Comparison of percentage steel and concrete

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 02 Issue: 07 | Jul-2013, Available @ http://www.ijret.org 124
COMPARISON OF PERCENTAGE STEEL AND CONCRETE
QUANTITIES OF A R.C BUILDING IN DIFFERENT SEISMIC ZONES
Kiran Kumar1
, G. Papa Rao2
1
M. Tech Scholar, 2
Associate Professor, Department of Civil Engineering, GVP College of Engineering (A)
Visakhapatnam – 530 048, India, kirankumaradapa@gmail.com, gprao_74@yahoo.co.in
Abstract
This paper addresses the performance and variation of percentage steel and concrete quantities of R.C.C framed structure in different
seismic zones. One of the most frightening and destructive phenomena of a nature is a severe earthquake and it terrible after effect. It
is highly impossible to prevent an earth quake from occurring, but the damage to the buildings can be controlled through proper
design and detailing. Hence it is mandatory to do the seismic analysis and design to structures against collapse. Designing a structure
in such a way that reducing damage during an earthquake makes the structure quite uneconomical, as the earth quake might or might
not occur in its life time and is a rare phenomenon. The present IS code 1893:2002 doesn’t provide information about the variation of
concrete and percentage of steel from zone to zone. This study mainly focus on the comparison of percentage steel and concrete
quantities when the building is designed for gravity loads as per IS 456:2000 and when the building is designed for earthquake forces
in different seismic zones as per IS 1893:2002.
Keywords: Earthquakes, Reinforcement, Ductility, Damageability, STAAD-Pro.
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1. INTRODUCTION:
When planning a building against natural hazards like
earthquakes, we can design it to behave in one of the
following three limit states depending on the importance of
the structure:
• Serviceability limit state: In this case, the
structure will undergo little or no structural damage.
Important buildings such as hospitals, places of
assembly, atomic power plants, which are structures
affecting a community, should be designed for elastic
behaviour under expected earthquake forces. These
structures should be serviceable even after the
earthquake has taken place.
• Damage controlled (Damageability) limit state
(Damage threshold level): In this case, if an earthquake
occurs there can be some damage to the structure but it
can be repaired after the event and the structure can
again put to use. Most of the permanent buildings
should come under this category. For this purpose, the
structure should be designed for limited ductile
response only.
• Survival(Collapse threshold level) Limit state: In this
case, the structure may be allowed to be damaged in
the event of an earthquake, but the supports should
stand and be able to carry the permanent loads fully so
that in all cases there should be no caving in of the
structure and no loss of life.
Earthquakes produce large magnitude forces of short duration
that must be resisted by a structure without causing collapse
and preferably without significant damage to the structural
element. The lateral forces due to earthquakes have a major
impact on structural integrity. Lessons from past earthquakes
and research have provided technical solution that will
minimize loss of life and property damage associated with
earthquake. Special detailing is required, and for materials
without inherent ductility, such has concrete and masonry, a
critical part of the solution is to incorporate reinforcement in
the design and construction to assure a ductile responds to
lateral forces. The ductility of the building can be increased
by increasing the reinforcement in the structure. In the case of
Earthquake design, ductility is an essential attribute of a
structure that must respond to strong ground motions
(Andreas, 2001). So, the ductility is related to the control of
whether the structure is able to dissipate the given amount of
seismic energy considered in structural analysis (Pankaj
Agarwal, 2006). Ductility serves as the shock absorber in
building, for it reduces the transmitted force to one that is
sustainable. But the reinforcement plays an important role in
the economy of the structure. The present IS code 1893: 2002
provides information regarding the excess amount of
reinforcement to be used in the earthquake design but it does
not provide the information about the percentage of the steel
that should be increased in the earthquake resistant design
when compared with the normal design as per IS:456-2000.
This study mainly focus on the comparison of percentage
steel and concrete quantities when the building is designed for
gravity loads as per IS: 456-2000 and when the building is

