- 1 -

6.1 General

Every structure, and portion thereof, shall as a minimum, be designed and constructed

to resist the effects of earthquake motions as prescribed by Section 6.

6.1.1 Addi ti ons to Exi sti ng Bui ldi ngs

An addition that is structurally independent from an existing structure shall be designed and

constructed as required for a new structure in accordance with the seismic requirements for

new structures. An addition that is not structurally independent from an existing structure

shall be designed and constructed such that the entire structure conforms to the

seismic-force resisting requirements for new structures unless the following conditions are

satisfied.

(1) The addition conforms with the requirement for new structures.

(2) The addition does not increase the seismic forces in any structural element of the

existing structure by more than 5 percent, unless the capacity of the element

subject to the increased forces is still in compliance with these provisions.

(3) The addition, which is limited to the extension of 1/10 in total floor areas or of 1

story in height, or remodelling of the existing buildings that have been used for

more than five years since the acknowledgements for use of buildings were issued.

6.1.2 Ch ang e o f Oc c u p anc y

When a change of occupancy results in a structure being reclassified to a higher

seismic use group, the structure shall conform to the seismic requirement for a new

structure.

6.1.3 Alt ernat i o ns

Existing structures being altered need not comply with Chapter 6, provided that the

following conditions are met.

(1) The alternation do not create a structural irregularity as defined in Section 6.4.4 or

make an existing structural irregularity more severe.

(2) The alternation does not increase the seismic forces in any structural element of

the existing structure by more than 5 percent, unless the capacity of the element

subject to the increased forces is still in compliance with Chapter 6.

(3) The alternation does not decrease the seismic resistance of any structural element

of the existing structure to less than that required for a new structure.

(4) The alternations do not result in the creation of an unsafe condition.

6 Earthquake Loads

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6.2 Lo ad Co m b i nat i o ns

6.2 .1 Ult i m at e S t reng t h Des i g n

Where Ultimate strength design or limit state design is used, the factor for seismic

load incorporated with each design methodology shall be 1.0.

6.2 .2 Allo w ab le S t res s Des i g n

Where allowable stress design(working stress design) is used, the factor for seismic load in

the load combination involving seismic load shall be 0.7. In this case, increases in allowable

stresses are permitted by this code or the material reference standard.

6.2 .3 S p ec i al S ei s m i c Lo ad

Where the design of the members like a piloti structure causing instability of entire

structure, or members inducing a significant change of seismic loads, special seismic

load (Em) shall be used as seismic load combination involving seismic loads in lieu of

using seismic load (E).

E m=Ω0E ± 0.2S DSD (6.3.1)

where, Ω0

= A redundancy coefficient obtained in accordance with <Table

6.6.1>.

The term Ω0E need not exceed the maximum force that can be transferred to

the element by the other elements of the lateral-force-resisting system.

Where allowable stress design methodologies are used with the special load

combination, design strengths are permitted to be determined using an allowable stress

increase of 1.7 and a resistance factor, φ, of 1.0. This increase shall not be combined

with increases in allowable stresses or load combination reduction.

6.3 Si te Ground Moti on

6.3.1 Sei smi c Zone and Si te Coeffi ci ent

Seismic zones and corresponding site coefficients are set forth in <Table 6.3.1>

<Table 6.3.1> Seismic Zone and Site Coefficient ( A )

Seismic zone Areas in KoreaSeismic numerical

coefficient (A)

1 All areas not included in zone 2 0.11

2Northern area of KangwonDo, Southwestern area of

JeollaNamdo, JejuDo0.07

※ Northen area of KangwonDo (County, City) : Hongcheon, Cheorwon, Hwacheon, Pyeongchang, Yanggu, Inje, Goseong,

Chunchon City, Sokcho City

Southwestern area of JellaNamdo : Muan, Sinan, Wando, Yeonggwang, Jindo, Haenam, Yeongam, Gangjin, Goheung,

Hampyeong, Mokpo City.

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6.3.2 Si te Class Defi ni ti ons

The site shall be classified as one of the site classes in <Table 6.3.2> considering the

effects of soil properties, geological conditions, surface or underground topography on

the ground motion.

Site

ClassSoil profile name

Average properties in top 30m

Soil shear wave

velocity, v s

( m/s)

Standard penetration

resistance,

N (the number of

blows /300mm)

Soil undrained shear

strength, s u

( × 10 -3 N/mm 2)

SA Hard rock v s>1500 - -

SB Rock 760< v s ≤1500

SCVery dense soil and

soft rock360< v s ≤760 N＞50 ＞ 100

SD Stiff soil profile 180< v s ≤360 15≤ N ≤50 50≤ s u ≤100

SE Soft soil pofile v s<180 N＜ 15 ＜50

<Table 6.3.2> Site Class Definitions

6.3.3 Desi gn Spectral Response Accelerati on

The design spectral response accelerations for short period, SDS , and the design spectral

response accelerations for 1-second period, SD1, shall be determined based on <Table

6.3.3> and on <Table 6.3.4>, respectively.

Site ClassSeismic zone

1 2

SA 2.0M1)A 1.8MA

SB 2.5MA 2.5MA

SC 3.0MA 3.0MA

SD 3.6MA 4.0MA

SE 5.0MA 6.0MA

1) M＝1.33 (In this case, the design spectral response acceleration is for ultimate level equivalent

to two thirds of the earthquake, the recurrence time of 2400 years.

<Table 6.3.3> Design Spectral Response Acceleration for Short Periods,

SDS

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Site Class

Seismic zone

1 2

SA 0.8MA 0.7 MA

SB 1.0MA 1.0MA

SC 1.6MA 1.6MA

SD 2.3MA 2.3MA

SE 3.4MA 3.4MA

<Table 6.3.4> Design Spectral Response Acceleration for 1 Second Period,

SD1

6.3.4 General Procedure Response Spectrum

The general design response spectrum curve shall be developed as indicated in [Fig.

6.3.1].

(1) For periods less than or equal to T 0, the design spectral response acceleration, S a ,

shall be determined from Eq. (6.3.2).

(2) For periods greater than or equal to T 0 and less than or equal to T S

, the design

spectral response acceleration, S a , shall be taken equal to S DS.

(3) For periods greater than T S, the design spectral response acceleration, S a , shall be

given by Eq. (6.3.3).

S a=0.6S DST o

T+0.4S DS (6.3.2)

S a=S D1T

(6.3.3)

where, T = Fundamental period(in second) of the structure.

T o = 0.2S D1/S DS

T S = S D1/S DS

- 5 -

0

0

0.6 0.4DSDS

O

S T ST

+

1 /a DS S T=

OT ST 1.0 period

aS

DSS

1DS

2.5DSS

T(Period)

[Fig. 6.3.1] Design Response Spectrum.

6.4 Earthquake Loads-Cri teri a Selecti on

6.4.1 General

Each structure shall be assigned to a seismic design category in accordance with

Section 6.4.3. Seismic design categories are used to determine permissible structural

systems, limitations on height and irregularity, those components of the structure that

must be designed for seismic resistance and the types of lateral force analysis that

must be performed,

6.4 .2 S ei s m i c Us e Gro u p s and Oc c u p anc y I m p o rt anc e F ac t o rs

Each structure shall be assigned a seismic use group and corresponding occupancy

importance factor as indicated in <Table 6.4.1>.

