INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD – 382 481, 08-10 DECEMBER, 2011
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Comparative Study of R.C.C, Steel and
Composite (G+30 Storey) Building
D. R. Panchal and P. M. Marathe
Abstract - Steel-concrete composite systems for buildings are
formed by connecting the steel beam to the concrete slab or
profiled deck slab with the help of mechanical shear connectors
so that they act as a single unit. In the present work, steelconcrete composite, steel and R.C.C. options are considered for
comparative study of G+30 storey commercial building which is
situated in earthquake zone IV. Equivalent Static Method of
Analysis is used. For modeling of Composite, Steel and R.C.C.
structures, ETABS software is used and the results are
compared; and it is found that composite structure is found to
be more economical.
Index Term--Composite beam, Composite column, Shear
connector, ETAB software.
I.
A need to study the composite design of the multi-story
buildings keeping in view of the rapid development in this
field. In India, it is comparatively new and no updated design
codes are available for the same. [1]
INTRODUCTION & OBJECTIVE
S
teel-concrete composite systems have become quite
popular in recent times because of their advantages
against conventional construction. Composite construction
combines the better properties of the both i.e. concrete and
steel and results in speedy construction. In the present work
included Comparative study of R.C.C., STEEL and
COMPOSITE (G+30 STORY) building. In the comparative
study includes deflections of the members, size and material
consumption of members in composite with respect to R.C.C.
and Steel sections, seismic forces and behavior of the
building under seismic condition in composite with respect to
R.C.C. and Steel, foundation requirements and type of
foundation can be selected for Composite structure with
respect to R.C.C. and Steel and total cost of the building.
II. COMPOSITE CONSTRUCTION
In the past, for the design of a building, the choice was
normally between a concrete structure and a masonry
structure. But the failure of many multi-storied and low-rise
R.C.C. and masonry buildings due to earthquake has forced
the structural engineers to look for the alternative method of
construction. Use of composite or hybrid material is of
particular interest, due to its significant potential in
improving the overall performance through rather modest
changes in manufacturing and constructional technologies. In
India, many consulting engineers are reluctant to accept the
use of composite steel-concrete structure because of its
unfamiliarity and complexity in its analysis and design. But
literature says that if properly configured, then composite
steel-concrete system can provide extremely economical
structural systems with high durability, rapid erection and
superior seismic performance characteristics.
Fig.1. Typical composite beam-slab details.
Formally the multi-story buildings in India were
constructed with R.C.C framed structure or Steel framed
structure but recently the trend of going towards composite
structure has started and growing.
In composite construction the two different materials are
tied together by the use of shear studs at their interface
having lesser depth which saves the material cost
considerably. Thermal expansion (coefficient of thermal
expansion) of both, concrete and steel being nearly the same.
Therefore, there is no induction of different thermal stresses
in the section under variation of temperature.
1) Composite beam definition
A steel concrete composite beam consists of a steel beam,
over which a reinforced concrete slab is cast with shear
connectors.
The composite action reduces the beam depth. Rolled steel
sections themselves are found adequate frequently for
buildings and built up girders are generally unnecessary.
The composite beam can also be constructed with profiled
sheeting with concrete topping or with cast in place or precast
reinforced concrete slab.
2) Composite Column definition
A steel – concrete composite column is conventionally a
compression member in which the steel element is a
structural steel section. There are three types of composite
columns used in practice which are Concrete Encased,
Concrete filled, Battered Section.
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III. EARTHQUAKE ANALYSIS AND DESIGN PROCEDURE
The traditional codes gives us procedure attempts to satisfy
implicitly all three objectives. [3]
A. Negligible damage in once in a lifetime earthquake
shaking demands having a return period of about 50
years. This can be achieved by elastic structural
response and limiting the storey drifts to minimize
damage to non-structural components such as cladding
and internal walls.
