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SEISMIC DESIGNUNDER UBC-97

Purdue Universi ty

CE571 - Ear thquake Engineer ing

Spring 2003

Lu is E. Garca and Mete A . Sozen

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1Pre-dimensioning and

coordination with other design

professionals

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2Definition of all

dead and live loads

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Seismic Zone from Map in Figure 16-2

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Value of Z from Table 16-I

0.400.300.200.150.075Z

432B2A1Zone

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4Define Occupancy Category

(I)

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Occupancy Category from Table 16-K

1.001.001.00Utilities, except towers.5. Misc ellan.

structures

1.001.001.00All occupancies not listed in 1 to 3, andtowers belonging to Utilities

4.

Standardoccupancy

1.001.001.00Schools > 300 students, universities >500 students, any buildings > 5,000occupants, occupants restricted > 50

3.

Specialoccupancy

1.151.501.25Housing toxic or explosive substances.2.

Hazardousfacilit ies

1.151.501.25

Needed after the emergency(Hospitals,fire and police stations,emergency vehicle garages, aviationcontrol towers, communication centers,fire suppressing equipment, etc.

1.

Essentialfacilit ies

IwIpIOccupancy or funct ion

of the structureOccupancyCategory

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5Define Site geology

and soil characteristics

(S?)

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Soil profile types are defined in Table 16-JSection 1636 gives Site Characterization

Procedure

Stiff Soil ProfileSD

Soft Soil ProfileSE

Soils Requiring

Site-Specific Evaluation

SF

Very Dense Soil and Soft RockSC

RockSB

Hard RockSA

Generic DescriptionSoil Profile Type

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Definition of the soil profile is based onaveraged soil properties for the

upper 100 feet of soil profile.The propert ies u sed are:

lAverage shear wave velocity

lAverage standard penetration resistance

lAverage standard penetration resistance for

the cohesionless soils onlylAverage undrained shear strength in case of

cohesive soils

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Site characterization

< 2000< 15< 600Soft soilSE

1000 -200015 - 50600 - 1200Stiff soilSD

> 2000> 501200 2500Very dense soil

or soft rockSC

--2500 5000RockSB

-->5000Hard rockSA

(psf)(ft/sec)

DescriptionType sv CHNorN us

If not enough information use Type SD

For Type SEthe Build ing Off icial mus t determ ine if it may exist.

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Site-specific evaluation for SFIs meant for s oi ls v ulnerable to p otent ial fa ilure or col lapse

under seismic ground mo t ions

Such as:

l Liquef iable so i lslQuick and h ighly sensi t ive clays

lCol laps ib le weakly cemented so i ls

l Peats and h igh ly organic clays (H >10 ft)

l Very hig h plast ici ty clays (PI > 75, H > 25 ft)

l Very th ick soft to m edium so ft clays (H >120 ft .)

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SOIL PROFILE TYPE

Soft soil ?

rock

> ?

surface

?

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6Define Seismic Hazard

Characteristics

(Na, Nv)

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Seismic Hazard Characteristics

Are based on:

lThe seismic zone

lThe proximity of the site to activeseismic sources

lThe site soils characteristics, andlThe structures importance factor.

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Proximity evaluation of the siteto active seismic sources

lIt is required only in UBC Zone 4.

lTable 16-U divides the type of seismic

sources in A, B and C, depending upon:Maximum magnitude the source can

generate

Slip rate (in mm/year) of the source

l Once the type of source(s) is definedtwo Near Source Factors (Naand Nv)must be obtained, depending on thedistance to the seismic source(s).

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7Define Seismic Response

Coefficients

(Ca, Cv)

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Seismic Coefficients (CaandC

v)

lThey are defined in Tables 16-Q and 16-R

Z

S?

Soil Prof i le Type Seism ic Zone Factor

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Design Ground MotionsPeak acc elerat ion

Peak veloc i ty

Thedesigngroundmotions sodefined

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The design ground motions so defined,take into account:

lThe seismic hazard at the sitelThe site geotechnical

characteristics

lThe importance of theoccupancy of the structurebeing built

But we have not talked about resonance of

the ground m ot ion f requency content and

the struc ture vibrat ion character ist ics , yet!

