Experimental Study of Bolted Connections Using Light Gauge Channel Sections, Using Stiffener/Packing Plates at the Joints

Experimental Study of Bolted Connections Using Light Gauge Channel Sections, Using Stiffener/Packing Plates at the Joints

Ravindra B. Kulkarni* and Vishal Vaghe**

*Asst. Professor, ** M-Tech. Student.

Department of Civil Engineering

Gogte Institute of Technology, Belgaum 590008 (Karnataka)

Abstract

Cold-formed structural members are being used more widely in routine structural design as the world steel industry moves from the production of hot-rolled section and plate to coil and strip, often with galvanised and/or painted coatings. Steel in this form is more easily delivered from the steel mill to the manufacturing plant where it is usually cold-rolled into open and closed section members. The present study is focus on examining the experimental investigation to study the effect of Stiffener/Packing plate (Mild steel Plates) only at the joints in cold formed channel sections by using bolts at the joints and which may increase the load carrying capacity of the bolted channel section subjected to axial tension. In the present study, the strength of the joint is increased by increasing the various thicknesses of Stiffener/Packing plates at the joints with three numbers of bolts at the connection. And also the experiment is executed with a single bolt to study the of failure pattern at the joints. Total Twelve experimental tests have been carried out on cold formed channel tension members fastened with bolts, to calculate the failure capacity and increase in strength of the member and also to trace the entire load versus elongation path, so that the behavior of the connection is examined.

Keywords: Light Gauge Steel Sections, Steel Plates, Strain/Elongation, Failure Patterns.

Introduction

The use of cold-formed steel members in building construction began in the 1850s in both the United States and Great Britain. In the 1920s and 1930s, acceptance of cold-formed steel as a construction material was still limited because there was no adequate design standard and limited information on material use in building codes. One of the first documented uses of cold-formed steel as a building material is the Virginia Baptist Hospital, constructed around 1925 in Lynchburg, Virginia. The walls were load bearing masonry, but the floor system was framed with double back-to-back cold- formed steel lipped channels. According to

Chuck Greene, P.E of Nolen Frisa Associates [2], the joists were adequate to carry the initial loads and spans, based on current analysis techniques. Greece engineered a recent renovation to the structure and said that for the most part, the joists are still performing well. A site observation during this renovation confirmed that "these joists from the 'roaring twenties' are still supporting loads, over 80 years later!" In the 1940s, Lustron Homes built and sold almost 2500 steel-framed homes, with the framing, finishes, cabinets and furniture made from cold-formed steel.[1]

Cold-Formed Steel (CFS) is the common term for products made by rolling or pressing thin gauges of sheet steel into goods. Cold-formed steel goods are created by the working of sheet steel using stamping, rolling, or presses to deform the sheet into a usable product. The use of cold- formed steel construction materials has become more and more popular since its initial introduction of codified standards in 1946. In the construction industry both structural and non-structural elements are created from thin gauges of sheet steel. The material thicknesses for such thin-walled steel members usually range from 0.0147 in. (0.373 mm) to about ¼ in. (6.35 mm). Steel plates and bars as thick as 1 in. (25.4 mm) can also be cold-formed successfully into structural shapes. These building materials encompass columns, beams, joists, studs, floor decking, built-up sections and other components. The manufacturing of cold- formed steel products occurs at room temperature using rolling or pressing. The strength of elements used for design is usually governed by buckling. [2]

Tension Member

Tension members are structural elements or members that are subjected to axial tensile forces. Fig.1 shows a member under tension. They are usually used in different types of structures. Examples of tension members are: bracing for buildings and bridges, truss members and cables in suspended roof systems.

Figure 1: Member under Tension

Stress is given by, F =P/A

Where, P is the magnitude of the load

A is the cross-sectional area

The increase in the length of a member due to axial tension under service load is

=PL / (E.Ag)

Where,

is the axial elongation of the member (mm),P is the axial tensile force (un- factored) in the member (N),L is the length of the member (mm) and E is the modulus of elasticity of steel=2.0×105 MPa.

