International Journal of u- and e- Service, Science and Technology

Vol.8, No.4 (2015), pp.85-102

http://dx.doi.org/10.14257/ijunesst.2015.8.4.10

Effect of Column Spacing on Economy of G+5 R.C Moment

Resisting Frame – A Typical Computer Aided Case Study

Markandeya Raju Ponnada

Professor and Head, Department of Civil Engineering,
MVGR College of Engineering,
Chintalavalasa, VIZIANAGARAM, PIN 535005, A.P, INDIA.
Mobile: +91 9440528403, markandeyaraju@gmail.com

Abstract
The economy of a multistory building depends on the spacing of columns which in turn
depends on panel size of slab. The objective of this work is to design an economical G+5
building by finding the optimum spacing of columns. This work is limited to plot area of
30 m X 30 m (with Aspect ratio of Panel varied from 1 to 4) for first case and in second
case they were 30 m x 30 m, 30 m X 24 m, 30 m X 18 m and 30 m X 12 m (with Aspect
ratio of sites varied from 1, 0.8, 0.6 and 0.4 respectively). In case two each plot area is
again divided into panels of different aspect ratios. Here, Aspect ratio is ratio of longer
dimension to shorter dimension of panel. The structure is modeled, analysed and designed
as per IS : 456 – 2000 using Staad.Pro. Failed members are re-designed till all members
are safe. This procedure is repeated for all cases and the quantities of steel and concrete
are noted. It was observed that for 30 m x 30 m plot area for aspect ratio = 1, in Case 1-
Case 41 with 25 columns and in Case 2- Case 31 with 12 columns were observed to be
the most economical. In these two cases, Case-1 is more economical. In Case 1, Square
module 30 m X 30 m with spacing of columns at 5 m and 25 panels in both sides was
found to be cost effective. In Case-2 rectangular module 30 m X 24 m for aspect ratio 0.8
with spacing of columns 15 m X 12 m and 4 panels in both sides was found to be cost
effective. For rectangular module 30 m X 18 m for aspect ratio 0.6 with spacing of
columns 15 m X 6 m and 6 panels in both sides was found to be cost effective. For
rectangular module 30 m X 12 m for aspect ratio 0.4 with spacing of columns 15 m X 6 m
and 4 panels in both sides was found to be cost effective.

Keywords: multistory building, Optimum column spacing, aspect ratio, plot area,
panel size, Staad.Pro, re-design, concrete and steel quantity

1. Introduction
With increased population and land requirement for residential and commercial
purposes in urban areas, multistoried buildings are becoming common in construction
industry. When compared to low-rise buildings, apartments and multistory buildings
accommodate more people per unit of area of land and also decrease the cost per unit area
of the construction. The quantity of steel and concrete requirement for footings, beams,
columns and slabs contribute mostly to the overall cost of the structure. Further these
quantities are variable while cost of finishing’s and building services is constant for a
constant built up area. Hence, in the economy point of view, it is important to reduce the
quantities of both steel and concrete without compromising on quality and design
requirements.
The total quantity of steel and concrete requirement depends on the spacing’s of
columns which is the panel size of the slab. If the spacing of columns is more, the number
of columns is less and hence

ISSN: 2005-4246 IJUNESST

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Vol.8, No.4 (2015)

- the quantity of concrete requirement in columns will be less

- the quantity of steel requirement in columns will be more
- the quantity of concrete requirement in beams will be more
- the quantity of steel requirement in beams will be less

Hence, as spacing of columns increases, bending moments increase and ultimately

design may become uneconomical.

If the spacing of columns is less, number of columns is more and hence

- the quantity of concrete requirement in columns will be more
- the quantity of steel requirement in columns will be less
- the quantity of concrete requirement in beams will be less
- the quantity of steel requirement in beams will be more

Hence, reduced spacing of columns may also lead to uneconomical design.

Therefore, if in a multistory building, column positioning is not a constraint, then it is
advisable to arrive at optimum spacing of columns that results in minimum quantities of
steel and concrete requirement for a given built up area and hence economical design. In
some countries, concrete would be very costly while in others, steel. Perhaps the best
option here would be an interactive, trial and error approach using good software, and the
governing minimum quantities.
The optimal spacing of columns in a building generally depends on some of the
following factors.