Where a structure is occupied for two or more occupancies not included in the same

seismic use group, the structure shall be assigned the classification of the highest

seismic use group corresponding to the various occupancies. Where structures have

two or more portions that are structurally separated in accordance with Section 6.8

each portion shall be separately classified. Where a structurally separated portion of a

structure provides required access to, required egress from or shares life safety

components with another portion having a higher seismic use group, both portions

shall be assign the higher seismic use group.

6.4.3 Determi nati on of Sei smi c Desi gn Category

All structure shall be assigned to a seismic design category based on their seismic use

group and the design spectral response acceleration coefficients, SDS and SD1 ,

determined in accordance with Section 6.4.2 and 6.3.3. Each building and structure shall

be assigned to the most severe seismic design category, if seismic design categories

determined based on <Table 6.4.2> and <Table 6.4.3> are discrepant.

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Seismic use group Nature of occupancy

Occupancy importance

factor(IE)

City planning

regionsBesides

S

Buildings and other

structures that present

essential facilities or

hazardous facilities

therein housing or

supporting toxic or

explosive chemical and

substances.

∙Building or structure containing toxic or explosive substances with total floor area

more or equal to 1000 m2, hospitals, fire

stations, power generation stations,

buildings and other structures having

critical national defense functions, foreign

diplomatic establishments, facilities for

children, welfare facilites for the aged,

public welfare facilities and labor welfare

facilities

∙Apartment or office building higher than or

equal to 15 stories.

1.5 1.2

I

Buildings and other

structures that

represent a substantial

hazard to human life in

the event of failure

∙Facilities for public performance, gathering,

inspection, exhibition, business or

commercial pursuit larger than or equal

to 5000m2 of the total floor area.

∙ Building or structure for accomodations,

office buildings, dormitories or apartments

higher than or equal to 5 stories.

∙School higher than or equal to 3 stories.

1.2 1.0

II

Buildings and other

structures except those

listed in Categories S

and I.

∙Buildings except those listed in Categories (S) and I.

1.0 0.8

<Table 6.4.1> Seismic Use Groups and Occupancy Importance Factors

6.4.4 Bui ldi ng Confi gurati on

Buildings shall be classified as regular or irregular based on the criteria in this

section. Such classification shall be based on the plan and vertical configuration.

6.4.4.1 Plan Irregularity

Buildings having one or more of the features listed in <Table 6.4.4> shall be designed

as having plan structural irregularity, and shall comply with the requirements in the

sections referred in <Table 6.4.4>.

6.4.4.2 Vertical Irregularity

Buildings having one or more of the features listed in <Table 6.4.5> shall be designed

as having vertical irregularity, and shall comply with the requirements in the section

referred in <Table 6.4.5>.

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Exceptions:

(1) Structural irregularity of Type 1 or Type 2 in <Table 6.4.5> do not apply where

no story drift ratio under design lateral load is greater than 130 percent of the

story drift ratio of the next story above. Torsional effects need not be considered

in the calculation of story drifts for the purpose of this determination. The story

drift ratios for top two stories of the building are not required to be evaluated.

(2) Irregularities of Types 1 and 2 of <Table 6.4.5> are not required to be considered

for buildings with less or equal to two stories in any seismic design category.

Value of SDS

Seismic use group

S I II

0.50g ≤ SDS D D D

0.33g ≤ SDS ＜ 0.50g D C C

0.17g ≤ SDS ＜ 0.33g C B B

SDS ＜ 0.17g A A A

<Table 6.4.2> Seismic Design Category Based on Short-period Response Accelerations

Value of SD1

Seismic use group

S I II

0.20g≤ SD1 D D D

0.14g≤ SD1 ＜ 0.20g D C C

0.07g≤ SD1 ＜ 0.14g C B B

SD1 ＜ 0.07g A A A

<Table 6.4.3> Seismic Design Category Based on 1 Second Period Response Acceleration

6.4.5 Analysi s Procedures

A structural analysis shall be made for all structures in accordance with the

requirements of this section.

6.4.5.1 Analysis for Structures Assigned to Seismic Design Category A, or B

Structural analysis of structures assigned to Seismic Design Category A, or B is

permitted to carry out through equivalent lateral force analysis in Section 6.5.

6.4.5.2 Analysis for Structures Assigned to Seismic Design Category C

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Structures assigned to Seismic Design Category C may be designed based on

equivalent lateral force analyses in Section 6.5.

Exceptions:

(1) Structures assigned as having regular configuration with more or equal to 70m in

height or 21 story;

(2) Irregular structures with more or equal to 20m in height or 6 story; shall be

designed based on dynamic analysis.

6.4.5.3 Analysis for Structures Assigned to Seismic Design Category D

The analysis procedures identified in <Table 5.4.6> shall be used for structures

assigned to Seismic Design Category D, or more rigorous analysis shall be made. If

the structures are categorized as having plan irregularity of Type 1 or 4 by <Table

6.4.4>, or as having vertical irregularity of Type 1, 4, or 5 by <Table 6.4.5>, those

may be divided into having regularity.

No. Type DescriptionReference

section

Seismic

Design

Category

Application

1Torsional

irregularity

To be considered when diaphragms are not flexible.

Torsional irregularity shall be considered to exist

when the maximum story drifts, computed including

accidental torsion, at one end of the structure

transverse to an axis is more than 1.2 times the

average of the story drifts at the two dens of the

structure.

6.5.6.4 C, D

<Table

6.4.6>D

6.5.7.1 C, D

2Re-entrant

Corners

Plan configuration of a structure and its

lateral-force-resisting system contain re-entrant

corners where both projections of the structure

beyond a re-entrant corners are greater than 15

percent of the plan dimension of the structure in

the given direction.

- -

3Diaphragm

Discontinuity

Diaphragms with abrupt discontinuities or variations

in stiffness, including those having cutout or open

areas greater than 50 percent of the gross enclosed

diaphragm area, or changes in effective diaphragm

stiffness of more than 50 percent from one story

to the next

- -

4Out-of-Plane

Offsets

Discontinuities in a lateral-force-resistance path,

such as out-of-plane offsets of the vertical

elements.

6.8.3 B, C, D

5Nonparallel

Systems

The vertical lateral -force-resisting elements are

not parallel to or symmetric about the major

orthogonal axes of the lateral -force-resisting

system.

6.8.4.2 C

6.8.4.3 D

<Table 6.4.4> Plan Structural Irregularities

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<Table 6.4.5> Vertical Structural Irregularities

No. Type DescriptionReference

Section

Seismic

Design

Category

Application

1

Stiffness

Irregularity-soft

story

A soft story is one in which the lateral stiffness

is less than 70 percent of that in the story

above or less than 80 percent of the average

stiffness of the three stories above.

<Table

6.4.6>D

2Weight

Irregularity

Mass irregularity shall be considered to exist

where the effective mass of any story is more

than 150 percent of the effective mass of an

adjacent story. A roof that is lighter than the

floor below need not be considered.

<Table

6.4.6>D

3

Vertical

geometric

Irregularity

Vertical geometric irregularity shall be considered

to exist where the horizontal dimension of the

lateral-force-resisting system in any story is

more than 130 percent of that in an adjacent

story.

<Table

6.4.6>D

4

In-plane

Discontinuity in

Vertical

Lateral-Force-

Resisting

Elements

An in-plane offset of the lateral-force-resisting

elements greater than the length of those

elements or a reduction in stiffness of the

resisting element in the story below.

6.8.3 B, C, D

5

Discontinuity in

Capacity-Weak

Story

A weak story is one in which the story lateral

strength is less than 80 percent of than in the

story above. The story strength is the total

strength of seismic-resisting elements sharing

the story shear for the direction under

consideration.

