INFLUENCE OF OPTIMAL COLUMN SPACING FOR G+11 STOREY RC MOMENT RESISTING FRAME

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International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 1, January 2017, pp. 397–408, Article ID: IJCIET_08_01_045

Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=1

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication

INFLUENCE OF OPTIMAL COLUMN SPACING

FOR G+11 STOREY RC MOMENT RESISTING

FRAME

G Sri Lakshmi

PG Student, Department of Civil Engineering,

K L UniversityVaddeswaram-522502, A.P, India

J D Chaitanya Kumar

Asst. Professor, Department of Civil Engineering,

K L University, Vaddeswaram-522502, A.P, India

ABSTRACT

Objective: To analyze a safe G+11 commercial by obtain the ideal space parameters of

varied columns. Method of analysis: The following work is limited to plot frames of 50m X

50m (with aspect ratio of panel sizes varying from 1 to 4) for the first case and for second

case the size of the panel are 50m x 50m, 50m x 30m, 50m x 25m and 50m x 20m (with an

aspect ratio of 1, 0.6, 0.5, and 0.4 respectively). The structure is modeled, analyzed for

gravity and lateral (seismic) loads then designed as per IS: 456-2000 and analyzed in

STAAD. Pro. Failed members are again modulated until all the members are safe. By

observations and calculations, the most economical panel size is suggested and its spacing

is noted. Findings: According to aspect ratio which panel shows more story drift and which

is having more self-weighted respectively which leads to economical column spacing design

further. Applications: The database is prepared for worst load combination and the

structural elements are designs for the worst load.

Key words: Column Spacing, Commercial Building, STAAD. Pro, Panel Size, Aspect

Ratio and Lateral Loads.

Cite this Article: G Sri Lakshmi and J D Chaitanya Kumar, Influence of Optimal Column

Spacing For G+11 Storey RC Moment Resisting Frame. International Journal of Civil

Engineering and Technology, 8(1), 2017, pp. 390–396.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=1

1. INTRODUCTION

With increasing population people has focused on space efficient living with use of largest space

parameters. Nowadays the trend off multistory structures is increasing day by day which are

motivating builders and designers to go for space utilization structures. This urbanization has led to

the concept of more space with less structural elements which tend to poor plinth area. As they

occupy more space in the structure. By keeping all these factors under consideration a small attempt

has made to eliminate columns and influence of this reduction technically in a multi-storey structure.

G Sri Lakshmi and J D Chaitanya Kumar


The analysis made is purely a design criterion in which without setting a known value the concept

of extending the width of the structure by extending the column to column spacing respectively.

To carry over further with the spacing phenomenon to get it analyzed the first step was to consider

2 cases simultaneously with different aspect ratios (the proportional relationship between two sides

of the considering element) as well as plot areas of varying dimensions. In case 1 the plot area will

be constant with varying aspect ratios i.e. (1 to 4). For the above aspect ratios, the plot areas will be

constant. Here the plot areas considered are for case 1 (50mx50m). But for next case which is

considered as case 2 the plot areas are varying with varying aspect ratios such as

• For plot area, 50mx50m aspect ratio is 1.

• For plot area, 50mx30m aspect ratio is 0.6.



The major advantages of reduction of columns in a structure are:

• More plinth area is introduced.

• A commercial structure like hotels, hospitals will get an aesthetic appearance with more area.

• Less the columns less will be the self-weight of the structure

• Reduction of self-weight will lead to less reinforcement which will make the structure more

economical.

Nowadays with increasing natural calamities construction must always be an earthquake resistant

building with specific zonal considerations. Analysis of the whole unit was done in STAAD pro. In

designing the structure every aspect was considered according to IS code provisions and earthquake

analysis was also taken place. While designing the structure dead load, live load and earthquake load

in zone 3 was considered respectively. By this concept of analyzing the structure for spacing of

columns and its effect on the structure is a new concept being introduced in order to begin a new

practice of construction by eliminating such elements which can be reduced practically without

compromising safety? The thought of providing constraint spacing of column has to be avoided by

providing column spacing and its influence on a multi-storey structure1. The new materials being

introduced to withstand high raised buildings with less weight, a detailed note work on cost

comparison of conventional and flat slab structure with this paper a view of using flat slabs by

reducing columns and its cost analysis is carried out ultimately resulting for economic structure2.