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8Define the Structural System

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Two parameters are relevant

l

The structural material

lThe lateral-load resistingsystem

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Structural materials

Reinforced concrete

Structural mason ry

Struc tural Steel

Wood

STRUCTURAL SYSTEMS

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STRUCTURAL SYSTEMS

SYSTEMGRAVITY

LOADS

LATERAL

FORCES

BEARING

WALL

FRAME

MOMENT

RESISTINGFRAME

DUAL

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But there is more to it!

lConfiguration of the structureRegular

Irregular

lMaterial detailing requirementsOrdinary

Intermediate

Special

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9Define the Structural

Configuration

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Configuration

=Regular or Irregular

lIrregularities in height aredefined in Table 16-L

lIrregularities in plan aredefined in Table 16-M

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Vertical 1 -Soft Story

AB

C

D

EF

(( ))

3

KKK80.0K

or

K70.0K

FEDC

DC

++++

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Vertical 2 -Mass Distribution

AB

C

D

E

F

CD

ED

w50.1w

or

w50.1w

>>

>>

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Vertical 3 -Geometric Irregularity

AB

C

D

E

F

a

b

b30.1a>>

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Vertical 4 - In-Plane Displacement

AB

CD

EF

a

b ab>>

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Vertical 5 -Weak Story

AB

CD

EF

CStrength70.0

BStrength

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Plan 1 -Torsional Irregularity

1

2

++>>

22.1 211

l b k

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Plan 2 -Setbacks

AB CD

D15.0CorB15.0A >>>>

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Plan 3 -Diaphragm Irregularities

AB

CD

AB

CD

E

BA5.0DC >>

(( ))

BA5.0

ECDC

>>

++

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Plan 4 -Action Plane Displacement

DisplacementAction plane

Direction understudy

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Plan 5 -Non-Parallel Systems

PLAN VIEW

Non paral lel

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10Define the Structural Material

Detailing Requirements

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The objective

lFor stronger ground motions, we wantmore energy dissipation capacity.

lTherefore, we must detail our structurefollowing requirements that warrant thisenergy dissipation capacity.

lWe can employ brittle type requirementsin the low seismic hazard regions, andshould employ ductile type requirementsin the high seismic hazard regions.

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Use of the structural materials

nono nono

nono

Energy

Dissipat ion

Capacity

Seism ic Hazard

Low Moderate High

Ordinary

Intermediate

Special

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Using reinforced concrete as anexample:

Chapter 21

(Except 21.12)Special

Section 21.12Intermediate

Chapters 1 to 20Ordinary

Requ irements of

ACI 318-02

Energy Dissipat ion

Character ist ics

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11Selection of the

Lateral-Force Procedure

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UBC-97 defines

three analysis procedures

1. Simplified Static

2. Static

3. Dynamic

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Selection of the procedure

(Sect. 1629.8) depends on:l Importance of the structure

lBuilding heightlConfiguration of the structure (regular or

irregular)

lSeismic zone

lLateral-load structural system

lSoil profile type

lBuilding fundamental period

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12Definition of the

design lateral forces

D fi i i f h d i l l f

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Definition of the design lateral forces

LATERAL STORY FORCES

DESIGN BASE SHEAR

TFundamenta lPeriodMass

STRUCTURE VIBRATION CHARACTERISTICS

Stiffness

SaSpectralAccelerat ion

DESIGN EARTHQUAKE GROUND MOTIONS

WWeight of

the bui ld ingNon -structu ral elements

Structure self-weigh t

Mechanical equipment

MASS

Vs

Fi

T

Sa

RResponse

modif icat ion

factor

Structural system

STRUCTURE DISSIPATION CHARACTERISTICS

Structu ral Material

va

a a

v

C I2.5 C I

T

S 0.11 C I

0.8 Z N I

= =

W

R

SV a ==

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13Analysis

Analysis

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Analysis

Analysis o f the

st ructure

us ing the analysisprocedure

and the defined

lateral fo rces

acc identa l tors ion

Fix

Fiy

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From the analysis we obtain

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ythe lateral design displacements

xistoryi

yi

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15Internal forces

Internal forcesfromtheanalysis

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Internal forces from the analysis

lAxial forces

l

Flexu ral momentslShear fo rces

lTors ion forces

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16Story drift verification

Storydrift

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Story drift

5

4

3

2

1

h

h

h

h

h

p5

p4

p3

p2

p1

F

F

F

F

F

5

4

3

2

1

5

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Inelastic story displacements

SM R7.0 ==

Inelastic story drift

)1i()i( MMiDiftStory ==

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Story drift limits

lStruc tu res w ith T0.7 sec.

2.0% hstory