Technical Reference 2007.Ch

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5.31.2.11 Canadian Seismic Code (NRC)

This set of commands may be used to define the parameters for generation ofequivalent static lateral loads for seismic analysis per National Building Code(NRC/CNRC) of Canada- !!" #olume $ edition% &epending on this definition'equivalent lateral loads ill be generated in horiontal direction(s)%

The seismic load generator can be used to generate lateral loads in the * + ,directions for up or * + for , up% up or , up is the vertical a.is and the directionof gravity loads (ee the SET Z UPcommand in ection "%")% 0ll vertical coordinatesof the floors above the base must be positive and the vertical a.is must beperpendicular to the floors%

Methodology

The minimum lateral seismic force or base shear (#) is automatically calculated by

T00& using the appropriate equation (s)%

as per section 1%$%2%$$() of NBC of Canada !!"' #olume $

3.cept that # shall not be less than4

and for an Rd5 $%"' # need not be greater than4

(i%e%' the upper limit of #)

&escription of the terms of the equation to calculate #4

Tais the fundamental lateral period in the direction under consideration and is

determined as4

a% 6or moment-resisting frames that resist $!!7 of the required lateral forcesand here the frame is not enclosed by or ad8oined by more rigid elements

that ould tend to prevent the frame from resisting lateral forces' and iscalculated by the empirical formulae as described belo provided h

nis in

meter

i% !%!2"(hn)9/1for steel moment frames'

ii% !%!:"(hn)9/1for concrete moment frames' or

b% The period is also calculated in accordance ith the Rayleigh method butcould be overridden by user specified time period (;*' ;,)%


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(a)' the former is used for further calculation% =therise' the later timeperiod is used%

c% =ther established methods of mechanics using a structural model thatcomplies ith the requirements of entence 1%$%2%9%(2)' e.cept that

i% for moment resisting frames' Ta shall not be greater than $%" times

that determined in Clause (a)%ii% for braced frames' Ta shall not be greater than %! times that

determined in Clause (b)%

iii% for shear all structures' Ta shall not be greater than %! times thatdetermined in Clause (c)' and

iv% for the purpose of calculating the deflections' the period ithout theupper limit specified is referred from 0ppendi. 0%

(Ta) is the design spectral acceleration and is determined as follos' using

linear interpolation for intermediate values of Ta4

S(Ta) = F

aS

a(0.2) for T

a 0.2s

5 6va(!%") or 6aa(!%)' hichever is smaller for Ta5 !%"s

5 6v

a($%!) for T

a5 $%!s

5 6v

a(%!) for T

a5 %!s

5 6v

a(%!)/ for T

a> 1%!s

The above terms a(!%)' a(!%")' a($%!) and a(%!) are the eismic &ata and are

obtained as user input from the Table C-2.

Based on the above values of a(Ta)' 6a and6v'the acceleration- and velocity

based site coefficients are determined from the Tables 1%$%2%1%B and 1%$%2%1%C'using linear interpolation for intermediate values of

a(!%) and

a($%!)%


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E /

F is the eight of the building and shall be calculated internally using thefolloing formula4

Fhere Fiis the portion of F that is located at or assigned to level i%

Rdis the ductility-related force modification factor reflecting the capability of a

structure to dissipate energy through inelastic behavior as described in article1%$%2%G%

Rois the over-strength-related force modification factor accounting for the

dependable portion of reserve strength in a structure designed according to theprovision of the 0rticle 1%$%2%G%

These Rdand R

ovalues are the user inputs depending on the type of 6R

0s per 1%$%2%$$(H)' the total lateral seismic force' #' shall be distributed such that aportion' 6tshall be concentrated at the top of the building' here'

6t5 !%!:T

a#

but 6tis not greater than !%"# and 6

t5 ! hen T

ais not greater than !%:s%

The remainder (#- 6t)' shall be distributed along the height of the building' including

the top level' in accordance ith the folloing formula Ias per section 1%$%2%$$(H)J4

Fhere4

6.

is the lateral force applied to level .%

6t

is the portion of # to be concentrated at the top of the structure%

Fi'F. are the portion of F that is located at or assigned to level i or .respectively%

hi'h. are the height above the base(i5!) to level i or . respectively%

level i is any level in the building' i5$ for first level above the base%

level n is uppermost in the main portion of the structure%

General Format

T00& utilies the folloing format to generate the lateral seismic loads%

DEFINE NRC2005LOAD

nrc-spec

SELFWEIGHT

JOINT WEIGHT

Pgina 3 de 55.31.2.11 Canadian Seismic Code (NRC) 2005 !o"#me 1

1$%03%201$m&'S*TS+ore'C',SPro!-i,ST/,e",Tecnica"Reference2004.cm''%Comm...


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joint-list WEIGHT w

ee KEBC $GG1 or $G2" oad &efinitionKfor complete eight input definition%

Fhere4

nrc-spec= { SA1 f1 SA2 f2 SA3 f3 SA4 f4 !" f5 !Z f# J" f$ JZ

f% IE f& RD" f10 RO" f11 RDZ f12 ROZ f13 SCLASS f14 '

f$' f

' f

9' and f

15 eismic &ata as per Table C- and are you input%

f"' f

H5 The higher mode factor along * and , directions respectively% These

are user input and please refer Table 1%$%2%$$%

f:' f2 5 The numerical reduction coefficient for base overturning moment

along * and , directions respectively% These are user input and please refer

Table 1%$%2%$$%

fG

5 the earthquaDe importance factor of the structure% This is a user input

depending on


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on the plates are to be considered in eight calculation%

6loor Feight is used if the pressure is on a region bounded by beams' but the entityhich constitutes the region' such as a slab' is not defined as part of the structuralmodel%

Technical Reference 2007.Ch

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