6.8.1 B, C, D

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Structural Description Analysis Procedure for Seismic Design

1. Seismic Use Group II buildings of light-framed

construction not exceeding 3 stories in height

Equivalent lateral force procedure or

Dynamic analysis

2. Other structures not exceeding 70m in height in

addition to those illustrated in item 1 above.

Equivalent lateral force procedure or

Dynamic analysis

3. Structures having vertical irregularity of Type 1, 2

or 3 in <Table 6.4.5>; regular structure exceeding

70m in height; or structure exceeding 5 stories or

20m in height with having irregularity of Type 1 in

<Table 6.4.4>

Dynamic analysis

4. Other structure having plan or vertical irregularity. Dynamic analysis

<Table 6.4.6> Analytical Procedures for Seismic Design Category D

6.4.6 Deflecti on and Dri ft Li mi ts

The design story drifts, Δ, as determined in Section 6.5.7, shall not exceed the

allowable story drift, Δa

, as obtained from <Table 6.4.7>.

Seismic use group

S I II

Allowable story drift Δa 0.010h sx 0.015h sx 0.020h sx

<Table 6.4.7> Allowable Story drift, Δa

h sx : Story height below Level x.

6.5 Equi valent Lateral Force Procedure f or Sei smi c Desi gn

6.5.1 Sei smi c Base Shear

The seismic base shear, V, in a given direction shall be determined in accordance with

the following equation.

V=C sW (6.5.1)

where, Cs : the seismic response coefficient determined in accordance with

Section 6.5.2

W : the effective seismic weight including the total dead load and other

loads listed below:

(1) In area used for storage, a minimum of 25 percent of the reduced floor live

load (floor live load in public garages and open parking structures need not be

included).

- 11 -

(2) Where an allowance for partitions is included in the floor load design, the

actual partition weight or a minimum weight of 0.5 kN/m2 of floor area,

whichever is greater.

(3) Total operation weight of permanent equipment.

(4) Twenty percent of flat roof snow load where the flat snow load exceeds 1.5

kN/m2.

6.5.2 Sei smi c Response Coeffi ci ent

The seismic response coefficient, Cs, shall be determined in accordance with Eq. (6.5.2).

C s=S D1

[ RI E ]T(6.5.2)

The value of Cs computed in accordance with Eq. (6.5.2) need not exceed the following:

C s=S DS

[ RI E ](6.5.3)

Cs shall not less than

C s=0.044S DS I E (6.5.4)

where,

I E : the occupancy importance factor determined in accordance with

<Table 6.4.1>

R : the response modification factor from <Table 6.6.1>

S DS : the design spectral response acceleration at short period as

determined from Section 6.3.3

S D1 : the design spectral response acceleration at 1-second period as

determined from Section 6.3.3

T : the fundamental period of the building (seconds) determined in

Section 6.5.3

6.5.3 Peri od Determi nati on

The fundamental period of the structure, T, in the direction under consideration shall

be established using the structural properties and deformational characteristics of the

resisting elements in a properly substantiated analysis, or shall be taken as the

approximate fundamental period, Ta , determined in accordance with the requirements

of Section 6.5.4. The calculated fundamental period determined by a properly

substantiated analysis shall not exceed the product of 1.2 and approximate building

period, Ta.

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6.5.4 Approxi mate Fundamental Peri od

The approximate fundamental period ( Ta), in s, shall be determined from the following

equation.

T a=C T h3/4n

(6.5.5)

where, C T＝ 0.085 : moment-resisting frames system of steel

＝ 0.073 : moment-resisting frame systems of reinforced concrete,

and eccentrically braced steel frames

＝ 0.049 : all other building systems

h n ＝ the height in m above the base to the highest level of the

building (m)

Alternatively, determination of the approximate fundamental period , T a, in

seconds, from the following equation for concrete and steel-moment resisting

frame buildings not exceeding 12 stories in height and having a minimum story

height of 3 m is permitted.

T a = 0.1N (6.5.6)

where, N = number of stories

The approximate fundamental period, T a, in s for concrete shear wall structure is

permitted to be determined by Eq. (6.5.5) or from Eq. (6.5.7).

T a=0.0743(h n)3/4/ A c

(6.5.7)

A c=∑A e[0.2+(D e/h n)2]

D e/h n≤ 0.9.

where, A e : shear section area in m2 of shear wall parallel to the direction of the

seismic load at 1st level

D e : length in m of shear wall at 1st level.

6.5.5 Verti cal Di stri buti on of Sei smi c Forces

The lateral force, F x, included at any level shall be determined from the following

equations:

F x=C vxV (6.5.8)

C vx=w xh

kx

∑n

i=1w ih

ki

(6.5.9)

- 13 -

where, C vx : vertical distribution factor.

k : a distribution exponent related to the building period as follows:

k=1 : for buildings having a period of 0.5 second or less.

k=2 : for buildings having a period of 2.5 seconds or less.

For buildings having a period between 0.5 and 2.5 seconds, k shall be

determined by linear interpolation between 1 and 2.

h i, h x : the height from the base to level i or x.

V : total design lateral force or shear at the base of the building.

w i,w x : the portion of the total gravity load of the building, W , located

or assigned to level i or x.

n : number of stories.

6.5.6 Hori zontal Shear Di stri buti on

The seismic design story shear in any story, V x, shall be determined from the

following equation:

V x= ∑n

i= xF i

(6.5.10)

where, F i : the portion of the seismic base shear induced at level i.

6.5.6.1 Rigid Diaphragms

For rigid diaphragms, the seismic design story shear, V x, shall be distributed to the

various vertical element of the seismic force-resisting system in the story under

consideration based on the relative lateral stiffness of the vertical resisting elements and the

diaphragm.

6.5.6.2 Flexible Diaphragms

For flexible diaphragms, the design story shear shall be distributed to various vertical

elements based on the tributary area of the diaphragm to each line of resistance.

6.5.6.3 Torsion

Where diaphragms are not flexible, design shall include the torsional moment.

which is the sum of the torsional moment, M t, resulting from the difference in

locations of the center of mass and the center of stiffness and accidental torsional

moments, M ta, where M t

shall be computed as story shear multiplied by the

eccentricity and M ta shall be equal to story shear caused by assumed

displacement of the center of mass each way from its actual location by a distance

equal to 5 percent of the dimension of the building perpendicular to the direction

- 14 -

of the applied forces.

6.5.6.4 Dynamic Amplification of Torsion

For structures assigned to Seismic Design Category C or D having plan irregularity

Types 1 of <Table 6.4.4>, the effects of torsional irregularity shall be accounted

for by multiplying the sum of M t plus M ta

at each level by a torsional

amplification factor, A x, determined from the following equation:

A x= [δ

max

1.2δ avg ]2

(6.5.11)

where, δmax

: the maximum displacement at Level x

δavg

: the average of the displacements at the extreme points of the

structure at Level x

The torsional amplification factor, A x, is not required to exceed 3.0. The more

severe loading for each element shall be considered for design.