1) Scale of economics in project. For small projects, even if % saving is high, net
saving is less.
2) Bearing capacity of soil as close proximity of columns end up in designing
combined strip footings which is obviously not cost effective compared to
isolated footings.
3) Column height which affects buckling and bending moments derived from the
horizontal loads.
4) Material of construction. If it is steel structure the spacing is determined by steel
sections like girders, channel sections or angles and impact of live load has to be
considered. Structural engineer likes closer columns to give economical floor
plate (with or without beams). However, foundations are not cost effective with
closer columns. It is variable by SBC.
5) Required stiffness (1/150 to 1/1000...) in the earthquake resistance requirement
point of view.
6) Limitations on height, size and number of floors based on local building bye laws
7) Function / usage of the building space i.e. if it is a carpark then the gap between 3
car bay spaces ( 3 m to 8 m) dictates the spacing of columns, if it is a concrete
deck, it is different.
8) Economic span/depth ratios of the supporting beams in limiting deflections.
Generally 6 m to 9 m practical span of beams and thus column spacing’s are
adopted.
9) Cost and user's convenience via-a-vis architect's planning. The architect would
like large spans and hence will place columns more for aesthetic values rather
than economics.

The economy from a builder's point of view is, more the number of car parks, more
the earning compared to saving by reducing the spacing of columns. Service
engineer, Likes larger open spaces and very thin floor plate to accommodate services and
less floor volume for energy efficiency. Contractor wants simple structure without

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cantilevers, transfer girders. Hence, to determine the true and optimum values of column
spacing is more a research problem of mathematics and not engineering alone. The
objective of this work is to arrive at the optimum spacing of columns assuming that the
above factors do not interfere with the spacing of columns.

2. Literature Review
Vyas and Raisinghani, 2007 [1] conducted a study on Optimum spacing of Columns
based on Cost of Construction in Laboratory Buildings. Several engineering laboratory
modules for technical institutions have been investigated with respect to structural cost
per unit floor area. The module with a spacing of columns at 6 m (20 ft) centre distance
along length was found to be cost effective for laboratory blocks up to two storey’s and
columns with 4.27 m centre distance along length are cost effective for laboratory blocks
more than two storey’s high. Detailed cost analysis of structure and material requirement
revealed that the volume of M20 cement concrete for RCC structure will be 22.9 % of
floor area for laboratory buildings. Vyas and Raisinghani, 2005 [2] determined the
optimum spacing of columns and Material consumption in library buildings. They
observed that optimum spacing between columns is 5.94 m centre to centre both ways
assuming size of columns as 450 mm × 350 mm. The cost of library module does not vary
much for 6.86 m spacing of column. Clark and Kingston [3] made an observation that
High-rise office buildings, which are developed as a response to population growth, rapid
urbanization and economic cycles, are indispensable for a metropolitan city development.
The political ideology of the city plays an important role in the globalization process
(Newman and Tornely [4]; Abu-Ghazalah [5]). The current trend for constructing office
buildings is to build higher and higher, and developers tend to compete with one another
on heights. The high technology styles have accompanied nearly all new tall buildings
and became landmark of many cities internationally (McNeill and Tewdwr-Jones [6]).
Nonetheless high-rise office buildings are more expensive to construct per square meter,
they produce less usable space and their operation costs are more expensive than
conventional office buildings. By the end of 1990s, at more than 30 stories, net to gross
floor area ratios of 70-75% were common in office buildings (Davis Langdon and Everest
[7]). However, Yeang [8] stated in his book “The Skyscraper: Bioclimatically
Considered” that net-to-gross floor area should not be less than 75%, while 80% to 85% is
considered appropriate. Watts and et al. [9] compared and revealed the similarities and
differences between tallest office buildings at abroad and in Turkey in terms of space
efficiency. Although there are no universal formulas for responding to the client’s needs
or to local influences and constraints such as climate, codes or constructional conditions
related to floor slab size and shape, the fundamental design considerations are almost
identical almost in office buildings (Kohn and Katz [10]; Strelitz [11]). The space
efficiency of a high-rise office building can be achieved by maximizing the Gross Floor
Area (GFA) and Net (usable) Floor Area (NFA) as permitted on the local site by the
codes and regulations, and in order to enable the developer and owner to get maximum
returns from high cost of land, the floors must have sufficient functional space (Kim and
Elnimeiri [12]). According to Yeang [13], floor slab efficiency of a typical high-rise
office building should generally not be less than 75%, unless the site is too small or too
irregular to permit a higher level of space efficiency. Watts et al. [9] state in their recent
article, floor slab efficiency is adversely affected by height of a high-rise office building,
as the core and structural elements expand relatively to the overall floor slab to satisfy
requirements of vertical circulation as well as lateral-load resistance. Square, circular,
hexagonal, octagonal and similar plan forms are more space efficient than rectangular
plans with high aspect ratios and irregular shapes. Buildings with symmetrical plan
shapes are also less susceptible to wind and seismic loads (Arnold [14]; Taranath [15];
Kozak [16]). Leasing depth or lease span is distance of usable area between exterior wall