Note: That displacement is a serviceability limit state criterion and hence is checked

Material Details

Fig 2: Cross section details of channal section

Where,

400.00

350.00

400.00

350.00

Sample

1.5mm Thick Cold Form Plate

Sample

1.5mm Thick Cold Form Plate

300.00

250.00

200.00

150.00

100.00

50.00

300.00

250.00

200.00

150.00

100.00

50.00

h – is the height of the section b – is the width of the section

Stress N/mm2

Stress N/mm2

t – is the thickness of the section r – is the radius section

Ixx and Iyy is the moment of inertia about x and y axis

1.5mm thick plate

1.5mm thick plate

Yield Strength and Youngs Modulus of the Cold Form Channel Specimen

The parallel length is kept between Lo + b/2 & Lo + 2b

Fig 3: Tensile Test on Cold Formed steel Sheet

0.00

0.00

Strian

Strian

0.0000

0.0119

0.0238

0.0358

0.0477

0.0596

0.0715

0.0835

0.0954

0.1073

0.1192

0.1312

0.1431

0.1531

0.1574

0.1693

0.1812

0.1932

0.0000

0.0119

0.0238

0.0358

0.0477

0.0596

0.0715

0.0835

0.0954

0.1073

0.1192

0.1312

0.1431

0.1531

0.1574

0.1693

0.1812

0.1932

Fig 5: Graph Between Force and Elongation for 1.5mmThick Cold form plate

Test Samples	Thickness of sample	Yield Stress	ultimate strength	Young's Modulus
No	mm	N/mm2	N/mm2	KN/mm2
1	1.2	231.67	358.33	191.81
2	1.5	233.55	357.77	207.57

Test Samples	Thickness of sample	Yield Stress	ultimate strength	Young's Modulus
No	mm	N/mm2	N/mm2	KN/mm2
1	1.2	231.67	358.33	191.81
2	1.5	233.55	357.77	207.57

Table -1: Yield Strength and Youngs Modulus Cold form steel plate

Where,

400.00

350.00

Stress N/mm2

Stress N/mm2

300.00

p>250.00

200.00

150.00

100.00

50.00

0.00

Lo = Original Gauge length Le = Parallel length

Lt = Total length

b = Width of the test piece

Sample 1

1.2mm Thick Cold Form Plate

0.0000

0.0164

0.0328

0.0492

0.0655

0.0819

0.0983

0.1147

0.1311

0.1475

0.1638

0.1759

0.1884

0.2048

0.2212

0.0000

0.0164

0.0328

0.0492

0.0655

0.0819

0.0983

0.1147

0.1311

0.1475

0.1638

0.1759

0.1884

0.2048

0.2212

1.2mm thick plate

Stain

Hence from the IS 1079-1973 the Grade of the steel is referred to as St.42 for the yield stress 235 N/mm2

Materials used as Stiffener/Packing Plate (Mild Steel Plate) at the Joint

1. A high amount of carbon makes mild steel different from other types of steel. Carbon makes mild steel stronger and stiffer than other type of steel. However, the hardness comes at the price of a decrease in the ductility of this alloy. Carbon atoms get affixed in the interstitial sites of the iron lattice and make it stronger.

2. Mildest grade of carbon steel or 'mild

   Fig 4: Graph Between Force and Elongation for 1.2mmThick Cold form plate

   steel' is typically carbon steel, with a

   comparatively mild amount of carbon (0.16% to 0.19%).

3. The calculated average industry grade mild steel density is 7.85 gm/cm3. Its Young's modulus, which is a measure of its stiffness, is around 210,000 Mpa.

4. Mild steel is the cheapest and most versatile form of steel and serves every application which requires a bulk amount of steel.

Connections

Connections designed more conservatively than members because they are more complex to analyse and discrepancy between analysis and design is large. Connections are normally made either by bolting or welding. Bolting is common in field connections, since it is simple and economical to make. Bolting is also regarded as being more appropriate in field connections from considerations of safety.