6.5.6.5 Overturning

The building shall be designed to resist overturning effects caused by the seismic

forces determined in Section 6.5. The overturning moment at Level x, M x, shall be

determined from the following equation:

M x= τ ∑n

i= xF i(h i-h x) (6.5.12)

where, F i ＝ the portion of the seismic base shear induced at level i

h i, h x : the height from the base to Level i or x (m)

τ ＝ the overturning moment reduction factor, determined as follows:

(1) 1.0 for the top 10 stories

(2) 0.8 for the 20th story from the top and below

(3) value between 1.0 and 0.8 determined by a straight line

interpolation for stories between the 20th and 10th stories below

the top

6.5.7 Dri ft Determi nati on and P-Δ Effects

Frames and columns shall be designed to resist both brittle fracture and

overturning instability during the maximum lateral excursion of each story, while

supporting full dead and live load.

6.5.7.1 Story Drift Determination

The design story drift, Δ , shall be computed as the difference of the deflections at

the center of mass at the top and bottom of the story under consideration. Where

- 15 -

allowable stress design is used, Δ shall be computed using earthquake forces

without dividing by 1.4. For structures assigned to Seismic Design Category C or D

having plan irregularity Types 1 of <Table 6.4.4>, the design story drift, Δ , shall be

computed as the largest difference of the deflections along any of the edges of the

structure at the top and bottom of the story under consideration.

The deflections of Level x, δx, shall be determined in accordance with following

equation:

δx=

C dδxe

I E(6.5.13)

where, C d : the deflection amplification factor in <Table 6.6.1>

δxe

: the deflections determined by an elastic analysis of the

seismic-force-resisting system

I E : the occupancy importance factor determined from <Table 6.4.1>

For determining compliance with the story drift limitation of <Table 6.4.7>, the

deflections of Level x, δx, shall be calculated as required in this section. For

purposes of this drift analysis only, the upper bound limitation specified in Section

6.5.4 on the computed fundamental period, T, in seconds, of the building, shall not

apply.

The design story drift, Δ , shall be increased by the incremental factor relating to

the P-Δ effects, ad=1.0/(1-θ), where θ is the stability coefficient as

determined in Section 6.5.7.2.

6.5.7.2 P-Δ Effects

P-delta effects on story shears and moments, the resulting member forces and

moments, and the story drifts induced by these effects are not required to be

considered when the stability coefficient, θ, as determined by the following

equation is equal to or less than 1.0:

θ=P xΔ

V xh sxC d

(6.5.14)

where, P x : the total unfactored vertical design load at and above Level x;

when calculating the vertical design load for purposes of

determining P-Δ, the individual load factors need not exceed 1.0

Δ : the design story drift occurring simultaneously with Vx

V x : the seismic shear force acting between Level x and x-1

h sx : the story height below Level x

C d : the deflection amplification factor in <Table 6.6.1>

- 16 -

The stability coefficient, θ, from Eq. (6.5.14) shall not exceed θmax

determined

as follows:

θmax =

0.5βC d

≤0.25 (6.5.15)

where, β : the ratio of shear demand to shear capacity for the story between

Level x and x-1. Where the ratio, β, is not calculated, a value of

β=1 shall be used.

When the stability coefficient, θ , is greater than 0.1 but less than or equal to

θmax

, interstory drifts and element forces shall be computed including P-Δ

effects. Where θ is greater than θmax

, the structure is potentially unstable and

shall be redesigned.

6.6 Sei smi c-Force-Resi sti ng Systems

The appropriate response modification coefficient, R, system overstrength factor, Ω0

,

and deflection amplification factor, C d, indicated in <Table 6.6.1> shall be used in

determining the base shear, element design forces and design story drift.

Seismic-force-resisting systems listed as "other structures" or not indicated in <Table

6.6.1> are permitted if analytical and test data are submitted that establish the

dynamic characteristics and demonstrate the lateral force resistance and energy

dissipation capacity to be equivalent to the structural systems indicated in <Table

6.6.1> for equivalent response modification coefficient, R, system overstrength

coefficient, Ω0

, and deflection amplification factor, C d, values.

6.6.1 Dual Systems

Total seismic force resistance is to be provided by the combination of the moment

frame and the shear walls or braced frames in proportion to their stiffness. The

moment frame shall be capable of resisting at least 25 percent of the design forces.

6.6.2 Combi nati on along the Same Axi s

For other than dual systems and shear wall-frame interactive systems, where a

combination of different structural systems is utilized to resist lateral forces in the

same direction, the value, R, used for design in that direction shall not be greater

than the least value for any of the systems utilized in that same direction.

6.6.3 Combi nati ons of Frami ng Systems

Where different seismic-force-resisting systems are used along the two orthogonal

axes of the structure, the appropriate response modification coefficient, R, system

- 17 -

overstrength factor, Ω0

, and deflection amplification factor, C d, indicated in <Table

6.6.1> for each system shall be used.

6.6.3.1 Combination Framing Factor

The response modification coefficient, R, in the direction under consideration at any

story shall not exceed the lowest response modification coefficient, R, for the

seismic-force-resisting system in the same direction considered above that story,

excluding penthouses. The system overstrength factor, Ω0

, in the direction under

consideration at any story shall not be less than the largest value of this factor for

the seismic-force resisting system in the same direction considered above that story.

Exceptions:.

(1) Detached one- and two-family dwellings constructed of light framing.

(2) The response modification coefficient, R, and system overstrength factor, Ω0

, for

supported structural systems with a weight equal to or less than 10 percent of the

weight of the structure are permitted to be determined independent of the values of

these parameters for the structure as a whole.

(3) The following two-stage static analysis procedure (③ and ④) is permitted to be

used provided the structure complies with the followings:

① The lower portion shall have a stiffness at least 10 times the upper portion.

② The period of the entire structure shall not be greater than 1.1 times the period

of the upper portion considered as a separate structure fixed at the base.

③ The flexible upper portion shall be designed as a separate structure using the

appropriate values of R.

④ The rigid lower portion shall be designed as a separate structure using the

appropriate values of R. The reactions from the upper portion shall be those

determined from the analysis of the upper portion amplified by the ratio of R of

the upper portion to R of the lower portion. This ratio shall not be less than

1.0.

6.6.3.2 Combination Framing Detailing Requirements

For structural components common to systems having different response modification

coefficients, detailing requirements corresponding to higher response modification

coefficient, R, shall be used.

6.6.4 System li mi tati ons for Sei smi c Desi gn Categori es D

Structures assigned to Seismic Design Categories D shall be subject to the followings.

6.6.4.1 Interaction Effects

Moment-resisting frames that are adjoined by stiffer elements not considered to be

part of the seismic-force-resisting system shall be designed so that the action or

- 18 -

failure of those elements will not impair the vertical load and

seismic-force-resisting capability of the frame. The design shall consider and

provide for the effect of these rigid elements on the structural system at

deformations corresponding to the design story drift, Δ, as determined in Section

6.5.7.1. In addition, the effects of these elements shall be considered when

determining whether a structure has one or more of the irregularities defined in

Section 6.4.4.

6.6.4.2 Deformational compatibility

Every structural component not included in the seismic-force resisting system in the

direction under consideration shall be designed to be adequate for vertical

load-carrying capacity and the induced moments and shears resulting from the design

story drift, Δ, as determined in accordance with Sections 6.5.7.1. Where allowable

stress design is used, Δ shall be computed without dividing the earthquake force by

1.4. The moments and shears induced in components that are not included in the

seismic-force-resisting system in the direction under consideration shall be calculated

including the stiffening effects of adjoining rigid structural and nonstructural elements.