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and fixed interior element, such as the core or the multi-tenant corridor. In Germany
maximum leasing depth is determined by building codes and cannot be more than 8.0 m,
whereas in Japan it is typically 18.0 m (Kohn and Katz [10]). According to Ali and
Armstrong [17] the depth of lease span must be between 10.0 and 14.0 m for office
functions, except where very large single tenant groups are to be accommodated. As
floors become deeper, the marketability of space decreases significantly (Crone [18]).
With reference to floor-to-floor / floor-to-ceiling height, Baum [19] defines quality in
office buildings and suggests that the plan layout and the ceiling height are more
significant than the following three determinants of building quality: (i) Services and
finishes; (ii) external appearance and (iii) durability of materials. Another research project
by Ho [20] reveals that functionality of the floor slab is the most important category
indicated by all the respondents of the investigation, except for users, who emphasized
services as the relative importance of functionality. Commercial functions require a
variety of floor-to-ceiling heights ranging between 2.7 and 3.7 m (Ali and Armstrong
[17]), and the depth of the structural floor system varies depending on the floor loads, size
of structural bay, and type of floor framing system. Layout of core is critical to the
development efficiency and operational effectiveness of a high-rise office building, while
also playing a significant role in the way the structure copes with lateral loads (Watts et al
[9]). This building type is very attractive to users without cellular offices and has until
recently been the standard in Japan and Korea (Kohn and Katz [10]). In United States,
steel is commonly used as the structural material and lightweight fire-rated drywall is
used to form the walls in order to reduce its thickness and save the foundation cost and
construction time (Ho [21]). In 1969 Fazlur Khan [22] classified structural systems for
high-rise buildings according to their height. Later, he upgraded these diagrams (Khan
[23], [24]), and developed schemes for both steel and concrete (Ali [25]; Ali and
Armstrong [17]; Schueller [26]; Iyengar [27]). As per literature review by Ali and Moon
[28], structural systems for high-rise buildings are divided into two categories, interior
and exterior structures. They are usually arranged as planar assemblies in two principal
orthogonal directions and may be employed together as a combined system in which they
interact. Another important system in this category is core-supported outrigger structure,
which is very widely used for super high-rise buildings (Ali and Moon [28]). The early
application of tubular concept is attributed to Fazlur Khan [22] in 1961 (Ali [25]). Widely
spaced framed tube, braced tube, tube-in-tube and bundled tube are subcategories of this
structural system (Taranath [15]). Other types of exterior structures include space trusses,
super frames and exoskeletons (Ali and Moon [28]). These systems are effective in
resisting to both lateral and gravity loads, thus enabling maximum space efficiency for
office workers, as in the case of Bank of China.

3. Objective and Scope

3.1 Aim and Objective
If the problem of optimizing the spacing of columns for economical design without
compromising on safety and structural stability in a multi-storey building is solved by
programming, then impractical values may be obtained like “adopt 25 mm sq columns at
110 mm centre to centre. To arrive at a practically executable solution to such
optimization problems, it takes a process of permutations and combinations. Main aim of
this project is to design an economical G+5 multistoried building for different sizes of
slabs and for different plot areas. An attempt is made to determine the optimum spacing
of columns in order to keep the cost minimum. Several multistoried buildings with
different spacing of columns have been designed using Staad.Pro software and their
indirect effect on the cost of the building was studied. A G+5 multistoried building
different panel sizes and combinations based on aspect ratios were adopted for design and

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variations on quantities of concrete and steel quantities was observed and compared.
Model plans, square and rectangular in shape were developed for different aspect ratios of
site area / slab panel for multistoried buildings. Detailed quantities were worked out and
relationships were established for cost of cement concrete and steel for a constant floor
area of multistoried buildings.

3.2 Scope
Without setting some known value, the cases to be studied would be infinite. Some
assumptions are inevitable in order to obtain a practicable output. This project was limited
for to plot area of 30 m X 30 m for first case and in second case they were 30 m x 30 m,
30 m X 24 m, 30 m X 18 m and 30 m X 12 m. For these plot areas based on aspect ratio,
area was divided into panels. It was assumed that quantities of steel and concrete alone
effect economy of a building. Cost comparison for steel and concrete quantities as per
existing rates (Concrete Rs.5000/per m3 and Steel Rs.50/per kg) for different panels for
the above mentioned sizes was performed. Based on different panel sizes and plot areas,
two cases are considered.

CASE 1

In this CASE 1, the Plot area size is constant and is equal to 30 m x 30 m and the
Aspect ratio of Panel is varied from 1 to 4. Aspect ratio of panel size is defined as ratio of
longer dimension of the panel to the shorter dimension of the panel.