Types of Failure Mode in Connections

1. Longitudinal shear failure of sheet (type I).

2. Bearing failure f sheet (type II). (c)Tensile failure of sheet (type III)

(d) Shear failure of bolt (type IV).

Fig 6: Types of failure of bolted connections

Experimental Tests Specimens Geometries

The experimental testing consists of

channel of tension specimens fabricated from rolled steel sheets. All specimens are of 500 mm length. All specimens are fastened, with a single row of 12 mm diameter HSFG GR 8.8 bolts, through their webs at both ends. The tests consist of 3 sets of channel of size 50x40mm specimens with the 1.2 and 1.5mm thickness, with the same connection length for all the samples. At the connection Stiffener/Packing plates are used of different thickness. The end distance and number of bolts for each specimen are held constant at 24 mm and 3 numbers respectively, with Holes for the 12mm GR

1. bolts were specified to be drilled to a 14 mm diameter.

   Table-2 Specimen Dimensions for 1.2mm Thick Channel with 3 Bolts Connection

   Specime n Size	No of Bolts	End Dist	Connecting Length	Thickness of plate	Dia of Bolt	Dia of Hole
   50X40	3	24	72	1.2	12	14
   50X40	3	24	72	1.2	12	14
   50X40	3	24	72	1.2	12	14
   50X40	3	24	72	1.2	12	14
   50X40	3	24	72	1.2	12	14

   (All dimensions are in mm)

   Table-3 Specimen Dimensions for 1.5mm Thick Channel with 3 Bolts Connection

   Specimen Size	No of Bolts	End Dist	Connecting Length	Thickness of plate	Dia of Bolt	Dia of Hole
   50X40	3	24	72	1.5	12	14
   50X40	3	24	72	1.5	12	14
   50X40	3	24	72	1.5	12	14
   50X40	3	24	72	1.5	12	14
   50X40	3	24	72	1.5	12	14

   (All dimensions are in mm)

   Table-4 Specimen Dimensions for 1.5mm Thick Channel with single Bolts Connection at the joint

   Specimen No	No of Bolts	End Dist	Connecting Length	Thickness of plate	Dia of Bolt	Dia of Hole
   50X40	3	24	72	1.5	12	14
   50X40	3	24	72	1.5	12	14

   (All dimensions are in mm)

   Set up of Channel section moulds, are used to transfer the load from a 1000 KN universal testing machine (UTM) to a Channel specimen.

   Fig 7: Channel moulds for the proper grip used for connecting channel section to UTM for Tensile test

   1. Sample without b) Sample with

Packing plate packing plate Fig 8: Specimen Geometries of the test sample with

3 bolts connection at the bottom

a) Sample without b) Sample with

Packing plate packing plate Fig 9: Specimen Geometries of the test sample with

single bolts connection at the bottom

Experimental Procedures and Results

Twelve full-scale bolted connections were tested in tension in a 1000 kN (tension) capacity universal testing machine. The load was applied quasi-statically. Readings of load and displacement were taken at regular intervals 12mm diameter HYSD Bolts were used, diameter hole of 14mm was drilled in both the 5mm thick plate as shown in the figure: 8. three such bolts were used to fasten these two plates together. These bolts were tightened using the turn of the nut method.

Fig 10: Arrangement made for tensile testing for UTM

Test Descriptions and Results

A summary of the test results and description of each test is presented in the following sections.

Specimens of Series A (1.2 mm Thick Channel Specimen with Three Numbers of Bolts at the Joint) Specimens of Series B (1.5 mm Thick Channel Specimen with Three Numbers of Bolts at the Joint)

In this five specimens are used having the same cross section and the only variable was the thickness of the Stiffener/Packing Plate, which was 2mm, 3mm, 4mm, and 5mm. and first sample is tested without Stiffener/ packing plate. The results will be plotted to Load vs. deformation curves for these five specimens.

