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International Journal of Engineering Research & Technology (IJERT)

ISSN: 2278-0181http://www.ijert.org

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Vol. 9 Issue 03, March-2020

Comparative of Study the Design Spectra Defined

by Various Seismic Codes

KHadar Elmi1, Assist Prof. Dr. Erdal Coskun2 1- Institute of Graduate, Structural Engineering Program İstanbul Kültür Üniversitesi

2- Department of Civil Engineering İstanbul Kültür Üniversitesi

Abstract:- The main objective of this study is to compare

various seismic design codes, to evaluate and assess the

performance of seismic structures. The standard seismic

codes USA, European, Turkey, and Indian which mainly

considered the most seismic active regions are covering for

this study; focus on some fundamental points such as seismic

hazard specifications, soil amplification, elastic design spectra,

reduction and behavior factors, and seismic analysis

procedure. In this study Reinforced Concrete Moment

Frames are considered in the design and the structure is

applied the seismic input obtained from these contemporary

seismic codes, the seismic analysis was performed the SAP

2000 v 20. 2 Software and the result obtained from these

seismic codes, were emphasized the alteration and

resemblances among these building codes, Such as the base

shear and Inter-story drift of the structure.

Key words: Seismic Codes, Comparative Study, Drift Ratio, Base

Shear, Design Spectra, Site Classification

INTRODUCTION

Since the earthquake has become the major disaster for

structures, the seismic codes were designed to reduce the

damage of structure and to keep quality structures also to

minimize the economic loss caused by the earthquakes.

The seismic codes are updated and revised when a strong

earthquake occurs frequently, notably, Turkish is the most

seismic active regions in the world, a numerous strong

earthquake ground motions were happened for the past

decades, the Turkish seismic code is revised several times.

Two remarkable earthquake were strike Turkey in 1999

(Kocaeli and Düzce) due to these earthquakes over 18,000

are recorded for death and more than 51,000 building are

heavily damaged or collapsed. The material used for the

construction had less quality, poor design for the structures

and the range of strong ground motions are caused that

earthquake problem. (1) The Turkish seismic code 1998

were revised in 1997, however due to this strong

earthquake, another seismic code is published 2007 and

finally 2018, however during that past earthquakes are

recognized that structures are designed for lateral loads due

to the wind loads are much better than the structures are

designed for the gravity loads only, the modern seismic

codes based on the seismic design force based

methodology for elastic analysis. (2) Structures will be

expected to behave non-linear variety, producing huge

deformation and dissipating an enormous quantity of

energy, according to this the structures will be intended and

detailed imperatively to convince the essential capacity of

energy dissipation. But later is developed the displacement

based design which is importance of displacement control

for the structures particularly the damage of non-structural

elements. The perspectives of seismic codes are to control

the parameters such as base shear, drift ratio, ductile

demand and capacity demand to endorse the behavior of

structure. (3) The design base shear for structures is very

crucial to control the performance of structures given by a

ductility class. This study is covering the comparative of

major seismic building codes by studying the independent

and the multiple aspects that affects the building codes for

the design base shear.

SOIL CLASSIFICATION

The effects of soil in to the structures plays vital important

for damage structures in to contrary ways, Structures

behave differently when subject to earthquake in different

types of soil conditions for example dense soil and soft

soil. [4]. The response of structure for flexible soil and hard

soil is not same, so for that mostly seismic codes defined

soil classes or ground types based on the average shear

wave velocity at top of 30 m(Vs 30) and SPT. The seismic

codes such as Eurocode defines five different ground types

vary A to E and two soil factors which is depends on the

damping factor, the Indian seismic code defines three

different soil types, Type I, Type II and Type III, which is

represented by hard rock soil, medium and soft soil

respectively and Indian code not considered or based on the

soil average wave velocity but considered the SPT. The

Turkish soil are classify five different soil vary A to E.

Table 1 Comparison of Site Classes of EC8, ASCE7-16 and TSC-2018 Soil Classification