For Panel Aspect ratio = 1

CASE 21, Number CASE 31, Number CASE 41, Number of CASE 51, Number
of panels 4, panel of panels 9, panel panels 16, panel of panels 25, each
size is 15 X 15 size is 10 X 10 size is 7.5 X 7.5 panel size 5 X 5
Figure 1. Plot Area of 30m X 30m with Aspect Ratio of Panel as One

For Panel Aspect ratio = 2

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CASE 22, Number CASE 32, Number CASE 42, Number CASE 52, Number
of panels 8, panel of panels 18, panel of panels 32, panel of panels 50, panel
size is 15 X 7.5 size is 10 X 5 size is 7.5 X 3.75 size is 6 X 3

Figure 2. Plot Area of 30m X 30m with Aspect Ratio of Panel as Two
For Panel Aspect ratio = 3

CASE 23, Number CASE 33, Number CASE 43, Number CASE 53, Number
of panels 12, panel of panels 27, panel of panels 48, panel of panels 75, panel
size is 15 X 5 size is 10 X 3.3 size is 7.5 X 2.5 size is 6 X 2
Figure 3. Plot Area of 30m X 30m with Aspect Ratio of Panel as Three

For Panel Aspect ratio = 4

CASE 24, Number CASE 34, Number CASE 44, Number CASE 54, Number
of panels 16, panel of panels 36, panel of panels 64, panel of panels 100, panel
size is 15 X 3.75 size is 10 X 2.5 size is 7.5 X 1.875 size is 6 X 1.5
Figure 4. Plot Area of 30m X 30m with Aspect Ratio of Panel as Four

CASE 2

In this CASE 2, the plot area is not constant. The plot area sizes studied are 30m x
30m, 30m x 24m, 30m x 18m and 30m x 12m. The Aspect ratio’s of sites considered are
respectively 1, 0.8, 0.6 and 0.4. Each plot area is again divided into panels of different
aspect ratios.

Aspect ratio = 1 (Plot area 30m X 30m)

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CASE 21, Number CASE 31, Number CASE 41, Number CASE 51, Number
of panels 4, panel of panels 6, panel of panels 8, panel of panels 10, panel
size is 15 X 15 size is 15 X 10 size is 15 X 7.5 size is 15 X 6

Figure 5. Plot Area of 30m X 30m with Aspect ratio of Panel as One

Aspect ratio – 0.8 (Plot area 30m X 24m)

CASE 22, Number CASE 32, Number CASE 42, Number CASE 52, Number
of panels 4, panel of panels 6, panel of panels 8, panel of panels 10, panel
size is 15 X 12 size is 15 X 8 size is 15 X 6 size is 15 X 4.8
Figure 6. Plot Area of 30m X 24m with Aspect Ratio of Panel as 0.8

Aspect ratio – 0.6 (Plot area 30m X 18m)

CASE 23, Number CASE 33, Number CASE 43, Number CASE 53, Number
of panels 4, panel of panels 6, panel of panels 8, panel of panels 10, panel
size is 15 X 9 size is 15 X 6 size is 15 X 4.5 size is 15 X 3.6m
Figure 7. Plot Area of 30m X 18m with Aspect Ratio of Panel as 0.6

Aspect ratio – 0.4 (Plot area 30m X 12m)

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CASE 24, Number CASE 34, Number CASE 44, Number CASE 54, Number
of panels 4, panel of panels 6, panel of panels 8, panel of panels 10, panel
size is 15m X 6m size is 15m X 4m size is 15m X 3m size is 15 m X 2.4 m
Figure 8. Plot Area of 30m X 12m with Aspect Ratio of Panel as 0.4

4. Methodology

4.1 Method of Analysis

The entire G+5 structure can be analyzed based on the concept of building frames
which consists of multi storied and multi paneled network of beams and columns which
are built monolithically and rigidly with each other at their junctions. All the members of
such a frame are continuous at their ends. Besides the reduction of moments due to
continuity, such structures tend to distribute the loads more uniformly and eliminate the
excessive effects of localized loads. The structure can be analyzed as 3 – dimensional
structure or it can be broken down into 2 – dimensional plane frames and analyzed.
Staad.Pro software was used for the analysis of buildings. The methodology is described
in the following flowchart. (See Figure 9)

4.2 Modeling Structural Framework

The flow chart shown in Fig. 9 describes the generalized procedure adopted for
STAAD.Pro analysis.

Plan with Dimensions

The plan is generated based upon plotting of the nodes from join 1 to 216. The 3-D
model of the proposed structure is shown in Figure 10.

Figure 10. 3D Frame Model of a Multistoried Building

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4.3 Loads and Load Combinations Considered

This multistoried building is subjected to self-weight of the slab, beam and columns
self-weight, Weights of parapet wall and outer walls in each floor and inner walls in the
each floor and also live load on floor. Slab self-weight includes the floor finish. The loads
and load combinations considered are as per IS: 875 – 1987 [29].