Specimens of Series C (1.5mm Thick Channel Specimen with Single Number of Bolt at the Joint)

In this two specimens are used having the same cross section and the thickness of the Stiffener/Packing Plate used was 4mm, and first sample is tested without Stiffener/packing plate. The results will be plotted to Load vs. deformation curves for these five specimens.

Results

Specimens of Series A (1.2 mm Thick Channel Specimen with Three Numbers of Bolts at the Joint)

Sample -1

			350.00
250.00			300.00
200.00 150.00 100.00 50.00 0.00	Without stiffener plate Strain		250.00 200.00 150.00 100.00 50.00 0.00

			350.00
250.00			300.00
200.00 150.00 100.00 50.00 0.00	Without stiffener plate Strain		250.00 200.00 150.00 100.00 50.00 0.00

300.00 50x40x1.2 without stiffner plate

Sample -4

50x40x1.2 with 4mm stiffner plate

Stress N/mm2

Stress N/mm2

0.0000

0.0055

0.0110

0.0165

0.0220

0.0275

0.0330

0.0385

0.0440

0.0495

0.0550

0.0605

0.0660

0.0715

0.0770

0.0825

0.0000

0.0055

0.0110

0.0165

0.0220

0.0275

0.0330

0.0385

0.0440

0.0495

0.0550

0.0605

0.0660

0.0715

0.0770

0.0825

Stress N/mm2

Stress N/mm2

0.0000

0.0090

0.0180

0.0270

0.0360

0.0450

0.0540

0.0630

0.0720

0.0810

0.0900

0.0968

0.1058

0.1148

0.1220

0.0000

0.0090

0.0180

0.0270

0.0360

0.0450

0.0540

0.0630

0.0720

0.0810

0.0900

0.0968

0.1058

0.1148

0.1220

Without stiffener plate 4mm thick Stiffener Plate

Fig 11: Graph between stress and strain for SMPL-1 without Stiffener/Packing plate

Strain

Fig 14: Comparison Graph between stress and strain for SMPL-4 with 4mm thick Stiffener/Packing plate

300.00

250.00

Stress N/mm2

Stress N/mm2

200.00

Sample -2

350.00

350.00

Sample -5

50x40x1.2 with 5mm stiffner plate

Sample -5

50x40x1.2 with 5mm stiffner plate

50x40x1.2 with 2mm stiffner plate

300.00

250.00

200.00

150.00

100.00

50.00

300.00

250.00

200.00

150.00

100.00

50.00

Stress N/mm2

Stress N/mm2

150.00

100.00

without stiffner plate 5mm thick Stiffener Plate

without stiffner plate 5mm thick Stiffener Plate

50.00 Without stiffener plate

with 2mm stiffner plate

0.00

0.00

0.0000

0.0063

0.0125

0.0188

0.0250

0.0313

0.0375

0.0437

0.0500

0.0562

0.0625

0.0687

0.0725

0.0737

0.0792

0.0854

0.0917

0.0979

0.1042

0.0000

0.0063

0.0125

0.0188

0.0250

0.0313

0.0375

0.0437

0.0500

0.0562

0.0625

0.0687

0.0725

0.0737

0.0792

0.0854

0.0917

0.0979

0.1042

0.0000

0.0070

0.0140

0.0210

0.0280

0.0350

0.0420

0.0490

0.0560

0.0630

0.0700

0.0770

0.0840

0.0910

0.0980

0.1031

0.1097

0.1167

0.1237

0.1288

0.0000

0.0070

0.0140

0.0210

0.0280

0.0350

0.0420

0.0490

0.0560

0.0630

0.0700

0.0770

0.0840

0.0910

0.0980

0.1031

0.1097

0.1167

0.1237

0.1288

0.00

Strain

Fig 12: Comparison Graph between stress and strain for SMPL-2 with 2mm thick Stiffener/Packing plate

