum expected displacement of the roof of a building calculated for the design EQ.

Tie

Same like drag strut: A component parallel to the applied load that collects and transfers diaphragm shear forces to the vertical lateral-force-resisting elements, or other portions of the diaphragm. Also called collector, diaphragm strut, or tie.

Tie-down

Hardware used to anchor the vertical chord forces to the foundation or framing of the structure in order to resist overturning of the wall.

Tie-down system

The collection of structural connections, components, and elements that provide restraint against uplift of the structure above the isolation system.

Timbers

Lumber of nominal five or more inches in cross-section dimension.

Time effect factor

A factor applied to adjusted resistance to account for effects of duration of load. (See load duration.)

Total design displacement

The BSE-1 displacement of an isolation or energy dissipation system, or elements thereof, including additional displacement due to actual and accidental torsion.

Total maximum displacement

The maximum EQ displacement of an isolation or energy dissipation system, or elements thereof, including additional displacement due to actual and accidental torsion.

Transverse wall

A wall that is oriented transverse to in-plane shear walls, and resists lateral forces applied normal to its plane. Also known as an out-of-plane wall.

Unreinforced masonry (URM) wall

A masonry wall containing less than the minimum amounts of reinforcement as defined for masonry (RM) walls. An unreinforced wall is assumed to resist gravity and lateral loads solely through resistance of the masonry materials.

V-braced frame

A concentric braced frame (CBF) in which a pair of diagonal braces located either above or below a beam is connected to a single point within the clear beam span.

Velocity-dependent energy dissipation devices

Devices having mechanical characteristics such that the force in the device is dependent on the relative velocity in the device.

Veneer

A masonry wythe that provides the exterior finish of a wall system and transfers out-of-plane load directly to a backing, but is not considered to add loadresisting capacity to the wall system.

Vertical irregularity

A discontinuity of strength, stiffness, geometry, or mass in one story with respect to adjacent stories.

Waferboard

A non-veneered structural panel manufactured from two- to three-inch flakes or wafers bonded together with a phenolic resin and pressed into sheet panels.]

Wind-restraint system

The collection of structural elements that provides restraint of the seismic-isolated structure for wind loads. The wind-restraint system may be either an integral part of isolator units or a separate device.

Wood structural panel

A wood-based panel product bonded with an exterior adhesive, meeting the requirements of PS 1-95 or PS 2-92, including plywood, oriented strand board, waferboard, and composite panels.

Wrought Iron

An easily welded or forged iron containing little or no carbon. Initially malleable, it hardens quickly when rapidly cooled.

Wythe

A continuous vertical section of a wall, one masonry unit in thickness.

X-braced frame

A concentric braced frame (CBF) in which a pair of diagonal braces crosses near the midlength of the braces.

Y-braced frame

An eccentric braced frame (EBF) in which the stem of the Y is the link of the EBF system.