- 19 -

Basic Seismic-force-resisting system1)

Design Coefficients and Factors

Response

modification

coefficient

R

System

overstrength

factor, Ω0

Deflection

amplification

factor, C d

1. Bearing Wall Systems

1-a. Ordinary reinforced concrete shear walls 4.5 2.5 4

1-b. Ordinary reinforced masonry shear walls 2.5 2.5 1.5

1-c. Ordinary plain masonry shear walls 1.5 2.5 1.5

2. Building Frame Systems

2-a. Steel eccentrically braced frames, moment-

resisting, connections at columns away from

links

8 2 4

2-b. Steel eccentrically braced frames, moment-

resisting, connections at columns away from

links

7 2 4

2-c. Ordinary steel concentrically braced frames 5 2 4.5

2-d. Steel plate shear walls 6.5 2.5 5.5

2-e. Ordinary reinforced concrete shear walls 5 2.5 4.5

2-f. Reinforced masonry shear walls2)

3 2.5 2

2-g. Ordinary plain masonry shear walls2)

1.5 2.5 1.5

3. Moment-resisting Frame Systems

3-a. Ordinary steel moment frames 6 3 3.5

3-b. Intermediate reinforced concrete moment frames 5 3 4.5

3-c. Ordinary reinforced concrete moment frames 3 3 2.5

4. Dual Systems with Intermediate Moment Frames

4-a. Ordinary steel concentrically braced frames 5 2.5 4.5

4-b. Ordinary reinforced concrete shear walls 5.5 2.5 4.5

4-c. Steel plate shear walls 6.5 2.5 5

4-d reinforced masonry shear walls1)

3 3 2.5

<Table 6.6.1> Design Coefficients and Factors for Basic Seismic-Force-Resisting Systems

- 20 -

Basic Seismic-force-resisting system1)

Design Coefficients and Factors

Response

modification

coefficient

R

System

overstrength

factor Ω0

Deflection

amplification

factor C d

5. Inverted Pendulum Systems

5-a. Cantilevered column systems 2.5 2 2.5

5-b. steel moment frames 1.25 2 2.5

6. other structures

6-a. other structures 3 2 2.5

1) The selected seismic force-resisting system shall be designed and detailed in accordance with the specific

requirements per material specific seismic design Standards or experimental or analysis results performed by reliable

research institutes.

2) Masonry shear walls are not permitted for structures assigned to Seismic Design Category C or D.

6.7 Dynami c Analysi s Procedure

6.7.1 Analysi s Procedure Selecti on

One of the following dynamic analysis procedures performed in accordance with the

requirements of this section may be used in lieu of equivalent lateral force procedure.

(1) Modal Response Spectra Analysis

(2) Linear Time-history Analysis

(3) Nonlinear Time-history Analysis

6.7.2 Modeli ng

A mathematical model which represents the spatial distribution of mass and stiffness

throughout the structure shall be constructed. For regular buildings with independent

orthogonal seismic-force resisting systems, independent two-dimensional models may

be constructed to represent each system. For irregular buildings without independent

orthogonal systems, a three-dimensional model incorporating a minimum of three

dynamic degrees of freedom consisting of translation in two orthogonal plan directions

and torsional rotation about the vertical axis shall be included at each level of the

building. Where the diaphragms are not rigid compared to the vertical elements of the

lateral-force-resisting system, the model shall include representation of the diaphragm's

flexibility and such additional dynamic degrees of freedom as are required to account

for the participation of the diaphragm in the structure's dynamic response. In addition,

the model shall include the effects of cracked sections for concrete and masonry

elements and the contribution of panel zone deformations to overall story drift for steel

moment frame systems.

6.7.3 Modal Properti es

The period of each mode, the modal shape vector, the mass participation factor, and

- 21 -

the modal mass of the building shall be calculated by established methods of structural

analysis for the fixed base condition using the masses and elastic stiffnesses of the

seismic-force-resisting system. The analysis shall include a sufficient number of

modes to obtain a combined modal mass participation of at least 90 percent of the

actual building mass in each of two orthogonal directions.

6.7.4 Modal Base Shear

The portion of the base shear contributed by the mth mode, V m

, shall be

determined from the following equations:

V m=C sm W m(6.7.1)

W m =( ∑n

i=1w i

φim )

2

∑n

i=1w i

φ 2im

(6.7.2)

where, C sm : the modal seismic response coefficient determined in Eq. (6.7.3).

W m : the effective modal gravity load.

w i : the portion of the total gravity load, W , of the building at Level

i, where W = the total dead load and other loads listed below:

① In areas used for storage, a minimum of 25 percent of the reduced

floor live load (floor live load in public garages and open parking

structures need not be included)

② Where an allowance for partition load is included in the floor load

design, the actual partition weight or a minimum weight of 0.5

kN/m 2 of floor area, whichever is greater

③ Total operating weight of permanent equipment

④ 20 percent of flat roof snow load where the flat roof snow load

exceeds 1.5 kN/m 2

φim

: The displacement amplitude at the ith level of the building when

vibrating in its mth mode

The modal seismic response coefficient, C sm, shall be determined by the following

equation:

C sm=S am

( RI E )(6.7.3)

where, I E : the occupancy importance factor determined in accordance with

Section 6.4.2

S am : the modal design spectral response acceleration at period T m

- 22 -

determined from either the general design response spectrum or

a site-specific response spectrum

R : the response modification factor determined from <Table 6.6.1>

Exception: For buildings on Site Class SD, or SE, the modal seismic design

coefficient, C sm, for modes other than the fundamental mode that have periods

less than 0.3 second is permitted to be determined by the following equation:

C sm=S DS

2.5( RI E )(1.0+5.0 T m ) (6.7.4)

where, I E : the importance factor determined in accordance with Section 6.4.2

R : the response modification factor determined from <Table 6.6.1>

S DS : the design spectral response acceleration at short periods

determined from <Table 6.3.3>

T m : the modal period of vibration of the m

th mode of the building

6.7.5 Modal Forces, Deflecti ons and Dri fts

The modal force, F xm, at each level shall be determined by the following equations:

F xm=C vxm V m(6.7.5)

C vxm=w x

φxm

∑n

i=1w i

φim

(6.7.6)

where, C vxm : the vertical distribution factor in the m

th mode

V m : the total design lateral force or shear at the base in the m

th

mode as determined from Eq. (6.7.1)

w i, w x

: the portion of the total gravity load of the building, W, located

or assigned to Level i or x

φim

: the displacement amplitude at the ith level of the building when

vibrating in its mth mode

φxm

: the displacement amplitude at the xth

level of the building when

vibrating in its mth mode

The modal deflection at each level, δxm

, shall be determined by the following

equation:

δxm=

C dδxem

I E(6.7.7)

- 23 -

where, C d : the deflection amplification factor determined from <Table 6.6.1>

I E : the importance factor determined in accordance with Section 6.4.2

δxem

: the deflection of Level x in the mth

mode at the center of the

mass at Level x determined by an elastic analysis

The elastic modal deflection, δxem

, shall be determined by the following equation:

δxem=( g

4π 2 )(T 2mF xm

w x ) (6.7.8)

where, F xm : the portion of the seismic base shear in the m

th mode, induced at

Level x

g : the acceleration due to gravity

T m : the modal period of vibration, in seconds, of the m

th mode of the

building

w x : effective weight of level x

The modal drift in a story, Δm, shall be computed as the difference of the

deflections, δxm

, at the top and bottom of the story under consideration.

6.7.6 Modal Story Shears and Moments

The story shears, story overturning moments, and the shear forces and

overturning moments in vertical elements due to the seismic forces determined

from Section 6.7.5 shall be computed for each mode by linear static methods.