Dead load

1. Beam and column self-weight

The Multistory building is assigned self-weight of beam and column.

2. Slab self-weight
Assuming 150 mm thick slab
Total slab self weight including floor finish = 0.15 X 25 + 1 = 4.75 k N/ m2

3. Self weight of parapet wall

Assuming Wall thickness = 230 mm, Wall height = 0.9 m and Unit weight of brick =
18.85 kN/m3
Total load = 0.23 X 18.85 X 0.9 = 3.9 kN /m

4. Weight of outer walls in the multistoried building

Assuming Outer wall thickness = 0.23 m and Height of the wall = 3m
Total weight of outer wall = 0.23 X 18.85 X 3 = 13 kN /m

5. Weight of inner walls in the building

Assuming Inner wall thickness = 0.115 m and Height of the wall = 3m,
Total weight of inner wall = 0.115 X 3 X 18.85 = 6.50 k N /m

6. Live load
Live load was taken as 4 k N / m2 as it is considered as an office building.

4.4 Analysis

The above loads are applied and the structure is modeled, analysed and designed as per
IS : 456 – 2000 using Staad.Pro. Then the output file is checked for failed members.

4.5 Re-Designing

New properties with increased dimensions are applied to failed members to get the
member safe and then the quantities of steel and concrete quantities are obtained. Re-
design continues till all the members are safe and then the quantities of steel and concrete
for all members are obtained.

4.6 Steel and Concrete Quantities

After running the analysis for the input file in Staad.Pro we get the output file. Output
file contains the design details of the members of the building and also the quantities of
steel and concrete. The steel and concrete quantities are noted and this procedure should
be repeated for all cases and the obtained quantities are noted and listed in the below table
for further calculations.

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START

CREATING STRUCTURAL GEOMETRY

Create the G+5 frame for the structural plane area.

ASSIGNING THE MEMBER PROPERTY

Assign the assumed minimum dimension of the member to each
member.

SUPPORT CONDITION
Assign the all the supports as fixed support.

LOADING
Define and assign Dead Load and Live load coming on to the structure.

ANALYSIS
Perform Analysis and Check for results.

Yes
Any Check the
Warnings entire
or Errors? input data

N
o
DESIGN
Assign necessary design parameters and Design all beams & columns.

Yes
Any
Change
members
dimension
failing in
s of failed
design?
members

N
o
RESULTS
View and note the necessary results from Output file.

STOP

Figure 9. Analysis and Design of Multistoried Buildings Using Staad.Pro

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5. Observations and Discussions

5.1 CASE 1
For Aspect ratio = 1 and size of plot 30 m X 30 m, the concrete quantities are as
follows.

Table 1. Concrete Quantity for Different Cases (Plot Size 30m x 30m, Aspect
Ratio One)
Quantity
Footings Slab Total cost of
of
No of concrete concrete concrete concrete
Case Beams+
column quantity in quantity quantity 5000/-
columns
cu.m ( cu.m) (cu.m) per cu.m
concrete
21 9 48.6 271.83 810 1130.43 5652150
31 16 86.4 202.09 810 1098.49 5492450
41 25 135 191.22 810 1136.22 5681100
51 36 194.4 180.35 810 1184.75 5923750

Steel quantities are as follows.

Table 2. Steel Quantity for Different Cases (Plot Size 30m x 30m, Aspect
Ratio One)
Qty of steel
Qty of steel
No of for Total steel Cost of steel
Case slab+
columns beams + Qty (kgs) (50/kg)
footings
columns
21 9 57063.86 24423.33 81487.19 4074359.6
31 16 41911.36 17938.06 59849.42 2992471.1
41 25 42537 18205.84 60742.84 3037141.8
51 36 43163.32 18473.9 61637.22 3081861.05

For aspect ratio = 2 and size of plot 30 m X 30 m, the concrete quantities are as follows.

Table 3. Concrete Quantity for Different Cases (Plot Size 30m x 30m, Aspect
Ratio Two)
Footings Quantity Slab Total cost of
No of concrete of Beams concrete concrete concrete
Case
column quantity in + columns quantity quantity 5000/-
cu.m concrete ( cu.m) (cu.m) per cu.m
22 15 81 261.1 810 1152.1 5760500
32 28 151.2 233.81 810 1195.01 5975050
42 45 243 235.16 810 1288.16 6440800
52 60 324 259.06 810 1393.06 6965300

Steel quantities are as follows.

