seismic design criteria 2007 cbc by mehran pourzanjani

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Seismic Design Criteria & Requirements Seismic Design Criteria & Requirements Per CBC 2007 Per CBC 2007 by by Mehran Pourzanjani S.E Mehran Pourzanjani S.E . . SEAOSC Seismology Committee SEAOSC Seismology Committee January 26, 2008 January 26, 2008

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Page 1: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Seismic Design Criteria & Requirements Seismic Design Criteria & Requirements Per CBC 2007Per CBC 2007

byby

Mehran Pourzanjani S.EMehran Pourzanjani S.E..

SEAOSC Seismology CommitteeSEAOSC Seismology Committee

January 26, 2008January 26, 2008

Page 2: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Overview of the PresentationOverview of the PresentationStructure of CBC 2007Structure of CBC 2007

Ch 16 of CBC 2007: Ch 16 of CBC 2007: Structural DesignStructural Design

Ch 11 of ASCE 7Ch 11 of ASCE 7-- 05:05:Seismic Design Criteria Seismic Design Criteria

Ch 12 of ASCE 7Ch 12 of ASCE 7-- 05:05:Seismic Design Requirements for BuildingsSeismic Design Requirements for Buildings

Presentation highlights select provisions of interestPresentation highlights select provisions of interest

Emphasize on understanding the intent and the basis for the Emphasize on understanding the intent and the basis for the code provisionscode provisions

Comparison of provisions with UBC 97 where applicableComparison of provisions with UBC 97 where applicable

CBCCBC-- Ch 16, ASCE Ch 16, ASCE -- Ch 11 & 12Ch 11 & 12

Page 3: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

The Structure of CBC 2007The Structure of CBC 2007CBC 2007 adapts other codes by reference with CBC 2007 adapts other codes by reference with

modifications noted in the corresponding chapters:modifications noted in the corresponding chapters:

Commentary Commentary --The SetThe Set--up of CBC 2007up of CBC 2007

Page 4: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Code Seismic DesignCode Seismic Design CriteriaCriteria PhilosophyPhilosophy

Commentary Commentary –– NEHRP 2003, Understanding The CodeNEHRP 2003, Understanding The Code

Set a proper design level to achieve the performance objective for the building

Consider an appropriate E.Q. hazard

Page 5: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

EQ Levels Considered by CodeEQ Levels Considered by CodeMaximum Considered EQ (MCE):Maximum Considered EQ (MCE):

Basis E.Q.: Probabilistic approach with 2% chance of (Most Areas) exceedance in 50 year

Return period of 2500 year

Near Fault Areas: Deterministic (cap) event with varying recurrence (i.g. Coastal California) interval ranging from less than 500 year to 1300

year or more depending on the site.

Design (Basis) EQ= 2/3 of MCEDesign (Basis) EQ= 2/3 of MCE

Maximum Probable EQ (MPE):Maximum Probable EQ (MPE): 50% chance of exceedance in 50 years Return period of 72 year

Commentary Commentary –– NEHRP 2003, Understanding The CodeNEHRP 2003, Understanding The Code

Page 6: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Code Performance ObjectivesCode Performance ObjectivesPerformance Levels:Performance Levels:

Operational: Operational: Negligible damage to the structural systemNegligible damage to the structural system

Immediate Occupancy: Immediate Occupancy: Slight damage to the structural system. Retains nearly all preSlight damage to the structural system. Retains nearly all pre--EQEQstrength and stiffnessstrength and stiffness

Life Safety: Life Safety: Structural stiffness loss significant, but building retains signStructural stiffness loss significant, but building retains significant marginificant marginagainst collapseagainst collapse

Collapse Prevention: Collapse Prevention: Substantial degradation, little margin against collapse. AftersSubstantial degradation, little margin against collapse. Aftershocks canhocks cancause collapse.cause collapse.

Commentary Commentary –– NEHRP 2003, Understanding The CodeNEHRP 2003, Understanding The Code

Page 7: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Building Performance ObjectiveBuilding Performance Objective

Commentary Commentary –– NEHRP 2003, Understanding The CodeNEHRP 2003, Understanding The Code

Page 8: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Actual Performance of StructuresActual Performance of Structures

Variation in performance of buildings will occur even Variation in performance of buildings will occur even when designed to the same criteria, due to:when designed to the same criteria, due to:

Site conditionsSite conditions

Quality of constructionQuality of construction

Structural systemsStructural systems

DetailingDetailing

Overall configuration of the buildingOverall configuration of the building

Inaccuracies in our analysis techniquesInaccuracies in our analysis techniques

OthersOthers

Commentary Commentary –– NEHRP 2003, Understanding The CodeNEHRP 2003, Understanding The Code

Page 9: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

CBC Ch. 16 CBC Ch. 16 –– Structural DesignStructural DesignCh 16Ch 16-- Structural Design IssuesStructural Design Issues

1601 & 1602: Scope, Definitions and Notations1601 & 1602: Scope, Definitions and Notations1603: Construction Documents 1603: Construction Documents –– Information required on the CD documentsInformation required on the CD documents1604: General Design Requirements 1604: General Design Requirements –– Deflections, Deflections, Occupancy CategoryOccupancy Category, , Anchorage, Anchorage,

Refers to ASCE for wind & Seismic DetailingRefers to ASCE for wind & Seismic Detailing1605: Load Combinations1605: Load Combinations1606, 1607, 1608, 1609, 1610, 1611, 1612: Dead Loads, Live loads1606, 1607, 1608, 1609, 1610, 1611, 1612: Dead Loads, Live loads, Snow Loads, Wind , Snow Loads, Wind

Loads, Soil Loads, Rain Loads, Flood LoadsLoads, Soil Loads, Rain Loads, Flood Loads

1613 1613 –– Earthquake LoadsEarthquake Loads

Site Classification & coefficients, SDC, Maps, Alternates to ASSite Classification & coefficients, SDC, Maps, Alternates to ASCE 7CE 7--i.g. Flexible i.g. Flexible diaphdiaph..

1613.1: 1613.1: ““Every structure, and portion thereof, including nonstructural coEvery structure, and portion thereof, including nonstructural components that mponents that are permanently attached to structures and their supports at attare permanently attached to structures and their supports at attachments, shall be achments, shall be designed and constructed in accordance with ASCE 7, designed and constructed in accordance with ASCE 7, excluding Chapter 14 and excluding Chapter 14 and Appendix 11AAppendix 11A. . The seismic design category for a structure is permitted to be dThe seismic design category for a structure is permitted to be determined etermined in accordance with Section 1613 or ASCE 7.in accordance with Section 1613 or ASCE 7.””