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designed for earthquake forces in different earthquake zones
as per IS 1893:2002.This gives the approximate percentage in
the economy compared with normal design (H J Shah, 2008).
2. METHODOLOGY
Seismic analysis of the structures is carried out on the basis of
lateral force assumed to act along with the gravity loads. The
base shear which is the total horizontal force on the structure
is calculated on the basis of structure mass and fundamental
period of vibration and corresponding mode of shape. The
base shear is distributed along the height of the structure in
terms of lateral forces according to codal provisions
(Kazuhiro, 1987). In this study, a five (G+4) storied RC
building has been analyzed using the equivalent static method
in STAAD-Pro. The plan and elevation of the building taken
for analysis is shown in Fig.1 and Fig.2. The nomenclature of
columns is shown in Fig.3. Three Dimensional view of the
whole structure is shown in Fig.4. Fig.5 is showing the
structure subjecting to the vertical loading and Fig.6 & Fig.7
are showing the structure subjected to loading of earthquake
in “+X” and “+Z” directions.
In the earthquake analysis along with earthquake loads,
vertical loads are also applied. For the earthquake analysis, IS
1893-2002 code was used .The total design seismic base
shear (Vb) along any principal direction shall be determined
by multiplying the design horizontal acceleration in the
considered direction of vibration (Ah)and the seismic weight
of the building.
The Design base shear
(V A ∗ W
Ah = design horizontal acceleration in the considered
direction of vibration
= (Z/2)*(I/R)*(Sa /g)
W = total seismic value of the building
The design base shear (Vb) computed shall be distributed
along the height of the building as per the following
expression (BIS1893: 2000)
Qi =Vb*(Wi*hi2/ Wi*hi2)
Where,
Qi is the design lateral forces at floor i,
Wi is the seismic weights of the floor i, and
hi is the height of the floor i, measured from base
The lateral force on each storey is again distributed based on
the deflection and stiffness of the frame. The total lateral
load in proportion to the stiffness of each frame in all the four
zones (H M Salem, 2011) .The distributed lateral forces
shown in the Fig.6 and Fig.7.

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Fig. 4 3D view of the whole structure Fig. 5 Whole structure subjected to vertical loading

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Fig.6 Structure subjected to Earthquake loading in Fig. 7 Structure subjected to Earthquake loading in
+X direction +Z direction
2.1 Preliminary Data for the Problem Taken:
Table 1: Preliminary Data of the structure considered for seismic analysis
Type of the structure RCC Framed structure
Number of stories G+4
floor to floor height 3.6 m
Plinth height 0.6 m
Walls thickness 230 mm
Grade of concrete M 25
Grade of steel Fe 415
Earthquake load As per IS1893 (Part 1) : 2002
Size of the columns 0.4mx0.4m and 0.45mx0.45m
Size of the beams 0.23mx0.4m
Slab thickness 0.13m
SBC of soil taken 200kN/m²
Type of soil Hard rocky soil
Live load 3kN/m²
Floor finishes 1kN/m²
Seismic zones considered II,III,IV,V
Type of wall Brick masonry

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1.2 Loading Data:
1.2.1 Dead Load (DL)
1. Self weight of slab = 0.13x25 = 3.25kN/m2
2. Floor finishes = 1.00kN/m2
------------------------------
Total DL = 4.25kN/m2
--------------------------------
(Assume 130mm total depth of slab)
3. Weight of walls = 0.23x19x 3.6 = 15.73kN/m
1.2.2 Live Load (LL)
Live Load on each slab = 3.00kN/m2
1.2.3 Earth quake Load (EQL)
As per IS-1893 (Part 1): 2002
1.3 Load Combinations:
The following load combinations are used in the seismic
analysis, as mentioned in the code IS 1893(Part-1): 2002,
Clause no. 6.3.1.2.
1. 1.5(DL+LL)
2. 1.2(DL+LL+EQX)
3. 1.2(DL+LL- EQX)
4. 1.2(DL+LL+ EQZ)
5. 1.2(DL+LL- EQZ)
6. 1.5(DL+ EQX)
7. 1.5(DL- EQX)
8. 1.5(DL+ EQZ)
9. 1.5(DL-EQZ)
10. 0.9DL+ 1.5EQX
11. 0.9DL- 1.5EQX
12. 0.9DL+ 1.5EQZ
13. 0.9DL-1.5EQZ
Earthquake load was considered in +X,-X, +Z and –Z
directions. Thus a total of 13 load combinations are taken for
analysis. Since large amount of data is difficult to handle
manually (M.H. Arslan, 2007), all the load combinations are
analyzed using software STAAD Pro. All the load
combinations are mentioned above.
2. RESULTS:
The variation of support reactions at each location of the
columns and the percentage difference in different seismic
zones with respect to gravity loads is represented in the in
Table 2 and Fig.8. It is observed that in edge columns,
variations are 17.72, 28.35, 42.53, and 63.7% between gravity
load to seismic zones II, III, IV and V respectively. In
exterior columns, the variations are 11.59, 18.54, 27.81, and
41.71% between gravity load to seismic zones II, III, IV and
V respectively. The variation is very small in interior
columns.
Table 2 Comparison of support reactions in different seismic zones
Support Reaction in kN Percentage difference between
LOCATION
OF THE
COLUMNS
DUE TO
GRAVITY
LOAD
(GL)
IN
SEISMIC
ZONE-
II
IN
SEISMIC
ZONE-
III
IN
SEISMIC
ZONE-
IV
IN
SEISMIC
ZONE-
V
GL&
ZONE-
II
GL&
ZONE-
III
GL&
ZONE-
IV
GL&
ZONE-
V
EDGE
COLUMNS
543.40 640.20 698.04 775.13 890.78
17.72% 28.35% 42.53% 63.7%
EXTERIOR
COLUMNS
867.94 968.50 1028.84 1109.24 1129.97
11.59% 18.54% 27.81% 41.71%
INTERIOR
COLUMNS
1295.68 1309.92 1318.46 1329.84 1346.92
1.10% 1.76% 2.64% 3.95%

