1 International Building Code of USA 2000
2 New Zealand Standards NZS 1170.5
3 Eurocode 8 procedure (EC-8)
4 Uniform Building Code (UBC) 1997
5 National Building Code (NBC) of Canada (1995)
6 Mexican Federal District Code (MFDC) 1993
7 Japanese Society of Civil Engineers (JSCE) 2000

**Codal provisions
for seismic design **

1 International Building Code of USA 2000

The base shear is given by

*V _{b} *=

where *W* is the total
weight and applicable portions of other loads and the seismic coefficient *C _{S}*
is given by

This coefficient corresponding to
*R* = 1 is known as the *elastic seismic* *coefficient*.

*C _{e} *=

where *I* is the *importance
factor*: *I* = 1 for most structures, *I* = 1.25 for structures
that have substantial public hazard due to occupancy and *I* = 1.5 for
essential facilities that are required for post earthquake recovery.

The period coefficient *C*
depends on the location of the structures and site class.

where *T*_{1} is the
fundamental natural vibration period of the structure in seconds

where *w _{i}* is the
weight of the

The response modification factor *R*
depends on several factors, including ductility capacity and inelastic
performance of structural materials and systems during past earthquake. Specified
values of *R* vary between 1.5 and 8.

The distribution of lateral force
over the height of building is given by

The deterministic overturning
moments are multiplied by a factor *J*. *J* = 1.0 for the top 10
storeys, 1â€“0.8 for next ten storeys from top and varying linearly with the
height 0.8 for remaining floors.

2 New Zealand
Standards NZS 1170.5

Seismic design in New Zealand has
evolved over the past 30 years from an â€˜*allowable stress* basisâ€™ to â€˜*strength
capacity*â€™ approach. The concept of â€˜*Capacity design*â€™ is well
established as a way of thinking for New Zealand structural engineers and
dominates their design approach. Over the past 15 years, the loading standards
(NZS 4203-92, NZS 1170.5) have been used as a basis of design a â€˜*constant
hazard design spectrum*â€™. The spectra is not intended to be an *â€˜earthquakeâ€™
spectrum* but a spectrum for which the acceleration at each spectral period
has an equal likelihood of being exceeded over some passage of time. New
Zealand design spectra are anchored back to a constant hazard approach.

The forces acting on a structure
as a result of ground shaking are usually determined by one of the following
methods:

â€¢ Static
analysis: using equivalent static force obtained from acceleration response
spectra from horizontal earthquake motions.

â€¢ Dynamic
analysis: either the modal response spectrum method or numerical integration
time history method using earthquake records:

According to New Zealand standard
for general structural design loading for buildings the equivalent static
method of analysis can be applied only where at least one of the following
criteria is satisfied:

â€¢ The
height between the base and top of the structure does not exceed 15 m.

â€¢ The
calculated fundamental period of vibration of the structure does not exceed
0.45 s.

â€¢ The
structure satisfies the horizontal and vertical regularities requirement
standard and has a fundamental period of vibration <2 s.

According to NZS 4203:1993[1.3]
when the equivalent static force method is used, the design horizontal seismic
forces acting at the base of the structure or at the serviceability limit state
is

*C _{h}*(

*C _{h}*(

The horizontal seismic design force *V* given
by Eqs 19.11 and 19.12 are distributed appropriately up to the height of the
structure. *Âµ* is the structural ductility
factor given by âˆ†_{max}/âˆ†* _{y}*.

According to NZS 4203: 1992 (1.3) structural
performance factor *S _{P}* is taken as 2/3 unless specified
otherwise in the material standard. A value of 2/3 is justified as a result of
beneficial effects.

In some structures *S _{p}* â‰ˆ 1 may be more appropriate. The risk factor

The above elastic response spectra for ultimate
limit state have an assured return period of 450 years (approximately 10% of
probability of exceedence in 50 years). NZS 3101: 1995[1.5] specifies values
for displacement factors and design procedures for various categories of
ductility of reinforces concrete (RC) structures.

3 Eurocode 8 procedure (EC-8)

The method is referred to as
â€˜simplified modal response spectrum analysisâ€™ rather than â€˜equivalent static
analysisâ€™ and is restricted to structures that are not significantly affected
by higher modes and/or stiffness irregularities. The base shear is calculated
as

*V _{B} *=

*S _{d}*(

The inertia forces are taken as
permanent loads *G* and portion *Ïˆ*_{E}*Q* of
variable live loading *Q*. The fundamental period *T*_{1} can
be estimated for a proper eigen value analysis or from empirical formula
included in the code.

