COMPARATIVE ANALYTICAL INVESTIGATION OF 2D STEEL … · Material property of steel sections (ISHB 400, ISMB 350, ISA 110x110x10) and steel cable profiles (8mm and 10mm diameter cables)

http://www.iaeme.com/IJCIET/index.asp 734 [email protected]

International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 4, April 2017, pp. 734–743 Article ID: IJCIET_08_04_085

Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=4

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

© IAEME Publication Scopus Indexed

COMPARATIVE ANALYTICAL

INVESTIGATION OF 2D STEEL FRAMES

SUBJECTED TO LATERAL LOAD USING

STEEL CABLE BRACING

Ashok Shaji

Post Graduate Student, Structural Engineering, SRM University,

Kattankulathur Campus, Kanchipuram – 603203, India

N. Lokeshwaran

Assistant professor (O.G), Department of Civil Engineering,

SRM University, Kattankulathur Campus, Kanchipuram – 603203, India

ABSTRACT

Steel structures can be strengthened against lateral loads in different ways. The

most common and efficient way of strengthening steel structures is by providing bracing

systems to them. From the past studies, it’s clear that braced frames or bracing systems

helps in maintaining more structural stability or gives better resistance when lateral

loads are applied. The efficiency of the braced frame when compared with unbraced

frames depends upon the selection of bracing system. The rapid development in

construction industry globally demands for new bracing systems. So, this paper deals

with the analytical study of a new and innovative steel cable bracing connection for

strengthening and for reducing the effect of lateral load acting to the structure. For this

purpose, G+11 multi storied 2D steel frames were considered. The 2D steel frames

considered for this purpose are same in dimension but differentiable by their bracing

systems provided, which includes Unbraced, Single diagonal braced, X braced, V

braced, Inverted V braced, K braced, Knee braced and steel cable braced frames.

ANSYS Mechanical APDL 15.0 software package have been used for getting analytical

values like displacement, bending moment and shear force. Design and load

calculations had been done as per Indian Standard codes.

Key words: Displacement; Steel structures, 2D steel cable bracing, Bracing system,

Lateral load.

Cite this Article: Ashok Shaji and N. Lokeshwaran, Comparative Analytical

Investigation of 2D Steel Frames Subjected To Lateral Load Using Steel Cable Bracing.

International Journal of Civil Engineering and Technology, 8(4), 2017, pp. 734–743.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=4

Ashok Shaji and N. Lokeshwaran


1. INTRODUCTION

In the modernized world, vertical city concept is gaining a lot of importance, because of this

high-rise steel frame buildings are booming in metro cities as they are more time saving in

fabrication and erection process. Since most of the regions fall under seismic prone area

nowadays, it’s important to ensure more structural stiffness and resistance to lateral load. [1]

Strengthening of steel structures can be done in many ways for resisting the effect of lateral

load. From the steel frame design point of view, it’s important to have a good gravity and lateral

load resisting system for the structure. [2] The effect of lateral load high rise steel structures

may result in oscillatory movements, which may lead to discomfort for the occupants in the

building.

Also, lateral displacements should be limited to the maximum for avoiding structural

collapse. [3] The most commonly used method is the provision of braced frames, which

increases the stiffness and reduces the buckling of column and beam. [4] Provision of bracing

system may result in added weight to the structure but increases the effectiveness of the

structure against lateral displacement. Generally Concentric and Eccentric bracing systems are

used widely.

So, in this paper a new steel cable bracing system as shown Fig. 1 was analysed and studied

to check whether it outperforms the present conventional bracing systems. For this purpose,

steel cable profiles of 8mm and 10mm were diagonally cross braced in each floor levels of a

G+11 2D steel frame separately, which was subjected to earthquake analysis. Comparative

study is done at the end with conventional bracing systems.

Figure 1 Diagonally cross braced steel cable bracing system

2. MODELLING

For analytical study, nine G+11 2D steel frames were taken. All the 2D steel frames are same

in dimension but differentiable by the bracing systems provided to them. All the nine 2D steel

frames (Unbraced, V braced, Inverted V braced, X braced, K braced, Knee braced, Single

diagonal braced, 8mm steel cable braced and 10mm steel cable braced) were subjected to

earthquake analysis. Height and width of the 2D steel frames were taken as 3.5m and 5m

respectively for each floor. ISHB 400 were taken for column sections, ISMB 350 were

considered for beam sections and ISA 110x110x10 were used as bracing member for different

bracing systems. A new and innovative steel cable bracing system were provided to the 2D

Comparative Analytical Investigation of 2D Steel Frames Subjected To Lateral Load Using Steel

Cable Bracing


steel frames additionally when compared to the conventional bracing systems which comprises

8mm and 10mm steel cable profiles at 100mm spacing. The beams and columns used were

modeled as frame elements and were connected or jointed from nodes to nodes. Columns were

given fixed condition to the ground level. All the design and calculations were based on Indian

Standard codes. The analytical study was carried on ANSYS Mechanical APDL software

package for comparative purpose from the results obtained.