Table 4. Steel Quantity for Different Cases (Plot Size 30m x 30m, Aspect
Ratio Two)
No of Qty of steel Qty of steel Total steel Cost of steel
Case
columns for beams + slab+ Qty (kgs) (50/kg)

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columns footings
22 15 54380.79 23274.98 77655.77 3882788.41
32 28 47246.25 20221.4 67467.65 3373382.25
42 45 44185.53 18911.41 63096.94 3154846.84
52 60 45121.28 19311.91 64433.19 3221659.39

For aspect ratio = 3and size of plot 30 m X 30 m, the concrete quantities are as follows.
Table 5. Concrete Quantity for Different Cases (Plot Size 30m x 30m, Aspect
Ratio Three)

Footings Quantity Slab Total cost of

No of concrete of Beams+ concrete concrete concrete
Case
column quantity in columns quantity quantity 5000/-
cu.m concrete ( cu.m) (cu.m) per cu.m
23 21 113.4 305.43 810 1228.83 6144150
33 40 216 272.2 810 1298.2 6491000
43 65 351 277.18 810 1438.18 7190900
53 96 518.4 343.43 810 1671.83 8359150

Steel quantities are as follows.

Table 6. Steel Quantity for Different Cases (Plot Size 30m x 30m, Aspect
Ratio Three)
Qty of steel Qty of steel
No of Total steel Cost of steel
Case for beams + slab+
columns Qty (kgs) (50/kg)
columns footings
23 21 63439.77 27152.22 90591.99 4529599.58
33 40 58406.63 24998.04 83404.67 4170233.38
43 65 54738.47 23428.07 78166.54 3908326.76
53 96 55737.44 23855.62 79593.06 3979653.22

For aspect ratio = 4 and size of plot 30 m X 30 m, the concrete quantities are as follows.

Table 7. Concrete Quantity for Different Cases (Plot Size 30m x 30m Aspect
Ratio Four)
Footings Quantity of Slab Total cost of
No of concrete Beams+ concrete concrete concrete
Case
column quantity in columns quantity quantity 5000/-
cu.m concrete ( cu.m) (cu.m) per cu.m
24 27 145.8 321.32 810 1277.12 6385600
34 52 280.8 301.4 810 1392.2 6961000
44 85 459 336.19 810 1605.19 8025950
54 126 680.4 429.92 810 1920.32 9601600

Steel quantities are as follows.

Table 8. Steel Quantity for Different Cases (Plot Size 30 m x 30 m, Aspect

Ratio Four)
No of Qty of steel Qty of steel Total steel Cost of steel
Case
columns for beams + slab+ Qty (kgs) (50/kg)

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columns footings
24 27 77887.34 33335.78 111223.1 5561156.08
34 52 71595.86 30643.03 102238.9 5111944.4
44 85 69490.98 29742.14 99233.12 4961655.97
54 126 63696.11 27261.94 90958.05 4547902.25

5.2 CASE 2
For aspect ratio = 1 and size of plot 30 m X 30 m, the Concrete quantities are as
follows.

Footings Quantity Slab Total cost of

No of concrete of Beams+ concrete concrete concrete
Case
column quantity in columns quantity quantity 5000/-
cu.m concrete ( cu.m) (cu.m) per cu.m
21 9 48.6 288.41 810 1147.01 5735050
31 12 64.8 250.54 810 1125.34 5626700
41 15 81 274.74 810 1165.74 5828700
51 18 97.2 287.4 810 1194.6 5973000

Table 9. Concrete Quantity for Different Cases (Plot Size 30 m x 30 m,

Aspect Ratio One)
Steel quantities are as follows.

Qty of steel Qty of steel

No of Total steel
Case for beams + slab+ Cost of steel
columns Qty (kgs)
columns footings
21 9 65739.48 28136.5 93875.98 4693798.87
31 12 57677.46 24685.95 82363.41 4118170.64
41 15 56750.26 24289.11 81039.37 4051968.56
51 18 62921.62 26930.45 89852.07 4492603.67

Table 10. Steel Quantity for Different Cases (Plot Size 30 m x 30 m, Aspect
Ratio One)
For aspect ratio=0.8 and size of plot 30 m X 24 m, the concrete quantities are as follows.

