Minimum Design Loads for Buildings and Other Structures
This documentusesboth theInternational System of Units (SI)and customaryunits
Chapter11 SEISMICDESIGNCRITERIA
11.1 GENERAL
11.1.1 Purpose
11.1.2 Scope
ofqns samns o pue suiq jo uogonsuo Chapter 11 presents criteria for the design andto carthquake ground motions. The specified eath-quake loads are based upon post-elastic energy dissipation in the structure and because of this fact the requirements for design detailing and construc- tion shall be satisfied even for structures and membersfor which load binations that do not containearthquake loads indicate larger demands than binations that include earthquake loads. Minimumrequirements for quality assurance for seismic force-resisting systems are set forth in Appendix 11A.
nonstructural ponents shall be designed and Every structure and portion thereof includingconstructed to resist the effects of earthquake motions as prescribed by the seismic requirements of thisstandard. Certain nonbuilding structures as describedin Chapter 15 are also within the scope and shall be designed and constructed in accordance with therequirements of Chapter 15. Requirements concerning alterations additions and change of use are set forthin Appendix 11B. Existing structures and alterations toos o m doo uo paou sns usixa requirements of this standard where required byfrom the seismic requirements of this standard: Appendix 11B. The following structures are exempt
1. Detached one- and two-family dwellings that arelocated where the mapped short period spectral response acceleration parameter Ss is less than 0.4or where the Seismic Design Category determined2. Detached one- and two-family wood-frame in accordance with Section 11.6 is A B or C.dwellings not included in Exception 1 with not more than two stories above grade plane satisfyingthe limitations of and constructed in accordance3. Agricultural storage structures that are intended with the IRC.4. Structures that require special consideration of theirregulations provide seismic criteria such as not addressed in Chapter 15 and for which other
vehicular bridges electrical transmission towers appurtenances and muclear reactors. hydraulic structures buried utility lines and their5. Piers and wharves that are not accessible to the general public.
11.1.3 Applicability
Structures and their nonstructural ponentsshall be designed and constructed in accordance with the requirement of the following sections based on thetype of structure or ponent:
a. Buildings: Chapter 12b. Nonbuilding Structures: Chapter 15 c. Nonstructural Components: Chapter 13d. Seismically Isolated Structures: Chapter 17 e. Structures with Damping Systems: Chapter 18
Buildings whose purpose is to enclose equipment ormachinery and whose occupants are engaged in maintenance or monitoring of that equipment s sssd psse ro rdesigned and detailed in accordance with Section 15.5 permitted to be classified as nonbuilding structuresof this standard.
11.1.4 Alternate Materials and Methods of Construction
Altermate materials and methods of constructionstandard shall not be used unless approved by the to those prescribed in the seismic requirements of thisauthority having jurisdiction. Substantiating evidenceshall be submitted demonstrating that the proposed altermate for the purpose intended will be at least
equal in strength durability and seismic resistance.
11.2 DEFINITIONS
The following definitions apply only to the seismic requirements of this standard.
ACTIVE FAULT: A fault determined to beproperly substantiated data (e.g. most recent mapping active by the authority having jurisdiction fromSurvey). of active faults by the United States Geological
ADDITION: An increase in building area aggregate flr area high or number of stories of a structure.
ALTERATION: Any construction or renovatione ue u o ms xo e o
APPENDAGE: An architectural ponent suchas a canopy marquee omamental balcony or statuary.
APPROVAL: The written acceptance by thethat establishes the qualification of a material the requirements of this standard for the intended system ponent procedure or person to fulfilluse.
tural ponents or supports of nonstructural po- ATTACHMENTS: Means by which nonstruc-force-resisting system of the structure. Such attach- nents are secured or connected to the seismicments include anchor bolts welded connections andmechanical fasteners.
BASE: The level at which the horizontal seismicground motions are considered to be imparted to the structure.
BASE SHEAR: Total design lateral force orshear at the base.
BOUNDARY ELEMENTS: Diaphragm andshear wall boundary members to which the diaphragm transfers forces. Boundary members include chords ad [em maus pue usenqdep 1e sinns Sep pueeters interior openings discontinuities and reentrant
and diaphragm edges strengthened by longitudinal and BOUNDARY MEMBERS: Portions along walltransverse reinforcement. Boundary members includechords and drag struts at diaphragm and shear wall perimeters interior openings discontinuities andreentrant corners.
BUILDING: Any structure whose intended useincludes shelter of human occupants.
seismic force-resisting system in which lateral forces CANTILEVERED COLUMN SYSTEM: Aare resisted entirely by columns acting as cantileversfrom the base.