All the 2D steel frames share the same structural dimensions as shown in Fig. 2 but they

are differentiable by the bracing systems provided to them.

Figure 2 Structural dimensions of the 2D steel frame

Following 2D steel frame models were considered for the analytical study.

1. Unbraced 2D steel frame (Fig. 3(a))

2. Single diagonal braced 2D steel frame (Fig. 3(b))

3. V braced 2D steel frame (Fig. 4(a))

4. K braced 2D steel frame (Fig. 4(b))

5. Inverted V braced 2D steel frame (Fig. 5(a))

6. X braced 2D steel frame (Fig. 5(b))

7. Knee braced 2D steel frame (Fig. 6(a))

8. 8mm and 10mm steel cable braced 2D steel frame (Fig. 6(b))



Figure 3 (a) Unbraced 2D steel frame, (b) Single diagonal braced 2D steel frame

Figure 4 (a) V braced 2D steel frame, (b) K braced 2D steel frame

Figure 5 (a) Inverted V braced 2D steel frame, (b) X braced 2D steel frame

Figure 6 (a) Knee braced 2D steel frame, (b) 8mm and 10mm steel cable braced 2D steel frame


Cable Bracing


2.1. Material properties used for the analytical study

Material property of steel sections (ISHB 400, ISMB 350, ISA 110x110x10) and steel cable

profiles (8mm and 10mm diameter cables) used for the analytical study have been discussed

below.

2.1.1. Steel

The general material characteristic properties of steel sections (ISHB 400, ISMB 350, ISA

110x110x10) are tabulated below in Table 1.

Table 1 Material characteristic properties of steel

Structural steel Fe 250

Density 7850 kg/m3

Young’s Modulus 2.1x105 N/mm2

Shear Modulus 80000 N/mm2

Poisson’s ratio 0.3

2.1.2. Steel Cable

High strength carbon steel cable profiles of 8mm and 10mm diameter were used in the

analytical study. The steel cable samples were brought from Marine & Allied Engineering

Company, Chennai. Three specimen samples of each 8mm and 10mm steel cables were

subjected to tensile strength test in lab and the following test values were observed for both the

specimens. Tensile strength test values for 8mm diameter steel cable are tabulated below in

Table 2.

Table 2 Tensile strength test values for 8mm specimen

Tensile strength test values for 10mm diameter steel cable are tabulated below in Table 3.

SL.

No

Breaking

load (kN)

Ultimate

load (kN)

Original

gauge length

(mm)

Final gauge

length (mm)

%

Elongation

Area of

the cable

(mm2)

Tensile

strength

N/mm2

1 40 51 200 202.2 1.1 5024 10.15

2 41 50 200 202 1 5024 9.952

3 41 52 200 203 1.5 5024 10.35



Table 3 Tensile strength test values for 10mm specimen

The loading setup for tensile strength test of steel cables in UTM is shown in Fig. 7(a) and

unwinding of steel cable profiles after the tensile strength test is shown in Fig. 7(b).

Figure 7 (a) Loading setup in UTM, (b) Unwinding of steel cable profile

2.2. Load calculations

The design and load parameters given to 2D steel frames for analytical study were in

accordance with Indian Standard codes and steel table [SP: 6 (1) – 1964].

1. The self-weight of the beams and columns were taken from SP: 6 (1) – 1964. Live load and

floor finish load for the frames were taken from IS 875 part 2.

2. The self-weight given by the steel cable profiles of 8mm and 10mm to the structure were

computed out after weighing the steel cable samples in the lab.

3. Seismic loading was done in accordance with IS 1893-2002 and the parameters considered are

listed below in Table 4.

SL.