The lateral force corresponding
to *V _{B}* can be calculated as

where *F _{i}* is the
horizontal force acting in storey

In order to cover uncertainties
in the distribution of mass and stiffness as well as spatial variability of
ground motion, an accidental eccentricity of the loads *F _{i}*
with respect to mass centre

*e*_{1i}* *=* *Â±0.05*L _{i } *19.15

where *L _{i}* is the
floor dimension perpendicular to the direction of force

â€˜+â€™ means to be combined with; *G*
= permanent dead load; *Q* = variable imposed load; *Î³*_{1}
important factor; *E _{d}* design value for seismic action.

The criterion for the required
number of modes to be included in the analysis is two-fold:

1. The sum
of effective modal mass should amount to at least 90% of the total mass.

2. All modes
with effective mass >5% of the total mass should be considered.

The modal action should be
combined with SRSS unless the period of two of them considered modes differ by
less than 10%, in which case CQC approach should be used.

4 Uniform Building
Code (UBC) 1997

The method is applicable to all
buildings in the low seismicity zone (zone 1 and usual structures in seismic
zone 2), regular structures up to 73 m and irregular structure having no more
than five stories. The design base shear is given by

*W *= seismic
dead load,* C _{a}*,

The load factor in the above
equations should be increased by 10% for design of RC and masonry structures.
There are two differences in the modal analysis procedure specified in UBC:

1. The
elastic rather than the design response spectrum is used for estimating actual
effect.

2. The
elastic force calculated above is then scaled down to account for inelastic
effects. This is done by adjusting them to 90% of *V _{B}* used in
the equivalent stated analysis in the case of regular structures 100% in case
of irregular structures.

5 National Building Code (NBC) of Canada (1995)

The base shear is expressed as

*V _{B} *=

The seismic coefficient *C _{s}*
is given by

*U *= 0.6 is
a* calibration factor *applied to maintain the design base shear at* *the
same level of protection (as in the preceding edition of the code) for
buildings with good to excellent capability of resisting seismic loads. The
elastic seismic coefficient is given by

1. *Zonal
velocity factor **Î³** *varies
between 0 for least seismic zone to 0.4 and* *the worst seismic zone.

2. *I *= 1.5,
1.3 and 1 for post-disaster building, for schools and for other* *buildings
respectively.

3. *F *= 1.0,
1.3, 1.5, 2.0 foundation factors depending on soil category.* *

4. *S *=*
seismic response factor *varies with* T*_{1}* *

For *T*_{1} < 0.5
s

*Z _{a}*,

The empirical formula for
calculating *T*_{1} is

where *u _{i}* is the
floor displacement of

The force modification factor *R*
varies from 1 for *brittle* structure to 4 for *ductile *moment
resisting space frames.

The distribution of lateral
forces over the height of the building is determined from

The National Building Code of
Canada (NBC) was revised in 2005. The seismic hazard map is given and the
seismic hazard is expressed as the most powerful ground motion that is likely
to occur in an area for a given probability level. Building design for various
earthquake loads is addressed in Sections 4.1.8, 9.20.1.2, 9.23.10.2 and
9.31.6.2 of the 2005 NBC. The seismic hazard values are described by spectral
acceleration values at periods 0.2, 0.5, 1.0 and 2.0 s. It is a better measure
of potential damage than the peak measure used by 1995 and thus improves
earthquake design. PGA is still used in foundation design. The probability used
in the 2005 NBC is 0.000404 per annum equivalent to 2% probability exceeding
over 50 years. A building designed to tolerate a sideward pushing force
equivalent to 40% of it own weight should prove earthquake-resistant.

6 Mexican Federal
District Code (MFDC) 1993

The seismic coefficient is
calculated as

*C _{s}
*=

Elastic seismic coefficient

*T*_{1}* *Fundamental
time period,* T _{b} *and

The elastic seismic coefficient

Overturning moments determined are multiplied by reduction
factor that varies linearly from 1.0 at the top of the building to 0.8 at its
base to obtain design values.

7 Japanese Society
of Civil Engineers (JSCE) 2000

All codes except the JSCE code
basically apply the concepts of the capacity design philosophy. Although the JSCE
code does not follow the capacity design principles, it should be noted that
basic ideas of seismic design are essentially similar and the JSCE code does
not prescribe any specific design earthquake motion. The seismic code of
buildings in Japan was revised in June 2000 to implement a performance-based
structural engineering framework. The code provides the performance objectives,
*life safety* and *damage* limitation of a building at the two
corresponding levels of earthquake.