6.7.7 Desi gn Values

6.7.7.1 The design value for the modal base shear, V t ; each of the story shear,

moment and drift quantities; and the deflection at each level shall be determined by

combining their modal values. The combination shall be carried out by taking the

square root of the sum of the squares (SRSS) of each of the modal values or by the

complete quadratic combination (CQC) technique.

6.7.7.2 The base shear, V, using the equivalent lateral force procedure shall be

calculated using a fundamental period of the building of 1.5 times the approximate

fundamental period of the building calculated in accordance with Section 6.5.4 for

regular structures and 1.2 times the approximate fundamental period of the building for

irregular structures. Where the calculated base shear, V , is greater than the modal

base shear, V t, the design values in accordance with Section 6.7.7.1 shall be

- 24 -

multiplied by C m, the modification factor:

C m=VV t

(6.7.9)

6.7.7.3 The modal base shear, V t, need not exceed the base shear calculated from the

equivalent lateral force procedure in Section 6.5.

6.7.8 Hori zontal Shear Di stri buti on

The distribution of horizontal shear shall be in accordance with the requirements

of Section 6.5.6 except that amplification of torsion per Section 6.5.6.4 is not

required for that portion of the torsion included in the modal analysis model.

6.7.9 P-Δ Effects

The P-Δ effects shall be determined in accordance with Section 6.5.7. The story

drifts and story shears shall be determined in accordance with Section 6.5.7.1.

6.7.10 Ti me-Hi story Analysi s

6.7.10.1 Time Histories

Time-history analysis shall be performed with pairs of appropriate horizontal

ground motion time-history components that shall be selected and scaled from not

less than three recorded events. If three time-history analyses are performed,

then the maximum response of the parameter of interest shall be used for design.

If seven or more time history analyses are performed, then the average value of

the response parameter of interest may be used for design. Where appropriate

recorded ground-motion time history pairs are not available, appropriate simulated

ground-motion time-history pairs shall be used to make up the total number

required. For each pair of horizontal ground-motion components, the square root

of the sum of the squares (SRSS) of the 5 percent damped site-specific spectrum

of the scaled horizontal components shall be constructed. The motions shall be

scaled such that the average value of the SRSS spectra is not less than 1.4 times

the 5 percent damped spectrum of the design earthquake (or maximum considered

earthquake) for periods from 0.2 T second to 1.5 T seconds.

6.7.10.2 Linear Time-History Analysis

Design parameters such as story shears, story overturning moments, or member forces,

which are obtained by the linear time-history analysis, shall be multiplied by the

- 25 -

importance factor and the inverse of response modification factor. The design

parameters determined may be modified in accordance with the requirements of Section

6.7.7.

6.7.10.3 Nonlinear Time-History Analysis

Capacities and characteristics of nonlinear elements shall be modeled consistent with

test data or substantiated analysis, considering the importance factor. The inelastic

responses may not be reduced by the quantity R/I E. The maximum inelastic response

displacement shall comply with Section 6.4.6.

6.8 Structural Component Desi gn Requi rements

The design and detailing of the components of the seismic-force-resisting system,

except those of the structures assigned to Seismic Design Category A, shall comply

with the requirements of this section.

6.8.1 Di sconti nui ti es i n Verti cal System

Structures with a discontinuity in lateral capacity, vertical irregularity Type 5, as

defined in <Table 6.4.5>, shall not be over two stories or 9 meters in height where

the weak story has a calculated strength of less than 65 percent of the story above.

Where the weak story is capable of resisting a total seismic force equal to the design

force multiplied by the 75 percent of deflection amplification factor C d, the height

limitation does not apply.

6.8.2 Inverted Pendulum-Type Structures

Supporting columns or piers of inverted pendulum-type structures shall be designed for

the bending moment calculated at the base determined using the procedures given in

Section 6.5 and varying uniformly to a moment at the top equal to one-half the

calculated bending moment at the base.

6.8.3 Elements Supporti ng Di sconti nuous Walls or Frames

Discontinuous walls, columns or other elements of structures having plan irregularity

Type 4 of <Table 6.4.4> or vertical irregularity Type 4 of <Table 6.4.5> shall have

the design strength to resist special seismic load combinations of Section 6.2.

6.8.4 Di recti on of Sei smi c Load

6.8.4.1 Seismic Design Category B

The direction of application of seismic forces used in design shall be that which will

produce the most critical load effect in each component. The requirement will be

deemed satisfied if the design seismic forces are applied separately and independently

- 26 -

in each of the two orthogonal directions.

6.8.4.2 Seismic Design Category C

The structures assigned to Seismic Design Category C shall conform to the

requirements of Section 6.8.4.1. For structures that have plan structural irregularity

Type 5 in <Table 6.4.4>, their components and foundations shall be designed for one

of the following combinations of prescribed loads.

(1) One hundred percent of the forces for one direction plus 30 percent of the forces

for the perpendicular direction. The combination requiring the maximum component

strength shall be used.

(2) The effects of the two orthogonal directions are permitted to be combined on a

square root of the sum of the squares (SRSS) basis.

6.8.4.3 Seismic Design Category D

The components and foundations of structures assigned to Seismic Design Category D

shall be designed for one of the following combinations of prescribed loads.

(1) One hundred percent of the forces for one direction plus 30 percent of the forces

for the perpendicular direction. The combination requiring the maximum component

strength shall be used.

(2) The effects of the two orthogonal directions are permitted to be combined on a

square root of the sum of the squares (SRSS) basis.

6.8.5 Verti cal Sei smi c Forces

In addition to the applicable load combinations, horizontal cantilever and horizontal

prestressed components of the structures assigned to Seismic Design Category D shall

be designed to resist a minimum net upward force of 0.2 times the dead load.

6.8.6 Bui ldi ng Separati ons

All structures assigned to Seismic Design Category D shall be separated from

adjoining structures. Adjacent buildings on the same property shall be separated by at

least δMT

where

δMT= (δ M1)

2+(δ M2)2 (6.8.1)

and δM1

and δM2

are the displacements as determined in Section 6.5.7 or 6.7.4 of the

adjacent buildings.

When a structures adjoins a property line not common to a public way, that structure

shall also be set back from the property line by at least the displacement, δM

, of that

structure.

- 27 -

6.9 Archi tectural, Mechani cal And Electri cal Components

6.9.1 General

Architectural, mechanical, electrical, and other nonstructural components in buildings

shall be designed and constructed to resist the equivalent static forces and

displacements determined in accordance with Section 6.9. Where the combined weight

of the supported components and nonbuilding structures exceeds 25 percent of the

weight of the structures, structures shall be designed in accordance with Section 6.10.

6.9.1.1 Applicability to Components

Components shall be considered to have the same seismic design category as that of

the structure that they occupy or to which they are attached, as described in Section

6.4. The following nonstructural components are exempt from the requirements of

Section 6.9.

(1) Components in Seismic Design Category A.

(2) Other than parapets supported by bearing walls or shear walls, architectural

components in Seismic Design Category B when the component importance factor,

I p , is equal to 1.0.

(3) Mechanical and electrical components in Seismic Design Category B.

(4) Mechanical and electrical components in Seismic Design Category C, provided that

the component importance factor, I p , is equal to 1.0.

(5) Mechanical and electrical components in all Seismic Design Categories that are

linked with ductwork or piping by flexible connections, mounted at 1.2 meters or

less above a floor level, and weigh 1,800 N or less, provided that the component

importance factor, I p , is equal to 1.0.