Seismic Code Design

EC8 ASCE7-

16

TSC-2018 EC8 ASCE7-16 TSC-2018

A A ZA Rock or other rock-Vs>800m/s Hard Rock Vs > 1524 m/s

Rugged, hard rocks Vs > 1500 m/s

B B ZB dense sand, gravel, 360m/s < Vs

< 800m/s

Rock 762 M/S < Vs > 1524

m/s

Slightly weathered, medium solid

rocks 760m/s < Vs >1500

C C ZC Deep deposits of dense or

medium dense sand, gravel or

stiff clay 180m/s < Vs < 360m/s

Very Dense Soil 366 m/s <

Vs > 762 m/s

Very tight layers of sand, gravel and

hard clay, or weathered, cracked weak

rocks 360 m/s < Vs >760m/s


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D D ZD Deposits of loose-to-medium

cohesion less soil Vs < 180m/

Stiff Soil 183 m/s< Vs >

366 m/s

Medium tight - layers of tight sand, gravel or very solid clay 180 m/s < Vs

>360m/s

E E ZE A surface of alluvium layer with

water table a layer of Type C or D on Rock

Soft Soil Vs > 366 m/s

Loose sand, gravel or soft Vs <

180m/s

S1 F ZF A layer of at least 10 m thick

soft clays/silt

requiring site-specific

research and evaluation

Floors requiring site-specific research

and evaluation

S2 Sensitive clays, or any other soil profile

not included in types A – E or

S1

SEISMIC HAZARD SPECIFICATIONS

Ground motion intensity and return period are two

fundamental concerns related to the hazard specifications,

seismic codes mostly use the seismic hazard as the single

parameter characterized by the peak ground acceleration

(PGA). As mentioned early that building codes considered

and defined different criteria for the hazard levels,

according to these seismic codes have been used in the

study was found that Eurocode 8 consider a reference peak

ground acceleration and IS1893 describes a zone factor

defined by “Effective Peak Ground Acceleration (EPGA)”

and obtained by the 0.4 times the 5% damped for average

spectral acceleration among the period 0.1 to 0.3 sec. The

Turkish new version 2018 and ASCE7-16 does not

consider seismic zone factor but uses for design ground

motion multiple spectral ordinates such as short and long

periods respectively, despite slightly difference the

construction design spectra. In addition to seismic codes

use for seismic hazard levels for probability of return

period and the seismic codes, but commonly EC8 describes

the seismic hazard at 10% probability exceedance in 50

years for return period 475 years as the seismic actions

reference.

Four different ground motion levels are defined by the new

Turkish seismic code, DD-1: 2% probability of exceeding

in 50 years, and recurrence is 2475, DD-2: 10%,

probability of exceeding in 50 years, and recurrence is 475,

DD-3: 50% probability of exceeding in 50 years, and

recurrence is 72 and finally DD-4: 50% probability of

exceeding in 50 years, and recurrence is 43.[5] IS 1893

does not consider for return period but use for the effective

peak ground acceleration design 0.5 times the effective

peak ground acceleration and ASCE7-16 describes the

return period 2475 years, the probability of 2% seismic

inputs exceeded in 50 years, corresponding the MCE.

DESIGN RESPONSE SPECTRA

Generally most of seismic design codes adopted 5%

damped for elastic response spectra, as the design spectrum

reference. The different soil classes that building codes

adopted changes the spectral shapes and it scaled by PGA

or spectral ordinate, return period and site conditions are

modified to get design spectra. The influence of soil

conditions it is important to consider the design spectrum,

each of soil classes were provided the soil amplification

factors. The building codes often use the design based-

force.

Figure 1 Typical Elastic Design Spectra [6]

The points TB and TC describe the acceleration control

region, where the TC and TD show the constant velocity

control region and the TD is where the displacement control

regions begin. The elastic design spectra in EC8 it

recommended to adopt two horizontal spectra Type 1

which commonly used for the higher seismicity regions

and the Type 2 which is adopt if the earthquake is less than

the magnitude 5.5 or less seismicity regions as defined the

probabilistic hazard assessments. As well as EC8 described

soil factor which is depend on the damping and the ground

types. The Indian building code IS1893, the design spectra

only provides 4 sec period and not consider the constant

displacement region. The Turkish new version 2018 and

ASCE7-16 does not consider seismic zone factor but is

based on seismic hazard map, not same as the old codes

which are based on seismic zonation map. This code is not

expressed the seismic hazard in terms of PGA, but

expressed in terms of spectral acceleration, the short period


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and long period T=0.2 s and 1s are defined by the site-

specific acceleration maps are developed for stiff soil sites.

The Turkish seismic code is also considered for the spectral

ordinates such as short and long periods. The Eurocode is

considered for two different spectra, but, for this case Type

1 is considered for the design and applied for strong ground

motion which produced a magnitude greater than 5.5, the

soil classes are considered the design is rock soil, soft soil,

and medium soil. The modal response spectrum in modes

should not be less than 90% the mass of the structure (EC8-

2004) while American code considers 85% the modal

analysis in base shear force [7].