(ASCE 7(ASCE 7-- Ch 14: exceptions to Material Standards, App 11A contains QA/QCCh 14: exceptions to Material Standards, App 11A contains QA/QC provisions) provisions) CBC provides similar provisions in lieu of these CBC provides similar provisions in lieu of these

CBC Ch 16CBC Ch 16

Page 10: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

ASCE 7ASCE 7-- 05 Seismic Chapters05 Seismic ChaptersCh 11Ch 11 -- Seismic Design CriteriaSeismic Design Criteria

Ch 12Ch 12 -- Seismic Design Requirements for Seismic Design Requirements for Building StructuresBuilding Structures

Ch 13Ch 13 -- Seismic Design Requirements for Seismic Design Requirements for Nonstructural ComponentsNonstructural Components

Ch 15 Ch 15 -- Seismic Design Requirements for Seismic Design Requirements for NonbuildingNonbuilding StructuresStructures

Ch 16 Ch 16 -- Seismic Seismic Response History ProcedureResponse History Procedure

Ch 17 Ch 17 -- Seismic Design Requirements for Seismic Design Requirements for Seismically Isolated StructuresSeismically Isolated Structures

Ch 18 Ch 18 -- Seismic Design Requirements for Seismic Design Requirements for Structures with Damping SystemsStructures with Damping Systems

Ch 19 Ch 19 -- Soil Structure InteractionSoil Structure Interaction for Seismic Designfor Seismic Design

Ch 20 Ch 20 -- Site Classification Procedure for Seismic Design (Soil Related)Site Classification Procedure for Seismic Design (Soil Related)

Ch 21 Ch 21 -- Site Specific Ground Motion Procedures for Seismic Design (SoilSite Specific Ground Motion Procedures for Seismic Design (Soil ))

Ch 22 Ch 22 -- Seismic Ground Motion and LongSeismic Ground Motion and Long-- Period Transition MapsPeriod Transition Maps

Ch 23 Ch 23 -- Seismic Design Reference DocumentsSeismic Design Reference Documents

ASCE 7ASCE 7-- 05 Seismic Chapters05 Seismic Chapters

Page 11: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Complexity of ASCE 7 Complexity of ASCE 7 –– 05 Code05 Code

Commentary Commentary -- ASCE 7ASCE 7-- 05 05

Six Levels of Design Categories

Five Different EQ Loading Procedures

F

Page 12: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Understanding Chapters 11 & 12:Understanding Chapters 11 & 12:EQ Loading & Design RequirementsEQ Loading & Design Requirements

The basic componentsThe basic components

1.1. Determine the EQ intensity (i.e. loading) based on the Determine the EQ intensity (i.e. loading) based on the location of the building: The location of the building: The DemandDemand Side Side

2.2. Determine EQ Design level to be implemented in Determine EQ Design level to be implemented in response to the EQ level: The response to the EQ level: The SupplySupply SideSide

3.3. Provide Detailed Seismic Design information Provide Detailed Seismic Design information ––i.gi.g. . System parameters, Analysis requirement, EQ loading System parameters, Analysis requirement, EQ loading combinations, drifts limits combinations, drifts limits

Commentary Commentary -- EQ Loading & Design EQ Loading & Design ReqReq’’mntmnt

Page 13: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Understanding Chapters 11 & 12:Understanding Chapters 11 & 12:EQ Loading & Design RequirementsEQ Loading & Design Requirements

Factors influencing EQ Intensity (loading) :Factors influencing EQ Intensity (loading) :Regional seismicity defined by acceleration Regional seismicity defined by acceleration parameters: Ss, Sparameters: Ss, S11

Site specific classification: Site specific classification: FFaa, F, Fvv–– adjustments for the adjustments for the local soil characteristicslocal soil characteristics

Commentary Commentary -- EQ Loading & Design EQ Loading & Design ReqReq’’mntmnt

Result:Result: Design Response Design Response Spectrum Spectrum -- i.e. EQ loading i.e. EQ loading demanddemand

Page 14: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Understanding Chapters 11 & 12:Understanding Chapters 11 & 12:EQ Loading & Design RequirementsEQ Loading & Design Requirements

Factors influencing the Seismic Design level to Factors influencing the Seismic Design level to be implemented: The be implemented: The SupplySupply Side Side

Occupancy CategoryOccupancy Category::Categorizes Buildings in Accordance to Hazard to Human Life and Categorizes Buildings in Accordance to Hazard to Human Life and Essentiality: Varies from IEssentiality: Varies from I-- Low hazard to human life to IVLow hazard to human life to IV--essential facilities.essential facilities.

Importance Factor:Importance Factor:Factor Assigned to Occupancy Category in Accordance to the Factor Assigned to Occupancy Category in Accordance to the ClassificationClassificationHigher Occupancy Category Higher Importance FactorHigher Occupancy Category Higher Importance Factor

ResultResult: Seismic Design Category (SDC):: Seismic Design Category (SDC):The appropriate design level for the EQ intensity considered. The appropriate design level for the EQ intensity considered. (6 SDC levels : A thru F)(6 SDC levels : A thru F)

Commentary Commentary -- EQ Loading & Design EQ Loading & Design ReqReq’’mntmnt

Page 15: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Structure Occupancy Category

Structure Location

Seismicity of Region -Acceleration SS, S1

Determining Seismic LoadingDetermining Design Level

Importance Factor

Seismic Design Category (SDC)

Incorporate Site Soil Conditions; Fa & Fv to

determine SDS SD1

Seismic Spectra

Understanding Chapters 11 & 12:Understanding Chapters 11 & 12:EQ Loading & Design RequirementsEQ Loading & Design Requirements

Commentary Commentary -- EQ Loading & Design EQ Loading & Design ReqReq’’mntmnt

Design Building

Page 16: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

The path to EQ load demand The path to EQ load demand and design requirementsand design requirements

The Quest for EQ Loads & Design RequirementsThe Quest for EQ Loads & Design Requirements

Ch 11 & Ch 12Ch 11 & Ch 12

BUILDING LOCATION

SPECTRAL ACCELARATION: SS & S1

(MAPS OR USGS WEBSITE)

SITE CLASSIFICATION ADJUSTMENT: Fa & Fv (Table 11.4-1 & 2)

CALCULATE MAXIMUM CONSIDERED EQ. (MCE) PARAMETER, SMS = FaSS & SM1 = FVS1

CONSTRUCT A DESIGN RESPONSE SPECTRA USING SPECTRAL ACCELERATION SDS = 2SMS/3 & SD1 = 2SM1/3

OCCUPANCY CATEGORY (CBC TABLE 1604.5)& IMPORTANCE FACTOR (ASCE TABLE 11.5-1)

SEISMIC DESIGN CATEGORY (SDC) A, B, C, D BASED ON SDS, SD1 & OCCUPANCY CATEGORY I, II, III, IV

(ASCE TABLE 11.6-1 & 2)

ANALYSE AND DESIGN THE BUILDING

(1)

(2)

(3)

(4)

(6)

(5)

Page 17: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

The MCE Ground Motion MapsThe MCE Ground Motion Maps

11.4 11.4 –– Seismic Ground Motion ValuesSeismic Ground Motion Values

Determine Regional Seismicity characteristicsDetermine Regional Seismicity characteristicsMaps from ASCE 7Maps from ASCE 7--05 or USGS web site:05 or USGS web site: http://eartquake.usgs.govhttp://eartquake.usgs.gov

May obtain coordinates at: May obtain coordinates at: http://http://stevemorse.org/jcal/latlon.phpstevemorse.org/jcal/latlon.php

(1)

Page 18: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Site Specific Adjustments to EQ loadingSite Specific Adjustments to EQ loadingSite Class: Site Class: ““AA””-- Hard Rock thru Hard Rock thru ““FF””-- Collapsible Soil Collapsible Soil (Not to be confused with SDC A(Not to be confused with SDC A--F)F)

Classifications from soils reportClassifications from soils reportIf soil property not known, If soil property not known, →→use Class use Class ““DD””

Site Coefficient: Site Coefficient: FFaa, F, FvvMaps normalized for Site Class B : RockMaps normalized for Site Class B : RockFFaa, F, Fvv adjust Sadjust Sss & S& S11 for the specific site characteristicsfor the specific site characteristicsSofter soils impact lower intensity SSofter soils impact lower intensity Sss more than higher intensity Smore than higher intensity Sss

Softer soils impact SSofter soils impact S11 more relative to Smore relative to Sss