Table 11. Concrete Quantity for Different Cases (Plot Size 30 m x 24 m,

Aspect Ratio 0.8)
Footings Quantity of Total cost of
Slab
No of concrete Beams + concrete concrete
Case concrete
column quantity in columns quantity 5000/-
quantity ( cu.m)
cu.m concrete (cu.m) per cu.m
22 9 48.6 203.5 648 900.1 4500500
32 12 64.8 225.53 648 938.33 4691650
42 15 81 234.31 648 963.31 4816550
52 18 97.2 264.58 648 1009.78 5048900

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Steel quantities are as follows

Table 12. Steel Quantity for Different Cases (Plot Size 30m x 24m, Aspect
Ratio of 0.8)
Qty of steel Qty of steel
No of Total steel Cost of steel
Case for beams + slab+
columns Qty (kgs) (50/kg)
columns footings
22 9 52184.41 22334.93 74519.34 3725966.87
32 12 50961.67 21811.59 72773.26 3638663.24
42 15 52045.3 22275.39 74320.69 3716034.42
52 18 54065.63 23140.09 77205.72 3860285.98

For aspect ratio = 0.6 and size of plot 30 m X 18 m, the concrete quantities are as follows

Table 13. Concrete Quantity for Different Cases (Plot Size 30m x 18m,
Aspect Ratio 0.6)
Footings Quantity Slab Total cost of
No of concrete of Beams concrete concrete concrete
Case
column quantity in + columns quantity quantity 5000/-
cu.m concrete ( cu.m) (cu.m) per cu.m
23 9 48.6 177.39 486 711.99 3559950
33 12 64.8 181.13 486 731.93 3659650
43 15 81 185.3 486 752.3 3761500
53 18 97.2 205.54 486 788.74 3943700

Steel quantities are as follows.

Table 14. Steel Quantity for Different Cases (Plot Size 30m x 18m, Aspect
ratio 0.6)
Qty of steel for Qty of steel
No of Total steel Cost of steel
Case beams + slab+
columns Qty (kgs) (50/kg)
columns footings
23 9 42692.42 18272.36 60964.78 3048238.79
33 12 40936.35 17520.76 58457.11 2922855.39
43 15 47094.12 20156.28 67250.4 3362520.17
53 18 49611.34 21233.65 70844.99 3542249.68

For aspect ratio = 0.4 and size of plot 30 m X 12 m, the concrete quantities are as follows.

Table 15. Concrete Quantity for Different Cases (Plot Size 30m x 12m
Aspect Ratio 0.4)
Footings Quantity of Slab Total Cost of
No of concrete Beams+ concrete concrete concrete
Case
column quantity in columns quantity quantity 5000/-
cu.m concrete ( cu.m) (cu.m) per cu.m
24 9 48.6 130.31 324 502.91 2514550
34 12 64.8 147.74 324 536.54 2682700
44 15 81 177.61 324 582.61 2913050
54 18 97.2 169.82 324 591.02 2955100

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Steel quantities are as follows.

Table 16. Steel Quantity for Different Cases (Plot Size 30m x 12m, Aspect
Ratio 0.4)
No of Qty of steel for Qty of steel Total steel Cost of steel
Case
columns beams + columns slab + footings Qty (kgs) (50/kg)
24 9 29671.16 12699.26 42370.42 2118520.82
34 12 34972.72 14968.32 49941.04 2497052.21
44 15 40636.39 17392.37 58028.76 2901438.25
54 18 44197.31 18916.45 63113.76 3155687.93

5.2 Cost Comparison

Based on observations from Section 5.1 and taking steel and concrete rates as per
present rate, costs for two cases and for different plot areas are compared as follows.

Table 17. CASE-1 Cost per Unit Area, Plot Area is 30m X 30m (Built-up Area
4500 m2)
Aspect ratio No of Cost of Cost of Total Cost per
Case
of panel columns concrete steel cost Unit area
1 21 9 5652150 4074359.60 9726509.60 2161.447
31 16 5492450 2992471.10 8484921.10 1885.538
41 25 5681100 3037141.80 8718241.80 1937.387
51 36 5923750 3081861.05 9005611.05 2001.247
2 22 15 5760500 3882788.41 9643288.41 2142.953
32 28 5975050 3373382.25 9348432.25 2077.429
42 45 6440800 3154846.84 9595646.84 2132.366
52 60 6965300 3221659.39 10186959.39 2263.769
3 23 21 6144150 4529599.58 10673749.58 2371.944
33 40 6491000 4170233.38 10661233.38 2369.163
43 65 7190900 3908326.76 11099226.76 2466.495
53 96 8359150 3979653.22 12338803.22 2741.956
4 24 27 6385600 5561156.08 11946756.08 2654.835
34 52 6961000 5111944.40 12072944.40 2682.877
44 85 8025950 4961655.97 12987605.97 2886.135
54 126 9601600 4547902.25 14149502.25 3144.334

For CASE-2

Plot area 30 m X 30 m with aspect ratio = 1(Built-up area is 4500)

Table 18. CASE 2 Cost per Unit Area, Plot Area 30m X 30m with Aspect
Ratio of One
No of Cost of Cost of Total Cost per
Case
columns concrete steel Cost unit area
9 21 5735050 4693798.87 10428848.87 2318
12 31 5626700 4118170.64 9744870.64 2166
15 41 5828700 4051968.56 9880668.56 2196
18 51 5973000 4492603.67 10465603.67 2326