No

Breaking

load (kN)

Ultimate

load (kN)

Original

gauge length

(mm)

Final gauge

length (mm)

%

Elongation

Area of

the cable

(mm2)

Tensile

strength

N/mm2

1 61 74 200 202 1 6280 11.783

2 62 75 200 202.5 1.25 6280 11.943

3 64 77 200 202 1 6280 12.261


Cable Bracing


Table 4 Factors considered from IS 1893 - 2002

Region Chennai

Zone factor 3

Soil type 2 (Medium soil)

Importance factor 1.5

Response reduction factor 4 (Concentric frames)

5 (Eccentric frames)

Damping 5%

The above table values are considered for all the 2D steel frames with different bracing

systems for the earthquake analysis in ANSYS Mechanical APDL software package.

3. RESULTS AND DISCUSSION

All the conventional 2D steel frames (Unbraced, Single diagonal braced, V braced, K braced,

Inverted V braced, X braced, Knee braced) and 2D steel cable braced steel frames were

subjected to earthquake analysis in ANSYS Mechanical APDL software package. The

following values of displacement, bending moment and shear forced were observed for

different types of bracing systems. Maximum lateral displacement observed are tabulated

below in Table 5.

Table 5 Maximum Lateral Displacement

Type of Bracing system

considered for 2D steel frame

Maximum Displacement

observed (mm) Reduction in Displacement (%)

Unbraced 197.06

Knee braced 26.70 86.45

V braced 10.52 94.66

Single diagonal braced 6.35 96.78

K braced 5.78 97.07

Inverted V braced 5.81 97.05

X braced 5.65 97.13

10mm steel cable braced at

100mm distance

4.66 97.64

8mm steel cable braced at

100mm distance

4.37 97.78

An active reduction of 86.45%, 94.66%, 96.78%, 97.07%, 97.05%, 97.13%, 97.64% and

97.78% in displacement were observed in Unbraced, Knee braced, V braced, Single diagonal

braced, K braced, Inverted V braced, X braced, 10mm steel cable braced and 8mm steel cable

braced 2D steel frames. Comparison of values is shown in Fig. 8.



Figure 8 Comparison of maximum lateral displacement

Maximum shear force observed in the 2D steel frames are tabulated below in Table 6.

Table 6 Maximum Shear force

Type of Bracing system considered for 2D steel

frame Maximum Shear force observed (N)

Unbraced 0.128x10-05

Knee braced 31.8071

V braced 27.6041

Single diagonal braced 3.32513

K braced 3.67759

Inverted V braced 1.20815

X braced 2.71853

10mm steel cable braced at 100mm distance 0.707x10-05

8mm steel cable braced at 100mm distance 0.680x10-05

From the tabulated values, it’s evident that shear forces in 8mm and 10mm steel cable

braced 2D steel frames are much better when compared to other conventional bracing systems.

Comparison of values is shown in Fig. 9.

Figure 9 Comparison of maximum Shear force

Maximum bending moment observed in the 2D steel frames are tabulated below in Table 7.

19

7.0

6

26

.7

10

.52

6.3

5

5.7

8

5.8

1

5.6

5

4.6

6

4.3

7

U N B R A C E D K N E E

B R A C E D

V B R A C E D S I N G L E

D I A G O N A L

B R A C E D

K B R A C E D I N V E R T E D

V B R A C E D

X B R A C E D 1 0 M M

C A B L E

B R A C E D

8 M M

C A B L E

B R A C E D

MAXIMUM DISPLACEMENT IN MM

Maximum Displacement in mm1

.28

E-0

6

31

.80

71

27

.60

41

3.3

25

13

3.6

77

59

1.2

08

15

2.7

18

53

7.0

7E

-06

6.8

0E

-06


B R A C E D


D I A G O N A L

B R A C E D


V B R A C E D


S T E E L

C A B L E

B R A C E D

8 M M S T E E L

C A B L E

B R A C E D

MAXIMUM SHEAR FORCE IN (N)

Maximum Shear force in (N)


Cable Bracing


Table 7 Maximum Bending moment

Type of Bracing system considered for 2D steel

frame Maximum Bending moment observed (Nmm)

Unbraced 0.32391

Knee braced 114916

V braced 102459

Single diagonal braced 9082.53

K braced 9697.14

Inverted V braced 4613.04

X braced 8684.54

10mm steel cable braced at 100mm distance 78.54

8mm steel cable braced at 100mm distance 50.27

From the tabulated values, it’s evident that bending moments in 8mm and 10mm steel cable

braced 2D steel frames are much better when compared to other conventional bracing systems.