Site Class & CoefficientsSite Class & Coefficients(2)

11.4 11.4 –– Seismic Ground Motion ValuesSeismic Ground Motion Values

Page 19: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Maximum Considered EQ (MCE) adjusted for site : SMaximum Considered EQ (MCE) adjusted for site : SMSMS= F= FaaSSs s && SSM1M1= F= FvvSS11

Design Spectral Parameter: SDesign Spectral Parameter: SDSDS= = 22 SSMSMS & S& SD1D1= = 22 SSM1M133 33

Code Response SpectraCode Response Spectra(3)

(4)

11.4 11.4 –– Seismic Ground Motion ValuesSeismic Ground Motion Values

Page 20: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

11.4 11.4 –– Seismic Ground MotionSeismic Ground Motion

ASCE 7ASCE 7--05 Response Spectra vs. UBC 9705 Response Spectra vs. UBC 97

ASCE & UBC spectra ASCE & UBC spectra are comparable. are comparable. However design forces However design forces may be different due to may be different due to differences in Sdifferences in Sss SS11, , Irreg. require., I, R, & Irreg. require., I, R, & ρρ

Soil type SB or B

Soil type SD or D

Page 21: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Importance Factor & OccupancyImportance Factor & Occupancy

Categorizes buildings based on Categorizes buildings based on hazard to human life and essentiality hazard to human life and essentiality after EQafter EQ

Amplifies design requirements for Amplifies design requirements for buildings with higher occupancy buildings with higher occupancy classificationclassificationModifies R lower and thus adjusts the Modifies R lower and thus adjusts the design base shear higher design base shear higher ––i.e. requiring higher strength i.e. requiring higher strength Modifies allowable drifts lower, thus Modifies allowable drifts lower, thus limits damage and also results into limits damage and also results into lower ductility demandlower ductility demand

Occupancy Category:Occupancy Category:

11.5 11.5 –– Importance Factor & Occupancy CategoryImportance Factor & Occupancy Category

Importance Factor:Importance Factor:

(5)

Note increase in Note increase in ““II”” for: for: Occupancy category III Occupancy category III –– i.e. Group A Occupancyi.e. Group A OccupancySelect Structures in Occupancy Category IV Select Structures in Occupancy Category IV -- Fire Fire StationsStations

Page 22: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Seismic Design Category (SDC)Seismic Design Category (SDC)

11.6 11.6 –– Seismic Design CategorySeismic Design Category

0.2 < SD1 D D D

FWhere Near Sourcewhich is SD1 > 0.750.5 < SDS D D D

(6)

EE

CommentaryCommentary

Use the more Use the more severe SDC per severe SDC per the two tablesthe two tables

Page 23: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Geotechnical ConsiderationGeotechnical ConsiderationSDC E and F: site shall not be located at a fault ruptureSDC E and F: site shall not be located at a fault rupture

Soils report for SDC C Soils report for SDC C -- F shall address:F shall address:Slope instability Slope instability LiquefactionLiquefactionDifferential settlementDifferential settlementSurface displacement due to faulting or lateral spreadingSurface displacement due to faulting or lateral spreading

Additional Requirement for SDC D Additional Requirement for SDC D –– F:F:Determination of lateral pressure on basement wall due to E.QDetermination of lateral pressure on basement wall due to E.QPotential for liquefaction or soil strength loss Potential for liquefaction or soil strength loss Consequences of liquefaction and soil strength loss Consequences of liquefaction and soil strength loss

Diff. settlement, lateral movement, lateral loads on foundationsDiff. settlement, lateral movement, lateral loads on foundations, reduction in , reduction in soil bearing, increased in lateral pressure on retaining walls asoil bearing, increased in lateral pressure on retaining walls and floatation of nd floatation of underground structuresunderground structures

Mitigation measures, selection of foundation type selection of Mitigation measures, selection of foundation type selection of structural structural systems to accommodate the displacementssystems to accommodate the displacements

11.8 11.8 –– Geological Hazards & InvestigationGeological Hazards & Investigation

Page 24: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Story above grade (i.e. grade being Seismic Base):Story above grade (i.e. grade being Seismic Base):Floor is entirely above gradeFloor is entirely above gradeWhere grade slopes along the length of building, floor is above Where grade slopes along the length of building, floor is above grade if:grade if:

1.1. More than 6 ft above More than 6 ft above Grade PlaneGrade Plane2.2. More than 6 ft above ground for 40% of building perimeterMore than 6 ft above ground for 40% of building perimeter3.3. More than12 ft above ground anywhere on the floorMore than12 ft above ground anywhere on the floor

Select New DefinitionsSelect New Definitions

Ch 11Ch 11-- Seismic Design CriteriaSeismic Design Criteria

Grade plane: Average ground level adjoining the Grade plane: Average ground level adjoining the structurestructure

For ground sloping away from structure:For ground sloping away from structure:Lowest adjacent point up to the property line Lowest adjacent point up to the property line or 6ft. away whichever is lessor 6ft. away whichever is less

Page 25: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Structural Systems for EQ ResistanceStructural Systems for EQ Resistance

Many New Lateral Load Resisting SystemsMany New Lateral Load Resisting Systems

Parameters Defining a Structural System:Parameters Defining a Structural System:

R = R = Response Modification Factor Response Modification Factor -- an indicator of an indicator of ductility for the systemsductility for the systems

Has changed for some of the systems from UBC 97Has changed for some of the systems from UBC 97

ΩΩ0 0 = Systems = Systems OverstrengthOverstrength FactorFactor-- an indicator of actual an indicator of actual system strength vs. calculated strengthsystem strength vs. calculated strength

Has changed for some of the systems from UBC 97Has changed for some of the systems from UBC 97

CCdd = Deflection Amplification Factor= Deflection Amplification Factor--Introduced to better Introduced to better predict inelastic deflections for various systemspredict inelastic deflections for various systems

12.2 12.2 –– Structural System SelectionStructural System Selection

Page 26: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Structural Systems Design CoefficientsStructural Systems Design Coefficients(R, (R, ΩΩ00, C, Cdd))

12.2 12.2 –– Structural System SelectionStructural System Selection

Page 27: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Structural Systems Design CoefficientsStructural Systems Design Coefficients(R, (R, ΩΩ00, C, Cdd))

12.2 12.2 –– Structural System SelectionStructural System Selection

Page 28: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Structural Systems Design CoefficientsStructural Systems Design Coefficients(R, (R, ΩΩ00, C, Cdd))

12.2 12.2 –– Structural System SelectionStructural System Selection

Page 29: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Combination of Framing SystemsCombination of Framing SystemsDifferent Orthogonal Directions:Different Orthogonal Directions:

Use applicable R, CUse applicable R, Cdd, and , and ΩΩ00 for each directionfor each direction

Horizontal Combination:Horizontal Combination:Use lowest applicable R in any given directionUse lowest applicable R in any given directionCombination in the same line permitted only if:Combination in the same line permitted only if:

Occupancy Occupancy Category I, IICategory I, IILess than Less than 2 stories2 storiesLight frame structure with flexible diaphragmLight frame structure with flexible diaphragmCCdd, and , and ΩΩ00 shall correspond to the R value usedshall correspond to the R value used

Vertical Combination:Vertical Combination:R for any story R for any story ≤≤ R used in any level aboveR used in any level aboveCCdd, and , and ΩΩ00 for any story for any story ≤≤ CCdd, and , and ΩΩ00 used in any level aboveused in any level above