The introduction of a multi-storey structure which reveled in the year 1972 both made a detailed

survey about the air pressure and flexibility concepts of multi-storey structure which will lead us to

consider wind loads while designing a high raised multi-storey structure3. The axial pressure and its

effect related to multi-storey structure and axial shortening and its influence on a structure were

mentioned4. The analysis of simple 2-D frame of varying floor heights and the behavior of shear

according to the size of the column was also analyzed5. The concept of flat slabs and totally

eliminating of columns as far as possible was worked out by them story shear as also analyzed using

E-tabs6-7. A study on computer aided design of reinforced concrete twin towers7. In this study

analyzing and designing of G+25 twin towers, the results are compared from STAAD. Pro and

manual designs.

2. METHODOLOGY

2.1. METHOD OF ANALYSIS

The multi-storey structure having G+11 stories are analyzed after detailed manual designing

considering dead load, live load and all the wall loads such as outer walls, inner walls and parapet

Influence of Optimal Column Spacing For G+11 Storey RC Moment Resisting Frame


walls. Apart from the reduction of columns, which leads to distribute the loads more uniformly and

abolish the excessive effects of structural loads. The plane frames and structure are analyzed.

STAAD. Pro software was used for the analysis.

2.2. NOTATIONS

The analysis was carried out for 32 different plot areas with 8 aspect ratios and 5 varying panel sizes

respectively. The plot sizes for case 1 are 50x50md and for case 2 are 50x50m, 50x30m, 50x25 and

50x20m. for all the above plots areas story drift and self-weight is analyzed.

The structure with G+11 is analyzed with the help of STAAD PRO software which consists of a

multi-paneled system of beams and columns which are flexurally rigid at each junction with

reduction of columns and distribution of loads evenly with more accuracy by eliminating the excess

effect of structural loads was also worked out manually whereas analysis was done using STAAD.

Pro software. In case 1, the plot sizes are constant with a panel area of 50x50m whereas the aspect

ratios varying from 1 to 4 respectively, specifications are mentioned in Tables 1-4. and Figure 1. In

case 2, plot size is also varying with panel size. The plot areas with aspect ratios are mentioned in

Tables 5-8. and Figure 2. The column specifications are mentioned in Table 9.

Figure 1



Figure 2

Table 1 Aspect ratio=1 (plot area is 50mX50m)

Case No. of panels Size of each panel(in mts)

21 4 25*25

31 9 16.67*16.67

41 16 12.5*12.5

51 25 10*10

Table 2 Aspect ratio = 2 (plot area is 50mX50m)


22 8 25*12.5

32 18 16.67*8.33

42 32 12.5*6.25

52 50 10*5



Table 3 Aspect ratio = 3 (plot area is 50mX50m)


23 12 25*6.33

33 27 16.67*5.56

43 48 12.5*4.67

53 75 10*3.33

Table 4 Aspect ratio = 4 (plot area is 50mx50m)


24 16 25*2.5

34 36 16.67*4.167

44 64 12.5*3.125

54 100 10*2.5

Table 5 Aspect ratio = 1 (Plot area 50m X 50m)


21 4 25*2.5

31 6 25*16.67

41 16 25*12.5

51 25 25*10

Table 6 Aspect ratio – 0.6 (Plot area 50m X 30m)


22 8 15*25

32 18 10*25

42 32 7.5*25

52 50 6*25



23 12 12.5*25

33 6 8.33*25

43 8 6.25*25

53 10 5*25



24 4 10*25

34 6 6.66*25

44 8 5*25

54 10 4*25



Table 9 Number of columns

CASE 1 NO OF COLUMNS CASE 2 NO OF COLUMNS

21 9 21 9

31 16 31 12

41 25 41 15

51 36 51 18

22 15 22 9

32 28 32 12

42 45 42 15

52 66 52 18

23 21 23 9

33 40 33 12

43 65 43 15

53 96 53 18

24 27 24 9

34 52 34 12

44 85 44 15

54 126 54 18

2.3. LOADS AND LOAD COMBINATIONS CONSIDERED

The multistoried structure is analyzed for self-weight of the slabs, beams and columns self-weight,

Weight of the parapet walls and outer walls of each floor and inner walls on each floor and also live

load on the floor. Slab self-weight includes the floor finish. The load calculations and load

combinations are considered as per IS: 875– 1987.