REDUCTION FACTOR IN SEISMIC CODES

The seismic design codes specify the inelastic dissipation

energy effects to design to decrease the design force [8].

Despite Seismic codes are use different for the design, but

commonly seismic codes use force based methodology,

however, the classification according to the structural type

is different such as detailing. Detailing significantly effects

the structural strength, the elastic response spectrum shape

as well are different however seismic codes considers

reduction factor which structures hold the capacity to resist

earthquake beyond the elastic limit, structures will be

expected to behave non-linear variety, producing huge

deformation and dissipating an enormous quantity of

energy, according to this the structures will be intended and

detailed imperatively to convince the essential capacity of

energy dissipation. The supply of ductility in structural

system tolerates the reduction of elastic response spectrum,

ductility reduction factor generally rely upon the period of

structure. Seismic codes describes reduction factors

changing in to elastic spectra in design spectra in a purpose

of structural systems, mostly the reduction factors defines

the purpose of ductility classes. In addition to seismic

codes use for different ductility classes ASCE7 defines

three ductility classes, Ordinary Moment Resistance

Frame, Intermediate Moment Resistance Frame and

Special Moment Resistance Frame and IS 1893 only

considered two ductility class Ordinary Moment Resistance

Frame and Special Moment Resistance Frame and each one

is corresponding to different reduction factor.

NUMERICAL EXAMPLE

The layout of the building basically bisymmetric in plan,

which assumed by regular form, the number of bays is four

that have a same width of 5 m in both directions. The

storey height is used for 3 m which is normally the height

of residential buildings and the bottom of the structure was

assumed for fixed. 12 story building for moment frame is

used for the design and three different soil conditions is

considered the design to understand the impact of soil

condition for design spectra, while four contrary seismic

codes is considered to perform the structure. The structural

concrete element of structure also is assumed as correctly

to keep the failure structure, the compressive strength of

concrete is considered grade C30 for design spectrum to

design a new structure. Hence the building is reinforced

concrete the constant properties such as modulus of

elasticity will be assumed poisons ration is 0.2. The density

of concrete used by 24 KN/m3 the damping ratio is taken

by 5%, the design for gravity loads includes the dead loads

and self-weight, the live load is considered 2.5kN/m2, for

another side the overall mass of the building including the

self-weight and floor cover plus 25% of live load will be

considered in the seismic design. The medium soil is

considered for the design and the ductility classes are

considered as the each seismic code defines. The spectral

acceleration for long period and short period for

considerations Turkish and American code were used

SS=0.927 and S1=0.259, SS=1.573 and S1=0.701,

respectively, [9] [10]. Where Eurocode was use the shape

of spectrum Type 1 and Ag = 0.25g and the Indian code is

consider the design zone IV [11] [12]. Table 2 describes

the required section elements for reinforced concrete

elements such as beam, column and slab.

Table 2 the section of RC elements

Element

Dimension(mm)

Column 500 X 500

Beam 350x 500

Slab 150


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Figure 2 Floor Plan

Figure: 3 3D Model

ANALYSIS AND RESULT

The analysis of the structure has been carried out by

SAP2000 v20.2 using four different seismic codes, the

results obtained the design response spectrum and

equivalent lateral force for the standard seismic codes has

been compared them, to make the possible comparison

such as base shear and displacement elastic spectra have

been performing the analysis and the reduction factors and

behavior factor are consider for the inelastic design spectra.

The fundamental period is obtained for the structure is

1.572 for longitudinal direction of the building and the

model analysis obtained the total mass of the building in

98% in horizontal direction and transversal direction.

STORY-DRIFT

The structures deform when subjected to the seismic

actions and that deform causes structure to move its actual

position to another potion except only the bottom of the

structure that is fixed. However, the story drift ratio of the

structure can be found to the percentage of displacement

between the two floors divided by the height of the

structure. The most codes give the drift ratio a limit, the

story drift indicates the damage of the building in both

structural and non-structural damages. According to the

ASCE7, the limit of story drift should not be less than for

the moment frames building 0.025 times the height of the

structure for the category III and 0.002 for the design

category I and II. If the drift ratio should be greater than the

allowable drift ratio should not be acceptable. The lower

floors are greater drift when compared to the top floors.

The IS 1893 limits the interstorey drift 0.4% for design

load. And it is depends on the ductility class.