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Fig. 8 Variation of support reactions in different seismic zones
The variation of volume of concrete at each location of the
column footing and the increase in percentage difference in
different seismic zones with respect to gravity loads is
represented in the in Table 3 and Fig.9. It is observed that in
edge column footings, variations are 17.75, 17.75, 27.17 and
42.0% between gravity load to seismic zones II, III, IV and V
respectively. In exterior column footings, the variations are
21.51, 21.51, 45.15 and 57.77% between gravity load to
seismic zones II, III, IV and V respectively. Therefore, the
volume of concrete in footings is increasing in seismic zones
III, IV and V due to increase of support reactions due to
lateral forces. However the variation is very small in interior
column footings.
Table 3 Comparison of volume of concrete in footings in different seismic zones
Volume of concrete in footings (cu m) Percentage difference between
LOCATION
OF THE
COLUMN
FOOTING
DUE TO
GRAVITY
LOAD
(GL)
IN
SEISMIC
ZONE-
II
IN
SEISMIC
ZONE-
III
IN
SEISMIC
ZONE-
IV
IN
SEISMIC
ZONE-
V
GL&
ZONE-
II
GL&
ZONE-
III
GL&
ZONE-
IV
GL&
ZONE-
V
EDGE
COLUMN
FOOTING
2.186
2.574 2.574 2.78 3.1042 17.75% 17.75% 27.17% 42.00%
EXTERIOR
COLUMN
FOOTING
1.506
1.83 1.83 2.186 2.376 21.51% 21.51% 45.15% 57.77%
INTERIOR
COLUMN
FOOTING
3.291 3.291 3.291 3.40 3.40 0.00 0.00 3.51% 3.51%
0
200
400
600
800
1000
1200
1400
1600
GRAVITY ZONE II ZONE III ZONE IV ZONE V
SUPPORTREACTIONS(KN)
TYPE OF LOADING
EDGE COLUMNS
EXTERIOR COLUMNS
INTERIOR COLUMNS