*Design response spectra at engineering bedrock*

The earthquake ground motion used for the seismic design at
the life safety limit is the site-specific motion of an extremely rare
earthquake which is expected to occur once in approximately 500 years. The
engineering bedrock is assumed to be the soil layer whose shear wave velocity
is >400 m/s. The basic design earthquake acceleration response spectra *S*_{0}
of the seismic ground motion at the exposed outcrop engineering bedrock is
given as

where *S*_{0} =
basic design acceleration response spectra in m/s^{2} and *T* =
natural period. The level of earthquake ground motion used for the seismic
design at the damage limit should be reduced to one-fifth of life safety.

*Design response spectra at ground motion*

*S _{a}*(

Where

*S _{a} *= design acceleration
response spectra at ground surface m/s

*G _{s}*

*G _{s}*

*T*_{1}* *= predominant
period of surface soil layer for first mode* T*_{2}* *=
predominant period of surface soil layer for second mode* *Minimum values
of *G _{s}*

8 Iranian code

Almost everywhere in Iran is
prone to earthquake as two major earthquake belts run through the country.
Every decade or so a major earthquake strikes Iran, resulting in many
fatalities and collapsed buildings. Traditional Iranian buildings, especially
in the rural areas, have very little resistance to earthquakes of higher
magnitude.

After numerous major earthquakes,
in particular that of 1963 in Bouein Zahra, the Iranian government began the
preparation of code of practice for earthquake protection in 1967. Iranâ€™s
Ministry of Housing first published a code of practice for earthquake-resistant
construction which requires buildings taller than 11 m to be made of RC or
steel frames.

In 1993 the Iranian Building Research Centre further revised
the code and after three stages of research, construction and design and the
updated and revised Iranian code for seismic resistant design was published in
1997 (IS2800). This code was revised in 1999 and covers seismic design of RC
and steel and masonry construction. According to IS2800 (1999) chapter 2, the
seismic base shear coefficient is obtained from

where

*V *= base shear

*w *= total
weight of the building (DL+0.2LL)* *

*C *= base shear coefficient

*A *= design base acceleration or
ratio to gravity which may be 0.2, 0.25, 0.3,* *0.35 depending on regions
(0.3*g* for Bamm in region 2 of the seismic micro-organization map of
Iran)

*B *=
building response factor obtained from design response spectrum* *(amplification
factor)

*I *=
importance factor of the building = 0.8, 1.0 or 1.2* T *= natural period
of the building

*T*_{0}* *= corner
period of the acceleration response spectrum dependent on soil* *type (0.4
0.5 0.7 1.0) 0.5 s for soil type in Bamm

*R *=*
building factor *varying from 4 to 11 (for example, 4 for simple masonry* *with
frame 6 for concentric steel-braced buildings)

*H *= height of the building from
base in m

For a two storey masonry building *B* = 2.5, *I* =
1, *R* = 4, the base shear coefficient *C* is estimated as 0.19.
Seismic lateral forces may be calculated from

9 Chinese code

Before 1964 there was no
seismic-resistant design code for buildings and other structures in China.
Earthquake-resistant design was not considered for most buildings. A draft of
seismic-resistant design code in China was prepared in 1964. The first official
seismic code of China was issued in 1974. In 1975 and 1976 China suffered two
strong earthquakes: 1975 earthquake of Haichung with a magnitude of 7.3 and
Tangshan with a magnitude of 7.8. These two earthquakes were considered to be
catastrophic disasters, killing 242 829 people. The code was revised and put
into effect in 1993. Equivalent lateral force method was recommended.

The total horizontal seismic action *F _{EK}*
(base shear) is given by

where *w _{eq}* is the total equivalent seismic
weight of a building and

where *T _{g}* is the

The total seismic weight should
be used when the structure is modelled as a single-degree-of-freedom (SDOF)
system, 85% of total seismic weight if it is modelled as a
multiple-degrees-of-freedom (MDOF) system. Table 19.5 gives values of *Î±*_{max}.

The horizontal seismic force *F _{i}* applied at
any level I of the building is given by

where *Î´** _{N}* is
called additional seismic action coefficient given in Table 19.6. The overturning
moment is given as

For any other country code one
may refer to the international handbook of earthquake engineering codes by
Maria Paz (1994).