(6) Mechanical and electrical components in Seismic Design Category D that are linked

with ductwork or piping by flexible connections and weigh 100 N or less, provided

that the component importance factor, I p , is equal to 1.0.

6.9.1.2 Equivalent Seismic Forces

Equivalent seismic forces, F p, shall be determined in accordance with Eq. (6.9.1). The

force F p shall be applied independently longitudinally and laterally in combination with

service loads associated with the component. When positive and negative wind loads

exceed F p for nonbearing exterior wall, these wind loads shall govern the design.

F p =0.4a pS DSW p

(R p

I p )( 1 + 2

zh ) (6.9.1)

F p is not required to be taken as greater than

F p = 1.6S DS I pW p(6.9.2)

- 28 -

and Fp shall not be taken as less than

F p = 0.3S DS I pW p(6.9.3)

where, a p : component amplification factor that varies from 1.0 to 2.5 (select

appropriate value from <Table 6.9.1> or <Table 6.9.2>)

F p : seismic design force centered applied at the component's center of gravity

and distributed relative to component's mass distribution

I p : component importance factor that is either 1.0 or 1.5, as determined in

Section 6.9.1.4

h : averaged roof height of structure with relative to the base elevation

R p: component response modification factor that varies from 1.0 to 5.0 (select

appropriate value from <Table 6.9.1> or <Table 6.9.2>)

S DS : design spectral response acceleration at short period as determined in Section

6.3.3

W p : component operating weight

z : height in structure of point of attachment of component.

z= 0 : for items at or below the base

z= h : for items at or above the roof

6.9.1.3 Seismic Relative Displacements

Seismic relative displacements, D p, shall be determined in accordance with the

equations in this Section. For two connection points on the same Structure A or the

same structural system, one at a level x and the other at a level y, D p shall be

determined as

D p= δxA-δ

yA(6.9.4)

D p is not required to be taken as greater than

D p = (X-Y )ΔaA

h sx(6.9.5)

For two connection points on separate Structure A and B or separate structural

system, one at a level x and the other at a level y, D p shall be determined as

D p = |δ xA| + |δ yB| (6.9.6)

D p is not required to be taken as greater than

D p =XΔ

aA

h sx+YΔ

aB

h sx(6.9.7)

where, Dp : relative seismic displacement that the component must be designed

- 29 -

to accomodate

h sx : story height used in the definition of the allowable drift in <Table

6.4.7>.

δxA

, δyA

, δyB

: deflection at building level x or y of Structure A or B,

determined by an elastic analysis as defined in Sections

from 6.5.3 to 6.5.7

X : height of upper support attachment at level x as measured from

the base

Y : height of lower support attachment at level x as measured from

the base

ΔaA

, ΔaB

: allowable story drift for Structure A or B as defined in

<Table 6.4.7>

6.9.1.4 Component Importance Factor

The component importance factor, I p , for other components shall be taken as 1.0, but

the factor shall be taken as 1.5 if any of the following conditions apply:

(1) Life-safety component is required to function after an earthquake.

(2) Component contains hazardous or flammable materials.

(3) Storage racks in occupancies open to the general public (eg. warehouse retail

stores)

(4) Component is in or attached to an Occupancy Category S structure in <Table

6.4.1> and it is needed for continued operation of the facility or it is its failure

could impair the continued operation of the facility.

6.9.1.5 Component Anchorage

Components shall be anchored in accordance with the following:

(1) The force in the connected part shall be determined based on the prescribed forces

for the component specified in Section 6.9.1.2. Where the component anchorage is

provided by shallow expansion anchors, shallow chemical anchors, or shallow (low

ductility) cast-in-place anchor, a value of R p= 1.5 shall be used in Section 6.9.1.2

to determine the forces on the connected part.

(2) Anchors embedded in concrete or masonry shall be proportioned to carry the lesser

of the following:

① the design strength of connected part

② 1.3 times the force in the connected part as given by F p×R p

③ The maximum force that can be transferred to the connected part by the

component structural system

(3) Determination of forces in anchors shall include the expected conditions of

installation including eccentricities and prying effects.

- 30 -

6.9.2 Archi tectural Component Desi gn

Architectural systems, components or elements listed in <Table 6.9.1> and their

attachments shall meet the requirements of section 6.9.1

6.9.3 Mechani cal and Electri cal Component Desi gn

Attachments and equipment supports for the mechanical and electrical systems,

components or elements shall meet the requirements of Section 6.9.1.

- 31 -

Architectural Component or Element ap1)

Rp

1. Interior Nonstructural Walls and Partitions

a. Plain (unreinforced) masonry walls 1.0 1.25

b. All other walls and partitions 1.0 2.5

2. Cantilever Elements (Unbraced or braced to structural frame below its center of mass)

a. Parapets and cantilever interior nonstructural walls 2.5 2.5

b. Chimneys and stacks when laterally braced or supported by structural

frame2.5 2.5

3. Cantilever Elements (Braced to structural frame above its center of mass)

a. Parapets 1.0 2.5

b. Chimneys and Stacks 1.0 2.5

c. Exterior Nonstructural Walls 1.0 2.5

4. Exterior Nonstructural Wall Elements and Connections

a. Wall Element 1.0 2.5

b. Body of wall panel connections 1.0 2.5

c. Fasteners of the connecting system 1.25 1.0

5. Veneer

a. Limited deformability elements and attachments 1.0 2.5

b. Low deformability elements and attachments 1.0 1.25

6. Penthouse (except when framed by an extension of the building frame) 2.5 3.5

7. Ceilings 1.0 2.5

8. Cabinets

a. Storage cabinets and laboratory equipment 1.0 2.5

9. Access Floors

a. Special access floors 1.0 2.5

b. All other 1.0 1.25

10. Appendages and Ornamentations 2.5 2.5

11. Signs and Billboards 2.5 2.5

12. Other Rigid Components

a. High deformability elements and attachments 1.0 3.5

b. Limited deformability elements and attachments 1.0 2.5

c. Low deformability elements and attachments 1.0 1.25

13. Other Flexible Components

a. High deformability elements and attachments 1.0 3.5

b. Limited deformability elements and attachments 2.5 2.5

c. Low deformability elements and attachments 2.5 1.25

1) Where justified by detailed dynamic analyses, a lower value for ap is permitted, but shall not be less than 1. The

reduced value of ap shall be between 2.5, assigned to flexible or flexibly attached equipment, and 1, assigned to

rigid or rigidly attached equipment.

<Table 6.9.1> Architectural Components Coefficients

- 32 -

Mechanical and Electrical Component or Element ap Rp

1. General Mechanical

a. Boilers and furnaces 1.0 2.5

b. Pressure vessels on skirts and free-standing 2.5 2.5

c. Stacks 2.5 2.5

d. Cantilevered chimneys 2.5 2.5

e. Other 1.0 2.5

2. Manufacturing and Process Machinery

a. General 1.0 2.5

b. Conveyors (nonpersonnel) 2.5 2.5

3. Piping Systems

a. High-deformability elements and attachments 1.0 3.5

b. Limited-deformability elements and attachments 1.0 2.5

c. Low-deformability elements and attachments 1.0 1.25

4. HVAC System Equipment

a. Vibration isolated 2.5 2.5

b. Nonvibration isolated 1.0 2.5

c. Mounted in-line with ductwork 1.0 2.5

d. Other 1.0 2.5

5. Elevator Components 1.0 2.5

6. Escalator Components 1.0 2.5

7. Trussed Towers (free-standing or guyed) 2.5 2.5

8. General Electrical

a. Distributed Systems (Bus Ducts, Conduit, Cable Tray) 1.0 3.5

b. Equipments 1.0 2.5

9. Lighting Fixtures 1.0 1.25

<Table 6.9.2> Mechanical and Electrical Components Coefficients

- 33 -

6.10 Sei smi c Desi gn Requi rements f or Nonbui ldi ng Structures

6.10.1 General

6.10.1.1 Nonbuilding Structures

The requirements of this section apply to self-supporting structures that carry gravity

loads that are not defined as buildings, vehicular or railroad bridges, nuclear power

generation plants, offshore platforms, or dams.