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Figure: 4 Story Drift for Medium Soil

BASE SHEAR

The Base shear is defined by the approximation of the

maximum contemplated lateral force which happens

according to the ground motion at bottom of the building.

however, the base shear rely upon some significance

factors such as the ground motion, natural period, and the

main factor which is reduced the base shear is reduction

factor. However, the result of base shear obtained from the

spectral analysis and the equivalent lateral force method

describes that spectral analysis is more conservative than

the equivalent lateral force method. However, as the figure

5 describes that base shear obtained from the TSC code is

more than the other codes and this significance difference

is due to the reduction and behavior factors are considered

for the design and as well as the difference peak ground

acceleration is considered when performing the design for

this contrary seismic design codes.

Figure: 5 Base Shear- X-Directio.

CONCLUSION

The main objective of this study is to compare various seismic design codes, to evaluate and assess the performance of seismic

structures. These contemporary seismic codes are fundamental for earthquake resistance design, the seismic codes provide level

ductility due to the energy dissipation range, however, seismic codes, are considered reduction factors and behavior factor to

reduce even the design force.

Seismic codes use for seismic hazard levels for probability of return period and the EC8 describes the seismic hazard at 10%

probability exceedance in 50 years for return period 475 years as the seismic actions reference. Four different ground motion

levels are defined by the new Turkish seismic code, DD-1: 2% probability of exceeding in 50 years, and recurrence is 2475,

DD-2: 10%, probability of exceeding in 50 years, and recurrence is 475, DD-3: 50% probability of exceeding in 50 years, and

recurrence is 72 and finally DD-4: 50% probability of exceeding in 50 years, and recurrence is 43. IS 1893 does not consider for

return period but use for the effective peak ground acceleration design 0.5 times the effective peak ground acceleration and

0

1

2

3

4

5

6

7

0 0.5 1 1.5 2 2.5 3 3.5

Sto

ry

Inter storey-drift ratio %

Story drift-medium soil

EC8-2004

IS 1893

TSC-2018

ASCE7-16

0 500 1000 1500 2000 2500 3000 3500

IS

ASC

TSC

EC8

Base Shear X Direction


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ASCE7-16 describes the return period 2475 years, the probability of 2% seismic inputs exceeded in 50 years, corresponding the

MCE

The base shear obtained the spectral analysis for Indian seismic code is underestimated and non-conservative when compared to

the other seismic codes because of the lack of soil amplification for the short period range, it only considered the longer period

range.

The main difference among these seismic codes is the design spectra, for the designing ground motion parameters ASCE7, and

TSC-2018 are used to spectral ordinates rather than seismic zone factor, the Indian seismic code is considered for the design

spectra 4 sec only, also ignores the soil amplification for the short period range.

REFERENCES [1] Erdick M (2004) Report on 1999 Kocaeli and Düzce (turkey) earthquakes

[2] Vijay Namdev, Khose, Yogendra Singh, Dominik Lang (2010) Limitations of Indian Seismic Design Codes for RC buildings [3] Vijay Namdev, Khose, Yogendra Singh, Dominik Lang (2012) “A Comparative Study of Design Base Shear for RC Buildings in Selected Seismic

Design Codes

[4] S. H. C. Santos, C. Giarlelis, M. Traykova, C. Bucur, L. Zanaica, S. S. Lima (2017) “Comparative Study of a Set of Codes for the Seismic Design of Buildings” 39th IABSE Symposium – Engineering the Future September 21‐23 2017, Vancouver, Canada.

[5] Halûk Sucuoğlu (2018) “New Improvements in the 2018 Turkish Seismic Code” International Workshop on Advanced Materials and Innovative

Systems in Structural Engineering: Seismic Practices [6] Doğangün, Adem, Livaoğlu, R. (2006) “A comparative study of the design spectra defined by Eurocode 8, UBC, IBC and Turkish Earthquake Code on

R/C sample buildings” Journal of Seismology, 3, 335–351

[7] Shehata E Abdel Raheem (2013) “Evaluation of Egyptian code provisions for seismic design of moment-resisting-frame multi-story buildings” International Journal of Advanced Structural Engineering 2013, 5:20

[8] Luis Sanchez-Ricart (2010) “Reduction factors in seismic codes: On the components to be taken into account for design purposes” [9] Turkish Earthquake Code (2018), “Specification for Structures to be built in Disaster Areas Ministry of Public Works and Settlement, Government of

Republic of Turkey”

[10] ASCE/SEI 7-16. “Minimum Design Loads and Associated Criteria for Buildings and Other Structures” [11] EN 1998-1: 2004 “Eurocode 8, Design of Structures for Earthquake Resistance– Part 1: General Rules, Seismic Actions and Rules for Buildings.

[12] IS1893-2016 part 1, “Criteria for earthquake resistance design for structures”

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