B. Collapse prevention under the largest earthquake
demanded that may occur at the site. Such earthquake
occurs with a return period of approximately 2500
years. The inelastic deformation demands are smaller
than their deformation capacities taking approximate
account of gravity loads, second order effects and
deterioration of stiffness and strength due to cyclic
loading. Also the story deformations are sufficiently
small so as to prevent catastrophic damage to non
structural elements.
Deformations are the key parameter for performance
based earthquake design rather than force or strength.
Deformation can be classified in to three categories.
a. Overall building movements.
b. Story drifts & other internal deformations.
c. Inelastic deformations for structural components
and elements.
These movements occur due to rigid body displacement
and shear deformations.
Fig.2. Plan view of building.
TABLE 1
PROJECT DETAILS
IV. CRITICAL ISSUES

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High base overturning moment and foundation design.
High shear capacity requirement at base.
High gravity stresses reducing the usable floor area
and more sectional area of components.
Development of ductility at base elements under high
compressive gravity stresses.
Controlling lateral acceleration and story drifts.
Controlling damage so as to permit repairs.
Ensuring ductile energy dissipation mechanism and
preventing brittle failures.
2) Beam grid and column positions.
For all the above issues regarding the performance of the
building under seismic forces the three types of model has
been studied and comparison of all the parameters are made
which can give us better idea about the behavior of the
building with different materials.
V.
PROJECT DETAILS
1) Architectural details
To study the behavior of high rise building under high
seismic forces as here taken Zone IV as per IS 1893 : 2002
where building is situated, a typical office building plan is
selected with area covering 24 m x 42 m.
Fig.3. Typical beam grid for all floors.
INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD – 382 481, 08-10 DECEMBER, 2011
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3) Modeling with ETABS
3-D model is being prepared for the frame static analysis
of the building in ETABS version 9.7.1.[2]
The basic parameters considered for the design
Slab depth : 125 mm thick
Live load in office area : 4 kN/sq m
Live load in passage area : 4 kN/sq m
Live load in urinals : 2 kN/sq m
Floor finish load : 1.5 kN/ sq m
Wall thickness : 150 mm thick wall
Stair case loading : 4 kN/sq m
Lift shaft : 300 mm thick shear wall
Earthquake parameters considered
Zone : IV
Soil type : Hard soil
Importance factor : 1
Time period : Program Calculated
Seismic zone factor : 0.24 for zone IV
Earthquake load in X and Z direction.
Rigid frame diaphragm
Codes used for analysis
R.C.C. design: IS 456: 2000 [5]
Steel design: IS 800: 1984 [8]
Composite design: AISC LRFD 99 [9]
R.C.C., Steel and Composite model has been made and
different column sizes were selected along with different
beam sizes.
Fig. 6. Open GL view from Etabs.
VI. SIZING OF THE MEMBERS
Fig. 4. Screenshot of Etabs.
The sizes of the members in different model have been
taken as per strength as well as displacement requirements.
For all the models the sizes are curtailed at every 10
story to achieve economy and reduce dead weight of the
structure.
Here is the summary of the final sizes achieved and
designed.
TABLE 1
COLUMN SECTIONS
Fig. 5. Typical Beam grid in Etabs.
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TABLE 2
BEAM SECTIONS
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Column Axial force
TABLE 5
COLUMN AXIAL FORCES IN KN
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Column bending Moments in X direction
TABLE 6
BENDING MOMENT IN X DIRECTION IN KN-M
VII. COMPARISON OF DIFFERENT MODELS.
1.
2.
Comparison Factors
The model has been compared with different
parameters.
 Max Story Displacement in X and Y direction
 Total Weight of Structure
Max Story Displacement in X and Y direction
TABLE 3
DISPLACEMENTS IN X AND Y DIRECTION IN M
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Column bending Moments in Y direction
TABLE 7
BENDING MOMENT IN Y DIRECTION IN KN-M
3.