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Fig .9 Variation of volume of concrete in footings in different seismic zones
The variation of weight of steel at each location of the column
footing and the percentage difference in different seismic
zones with respect to gravity loads is represented in the in
Table 4 and Fig.10. It is observed that in edge column
footings, variations are 0.0, 23.61, 47.92, and 98.96%
between gravity load to seismic zones II, III, IV and V
respectively. In exterior column footings, the variations are
38.17, 54.88, 70.79 and 91.04% between gravity loads to
seismic zones II, III, IV and V respectively. In the interior
columns footings, the variations are 22.07, 42.44, 56.03 and
67.91% between gravity loads to seismic zones II, III, IV and
V respectively.
Table 4 Comparison of weight of the steel in footings in different seismic zones
Weight of steel in footings(kg’s) Percentage difference between
LOCATION
OF THE
COLUMN
FOOTING
DUE TO
GRAVITY
LOAD
(GL)
IN
SEISMIC
ZONE-
II
IN
SEISMIC
ZONE-
III
IN
SEISMIC
ZONE-
IV
IN
SEISMIC
ZONE-
V
GL&
ZONE-
II
GL&
ZONE-
III
GL&
ZONE-
IV
GL&
ZONE-
V
EDGE
COLUMN
FOOTING
28.80 28.80 35.60 42.60 57.30 0.00 23.61% 47.92% 98.96%
EXTERIOR
COLUMN
FOOTING
46.90 64.8 72.64 80.10 89.60 38.17% 54.88% 70.79% 91.04%
INTERIOR
COLUMN
FOOTING
58.90 71.9 83.9 91.9 98.9 22.07% 42.44% 56.03% 67.91%
0
0.5
1
1.5
2
2.5
3
3.5
4
CONCRETEIN(CUM)
TYPE OF LOADING
EDGE FOOTINGS
EXTERIOR FOOTINGS
INTERIOR FOOTINGS

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Fig. 10 Variation of weight of steel in footings in different seismic zones
The variation of percentage of steel at each location of the
column in different seismic zones with respect to gravity
loads is represented in the in Table 5 and Fig.11. The
variation of percentage of steel in edge columns vary from
0.8% to 3%, exterior columns varying from 0.8% to 3.9% and
interior columns varying from 1.1% to 3.7% between gravity
loads to zone V. For the comparison purpose at each location,
the cross sectional dimension of column was kept same in all
the zones.
Table 5 Comparison of percentage of the steel in columns in different seismic zones
% of the steel reinforcement in columns
LOCATION
OF THE
COLUMN
DUE TO
GRAVITY
LOAD
IN SEISMIC
ZONE-
II
IN SEISMIC
ZONE-
III
IN
SEISMICZO
NE-
IV
IN SEISMIC
ZONE-
V
EDGE
COLUMN
0.8 0.9 1 1.5 3
EXTERIOR
COLUMN
0.8 0.9 1.5 2.3 3.9
INTERIOR
COLUMN
1.1 1.3 1.8 2.4 3.7
Note: For the comparison purpose at each location, the cross sectional dimension of column was kept same
in all the zones.
0.00
20.00
40.00
60.00
80.00
100.00
120.00
WEIGHTOFSTEELIN(KG'S)
TYPE OF LOADING
EDGE FOOTINGS
EXTERIOR FOOTINGS
INTERIOR FOOTINGS

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Fig. 11 Variation of percentage of steel in columns in different seismic zones
The variation of percentage of steel in beams in different
seismic zones with respect to gravity loads is represented in
the in Table 6 and Fig.12. The variation of percentage of steel
at supports, in external beams 0.54% to 1.23% and in internal
beams 0.78% to 1.4% varying from gravity loads to zone V.
At mid span locations of external and internal beams, the
percentage of reinforcement is same in all the zones.
Table 6 Comparison of percentage of the steel in beams in different seismic zones
LOCATION BEAMS
% of the steel reinforcement in beams
GRAVITY
LOAD
(G L)
IN
SEISMIC
ZONE-
II
IN
SEISMIC
ZONE-
III
IN
SEISMIC
ZONE-
IV
IN
SEISMIC
ZONE-
V
AT
SUPPORTS
EXTERNAL
BEAMS 0.54 0.64 0.75 0.93 1.23
INTERNAL
BEAMS 0.78 0.83 0.97 1.18 1.4
AT
MID SPAN
EXTERNAL
BEAMS 0.32 0.32 0.32 0.32 0.32
INTERNAL
BEAMS 0.42 0.42 0.42 0.42 0.42
Note: For the comparison purpose at each location, the cross sectional dimension of beams was kept
same in all the zones.
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
PERCENTAGEOFSTEEL
TYPE OF LOADING
EDGE COLUMNS
EXTERIOR COLUMNS
INTERIOR COUMNS