Comparison of values is shown in Fig. 10.

Figure 10 Comparison of maximum Bending moment

4. CONCLUSION

Based on analytical study and from the values obtained at the end, following conclusions were

framed out.

1. Modelling and analytical study were carried out in ANSYS Mechanical APDL software

package for obtaining values for displacement, shear force and bending moment.

2. X braced 2D steel frame showed better resistance in resisting lateral load among conventional

braced frames with 97.13% reduction in displacement when compared to the unbraced 2D steel

frame.

3. The new steel cable braced 2D steel frames topped the chart, by being most efficient in resisting

the lateral load by a reduction percentage of 97.64% and 97.78% in displacement.

4. The new 10mm steel cable braced 2D steel frame showed 97.64% reduction in displacement

when compared to the unbraced 2D steel frame.

5. The new 8mm steel cable braced 2D steel frame came out to be the most efficient in resisting

lateral load by 97.78% reduction in displacement when compared to the unbraced 2D steel

frame.

6. The weight of 8mm steel cable is less when compared to the 10mm steel cable, hence it performs

better at 100mm spacing.

0.3

23

91

11

49

16

10

24

59

90

82

.53

96

97

.14

46

13

.04

86

84

.54

7.8

5E

+0

1

50

.27


B R A C E D


D I A G O N A L

B R A C E D


V B R A C E D


S T E E L

C A B L E

B R A C E D

8 M M S T E E L

C A B L E

B R A C E D

MAXIMUM BENDING MOMENT IN (NMM)

Maximum Bending moment in (Nmm)



7. From the analytical study, it was observed that symmetrically braced frames perform better

under lateral load when compared to unsymmetrically braced frames. For example, in the

symmetrically cross braced frame bracing (X bracing), when lateral load is applied one brace

will be in tension and the other will be in compression. This will be vice versa when the load

direction is reversed.

8. From the results, it’s evident that the new bracing system performs better in terms of shear force

and bending moment when compared to present conventional bracing systems.

REFERENCES

[1] Jagadish J. S, Tejas D Doshi, “A study on bracing systems on high rise steel structures”,

International journal of engineering research and technology, ISSN : 2278 – 0181, Vol. 2,

Issue 7, July 2013

[2] Adithya M, Swathi Rani K. S, Shruthi H K, Dr. Ramesh B. R, “Study on effective bracing

systems for high rise steel structures”, SSRG international journal of civil engineering

(SSRG – IJCE), Volume 2, Issue 2, February 2015

[3] Y. U. Kulkarni, Prof. P. K. Joshi, “Analysis and design of various bracing system in high

rise steel structures”, International journal of advance research in science and engineering,

Vol. no. 3, Issue 11, November 2014

[4] Akshay Sonawane, Dipak Sonawane, Satish Jadhav, Rajendra Khemnar, Rohit Mahale,

Prof. Dumbare Sir, “Effect of bracing on critical storey of high rise frame structure”,

International conference on emerging trends in engineering and management research,

ICETEMR – 16, March 2016

[5] IS 800:2007, “General construction in steel – Code of practice”, Bureau of Indian standards,

New Delhi

[6] IS 1893 (part 1):2002, “Criteria for earthquake resistant design of structures”, Bureau of

Indian standards, New Delhi

[7] IS: 875 (part 1) – 1987, “Code of practice for design loads (other than earthquake) for

buildings and structures”, Part 1 Dead loads – unit weights of building materials and stored

materials, Bureau of Indian standards, New Delhi

[8] IS: 875 (part 2) – 1987, “Code of practice for design loads (other than earthquake) for

buildings and structures”, Part 2 Imposed loads, Bureau of Indian standards, New Delhi

[9] SP: 6 (1) – 1964 (Reaffirmed 2003), “Handbook for structural engineers”, 1. Structural steel

sections (revised), Bureau of Indian standards, New Delhi

[10] Design data, “Data book for engineers”, Published by kalaikathir chchagam, Coimbatore,

May 2015, pp 9.1-9.3

[11] IS 2266: 2002, “Steel wire ropes for general engineering purposes”, Specifications, Bureau

of Indian standards, New Delhi

Documents

COMPARATIVE ANALYTICAL INVESTIGATION OF 2D STEEL … · Material property of steel sections (ISHB 400, ISMB 350, ISA 110x110x10) and steel cable profiles (8mm and 10mm diameter cables)