Strain

Strain

Fig 15: Comparison Graph between stress and strain for SMPL-5 with 5mm thick Stiffener/Packing plate

Sample -3

50x40x1.2 with 3mm stiffner plate

300.00

All Five 1.2 mm Thick channel Samples

50.00 No Packing Plate

45.00

45.00

with 2mm thick stiffener plate with 3mm thick stiffener plate

250.00

Stress N/mm2

Stress N/mm2

200.00

150.00

100.00

50.00 without stiffener plate

40.00

35.00

Force kN

Force kN

30.00

25.00

20.00

15.00

10.00

with 4mm thick stiffener plate with 5mm thick stiffener plate

3mm thick Stiffener Plate

0.0000

0.0065

0.0130

0.0195

0.0260

0.0325

0.0390

0.0455

0.0520

0.0585

0.0650

0.0715

0.0780

0.0845

0.0893

0.0953

0.1018

0.1083

0.1148

0.0000

0.0065

0.0130

0.0195

0.0260

0.0325

0.0390

0.0455

0.0520

0.0585

0.0650

0.0715

0.0780

0.0845

0.0893

0.0953

0.1018

0.1083

0.1148

0.00

5.00

0.00

3.00

6.00

9.00

12.00

15.00

18.00

21.00

24.00

27.00

30.00

33.00

36.00

39.00

42.00

44.20

47.00

50.00

53.00

55.20

0.00

3.00

6.00

9.00

12.00

15.00

18.00

21.00

24.00

27.00

30.00

33.00

36.00

39.00

42.00

44.20

47.00

50.00

53.00

55.20

0.00

Strain

Fig 13: Comparison Graph between stress and strain for SMPL-3 with 3mm thick Stiffener/Packing plate

Elongation

Fig 16: Comparison Graph between Force and Elongation for all the five samples

54.00

Increase in the Ultimate Tensile Strength

300.00

Sample -2

50x40x1.5 with 2mm stiffner plate

54.00

Increase in the Ultimate Tensile Strength

300.00

Sample -2

50x40x1.5 with 2mm stiffner plate

Thickness of Packing plate mm

Strain

Thickness of Packing plate mm

Strain

53.00

52.00

51.00

50.00

49.00

53.00

52.00

51.00

50.00

49.00

Ultimate strength

Ultimate strength

48.00

47.00

48.00

47.00

0

0

2

2

3

3

4

4

5

5

250.00

200.00

150.00

100.00

50.00

250.00

200.00

150.00

100.00

50.00

without stiffener plate with 2mm stiffener plate

without stiffener plate with 2mm stiffener plate

0.00

0.00

Force kN

Force kN

Stress

Stress

N/mm2

N/mm2

0.0000

0.0075

0.0150

0.0225

0.0300

0.0375

0.0450

0.0525

0.0600

0.0675

0.0750

0.0825

0.0900

0.0975

0.1050

0.1080

0.1150

0.1225

0.1300

0.1370

0.0000

0.0075

0.0150

0.0225

0.0300

0.0375

0.0450

0.0525

0.0600

0.0675

0.0750

0.0825

0.0900

0.0975

0.1050

0.1080

0.1150

0.1225

0.1300

0.1370

Fig 17: Graph between Thicknesses of the Stiffener/Packing Plate to ultimate Strength

Fig 19: Comparison Graph between stress and strain for SMPL-2 with 2mm thick Stiffener/Packing plate

Table-5 Results of All the 1.2mm Thick Channel Specimen

300.00

Sample -3

50x40x1.5 with 3mm stiffner plate

N/mm2

N/mm2

			Thickness		%of
Specimen Net Section		Ultimate Tensile	of Stiffener	Elongatio n at Peak	increas	250.00
No Area		Strength	/Packing	Load	strengt	200.00
			plate		h
mm2		kN	mm	mm	%	150.00
SMPL-1 136.32		34.16	–	31.00	0.00	100.00
SMPL-2	136.32	35.90	2	35.40	4.60	50.00
SMPL-3	136.32	37.50	3	40.80	7.15	0.00
SMPL-4	136.32	40.90	4	41.20	19.60
SMPL-5	136.32	43.50	5	43.80	26.90		Strain