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Fig. 12 Percentage of steel in beams in different seismic zones
The variation of weight of steel at each location of the beams
and the percentage difference in different seismic zones with
respect to gravity loads is represented in the in Table 7 and
Fig.13. It is observed that in external beams, variations are
4.38, 13.8, 31.3, and 49.6% between gravity loads to seismic
zones II, III, IV and V respectively. In the internal beams, the
variations are 3.07, 15.3, 20.2 and 53.3% between gravity
loads to seismic zones II, III, IV and V respectively.
Table 7 Comparison of weight of the steel in beams in different seismic zones
Weight of the steel (kg’s)
% difference of weight of steel in
beams between
BEAMS
GRAVITY
LOAD
(G L)
ZONE
II
ZONE
III
ZONE
IV
ZONE
V
GL&
ZONE-
II
GL&
ZONE-
III
GL&
ZONE-
IV
GL&
ZONE-
V
EXTERNAL
BEAMS
137 143 156 180 205 4.38 13.8 31.3 49.6
INTERNAL
BEAMS
163 168 188 196 250 3.07 15.3 20.2 53.3
Note: For the comparison purpose at each location, the cross sectional dimension of beams was kept same in
all the zones.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
GRAVITY ZONEII ZONE III ZONE IV ZONE V
PERCENTAGEOFSTEEL
TYPE OF LOADING
AT SUPPORTS EXTERNAL
BEAMS
AT SUPPORTS INTERNAL
BEAMS
AT MID SPAN INTERNAL
BEAMS
AT MID SPAN EXTERNAL
BEAMS

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Fig. 13 Variation of weight of steel in beams in different seismic zones
CONCLUSIONS
The following conclusions can be made based on the analysis
and design of RC school building designed for gravity loads
and earthquake forces in all the zones.
1. The variation of support reactions in exterior columns
increasing from 11.59% to 41.71% and in edge
columns increasing from 17.72% to 63.7% in seismic
Zones II to V. However the variation of support
reactions are very small in interior columns.
2. The volume of concrete in exterior and edge column
footings is increasing in seismic zones III, IV and V
due to increase of support reactions with the effect of
lateral forces. However the variation is very small in
interior column footings.
3. The variation of percentage of steel at support
sections in external beams is 0.54% to 1.23% and in
internal beams is 0.78% to 1.4%.
4. In the external and internal beams, the percentage of
bottom middle reinforcement is almost the same for
both earthquake and non earthquake designs.
REFERENCES:
[1] Andreas J. Kappos, Alireza Manafpour (2001), “Seismic
Design of R/C Buildings with the Aid of Advanced
Analytical Techniques”, Engineering Structures,
Elsevier, 23, 319-332.
[2] 2. BIS: 1893 (PART 1)-2002 “Criteria For Earthquake
Design Of Structures: General provisions and
buildings”(Fifth revision), Bureau of Indian Standards ,
New Delhi
[3] 3. IS 456(2000), “Plain and Reinforced Concrete-
Code of Practice”, Bureau of Indian standards, New
Delhi.
[4] 4. Design Aids for Reinforced concrete to IS: 456-
1978(SP-16), Bureau of Indian standards, New Delhi.
[5] 5. H. M. Salem, A. K. El-Fouly, H.S. Tagel-Din (2011),
“Toward an Economic Design of Reinforced Concrete
Structures Against Progressive Collapse”,
Engineering Structures, Elsevier, 33,3341-3350.
[6] 6. H.J. Shah and Sudhir K. Jain (2008), “Final Report:
A -Earthquake Codes IITK-GSDMA Project on
Building Codes (Design Example of a Six Storey
Building)”, IITK-GSDMA-EQ26-V3.0
[7] 7. Kazuhiro Kitayama, Shunsuke Otani and Hiroyuki
Aoyama (1987), “Earthquake Resistant Design Criteria
for Reinforced Concrete Interior Beam-column Joints”,
Published in the Proceedings, Pacific Conference on
Earthquake Engineering, Wairakei, New Zealand,
August, 5-8, 1,315-326.
[8] 8. M.H. Arslan, H.H. Korkmaz (2007), “What is to be
Learned from Damage and Failure of Reinforced
Concrete Structures during Recent Earthquakes in
Turkey?”, Engineering Failure Analysis, Elsevier, 14,1–
22.
[9] 9. Pankaj Agrawal and Manish Shrikhande (2006),
“Earthquake Resistance Design Of Structures”, ISBN
978- 81-203-3892-1, PHI Learning Private
Limited.
0
50
100
150
200
250
300
WEIGHTOFSTEELIN(KG'S)
TYPE OF LOADING
EXTERNAL BEAMS
INTERNAL BEAMS

Comparison of percentage steel and concrete

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