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Plot area 30 m X 24 m with aspect ratio = 0.8 (Built-up area is 3600)

Table 19. CASE 2 Cost per Unit Area, Plot Area 30m X 24m with Aspect
Ratio of 0.8
Cost Cost
No of Cost of Total
Case of per unit
columns Steel cost
concrete area
9 22 4500500 3725966.87 8226466.87 2285
12 32 4691650 3638663.24 8330313.24 2314
15 42 4816550 3716034.42 8532584.42 2370
18 52 5048900 3860285.98 8909185.98 2475

Plot area 30 m X 18 m with aspect ratio = 0.6 (Built-up area is 2700)

Table 20 CASE 2 cost per unit area, Plot area is 30m X 18m with aspect ratio
of 0.6
No of Cost of Cost Cost per
Case Total cost
column concrete of steel unit area
9 23 3559950 3048238.79 6608188.79 2447
12 33 3659650 2922855.39 6582505.39 2438
15 43 3761500 3362520.17 7124020.17 2639
18 53 3943700 3542249.68 7485949.68 2773

Plot area 30m X 12m with aspect ratio = 0.4 (Built-up area is 1800)

Table 20. Cost per Unit Area for CASE-2, (Plot Area 30m X 12m, Aspect
Ratio 0.4)
Cost Cost
No of Cost of Total
Case of per unit
columns steel Cost
concrete area
9 24 2514550 2118520.82 4633070.82 2574
12 34 2682700 2497052.21 5179752.21 2878
15 44 2913050 2901438.25 5814488.25 3230
18 54 2955100 3155687.93 6110787.93 3395

6. Conclusions
The following general and specific conclusions can be arrived based on the study
conducted within the scope of this research work.

1. In Case 1 for aspect ratio = 1 and for Case 41 with 25 columns, the concrete quantity
is observed to be 1136.22 cu.m and the steel quantity is observed to be 60.74 MT.
This is the most economical case for 30m X 30m plot area.
2. For plot area of 30 m X 30 m in Case 2 and for aspect ratio = 1, Case 31with 12
columns was observed to be the most economical with 1125.34 cu.m of concrete and
82.36 M.T steel.
3. By comparing the above two results and costs the case-1 with aspect ratio =1 is seems
to be economical.
4. In Case 1, Square module 30 m X 30 m with spacing of columns at 5 m and 25 panels
in both sides was found to be cost effective.
5. In Case-2 rectangular module 30 m X 24 m for aspect ratio 0.8 with spacing of
columns 15 m X 12 m and 4 panels in both sides was found to be cost effective.

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6. For rectangular module 30 m X 18 m for aspect ratio 0.6 with spacing of columns 15
m X 6 m and 6 panels in both sides was found to be cost effective.
7. For rectangular module 30 m X 12 m for aspect ratio 0.4 with spacing of columns 15
m X 6 m and 4 panels in both sides was found to be cost effective.

Acknowledgements
I thank Mr. Srikanth, my post-graduate student for helping in modeling all the cases in
STAAD.Pro.

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Author

Markandeya Raju Ponnada, He was born on 25-08-1979 at

TUNI of Andhra Pradesh in INDIA. He did his B.Tech in Civil
Engineering from Nagarjuna University during 1997-2001 and M.E
in Structures from Andhra University during 2001-2003. He was
awarded Ph.D by JNTU Hyderabad for his work under the
Guidance of Dr.V.Ravindra, Professor of Civil Engineering, JNTU
Kakinada in the area of Prestressed steel beams in 2009. He has
more than 24 publications in various National and International
Journals and Conferences. He has more than 12 years of teaching
experience during which he taught subjects like Finite Element
Method, Applied Mechanics, Design of Steel Structures, Industrial
Structures, Highway Engineering and Prestressed Concrete to
Undergraduate and Post graduate Students. He is presently
Working as an Associate Professor and Head of the Department of
Civil Engineering, Maharaj Vijayram Gajapathi Raj College of
Engineering, Vizianagaram, Andhra Pradesh, INDIA. He has
considerable experstise in STAAD.Pro and his areas of interest are
Properties of Concrete, Analysis and Design of Pre-stressed
Structures and Computer Applications in Structural Engineering.
He has guided more than 23 B.Tech projects, 2 M.Tech
dissertations and is presently guiding a one student for his Ph.D. He
has vast experience in various consultancy assignments particularly
in the area of Multi-storey buildings and Composite bridges. He
has authored a book titled “Modified method of Prestressing Steel
Trusses by inducing Lack of fit A novel method of Optimizing /
Economizing Steel Truss Design” along with Mr.T.Rahuram
Sandeep.

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