ExceptionsExceptions: 1. Roof top structure < 2 stories and < 10% of bldg. weigh: 1. Roof top structure < 2 stories and < 10% of bldg. weight t 2. Supported systems < 10% of bldg. weight 2. Supported systems < 10% of bldg. weight 3. Detached 1 or 2 story dwellings 3. Detached 1 or 2 story dwellings

Combination Framing Detailing Requirements:Combination Framing Detailing Requirements:Components Components common common to different lateral systems shall be per to different lateral systems shall be per detailing requirement for highest Rdetailing requirement for highest R

12.2 12.2 –– Structural Systems SelectionStructural Systems Selection

Page 30: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Two Stage AnalysisTwo Stage AnalysisFor structures with a flexible upper & a rigid lower portion, provided:

Lower portion is = 10 X stiffer than upper portion T (entire structure) ≤ 1.1 x T (upper portion by itself)

Upper & lower portion designed as separate structuresApply reaction from upper portion to top of lower portion x

(R/ρ) upper(R/ρ) lower

≥ 1.0

Note: Building need not be Note: Building need not be ““regularregular”” for 2for 2-- stage analysis as required by UBC 97stage analysis as required by UBC 97

12.2 12.2 –– Structural Design BasisStructural Design Basis

++==

Page 31: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Diaphragm ClassificationDiaphragm Classification

CBC 1613.6.1 provides alternative provisions; CBC 1613.6.1 provides alternative provisions; wood panels and steel decks can be wood panels and steel decks can be considered as flexible diaphragms if:considered as flexible diaphragms if:

Conc. topping on wood Conc. topping on wood diaphdiaph. . ≤≤ 11--1/21/2””Drifts Drifts ≤≤ code allowablecode allowableLateral systems: light frame wall with wood or steel sheetLateral systems: light frame wall with wood or steel sheetCant. Diaphragm are designed per section 2305.2.5Cant. Diaphragm are designed per section 2305.2.5

12.3 12.3 –– Diaphragm Flex., Irregularity & RedundancyDiaphragm Flex., Irregularity & Redundancy

Note:Note:Must Consider SemiMust Consider Semi--Rigid if Rigid if Horizontal Irregularity Exists Horizontal Irregularity Exists or if Span or if Span D DepthDepth 3

Page 32: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Horizontal IrregularityHorizontal Irregularity

Provisions:12.3.3.1 Prohibited irregularity for SDC E & F → Horizontal irregularity 1b12.3.3.3 Support elements shall be designed for Em = ΩoQE ± Ev12.3.3.4 Design force shall be increased by 25% for diaphragm to vertical element connection and connection to collectors

and collector to vertical element. Or alternatively design for: 12.4.3.2 load combination: (1.2+0.2 SDS)D + ΩoQE + L + 0.2S

(0.9 – 0.2 SDS)D + ΩoQE + 1.6H12.7.3 Rigid elements shall not inhibit the performance of moment frames12.8.4.3 Amplify accidental torsion with Ax = δmax

2 ≤ 3. No amplification for light frame construction is required.1.2 δavg

12.12.1 Δ shall be computed at the edges of the building 16.2.2.3 3-D Non-Linear Time History Analysis requiredTable 12.6-1 Prescribes Analysis Procedure

12.3 12.3 –– Diaphragm Flex., Irregularity & RedundancyDiaphragm Flex., Irregularity & Redundancy

( )

Note: Note: 12.3.3.3 12.3.3.3 requires requires that that ΩΩooapply to apply to podium podium floors with floors with light frame light frame shear wallsshear walls

Page 33: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Vertical IrregularityVertical Irregularity

Exceptions:1.Type 1a, 1b, or 2 not applicable where all story drift is < 1.3 X the adjacent story drift. Torsional effects need not apply.

The top two stories need not be considered.2.Type 1a, 1b and 2 need not be considered in : a) One story structures in any category, b)2 story buildings in SDC B,C, D

Provisions:12.3.3.1 Prohibited irregularity: for SDC D →Vertical irregularity 5b, For SDC E & F → vertical irregularity 1b, 5a, or 5b12.3.3.3 Support elements shall be designed for Em = ΩoQE ± Ev12.3.3.4 Design force shall be increased by 25% for diaphragm to vertical element connection and connection to collectors

and collector to vertical element. Or alternatively design for: 12.4.3.2 load combination: (1.2+0.2 SDS)D + ΩoQE + L + 0.2S

(0.9 – 0.2 SDS)D + ΩoQE + 1.6HTable 12.6-1: Prescribes analysis procedure

12.3 12.3 –– Diaphragm Flex., Irregularity & RedundancyDiaphragm Flex., Irregularity & Redundancy

Note: Note: 12.3.3.3 12.3.3.3 requires requires that that ΩΩooapply to apply to podium podium floors with floors with light frame light frame shear wallsshear walls

Page 34: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Redundancy Factory by default is Redundancy Factory by default is ρρ = 1.3 for structural systems in = 1.3 for structural systems in SDC D SDC D –– F except as noted below:F except as noted below:

Members to be removed within a story

= LHs

2 x LHs

=

ρ

Redundancy Redundancy

12.3 12.3 –– Diaphragm Flex., Irregularity & RedundancyDiaphragm Flex., Irregularity & Redundancy

ρρ isis always = 1.0 for these conditionsalways = 1.0 for these conditions

Page 35: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Seismic Load Effects & CombinationSeismic Load Effects & CombinationE= EE= Ehh + E+ Evv & E= E& E= Ehh -- EEvv →→ use in load combinationuse in load combination 7 7 oror 88

EEhh = = ρρQQEEEEvv = 0.2S= 0.2SDSDSD (Zero for determining demand on soils for foundation designD (Zero for determining demand on soils for foundation design))

Load combination with EQ for strength design:Load combination with EQ for strength design: (Same as UBC 97)(Same as UBC 97)

5. (1.2+0.2 S5. (1.2+0.2 SDSDS)D + )D + ρρQQEE + L + 0.2S + L + 0.2S For LL For LL ≤≤ 100 psf 100 psf →→ Use 0.5 L Use 0.5 L →→ Except in garages or public assembly areasExcept in garages or public assembly areas

7. (0.9 7. (0.9 –– 0.2 S0.2 SDSDS)D + )D + ρρQQEE + 1.6H + 1.6H →→ If H counter acts E do not include itIf H counter acts E do not include it

Load combination with EQ for allowable stress design:Load combination with EQ for allowable stress design:5. (1.0+5. (1.0+0.14 S0.14 SDSDS)D + H + F + 0.7)D + H + F + 0.7ρρQQEE6. (1.0+6. (1.0+0.105 S0.105 SDSDS)D + H + F + 0.525)D + H + F + 0.525ρρQQEE + 0.75L + 0.75(Lr or S or R)+ 0.75L + 0.75(Lr or S or R)8. (8. (0.6 0.6 -- 0.14 S0.14 SDSDS)D + H + 0.7)D + H + 0.7ρρQQE E NEWNEW

Note: Note: CBCCBC section 1605.3.2 offers section 1605.3.2 offers ””Alternative basic load combinationAlternative basic load combination”” same same as UBC 97 for allowable stress design as UBC 97 for allowable stress design where where EEvv is zerois zero as follows:as follows:D+L+S+E/1.4 & 0.9D+E/1.4 (If these combinationsD+L+S+E/1.4 & 0.9D+E/1.4 (If these combinations are used for foundation design then are used for foundation design then

reduction of foundation forces per ASCE 12.13. 4 reduction of foundation forces per ASCE 12.13. 4 is not allowed)is not allowed)

Minimum Upward Forces for Horizontal Cantilevers for SDC D Minimum Upward Forces for Horizontal Cantilevers for SDC D -- F:F:Net upward force of 0.2 X DLNet upward force of 0.2 X DL

12.4 12.4 –– Seismic Load Effects & CombinationsSeismic Load Effects & Combinations

Page 36: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

EEmm = E= Emhmh + E+ Evv & E& Emm = E= Emhmh -- EEvv →→ use in combinationuse in combination 7 7 oror 88EEmhmh = = ΩΩooQQEE

EEmm need not exceed maximum mechanism load using expected values ofneed not exceed maximum mechanism load using expected values of the material. the material.