6.10.1.2 Nonbuilding Structures Supported by Other Structures

(1) If a nonbuilding structure is supported above the base by another structure and the

weigh of the nonbuilding structure is less than 25 percent of the combined weight

of the nonbuilding structure and the supporting structure, the design seismic forces

of the supported nonbuilding structure shall be determined in accordance with the

requirements of Section 6.9.

(2) If the weight of a nonbuilding structure is 25 percent or more of the combined

weight of the nonbuilding structure and the supporting structure, the design

seismic forces of the nonbuilding structure shall be determined based on the

combined nonbuilding structure and supporting structural system.

(3) Response modification factors shall be determined in accordance with following:

① For supported nonbuilding structures that have component dynamic

characteristics that are not rigid, the combined system R factor shall be a

maximum of 3.

② For supported nonbuilding structures that have rigid component dynamic

characteristics, the combined system R factor shall be the value of the

supporting structural system.

6.10.1.3 Architectural, Mechanical , and Electrical Components

Architectural, mechanical, and electrical components supported by nonbuilding

structures shall be designed in accordance with Section 6.9.

6.10.2 Structural Desi gn Requi rements

Design of nonbuilding structures to resist seismic loads shall conform to this section.

6.10.2.1 Weight

For purpose of calculating design seismic force in nonbuilding structures, the weight

shall include dead load and normal operating contents for items such as tanks, vessels,

bins, and contents of piping. The weight shall include snow and ice loads when these

loads constitute 25 percent or more of the seismic effective weight.

6.10.2.2 Fundamental Period

The fundamental period of nonbuilding structure shall be determined by method as

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described in Section 6.5.3, or by using other rational methods.

6.10.2.3 Drift Limits

The drift limitation of Section 6.4.6 need not apply to nonbuilding structures if a

rational analysis indicates they can be exceeded without adversely affecting structural

stability.

6.10.2.4 Seismic Design Forces

Nonbuilding structures shall be deisgned to resist minimum seismic lateral forces not

less than the requirements of Section 6.5.1 and following:

(1) The response modification coefficients shall be the lesser of the values given in

<Table 6.10.1> or the values in <Table 6.6.1>.

(2) For nonbuilding systems with response modification coefficients provided in <Table

6.10.1>, the minimum value specified in Eq. (6.5.4) shall be replaced by the

following:

C S=0.14 S DSI E (6.10.1)

(3) The importance factor shall be given in <Table 6.10.2>.

The vertical distribution of lateral seismic forces in nonbuilding structures covered by

this section shall be determined in accordance with Section 6.5.5.

6.10.2.5 Rigid Nonbuilding Structures

Nonbuilding structures that have a fundamental period, T, less than 0.06 second,

including their anchorages, shall be designed for the lateral force obtained from the

following:

V= 0.3S DSW I E (6.10.2)

where, I E : the importance factor as defined in <Table 6.10.2>

S DS : the site design response acceleration as determined from Section 6.3.3

V : the total design lateral seismic base shear force applied to a

nonbuilding structure

W : nonbuilding structure operating weight as defined in Section

6.10.2.1

The force shall be distributed with height in accordance with Section 6.5.5.

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Nonbuilding Structure Type R Ω0 Cd

1. Nonbuilding frame systems:

a. Concentric braced frames of steel 5 2 4.5

2. Moment-resisting frame systems:

a. Moment frames of steel

b. Intermediate moment frames of concrete

c. Ordinary moment frames of concrete

4

5

3

3

3

3

3.5

3.5

2.5

3. Steel storage racks 4 2 3.5

4. Elevated tanks, vessels, bins, or hoppers1)

a. On braced legs

b. On unbraced legs

c. Single pedestal or skirt supported

d. Welded steel

e. Concrete

3

3

2

2

2

2

2

2

2

2

2.5

2.5

2

2

2

5. Horizontal, saddle supported welded steel vessels 3 2 2.5

6. Tanks or vessels supported on structural towers similar to buildings 3 2 2

7. Flat bottom, ground-supported tanks, or vessels:

a. Mechanically anchored (welded or bolted steel)

b. Self-anchored (welded or bolted steel)

3

2.5

2

2

2.5

2

8. Reinforced or prestressed concrete

a. Tanks with reinforced nonsliding base

b. Tanks with anchored flexible base

2

32

2

2

2

9. Tanks with unanchored or unconstrained tanks

a. Flexible base

b. Other material

1.5

1.5

1.5

1.5

1.5

1.5

10. Cast-in-place concrete silos, stacks, and chimneys having walls

continuous to the foundation3 1.75 3

11. Other reinforced masonry structures not similar to buildings3)

3 2 2.5

12. Other nonreinforced masonry structures not similar to buildings3)

1.25 2 1.5

13. Oher steel and reinforced concrete distributed mass cantilever structures

not covered herein including stacks, chimneys, silos, and skirt-supported

vertical vessels that are not similar to buildings

3 2 2.5

14. Trussed tower (freestanding or guyed), guyed stacks and chimneys 3 2 2.5

15. Cooling towers

a. Concrete or steel

b. Wood frame

3.5

3.5

1.75

3

3

3

<Table 6.10.1> Seismic Coefficients for Nonbuilding Structures

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Nonbuilding Structure Type R Ω0 Cd

16. Telecommunication towers

a. Truss : Steel

b. Pole : Steel

Wood

Concrete

c. Frame : Steel

Wood

Concrete

3

1.5

1.5

1.5

3

2.5

2

1.5

1.5

1.5

1.5

1.5

1.5

1.5

3

1.5

1.5

1.5

1.5

1.5

1.5

17. Amusement structures and monuments 2 2 2

18. Inverted pendulum type structures (not elevated tanks)2)

2 2 2

19. Signs and billboards 3.5 1.75 3

20. Other selt-supporting structures, tank, or vessels not covered above 1.25 2 2.5

1) Tower with irregularity as defined in Section 6.4.4

2) Support for lighting, Spot lighting, etc.

3) Masonry structures shall not be allowed in Seismic Design Categories C and D.

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<Table 6.10.2> Importance Factor ( I E) and Seismic Use Group Classification

for Nonbuilding Structure

Importance Factor I E= 1.0 I E= 1.5

Seismic Use Group

as Defined in <Table 6.4.1>Ⅱ S

Hazard H-1 H-2

Function F-1 F-2

H-1 = The stored product is biologically or environmentally benign; low fire or low physical hazard.

H-2 = The stored product is rated high or moderate expansion hazard, high fire hazard, or high physical hazard as

determined by the authority having jurisdiction.

F-1 = Nonbuilding structures not classified as F-2

F-2 = Seismic Use Group S nonbuilding structures or designated ancillary nonbuilding structures (such as:

communication towers, fuel storage tanks, cooling towers, or electrical substation structures) required for

operation of Seismic Use Group S structures.)