2.4. DEAD LOAD

1. Self-weight of members

The Multistory structure is assigned self-weight of beam and column. 2. 2. Self-weight of slab

Assume slab thickness as 150mm

Total self weight of slab and floor finishers = (0.15X25) + 1 = 4.75 kN/ m2 3. 3. Parapet wall Self weight

Wall thickness = 230 mm,

Height of parapet wall = 0.9 m

Brick Unit weight = 18.85 kN/m3

Total load = 0.23 X 18.85 X 0.9 = 3.9 kN /m2

4. 4. Outer walls weight in the structure

Assuming thickness of Outer wall = 230mm and

Wall Height = 3m

Total weight = 0.23 X 18.85 X 3 = 13 kN/m 5. Inner walls weight in the structure

Assuming Inner wall thickness = 115 mm and

Height of the wall = 3m,

Total weight = 0.115 X 3 X 18.85 = 6.50 kN/m 6. Live load

Live load was taken as 4 kN/m2 as it is considered as a commercial building.



2.4. Load Combinations

As per IS 1893 (Part 1): 2002 Clause no. 6.3.1.2, the following load cases have to be considered for

analysis, mentioned in Table 10.

Table 10 Load combinations

S. NO LOAD COMBINATION S. NO LOAD COMBINATION

1 1.0(D.L+L.L) 10 1.2(D.L+L.L+EQ-Z)

2 1.5(D.L+L.L) 11 1.5(D.L+EQ+X)

3 1.0(D.L+L.L+EQ+X) 12 1.5(D.L+EQ-X)

4 1.0(D.L+L.L+EQ-X) 13 1.5(D.L+EQ+Z)

5 1.0(D.L+L.L+EQ+Z) 14 1.5(D.L+EQ-Z)

6 1.0(D.L+L.L+EQ-Z) 15 1.0(D.L+EQ+X)

7 1.2(D.L+L.L+EQ+X) 16 1.0(D.L+EQ-X)

8 1.2(D.L+L.L+EQ-X) 17 1.0(D.L+EQ+Z)

9 1.2(D.L+L.L+EQ+Z) 18 1.0(D.L+EQ-Z)

3. RESULTS AND DISCUSSIONS

The outcomes by analyzing all 32 panels are mentioned in Figure 3-10. The details of maximum

self-weight of structure are mentioned in Figure 11.

Figure 3 Storey drift with aspect ratio 1








Figure 7 Case 2 storey drift with aspect ratio 1

Figure 8 Case 2 storey drift with aspect ratio 0.6

Figure 9 Case 2 storey drift with aspect ratio 0.5



Figure 10 Storey drift with aspect ratio 0.4

Figure 11 Self weight of the structure

4. CONCLUSION

The following are the conclusion obtained for 32 cases analyzed:

By analyzing the cases for plot areas and calculating the storey drift values there are many

undulations in the graph for case 1 the aspect ratio for plot area 50mx50m is 1 and maximum storey

drift values are:

Cases 21 31 41 51

Max. storey drift (mm) 8.3348 2.626 2.809 7.043


undulations in the graph in case 1 the aspect ratio for plot area 50mx50m is 2 and maximum storey

drift values are:

Cases 22 32 42 52




drift values are:

Cases 23 33 43 53






drift values are:

Cases 24 34 44 54




drift values are:

Cases 21 31 41 51



undulations in the graph in case 2 the aspect ratio for plot area 50mx30m is 0.6 and maximum storey

drift values are:

Cases 22 32 42 52




drift values are:

Cases 23 33 43 53




drift values are:

Cases 24 34 44 54


By analyzing the self-weight of the structure with different panel sizes and maximum self-weight

is as follows:

Panel size 50x50 50x50(case 2) 50x30 50x25 50x20

Self weight 735141.653 63030.41 232525.668 229483.181 50446.732

5. ACKNOWLEDGMENT

The authors sincerely place gratitude to their parents and teachers, for their support and guidance for

completing this project. These authors wish to extend their thanks to Dr. A. Siva Sankar, Associate

Professor, K L University, Vaddeswaram , Andhra Pradesh for their valuable input to complete this

study.



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