Load Combinations for strength design:Load Combinations for strength design: (comparable to UBC 97)(comparable to UBC 97)

5. (1.2+0.2 S5. (1.2+0.2 SDSDS)D + )D + ΩΩooQQEE + L + 0.2S + L + 0.2S For LL For LL ≤≤ 100 psf 100 psf →→ 0.5 L 0.5 L →→ Except in garages or public assembly areasExcept in garages or public assembly areas

7. (0.9 7. (0.9 –– 0.2 S0.2 SDSDS)D + )D + ΩΩooQQEE + 1.6H + 1.6H →→ If H counter acts E do not include itIf H counter acts E do not include it

Load Combinations for allowable stress design:Load Combinations for allowable stress design: NEWNEW5. (1.0+5. (1.0+0.14 S0.14 SDSDS)D + H + F + 0.7)D + H + F + 0.7ΩΩooQQEE6. (1.0+6. (1.0+0.105 S0.105 SDSDS)D + H + F + 0.525)D + H + F + 0.525ΩΩooQQEE + 0.75L + 0.75(Lr or S or R)+ 0.75L + 0.75(Lr or S or R)8. (8. (0.60.6 -- 0.14 S0.14 SDSDS)D + H + 0.7)D + H + 0.7ΩΩooQQE E NEWNEW

Allowable Stress Increase: use a 1.2 x for combinations with oAllowable Stress Increase: use a 1.2 x for combinations with over strength ver strength factorfactor

Not to be combined with any other load duration factors except tNot to be combined with any other load duration factors except those in AF&PA NDShose in AF&PA NDS

Seismic Load Effects Including Seismic Load Effects Including Overstrength Factor Overstrength Factor ΩΩoo

12.4 12.4 –– Seismic Load Effects & CombinationsSeismic Load Effects & Combinations

Page 37: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Direction of LoadDirection of LoadLoads may be applied independently in each of the orthogonal Loads may be applied independently in each of the orthogonal direction. direction. Applied direction shall produce the most critical load effectApplied direction shall produce the most critical load effect ..

For nonFor non--parallel systems (horiz. Irreg. Type 5) the critical load effecparallel systems (horiz. Irreg. Type 5) the critical load effect is t is assumed to be satisfied if one of the following is used:assumed to be satisfied if one of the following is used:

1)1) Orthogonal Combination Procedure:Orthogonal Combination Procedure:Loading is applied independently in 2 orthogonal direction, usinLoading is applied independently in 2 orthogonal direction, using ELF, g ELF, response spectrum or time history analysis. Apply 100% of the fresponse spectrum or time history analysis. Apply 100% of the force in one orce in one direction + 30% in the orthogonal direction and alternate directdirection + 30% in the orthogonal direction and alternate directions. Use the ions. Use the maximum force generated in the element for design.maximum force generated in the element for design.

2)2) Simultaneous Application of Orthogonal Ground Motion:Simultaneous Application of Orthogonal Ground Motion:Using linear or nonUsing linear or non--linear time history with orthogonal pairs of ground motion linear time history with orthogonal pairs of ground motion applied simultaneously.applied simultaneously.

Columns or walls forming 2 intersecting seismic resisting systemColumns or walls forming 2 intersecting seismic resisting systems in s in SDC DSDC D--F:F:

If axial load due to EQ in either direction > 20% of capacityIf axial load due to EQ in either direction > 20% of capacity→→ they shall be they shall be designed for most critical load effect due to EQ in any directiodesigned for most critical load effect due to EQ in any direction. n. Either 1) or 2) above may be used to satisfy this requirement. Either 1) or 2) above may be used to satisfy this requirement. For flexible diaphragm 2For flexible diaphragm 2--D analysis is permitted.D analysis is permitted.

12.5 12.5 –– Direction of LoadingDirection of Loading

Page 38: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Analysis Selection ProcessAnalysis Selection Process

ELF procedure is allowed only for building with T< 3.5 TELF procedure is allowed only for building with T< 3.5 Tss

TABLE 12.6TABLE 12.6--1 PERMITTED ANALYTICAL PROCEDURES1 PERMITTED ANALYTICAL PROCEDURES

12.6 12.6 –– Analysis Procedure SelectionAnalysis Procedure Selection

Page 39: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Modeling CriteriaModeling CriteriaFoundation Modeling:Foundation Modeling:

Model shall be Fixed or Pin consistent with the design intentModel shall be Fixed or Pin consistent with the design intentSoil flexibility may be modeled per Ch 19 Soil flexibility may be modeled per Ch 19 –– i.e. Soili.e. Soil--Structure interactionStructure interaction

Structural Modeling:Structural Modeling:PP--ΔΔ must be consideredmust be consideredUse 3Use 3--D modeling for D modeling for torsionaltorsional, out of plane offset, & non, out of plane offset, & non--parallel system parallel system irregularitiesirregularitiesSemiSemi--rigid diaphragms shall have their stiffness modeled.rigid diaphragms shall have their stiffness modeled.Use cracked section property for CMU and Concrete elementsUse cracked section property for CMU and Concrete elementsContribution of panel zone deformation on drift shall be considContribution of panel zone deformation on drift shall be consideredered

Adjoining rigid elements shall not inhibit the performance Adjoining rigid elements shall not inhibit the performance of moments frames:of moments frames:

Their effects at Their effects at ΔΔmm must be consideredmust be consideredTheir effects on causing irregularity must be considered upon faTheir effects on causing irregularity must be considered upon failure of these ilure of these elementselements

12.7 12.7 -- Modeling CriteriaModeling Criteria

Page 40: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Equivalent Lateral Force MethodEquivalent Lateral Force Method

ELF is essentially the formulation of the code spectra for a givELF is essentially the formulation of the code spectra for a given T, R and I incorporated.en T, R and I incorporated.

Regular structures Regular structures ≤≤ 5 stories with T 5 stories with T ≤≤ 0.5S 0.5S →→ may use Ss =1.5 for determination of Csmay use Ss =1.5 for determination of Cs

12.8 12.8 -- Equivalent Lateral Force ProcedureEquivalent Lateral Force Procedure

V = CV = CSS WW

CCSS ==SSDSDS

RR

11

CCSS ==SSD1D1 for T for T << TTLLTT

CCSS = = SSD1D1TTLL for T > Tfor T > TLLTT22

(( ) ) RR

11

(( ))

(( ))RR

11

CCSS = 0.01= 0.01

CCSS = = 0.5 S0.5 S

11

RR

11

))

MaxMax

MaxMax

MinMin

MinMin Where SWhere S11 >> 0.60.6

((

Page 41: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

0.000

0.500

1.000

1.500

2.000

0.000 0.500 1.000 1.500 2.000 2.500 3.00

PERIOD (seconds)

SPECTRA

L A

CCELERA

TIO

N (g'

s)

12.8 12.8 –– ELF procedureELF procedure

ELF Base Shear ELF Base Shear -- ASCE vs. UBCASCE vs. UBC

Soil type SD or D

Soil type SB or B

ASCE & UBC base ASCE & UBC base shear are comparable shear are comparable however design however design forces may vary due forces may vary due to differences in irreg. to differences in irreg. require., I, require., I, ρρ & R.& R.