CHARACTERISTIC EARTHQUAKE: An e psssse magnitude equal to the best estimate of the maximumless than the largest magnitude that has occurred magnitude capable of occurring on the fault but nothistorically on the fault.
electrical or mechanical system. COMPONENT: A part of an architetural
architectural mechanical or electrical systemstructure. within or without a building or nonbuilding
Component Nonstructural: A part of an
Component Flexible: Nonstructural ponent u earpoud epun Su 0.06 s.to 0.06 s.
Component Rigid: Nonstructural ponent
having a fundamental period less than or equal
CONCRETE PLAIN: Concrete that is eitherminimum amount specified in ACI 318 for reinforced unreinforced or contains less reinforcement than theconcrete.
CONCRETE REINFORCED: Concretereinforced with no less reinforcement than theor nonprestressed and designed on the assumption minimum amount required by ACI 318 prestressedthat the two materials act together in resisting forces.
CONSTRUCTION DOCUMENTS:Thewritten graphic electronic and pictorial documents describing the design locations and physical charac-teristics of the project required to verify pliance with this standard.
COUPLING BEAM: A beam that is used toact together as a unit to resist lateral loads. connect adjacent concrete wall elements to make them
deformation to the limit deformation. DEFORMABILITY: The ratio of the ultimate
subjected to four fully reversed cycles at the whose deformability is not less than 3.5 wherelimit deformation.Limited-Deformability Element: An element that is neither a low-deformability nor aLow-Deformability Element: An element whose high-deformability element.deformability is 1.5 or less.
High-Deformability Element: An element
DEFORMATION:
Limit Deformation: Two times the initialdeformation that occurs at a load equal to 40 percent of the maximum strength.Ultimate Deformation: The deformation at which failure occurs and that shall be deemedto occur if the sustainable load reduces to 80percent or less of the maximum strength.
nonstructural ponents that require design in DESIGNATED SEISMIC SYSTEMS: Thoseaccordance with Chapter 13 and for which the ponent importance factor I is greater than 1.0.
DESIGN EARTHQUAKE: The earthquakeeffects that are two-thirds of the corresponding Maximum Considered Earthquake (MCEs) effects.
DESIGN EARTHQUAKE GROUND
Moment Frame: A frame in which members andjoints resist lateral forces by flexure as well as along the axis of the members. Moment framesare categorized as intermediate moment frames (IMF) ordinary moment frames (OMF) andspecial moment frames (SMF).
MOTION: The earthquake ground motions that are two-thirds of the corresponding MCE: groundmotions.
DIAPHRAGM: Roof floor or other membrane or bracing system acting to transfer the lateral forcesto the vertical resisting elements.
Structural System:
DIAPHRAGM BOUNDARY: A location whereshear is transfered into or out of the diaphragm element. Transfer is either to a boundary element or
Building Frame System: A structural systemwith an essentially plete space frame providing support for vertical loads. Seismicforce resistance is provided by shear walls orbraced frames.
ary element perpendicular to the applid load that is DIAPHRAGM CHORD: A diaphragm bound-assumed to take axial stresses due to the diaphragm moment.
Dual System: A structural system with anessentially plete space frame providing support for vertical loads. Seismic forceresistance is provided by moment-resistingprescribed in Section 12.2.5.1 frames and shear walls or braced frames as
DRAG STRUT (COLLECTOR TIE DIA-boundary element parallel to the applied load that PHRAGM STRUT): A diaphragm or shear wallcollects and transfers diaphragm shear forces to the vertical force-resisting elements or distributes forceswithin the diaphragm or shear wall.
Shear Wall-Frame Interactive System: A
structural system that uses binations ofordinary reinforced concrete shear walls anddesigned to resist lateral forces in proportion to ordinary reinforced concrete moment framestheir rigidities considering interaction between shear walls and frames on all levels.
walls. ENCLOSURE: An interior space surrounded by
members or assemblies of members or manufactured EQUIPMENT SUPPORT: Those structuralelements including braces frames legs lugs snuggers hangers or saddles that transmit gravity loads and operating loads between the equipment andthe structure.
Space Frame System: A 3-D structural systemthan bearing walls that is capable of support- posed of interconnected members othering vertical loads and where designed for such an application is capable of providing resis-tance to seismic forces.
FLEXIBLE CONNECTIONS: Those connec-tions between equipment ponents that permit rotational and/or translational movement without degradation of performance. Examples includeuniversal joints bellows expansion joints and flexible metal hose.
FRICTION CLIP: A device that relies onfriction to resist applied loads in one or more direc- tions to anchor a nonstructural ponent. Friction isprovided mechanically and is not due to gravity loads.
FRAME:
wall that extends beyond the edges of building floor GLAZED CURTAIN WALL: A nonbearingcurtain wall framing. slabs and includes a glazing material installed in the
Braced Frame: An essentially vertical truss ortype that is provided in a building frame its equivalent of the concentric or eccentricsystem or dual system to resist seismicforces.