10Indian Seismic Code 1893 â€“ Part 1 â€“ 2002

The first *Indian Seismic Code*
(IS 1893) was first published in 1962 and it has since been revised in 1966,
1970, 1975 and 1984. More recently it was decided to split this code into a
number of parts and Part 1 of the code containing general provisions
(applicable to all structures) and specific provisions for buildings has been
published. Some extracts of the code are given below.

The design horizontal seismic coefficient *A _{h}*
for a structure can be determined from

Provided that for any structure
with *T* â‰¤ 0.1 s
the value of *A _{h}* will not be less than

*Z *= zone
factor as given in Table 19.7 and it is for a* maximum considered earthquake *(MCE)
and service life of structure in a zone. The factor 2 is* *used in the
denominator to reduce MCE to *design basis earthquake* (DBE). *I *=
importance factor depending upon the functional use of the structure* *characterized
by hazardous consequences of its failure varying from 1 to 1.5. *R *=
response reduction factor depending on the perceived seismic damage* *performance
of the structure characterized y ductile or brittle deformations. However, the
ratio of *I*/*R* â‰¤ 1.

*S _{a}*/

The response spectrum for
IS1893-2002 is shown in Fig. 19.2 and the zone factors are shown in Table 19.7.

Table 19.8 gives the multiplying factors for obtaining
spectral values for various other damping ratios.

The seismic weight of each floor is its full dead load plus an
appropriate amount of imposed load. The total design lateral force or design
seismic base shear is given by

Dynamic analysis shall be performed to obtain the design seismic
force and its distribution to different levels along the height of the
building.

ï‚• Regular building >40 m in the zone IV and
V and >90 m in the height in Zones
II and III

ï‚• Irregular building. All framed buildings
>12 m in zones IV and V >40 m in
Zones II and III.

Dynamic analysis may be performed either by the time history
method or the response spectrum method. However, base shear *V _{B}*
is compared with

Modal mass is calculated as

The peak storey shear force *V _{i}*
in each first storey due to all modes considered is obtained by combining those
due to each mode in accordance with square root of sum of squares (SRSS) or
complete quadratic combination (CQC) rules.

**Program 19.1: MATLAB
program for IS1893 code **

A program in MATLAB is written to
calculate the shear in each storey as well as drift calculations for a
multi-storey frame. Example 19.8 is solved by the MATLAB program and the
results are also given below.

% IS1893 - 2002, Part 1
multistorey buildings % calculation of shear in each storey and drifts nst=6;

m=zeros(nst,nst);

K=zeros(nst,nst);

ma=zeros(nst,1); ak=zeros(nst,1);

t=zeros(nst,1);

sa=zeros(nst,1);

pf=zeros(nst,1);

d=zeros(nst,nst);

v=zeros(nst,nst);

vv=zeros(nst,nst);

vr=zeros(nst,1);

ah=zeros(nst,1);

sf=zeros(nst,nst);

% ***************************************************

%input data %*****************************************************

%give masses for various floors starting from ground

ma(1,1)=262.59e3;ma(2,1)=262.59e3;ma(3,1)=262.59e3;ma(4,1)=262.59e3;

ma(5,1)=262.59e3;ma(6,1)=229.934e3;

%give stiffnesses for various floors starting from ground

ak(1,1)=586926e3;ak(2,1)=586926e3;ak(3,1)=586926e3;ak(4,1)=318652e3;

ak(5,1)=318562e3;ak(6,1)=318562e3;

%soil s=1 for rocky soil s=2 medium soil s=3 for soft soil

s=1;

%give zone number

zo=4;

% give damping % for concrete 5% for steel 2% etc

da=5;

% importance of the structure

is=1;

% response reduction factor

r=3;

% height of the building

ht=21;

% width of the building

width=14;

%it=1 for rc frame buildig without brick infil panel

%it =2 for steel frame building with out brick infil panel

%it=3 for all buildings with brick infill panel

it=3;

% *******************************************************

% input completed

%********************************************************

if zo==2

z=0.1;

end

if zo==3

z=0.16;

end

if zo==4 z=0.24;

end

if zo==5 z=0.36;

end
fid=fopen(â€˜output.tableâ€™,â€˜wâ€™); fprintf(fid,â€˜zone = %2i\nâ€™,zo);
fprintf(fid,â€˜soil=%2i\nâ€™,s);

fprintf(fid,â€˜importance factor=%2i\nâ€™,is);

fprintf(fid,â€˜response reduction
factor=%2i\nâ€™,r); fprintf(fid, â€˜storey mass\nâ€™);

for i=1:nst

fprintf(fid,â€˜%2i ,
%f\nâ€™,i,ma(i,1)); end

fprintf(fid,â€˜ storey
stiffness\nâ€™); for i=1:nst

fprintf(fid,â€˜%2i,%f\nâ€™,i,ak(i,1));
end

ak(nst+1,1)=0.0; nstm1=nst-1;
weight=0.0;

for i=1:nstm1 ip1=i+1; m(i,i)=ma(i,1);