Page 42: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Determination of PeriodDetermination of PeriodPeriod Determination for Period Determination for strength demandstrength demand for ELF for ELF Procedure:Procedure:

Alternatively for buildings with: Alternatively for buildings with: steel or concrete moment frames steel or concrete moment frames ≤≤ 12 stories & Story Heights 12 stories & Story Heights ≥≥ 10 ft T10 ft Taa = 0.1N= 0.1Nmasonry or concrete shear walls Tmasonry or concrete shear walls Taa = 0.0019 h= 0.0019 hnn//√√CCww

12.8 12.8 -- Equivalent Lateral Force ProcedureEquivalent Lateral Force Procedure

Maximum T: Maximum T: ≤≤ CCu u TTaa

or Alternativelyor AlternativelyTa: Ta: ≤≤ CCt t h h xx

nn

Find build. T & limit itFind build. T & limit it Use TUse Taa

Page 43: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Vertical Distribution :Vertical Distribution :

Horizontal Distribution: Horizontal Distribution: Based on relative stiffness of vertical resisting elementsBased on relative stiffness of vertical resisting elements

Accidental Torsion: Accidental Torsion: Displace center of mass by 5% in the direction that produces Displace center of mass by 5% in the direction that produces mamaximum effectximum effect

Amplification of Accidental Torsion for Torsional Irregularity:Amplification of Accidental Torsion for Torsional Irregularity:

Ax=1.0 forAx=1.0 for light frame constructionlight frame construction

Distribution of ForcesDistribution of Forces

12.8 12.8 -- Equivalent Lateral Force ProcedureEquivalent Lateral Force Procedure

k=1 for Tk=1 for T≤≤ 0.5 sec0.5 seck=2 for Tk=2 for T≥≥ 2.5 sec 2.5 sec

For 0.5 < T < 2.5 InterpolateFor 0.5 < T < 2.5 Interpolate

Page 44: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Determination of DriftsDetermination of DriftsLocation where drift is measured: Location where drift is measured:

Difference of deflection at the Difference of deflection at the center of masscenter of massWhere Where torsional irregularity exists drift (torsional irregularity exists drift (ΔΔ) is calculated at edges of building) is calculated at edges of building

Inelastic Deflection Calculation:Inelastic Deflection Calculation: δδx x ==CCdd δδxexeII

δδxexe = Deflection = Deflection by elastic methodby elastic method with with ““II”” factor included in the EQ loadingfactor included in the EQ loadingCCdd = Amplification factor to simulate inelastic = Amplification factor to simulate inelastic δδ

NOTE: The importance factor ( I ) has been neutralized in the NOTE: The importance factor ( I ) has been neutralized in the calculation calculation of drifts. of drifts. i. e. The importance factor does not effect the i. e. The importance factor does not effect the calculation calculation of deflections.of deflections.

Drifts shall be calculated using strength level seismic forces Drifts shall be calculated using strength level seismic forces even when allowable stress approach is used.even when allowable stress approach is used.

Drifts are calculated using seismic base shear with Drifts are calculated using seismic base shear with no upper limit no upper limit on the period.on the period.

12.8 12.8 -- Equivalent Lateral Force ProcedureEquivalent Lateral Force Procedure

Page 45: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

At least 90% mass participation At least 90% mass participation

Use the Spectra in section 11.4 or a site specific spectra dividUse the Spectra in section 11.4 or a site specific spectra divided by ed by RR for the analysisfor the analysisII

Multiply displacements and drifts by Multiply displacements and drifts by CCdd (assumes (assumes ““II”” already included in the EQ loading)already included in the EQ loading)II

CQC method of combination shall be used when closely spaced modeCQC method of combination shall be used when closely spaced modes occurs occur

For force calculations: use analysis results but as a minimum scFor force calculations: use analysis results but as a minimum scale up the modal ale up the modal response shear response shear VVtt ≥≥ 0.85 V0.85 VELF ELF if lower if lower

NOTE: Scaling up for drifts calculations is not required. The NOTE: Scaling up for drifts calculations is not required. The CCdd factor does the required adjustmentsfactor does the required adjustmentsII

Amplification of torsion is not requiredAmplification of torsion is not required

Where loads applied concurrently in orthogonal directions the 5%Where loads applied concurrently in orthogonal directions the 5% eccentricity shall only eccentricity shall only be applied for the direction with maximum effectbe applied for the direction with maximum effect

P P -- Delta effects shall be consideredDelta effects shall be considered

Soil structure interaction reduction is permitted (Ch. 19)Soil structure interaction reduction is permitted (Ch. 19)

Modal Response Spectrum AnalysisModal Response Spectrum Analysis

12.9 12.9 -- Modal Response AnalysisModal Response Analysis

Page 46: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Diaphragm Design ForcesDiaphragm Design ForcesUse forces from analysis but not less than Use forces from analysis but not less than eqeq 12.1012.10--1:1:

eqeq 12.1012.10--1 1 withwith Max Max FFpxpx = 0.4S= 0.4SDSDSIwIwpxpx

Min Min FFpxpx = 0.2S= 0.2SDSDSIwIwpxpx

Where diaphragm transfers forces from one vertical load resistinWhere diaphragm transfers forces from one vertical load resisting g element to another due to offsets or changes in stiffness these element to another due to offsets or changes in stiffness these forces shall be added to the above forcesforces shall be added to the above forces

ρρ applies to diaphragmsapplies to diaphragms in SDC D in SDC D ––F in the following manner:F in the following manner:

For forces calculated per eq 12.10For forces calculated per eq 12.10--1 (above), 1 (above), ρρ=1.0 =1.0 For transfer forces For transfer forces ρρ = same as the building= same as the building

12.10 12.10 –– Diaphragms, Chords, and CollectorsDiaphragms, Chords, and Collectors

Page 47: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Min. & Max. Diaphragm ForcesMin. & Max. Diaphragm Forces

Parity in Min. & Max. Parity in Min. & Max. forces between forces between ASCE5ASCE5--07 and 07 and UBC 97UBC 97

12.10 12.10 –– Diaphragms, Chords, and CollectorsDiaphragms, Chords, and Collectors

ASCE7ASCE7--05 vs. UBC 9705 vs. UBC 97

Page 48: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Out of Plane Wall ForcesOut of Plane Wall ForcesOut of plane forces for structural walls = 0.4 SOut of plane forces for structural walls = 0.4 SDS DS II x wall weight x wall weight >>min. 10% x wall weightmin. 10% x wall weight

Anchorage of concrete or masonry wall force shall be the greaterAnchorage of concrete or masonry wall force shall be the greater of:of:Out of plane force above orOut of plane force above orForce = 400 SForce = 400 SDSDS II lbs/ft of wall lbs/ft of wall >> min. of 280 lbs/ft of wall (Concrete with UBC) min. of 280 lbs/ft of wall (Concrete with UBC)

Walls shall be designed to resist bending between anchors where Walls shall be designed to resist bending between anchors where anchor spacing > 4 ft.anchor spacing > 4 ft.

