COMPARISON OF SEISMIC CODES OF CHINA, INDIA, UK AND USA (STRUCTURAL IRREGULARITIES)

COMPARISON OF SEISMIC CODES OF CHINA, INDIA, UK AND USA
(STRUTURAL IRREGULARITIES)
Department of Civil Engineering
IIT(ISM) Dhanbad
(2017-19)
Supervise By:- Submitted By:-
Prof. Sekhar Chandra Dutta Shankar Kumar
(17MT001717)

INTRODUCTION
• Seismic code of China is the Code for Seismic Design of Buildings
GB 50011-2010.
• Seismic code of India is Criteria for Earthquake Resistant Design of
Structures Part 1 General Provisions and Buildings IS 1893 (Part-1) :
2016
• Seismic code of UK is Design of structures for earthquake resistance
Part 1 : General rules, seismic actions and rules for buildings
Eurocode 8 :2004
• Seismic code of USA is Minimum Design Loads for Buildings and
Other Structures ASCE -7 :2002

STRUCTURAL IRREGULARITIES
• Plan irregularities
1. Torsional Irregularity
2. Re-entrant Corners
3. Diaphragm Discontinuity
4. Out-of-Plane Offsets
5. Nonparallel Systems

• Vertical / Elevation irregularities
1. Stiffness Irregularity- Soft Storey
2. Mass irregularity
3. Vertical Geometric Irregularity
4. In-Plane Discontinuity in Vertical Elements resisting Lateral
Force
5. Strength Irregularity – Weak Storey
6. Floating or Stub Columns
7. Irregular Modes of Oscillations in Two Principal Plan Directions

Plan irregularities
1.Torsional Irregularity
• Torsional irregularity is defined to exist where the maximum story
drift computed including accidental torsion, at one end of the structure
transverse to an axis is more than K1 times the average of the story
drifts at the two ends of the structure.

Plan irregularities
2.Re-entrant Corners
• Plan configurations of a structure and its lateral force-resisting system
contain re-entrant corners, where both projections of the structure
beyond a re-entrant corner are greater than K2% of the plan dimension
of the structure in the given direction

Plan irregularities
3.Diaphragm Discontinuity
• Diaphragms with abrupt discontinuities or variations in stiffness,
including those having cut out or open areas greater than K3% of the
gross enclosed diaphragm area, or changes in effective diaphragm
stiffness of more than K3% from one-story to the next.

Plan irregularities
4. Out-of-Plane Offsets
• Discontinuities in a lateral force-resistance path, such as out-of-plane
offsets of the vertical elements.

Plan irregularities
5. Nonparallel Systems
• The vertical lateral force-resisting elements are not parallel to or
symmetric about the major orthogonal axes of the lateral force-
resisting system

Plan irregularities
1.Comparison of plan irregularities present in seismic codes
Seismic
codes
GB 50011-
2010
IS 1893
(Part-1) 2016
EUROCODE
-08 2004
ASCE 7-02
2002
Torsional
Irregularity
YES YES YES YES
Re-entrant
Corners
YES YES YES YES
Diaphragm
Discontinuity
YES YES YES YES
Out-of-Plane
Offsets
_ YES _ YES
Nonparallel
Systems
_ YES _ YES

Plan irregularities
2.Comparison of constant values define for plan irregularities
Seismic codes GB 50011-
2010
IS 1893 (Part-
1) 2016
EUROCODE
-08 2004
ASCE 7-02
2002
K1
1.2 1.5 _ 1.2-1.4
K2 %
30 15 _ 15
K3 %
A
30
50
_ 50
B 10

Vertical / Elevation irregularities
1.Stiffness Irregularity- Soft Storey
• A soft story is one in which the lateral stiffness is less than K4% of
that in the story above or less than K5% of the average stiffness of the
three stories above.

2. Mass irregularity
• Mass irregularity shall be considered to exist where the effective mass
of any story is more than K6% of the effective mass of an adjacent
story. A roof that is lighter than the floor below need not be considered

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 K7% of that in an adjacent story

4. In-Plane Discontinuity in Vertical Elements resisting Lateral Force
• In-plane discontinuity in vertical lateral force-resisting elements shall
be considered to exist where an in-plane offset of the lateral force-
resisting elements is greater than the length of those elements or there
exists a reduction in stiffness of the resisting element in the story
below.

5.Strength Irregularity – Weak Storey
• A weak story is one in which the story lateral strength is less than
K8% of that in the story above. The story strength is the total strength
of all seismic-resisting elements sharing the story shear for the
direction under consideration

6.Floating or Stub Columns
• Such columns cause concentrated damage in the structure and thus
highly undesirable. This type of columns should not be used in the
primary lateral load resisting system.

7.Irregular Modes of Oscillations in Two Principal Plan Directions
• Stiffnesses of beams, columns, braces and structural walls determine
lateral stiffness of a building in each principal plan directions. A
building is said to have lateral storey irregularity in a principal
direction if
a) First three modes contribute less than 65% mass participation factor in
each principal plan direction and
b) Fundamental lateral natural periods of building in two principal plan
directions are closer to each other by 10% of the larger value

1.Comparison of vertical irregularities present in seismic codes
Seismic codes GB 50011-
2010
IS 1893
(Part-1) 2016
EUROCODE
-08 2004
ASCE 7-02
2000
Stiffness Irregularity- Soft Storey YES YES YES YES
Mass irregularity _ YES YES YES
Vertical Geometric Irregularity _ YES YES YES
In-Plane Discontinuity in Vertical
Elements resisting Lateral Force
YES YES YES YES
Strength Irregularity – Weak Storey YES YES YES YES
Floating or Stub Columns _ YES _ _
Irregular Modes of Oscillations in
Two Principal Plan Directions
_ YES _ _

2.Comparison of constant values define for vertical irregularities
Seismic
codes
GB 50011-
2010
IS 1893 (Part-
1) 2016
EUROCODE
-08 2004
ASCE 7-02
2000
K4 % 70 100 100 60-70
K5 % 80 100 100 70-80
K6 % _ 150 150 150
K7 % _ 125 125-150 130
K8 % 80 100 100 80

Conclusions
• Difference between irregularity is in terms of constant value
multiplication of different seismic codes.
• Some irregularity is not defined in China, UK seismic codes.

Further Studies
• To compare the seismic response of various type of irregular
plan structure with equal plan area.

REFERENCES
• American Society of Civil Engineers ASCE 7-02 Second Edition Minimum
Design Loads for Buildings and Other Structures
• National Standard of the people’s republic of China GB 50011-2010 (GB
50011-2016) Code for Seismic Design of Buildings
• Eurocode 8: Design of structures for earthquake resistance Part 1 : General
rules, seismic actions and rules for buildings
• IS 1893 (Part-1) : 2016 Criteria for Earthquake Resistant Design of Structures
Part 1 General Provisions and Buildings (Sixth Revision)

COMPARISON OF SEISMIC CODES OF CHINA, INDIA, UK AND USA (STRUCTURAL IRREGULARITIES)

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COMPARISON OF SEISMIC CODES OF CHINA, INDIA, UK AND USA (STRUCTURAL IRREGULARITIES)