Total weight of Structure
TABLE 4
TOTAL DEAD WEIGHT OF STRUCTURE IN KN
INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD – 382 481, 08-10 DECEMBER, 2011
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11 Main beam bending moments
Secondary beam shear forces
TABLE 8
SHEAR FORCES IN SECONDARY BEAM IN KN
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TABLE 11
BENDING MOMENTS IN MAIN BEAM IN KN M
Secondary beam bending moments
12 Quantities for different models.
TABLE 9
BENDING MOMENTS IN SECONDARY BEAM IN KN M
TABLE 12
QUANTITIES
VIII. CONCLUSION
1.
10 Main beam shear forces
2.
TABLE 10
SHEAR FORCES IN MAIN BEAM IN KN
3.
4.
5.
6.
As the results show the Steel option is better than R.C.C.
But the Composite option for high rise building is best
suited among all three options.
The reduction in the dead weight of the Steel framed
structure is 32 % with respect to R.C.C. frame Structure
and Composite framed structure is 30 % with respect to
R.C.C. framed structure.
As the sizes of the steel members from steel option to the
composite option reduces about 25 % in main beams and
about 60 % in secondary beams.
Shear forces in secondary beams are increased by
average 83.3% in steel structure and reduced by average
10 % in composite structure as compared to R.C.C.
framed structure while in main beams shear forces are
increased by average 131% in steel structure and reduced
by average 100 % in composite structure as compared to
R.C.C. framed structure.
Bending moments in secondary beams are increased by
average 83.3% in steel structure and reduced by average
48 % in composite structure as compared to R.C.C.
framed structure while in main beams bending moments
are increased 131% in steel structure and increased by
average 117 % in composite structure as compared to
R.C.C. framed structure.
Axial forces in column have been reduced by average
46% in steel structure and reduced by average 7% in
Composite framed structure as compared to R.C.C.
framed structure.
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7.
Bending forces in X direction in column have been
reduced by average 34% in steel structure and increased
by average 5% in Composite framed structure as
compared to R.C.C. framed structure while bending
moments in Y direction in column have been reduced by
average 25% in steel structure and reduced by average
26% in composite framed structure as compared to
R.C.C. framed structure.
8. In all the options the values of story displacements are
within the permissible limits as per code limits.
9. Steel and composite structure gives more ductility to the
structure as compared to the R.C.C. which is best suited
under the effect of lateral forces.
10. Total saving in the composite option as compared to the
R.C.C. results in 10 % so as with Steel it will be 6-7%.
IX. REFERENCES.
[1]
Institute for steel development & Growth, "B+G+40 Storied
Residential Building With Steel-Concrete Composite Option” India
Dec 2007.
[2] M. Nageh, “How To Model and Design High Rise Building Using
ETABs Program” Cairo 2007.
[3] M. Willford, A. Whittaker and R. Klemencic, “Recommendations for
Seismic Design of High-Rise Buildings” Council of Tall building and
Urban habitat Feb 2008.
[4] J. Zils and J. Viis, “An Introduction To High Rise Design” Structure
Magazine Nov 2003.
[5] IS: 456, Code of practice for plain and reinforced concrete code of
practice, Bureau of Indian Standards, New Delhi, 2000.
[6] IS: 1893, Criteria for earthquake resistant design of structures - general
provisions for buildings, Part 1, Bureau of Indian Standards, New
Delhi, 2002.
[7] IS: 875, “code of practice for design load (other than earthquake) for
buildings and structures” Bureau of Indian Standards, New Delhi,
2002.
[8] IS: 800, Code of practice for general construction in steel, Bureau of
Indian Standards, New Delhi, 2007.
[9] AISC 360-05, Specification of structural steel building, An American
national stanadard, American Institute Of Steel Construction, Inc., 2005
[10] IS: 11384, Code of practice for composite construction in structural
steel and concrete, Bureau of Indian Standards, New Delhi, 1985.