Anchorage of conc. or CMU walls to Flexible Diaphragms: Anchorage of conc. or CMU walls to Flexible Diaphragms: FFpp = 0.8 S= 0.8 SDSDS II wwpp (Note 2 X the typical out of plane force)(Note 2 X the typical out of plane force)

Connection shall extend into the diaphragm sufficiently to develConnection shall extend into the diaphragm sufficiently to develop op the forces into the diaphragm. (i.e. Tear out of diaphragm shallthe forces into the diaphragm. (i.e. Tear out of diaphragm shall be be avoided)avoided)

12.11 12.11 –– Structural Walls & Their AnchorageStructural Walls & Their Anchorage

Page 49: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Wall Anchorage to DiaphragmWall Anchorage to Diaphragm

The forces shall be increased by 1.4 for the steel elements of tThe forces shall be increased by 1.4 for the steel elements of the he connection with the exception of anchor bolts and reinforcing stconnection with the exception of anchor bolts and reinforcing steeleel

Metal deck diaphragm shall not be used as continuous ties in theMetal deck diaphragm shall not be used as continuous ties in thedirection perpendicular to the deckdirection perpendicular to the deck..

Wood Diaphragms:Wood Diaphragms:

Continuous ties shall be in addition to the sheathing. Continuous ties shall be in addition to the sheathing.

Anchorage shall not be accomplished through: toe nailing, nails Anchorage shall not be accomplished through: toe nailing, nails in withdrawal or cross in withdrawal or cross grain bending in wood ledgers, or crossgrain bending in wood ledgers, or cross--grain tensiongrain tension

Diaphragm sheathing shall not be considered effective as providiDiaphragm sheathing shall not be considered effective as providing the ties or struts ng the ties or struts required by this sectionrequired by this section

12.11 12.11 –– Structural Walls & Their AnchorageStructural Walls & Their Anchorage

Page 50: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Out of Plane Wall ForcesOut of Plane Wall Forces

ASCE7ASCE7--05 vs. UBC 9705 vs. UBC 97

No min. limit No min. limit prescribed by ASCE. prescribed by ASCE.

12.11 12.11 –– Structural Walls & Their AnchorageStructural Walls & Their Anchorage

ASCE and UBC 97 ASCE and UBC 97 have comparable out have comparable out of plane forces for of plane forces for SsSs≥≥ 1.51.5

Page 51: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

ASCE 7ASCE 7--05 vs. UBC 9705 vs. UBC 97

Comparable Comparable anchorage forces anchorage forces for flexible for flexible diaphragmdiaphragm

ASCE has lower ASCE has lower anchorage forces anchorage forces for rigid diaphragmfor rigid diaphragm

Wall Anchorage ForcesWall Anchorage Forces

12.11 12.11 –– Structural Walls & Their AnchorageStructural Walls & Their Anchorage

Page 52: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Story Drift LimitsStory Drift LimitsASCE lowers the allowable drifts for buildings with higher ASCE lowers the allowable drifts for buildings with higher ““II”” factor. factor. UBC 97 calculates higher pseudo UBC 97 calculates higher pseudo ΔΔ for buildings with higher for buildings with higher ““II””. . ( i.e. UBC includes ( i.e. UBC includes ““I I ““ in EQ loading used for the calculations of in EQ loading used for the calculations of ““II””))

Moment frames in SDC DMoment frames in SDC D--F are limited to drifts F are limited to drifts << ΔΔaa//ρρThis forces additional bays of frame in the buildingThis forces additional bays of frame in the building

ASCE has lower drift limits for the critical occupancies III, & ASCE has lower drift limits for the critical occupancies III, & IV vs. UBC 97IV vs. UBC 97.

12 .12 12 .12 –– Drift & Deformation Drift & Deformation

Building Separation Clarification: Separation = Building Separation Clarification: Separation = √√ δδx1x122 + + δδx2x222

Page 53: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Foundation DesignFoundation DesignFoundation flexibility can be modeled per Ch. 19 (i.e. Soil Foundation flexibility can be modeled per Ch. 19 (i.e. Soil –– Structure Structure Interaction). Interaction).

Overturning for foundations may be reduced:Overturning for foundations may be reduced:by 25% with ELF procedure except for inverted pendulum system (nby 25% with ELF procedure except for inverted pendulum system (not ot permitted when the Alternative ASD Loadpermitted when the Alternative ASD Load”” per 1605.3.2 is used.)per 1605.3.2 is used.)by 10% for structures designed with the modal analysisby 10% for structures designed with the modal analysis

Note: These reductions not allowed for alternative basic load cNote: These reductions not allowed for alternative basic load combination per CBC 1605.3.2ombination per CBC 1605.3.2

Foundation Ties shall be provided for pile caps, drilled piers aFoundation Ties shall be provided for pile caps, drilled piers and nd caissons. Tension or compression strength = 0.1 Scaissons. Tension or compression strength = 0.1 SDSDS x the larger pile x the larger pile capacity or column factored (DL + LL). Restrain may be demonstracapacity or column factored (DL + LL). Restrain may be demonstrated ted to be provided by slab on grades or competent soilto be provided by slab on grades or competent soil

Foundation ties as defined above shall be provided for footings Foundation ties as defined above shall be provided for footings in in soil class E or Fsoil class E or F

The provisions provide requirements for pile anchorage to caps tThe provisions provide requirements for pile anchorage to caps to o resist uplift or provide rotational restraintresist uplift or provide rotational restraint

12.13 12.13 –– Foundation DesignFoundation Design

Page 54: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Requirements for Simplified Design ProcedureRequirements for Simplified Design ProcedureMay be used if the following limitations are met:May be used if the following limitations are met:

1.1. Occupancy Category I or II Occupancy Category I or II 2.2. Site shall not be Class E or FSite shall not be Class E or F3.3. Structure Structure << 3 stories3 stories4.4. Seismic lateral system: Either bearing wall or Building Frame sySeismic lateral system: Either bearing wall or Building Frame system stem

5.5. Minimum 2 lines of lateral resistance in each of the 2 major dirMinimum 2 lines of lateral resistance in each of the 2 major directionsections6.6. Minimum 1 line of resistance on each side of center of massMinimum 1 line of resistance on each side of center of mass7.7. For flexible diaphragms, overhangs beyond outside line of shear For flexible diaphragms, overhangs beyond outside line of shear walls or walls or

braced frames shall conform to: a braced frames shall conform to: a << d/5d/58.8. For buildings with non flexible diaphragm, the building shall noFor buildings with non flexible diaphragm, the building shall not have adequate t have adequate

torsional resistance per prescriptive requirements listed in thetorsional resistance per prescriptive requirements listed in the UBCUBC9.9. Lines of resistance shall be oriented at angles no more than 15 Lines of resistance shall be oriented at angles no more than 15 degrees from degrees from

major orthogonal directionsmajor orthogonal directions10.10. Simplified procedure shall be used for each major orthogonal dirSimplified procedure shall be used for each major orthogonal directionection11.11. System irregularities caused by in plane or out of plane offsetsSystem irregularities caused by in plane or out of plane offsets is not permittedis not permitted12.12. LateralLateral--LoadLoad--Resistance of any story shall not be < 80% of any other storyResistance of any story shall not be < 80% of any other story

12.14 12.14 -- Simplified Alternate Design CriteriaSimplified Alternate Design Criteria

Page 55: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Seismic Load EffectsSeismic Load Effects--Simplified MethodSimplified Method

E= EE= Ehh + E+ Evv & E= E& E= Ehh -- EEvv →→ use in load combination 7 or 8use in load combination 7 or 8EEhh = Q= QEE notice no notice no ρρEEvv = 0.2S= 0.2SDSDSD (Ev = Zero for determining demand on soil foundations)D (Ev = Zero for determining demand on soil foundations)