K(i,i)=ak(i,1)+ak(ip1,1); K(i,ip1)=-ak(ip1,1);
weight=weight+m(i,i)*9.81;

end K

m(nst,nst)=ma(nst,1);

K(nst,nst)=ak(nst,1);

weight=weight+ma(nst,1)*9.81; for
i=1:nst

for j=i:nst K(j,i)=K(i,j);

end end m

K ki=inv(K); kim=ki*m;

[v,d]=eig(kim); for i=1:nst

for j=1:nst v(i,j)=v(i,j)/v(nst,j);

end end

for i=1:nst om(i,1)=1/sqrt(d(i,i));
t(i,1)=2*pi/om(i,1);

end

fprintf(fid,â€˜mode period\nâ€™);

for i=1:nst fprintf(fid,â€˜%2i,%f\nâ€™,i,t(i,1));

end

for j=1:nst

fprintf(fid,â€˜mode shape for mode = %2i\nâ€™,j); for i=1:nst

fprintf(fid,â€˜%f\nâ€™,v(i,j)); end

end if s<2

ml=0.4;

co=1; elseif (s>2)

ml=0.67;

co=1.67; else

ml=0.55;

co=1.36; end

for i=1:nst

if t(i,1)<0.1 sa(i,1)=1+15*t(i,1); elseif t(i,1)>ml

sa(i,1)=co/t(i,1);

else

sa(i,1)=2.5;

end end

if da==0 mf=3.2;

end

if da==2; mf=1.4;

end

if da==5; mf=1.0;

end

if da==7; mf=0.9;

end

if da==10; mf=0.8;

end

fprintf(fid,â€˜ sa/g \nâ€™); for
i=1:nst

sa(i,1)=mf*sa(i,1);

fprintf(fid,â€˜%f\nâ€™,sa(i,1)); end

for i=1:nst sum=0.0; sum1=0.0; for j=1:nst

sum=sum+m(j,j)*v(j,i);

sum1=sum1+m(j,j)*v(j,i)^2; end

%sum

%sum1

pf(i,1)=sum/sum1;

pmas(i,1)=pf(i,1)*sum*9.81/weight;
end

fprintf(fid,â€˜mode participation
factor\nâ€™); for i=1:nst

fprintf(fid,â€˜%2i,
%f\nâ€™,i,pf(i,1)); end

fprintf(fid,â€˜ percentage of modal
masses\nâ€™); for i=1:nst

fprintf(fid,â€˜%2i,
%f\nâ€™,i,pmas(i,1)); end

for i=1:nst ah(i,1)=z*is*sa(i,1)/(2.0*r);

if t(i,1)<0.1 & ah(i,1) <z/2
ah(i,1)=z/2;

end end

fprintf(fid,â€˜mode Ah\nâ€™); for i=1:nst

fprintf(fid,â€˜%2i , %f\nâ€™,i,ah(i,1)); end

for i=1:nst for j=1:nst

sf(j,i)=pf(i,1)*ah(i,1)*m(j,j)*v(j,i); end

end %sf

for j=1,nst vv(nst+1,j)=0.0;

end

for j=1:nst for i=1:nst

ii=nst-i+1; vv(ii,j)=sf(ii,j)+vv(ii+1,j);

end end

for i=1:nst for j=1:nst

vv(i,j)=9.81*vv(i,j); end

end

fprintf(fid,â€™ shear in various
stories for various modes\nâ€™); for i=1:nst

fprintf(fid,â€™ for mode =%2i\nâ€™,i); for j=1:nst

fprintf(fid,â€™%2i %f\nâ€™,j,vv(j,i)); end

end

for i=1:nst vr(i,1)=0.0; for j=1:nst

vr(i,1)=vr(i,1)+vv(i,j)^2; end

vr(i,1)=sqrt(vr(i,1)); end

fprintf(fid,â€˜ base shear as per
modal calculation\nâ€™); fprintf(fid,â€˜%f\nâ€™,vr(1,1));