GLAZED STOREFRONT: A nonbearing walls p s ing entrances and includes a glazing material installedin the storefront framing.
Concentrically Braced Frame (CBF): Abraced frame in which the members are subjected primarily to axial forces. CBFs arecategorized as ordinary concentrically bracedframes (OCBFs) or special concentrically braced frames (SCBFs).
GRADE PLANE: A horizontal reference planerepresenting the average of finished ground levelfinished ground level slopes away from the exterior adjoining the structure at all exterior walls. Where thewalls the grade plane is established by the lowest points within the area between the structure and theproperty line or where the property line is more than 6and points 6 ft (1 829 mm) from the structure. ft (1 829 mm) from the structure between the structure
Eecentrically Braced Frame (EBF): A
diagonally braced frame in which at leastone end of each brace frames into a beam ashort distance from a beam-column or from another diagonal brace.
INSPECTION SPECIAL: The observation ofance with the approved construction documents and the work by a special inspector to determine pli-these standards in accordance with the qualityassurance plan.
Continuous Special Inspection: The full-timeobservation of the work by a special inspectorperformed.Periodic Special Inspection: The part-time or intermittent observation of the work by a d s o s
who is present in the area where work is being
where work has been or is being performed.
INSPECTOR SPECIAL (who shall be identi-fied as the owner’s inspeetor): A person approvedby the authority having jurisdiction to perform special inspection.
TURES: Structures in which more than 50 percent of INVERTED PENDULUM-TYPE STRUC-the structure’s mass is concentrated at the top of aslender cantilevered structure and in which stability of the mass at the top of the structure relies onrotational restraint to the top of the cantilevered element.
JOINT: The geometric volume mon tointersecting members.
LIGHT-FRAME CONSTRUCTION: A methodof construction where the structural assemblies (e.g walls floors ceilings and roofs) are primarily formedby a system of repetitive wood or cold-formed steelframing members or subassemblies of these members (e.g. trusses).
LONGITUDINALREINFORCEMENT
RATIO: Area of longitudinal reinforcement dividedby the cross-sectional area of the concrete.
(MCE) GROUND MOTION: The most severe MAXIMUM CONSIDERED EARTHQUAKEspecifically defined in the following two terms. earthquake effects considered by this standard more
MAXIMUM CONSIDERED EARTHQUAKEGEOMETRIC MEAN (MCE) PEAK GROUND ACCELERATION: The most severe earthquakeeffects considered by this standard determined for geometric mean peak ground acceleration andwithout adjustment for targeted risk. The MCEcpeak ground acceleration adjusted for site effects (PGAst) is used in this standard for evaluation ofliquefaction lateral spreading seismic settlements and other soil related issues. In this standard generalprocedures for determining PGAs are provided in in Section 21.5. Section 11.8.3; site-specific procedures are provided
ERED EARTHQUAKE (MCE) GROUND MOTION RESPONSE ACCELERATION:The RISK-TARGETEDMAXIMUM CONSID-
most severe earthquake effects considered by this standard determined for the orientation that results inthe largest maximum response to horizontal groundthis standard general procedures for determining motions and with adjustment for targeted risk. In the MCEa Ground Motion values are provided in Section 11.4.3; site-specific procedures are providedin Sections 21.1 and 21.2.
VESSELS: Tanks or vessels provided with mechani- MECHANICALLY ANCHOREDTANKS ORcal anchors to resist overtuming moments.
NONBUILDING STRUCTURE: A structure other than a building constructed of a type includedin Chapter 15 and within the limits of Section 15.1.1.
NONBUILDING STRUCTURESIMILAR TOdesigned and constructed in a manner similar to A BUILDING: A nonbuilding structure that isbuildings will respond to strong ground motion in afashion similar to buildings and has a basic lateral and vertical seismic force-resisting system conformingto one of the types indicated in Tables 12.2-1 or 15.4-1.
ORTHOGONAL: To be in two horizontaldirections at 90° to each other.
OWNER: Any person agent firm or corporationhaving a legal or equitable interest in the property.
PARTITION: A nonstructural interior wall that sframe subsidiary structural members or other support. The supports may be the basic buildingportions of the partition system.
P-DELTA EFFECT: The secondary effect onshears and moments of structural members due to theaction of the vertical loads induced by horizontal displacement of the structure resulting from variousloading conditions.
PILE: Deep foundation element which includespiers caissons and piles.
are connected including grade beams and mats. PILE CAP: Foundation elements to which piles
An architect or engineer registered or licensed to REGISTERED DESIGN PROFESSIONAL:practice professional architecture or engineering assional registrations laws of the state in which the defined by the statutory requirements of the profes-project is to be constructed.
SEISMIC DESIGN CATEGORY: A classifica-tion assigned to a structure based on its Risk Categoryand the severity of the design earthquake ground motion at the site as defined in Section 11.4.