Load combination with EQ for strength design: Load combination with EQ for strength design: (COMPARABLE TO UBC 97)(COMPARABLE TO UBC 97)

5. (1.2+0.2 S5. (1.2+0.2 SDSDS)D + Q)D + QEE + L + 0.2S + L + 0.2S For LL For LL ≤≤ 100 psf 100 psf →→ Use 0.5 L Use 0.5 L →→ Except in garages or public assembly areasExcept in garages or public assembly areas

7. (0.9 7. (0.9 –– 0.2 S0.2 SDSDS)D + Q)D + QEE + 1.6H + 1.6H →→ If H counter acts E do not include itIf H counter acts E do not include it

Load combination with EQ for allowable stress design: (same as CLoad combination with EQ for allowable stress design: (same as CBC BC 1605.3.1)1605.3.1)

5. (1.0+5. (1.0+0.14 S0.14 SDSDS)D + H + F + 0.7Q)D + H + F + 0.7QEE6. (1.0+6. (1.0+0.105 S0.105 SDSDS)D + H + F + 0.525Q)D + H + F + 0.525QEE + 0.75L + 0.75(Lr or S or R)+ 0.75L + 0.75(Lr or S or R)8. (8. (0.60.6-- 0.14 S0.14 SDSDS)D + H + 0.7Q)D + H + 0.7QEE

12.14 12.14 -- Simplified Alternate Design CriteriaSimplified Alternate Design Criteria

Page 56: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Seismic Load Effect Including a 2.5 Over Strength Factor:Seismic Load Effect Including a 2.5 Over Strength Factor:EEmm = E= Emhmh + E+ Evv & E& Emm = E= Emhmh –– EEvv →→ use in combination 7 or 8 use in combination 7 or 8 EEmhmh = 2.5Q= 2.5QEE

EEmm need not exceed maximum mechanism load using expected values ofneed not exceed maximum mechanism load using expected values of the the material.material.

Load Combinations with over strength factor for strength design:Load Combinations with over strength factor for strength design:5. (1.2+0.2 S5. (1.2+0.2 SDSDS)D + 2.5Q)D + 2.5QEE + L + 0.2S + L + 0.2S

For LL For LL ≤≤ 100 psf 100 psf →→ 0.5 L 0.5 L →→ Except in garages or public assembly areasExcept in garages or public assembly areas7. (0.9 7. (0.9 –– 0.2 S0.2 SDSDS)D + 2.5Q)D + 2.5QEE + 1.6H + 1.6H →→ If H counter acts E do not include itIf H counter acts E do not include it

Allowable Stress Design with over strength factorAllowable Stress Design with over strength factor5. (1.0+0.14 S5. (1.0+0.14 SDSDS)D + H + F + 1.75Q)D + H + F + 1.75QEE6. (1.0+0.105 S6. (1.0+0.105 SDSDS)D + H + F + 1.313Q)D + H + F + 1.313QEE + 0.75L + 0.75(Lr or S or R)+ 0.75L + 0.75(Lr or S or R)8. (8. (0.60.6 -- 0.14 S0.14 SDSDS)D + H + 0.7)D + H + 0.7ΩΩooQQEEQEQE

For allowable stress For allowable stress →→ use a 1.2 x increase use a 1.2 x increase Not to be combined with any other load duration factors except tNot to be combined with any other load duration factors except those in AF&PA NDShose in AF&PA NDS

Seismic Load Effects Seismic Load Effects –– Simplified MethodSimplified Method

12.14 12.14 –– Seismic Load Effects & CombinationsSeismic Load Effects & Combinations

Page 57: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Seismic Force Resisting SystemSeismic Force Resisting System

12.14 12.14 –– Simplified Alternative Design CriteriaSimplified Alternative Design Criteria

TABLE 12.14-1 DESIGN COEFFICIENTS AND FACTORS FOR SEISMIC FORCE-RESISTING SYSTEMS FOR SIMPLIFIED DESIGN PROCEDURE

Page 58: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Seismic Force Resisting SystemSeismic Force Resisting SystemHorizontal Combination: Horizontal Combination:

Two different systems along each of the two orthogonal directionTwo different systems along each of the two orthogonal directions is permitted. The s is permitted. The corresponding R for each direction shall be used.corresponding R for each direction shall be used.

Combination in the same direction permitted within the limitatioCombination in the same direction permitted within the limitation of each system. n of each system. The lowest R shall be used.The lowest R shall be used.

Exception: Light frame construction < 2 story or flexible diaphrException: Light frame construction < 2 story or flexible diaphragm, can use the agm, can use the lowest R value for the different seismic resisting system in eaclowest R value for the different seismic resisting system in each line of resistance. h line of resistance. The diaphragm shall be designed for the lowest R in the story.The diaphragm shall be designed for the lowest R in the story.

Vertical Combination: Vertical Combination: R used for any story shall be R used for any story shall be << R used in any level above in the same directionR used in any level above in the same direction

Components Components commoncommon to different lateral systems shall be designed to different lateral systems shall be designed per detailing requirement for highest R.per detailing requirement for highest R.

12.14 12.14 –– Simplified Alternative Design CriteriaSimplified Alternative Design Criteria

Page 59: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Simplified Design Procedure Simplified Design Procedure –– Base ShearBase Shear

12.14 12.14 –– Simplified Alternative Design CriteriaSimplified Alternative Design Criteria

Base Shear V =Base Shear V =FSFSDSDSWW

where Swhere SDSDS ==22

FFaaSSssRR 33

FFaa = 1.0 for rock sites or 1.4 for soil sites or per 11.4.3= 1.0 for rock sites or 1.4 for soil sites or per 11.4.3

SSss per the maps Max Sper the maps Max Sss = 1.5= 1.5

F = 1.0 for one story buildingsF = 1.0 for one story buildingsF = 1.1 for 2 story buildingF = 1.1 for 2 story buildingF = 1.2 for 3 story buildingF = 1.2 for 3 story building

Overturning: The foundation shall be designed for Overturning: The foundation shall be designed for >> 75% of foundation overturning75% of foundation overturning

Drifts are not required to be calculatedDrifts are not required to be calculated

For building separation, cladding design, etc. Drifts may be taFor building separation, cladding design, etc. Drifts may be taken as 0.01 x ken as 0.01 x building height, unless computed to be less.building height, unless computed to be less.

VERTICAL FORCE DISTRIBUTIONVERTICAL FORCE DISTRIBUTION

Fx =Fx =WWxxWW VV

Page 60: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

Simplified Procedure Base ShearSimplified Procedure Base ShearASCE 7ASCE 7--05 vs. UBC 9705 vs. UBC 97

12.14 12.14 –– Simplified Alternative Design CriteriaSimplified Alternative Design Criteria

ASCE simplified base shear ASCE simplified base shear is on par with UBC 97 for is on par with UBC 97 for 33--story structure but lower story structure but lower for a 1for a 1--story structurestory structure

ASCE7-05

Page 61: Seismic Design Criteria 2007 CBC by Mehran Pourzanjani

ConclusionConclusion

As the state of knowledge advances, the codes will As the state of knowledge advances, the codes will become more complex and expanded.become more complex and expanded.

The most effective way to stay abreast of the code The most effective way to stay abreast of the code changes is to understand the basis and the intent changes is to understand the basis and the intent of the design provisions. This enables one to of the design provisions. This enables one to proactively look for and apply the appropriate proactively look for and apply the appropriate provision. provision.

The commentary part of the code and the sited The commentary part of the code and the sited references are the best resource for understanding references are the best resource for understanding the basis of the provisions.the basis of the provisions.

CommentaryCommentary