fprintf(fid,â€˜ approximate
calculation as per the code\nâ€™); if it==1

tn=0.075*ht^0.75; end

if it==2 tn=0.085*ht^0.75;

end

if it==3 tn=0.09*ht/sqrt(width);

end

fprintf(fid,â€˜ fundamental natural
period = %f\nâ€™,tn); if tn<0.1

saf=1+15*tn; elseif tn>ml saf=co/tn;

else saf=2.5;

end ahf=saf*z*is/(2*r); if
tn<0.1 & ahf <z/2

ahf=z/2; end ahf=ahf*mf; weight
vb=ahf*weight

fprintf(fid,â€˜ base shear as per
codal approximate period %f\nâ€™,vb); factor=vb/vr(1,1);

if factor>1 for i=1:nst

vr(i,1)=factor*vr(i,1); end

end

fprintf(fid,â€˜ resultant shear in
various stories\nâ€™); for i=1:nst

fprintf(fid,â€˜%2i
%f\nâ€™,i,vr(i,1)); end

fprintf(fid,â€˜ drift in various stories\nâ€™); for
i=1:nst

dr(i,1)=vr(i,1)/ak(i,1); fprintf(fid,â€˜%2i %f \nâ€™,i,dr(i,1));

end dr;

fclose(fid);

OUTPUT

zone = 4 soil= 1

importance factor= 1 response
reduction factor= 3 storey mass 1,262590.000000 2,262590.000000 3,262590.000000
4,262590.000000 5,262590.000000 6,229934.000000

storey stiffness

1,586926000.000000

2,586926000.000000

3,586926000.000000

4,318652000.000000

5,318562000.000000

6,318562000.000000 mode period
1,0.589328 2,0.223705 3,0.138951 4,0.072667 5,0.104123 6,0.093019

mode shape for mode = 1 0.182786
0.356276 0.511647 0.749899 0.917955 1.000000

mode shape for mode = 2 â€“0.581337
â€“0.957496 â€“0.995713 â€“0.418807 0.430599 1.000000

mode shape for mode = 3 0.641094
0.695710 0.113885 â€“1.149675 â€“0.475857 1.000000

mode shape for mode = 4
â€“83.585291 112.412194 â€“67.595631 17.300351 â€“4.396286 1.000000

mode shape for mode = 5 â€“1.155218

â€“0.428418

0.996338

0.630861

â€“1.628296

1.000000

mode shape for mode = 6 3.061088
â€“0.126548 â€“3.055856 3.038515 â€“2.293290 1.000000

sa/g

1.696847

2.500000

2.500000

2.090004

2.500000

2.395278

mode participation factor 1,
1.329829 2, -0.472949 3, 0.210335 4, -0.001019 5, -0.110181 6, 0.043985

percentage of modal masses 1,
0.813473 2, 0.132582 3, 0.025087 4, 0.004336 5, 0.013297 6, 0.011226

mode Ah 1,0.067874 2,0.100000
3,0.100000 4,0.120000 5,0.100000 6,0.120000

shear in various stories for
various modes for mode = 1

1 835695.230296

2 793195.356194

3 710356.969254

4 591392.874440

5 417032.256536

6 203596.660163 for mode = 2

1 200671.454855

2 129845.975774

3 13192.337190

4 -108117.437477

5 -159141.610729

6 -106680.868269 for mode = 3

1 37970.806318

2 3234.813194

3 -34460.412555
4 -40630.981084 5 21661.132553 6 47444.203966 for mode = 4

1 7875.062753

2 -18466.077913

3 16959.597905

4 -4342.547766

5 1109.499737

6 -275.949577 for mode = 5

1 20126.010937

2 -12662.189159

3 -24821.840801
4 3456.897732 5 21362.427841 6 -24852.979108 for mode = 6

1 20389.068926

2 -21231.973689

3 -19511.317627
4 22038.591323 5 -19275.537688 6 11905.898799

base shear as per modal
calculation 860802.021330

approximate calculation as per the code

fundamental natural period = 0.505124

base shear as per codal
approximate period 1198572.993130 resultant shear in various stories

1 1198572.993130

2 1119971.883836

3 991684.516096

4 839604.037191

5 623536.713435

6 329037.218693 drift in various
stories

1 0.002042

2 0.001908

3 0.001690

4 0.002635

5 0.001957

6 0.001033

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail

Civil : Structural dynamics of earthquake engineering : Codal provisions for seismic design |

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