			Thickness		%of
Specimen Net Section		Ultimate Tensile	of Stiffener	Elongatio n at Peak	increas	250.00
No Area		Strength	/Packing	Load	strengt	200.00
			plate		h
mm2		kN	mm	mm	%	150.00
SMPL-1 136.32		34.16	–	31.00	0.00	100.00
SMPL-2	136.32	35.90	2	35.40	4.60	50.00
SMPL-3	136.32	37.50	3	40.80	7.15	0.00
SMPL-4	136.32	40.90	4	41.20	19.60
SMPL-5	136.32	43.50	5	43.80	26.90		Strain

e in

Stress

Stress

0.0000

0.0123

0.0247

0.0370

0.0493

0.0617

0.0740

0.0863

0.0987

0.1110

0.1233

0.1357

0.1394

0.1480

0.1603

0.1727

0.1850

0.0000

0.0123

0.0247

0.0370

0.0493

0.0617

0.0740

0.0863

0.0987

0.1110

0.1233

0.1357

0.1394

0.1480

0.1603

0.1727

0.1850

without stiffener plate with 3mm stiffener plate

Specimens of Series B (1.5 mm Thick Channel Specimen with Three Numbers of Bolts at the Joint)

Fig 20: Comparison Graph between stress and strain for SMPL-3 with 3mm thick Stiffener/Packing plate

Sample -4

Sample -1

50x40x1.5 without stiffner plate

Sample -1

50x40x1.5 without stiffner plate

350.00

300.00

300.00

250.00

200.00

150.00

100.00

50.00

250.00

200.00

150.00

100.00

50.00

300.00

N/mm2

N/mm2

N/mm2

N/mm2

250.00

200.00

Stress

Stress

Stress

Stress

150.00

100.00

50.00

without stiffener plate

without stiffener plate

0.00

0.00

0.0000

0.0060

0.0120

0.0180

0.0240

0.0300

0.0360

0.0420

0.0480

0.0540

0.0600

0.0660

0.0720

0.0780

0.0836

0.0848

0.0860

0.0920

0.0980

0.1040

0.0000

0.0060

0.0120

0.0180

0.0240

0.0300

0.0360

0.0420

0.0480

0.0540

0.0600

0.0660

0.0720

0.0780

0.0836

0.0848

0.0860

0.0920

0.0980

0.1040

0.00

50x40x1.5 with 4mm stiffener plate

0.0000

0.0077

0.0153

0.0230

0.0307

0.0383

0.0460

0.0537

0.0613

0.0690

0.0767

0.0843

0.0920

0.0935

0.0997

0.1073

0.1150

0.0000

0.0077

0.0153

0.0230

0.0307

0.0383

0.0460

0.0537

0.0613

0.0690

0.0767

0.0843

0.0920

0.0935

0.0997

0.1073

0.1150

without stiffener plate with 4mm stiffener plate

Strain

Strain

Fig 18: Graph between stress and strain for SMPL-1 without Stiffener/Packing plate

Strain

Fig 21: Comparison Graph between stress and strain for SMPL-2 with 2mm thick Stiffener/Packing plate

Sample -5

50x40x1.5 with 5mm stiffener plate

350.00

300.00

250.00

200.00

150.00

100.00

50.00 without stiffener plate

with 5mm stiffener plate

0.00

Strain

Sample -5

50x40x1.5 with 5mm stiffener plate

350.00

300.00

250.00

200.00

150.00

100.00

50.00 without stiffener plate

with 5mm stiffener plate

0.00

Strain

Stress

Stress

N/mm2

N/mm2

0.0000

0.0073

0.0147

0.0220

0.0293

0.0367

0.0440

0.0513

0.0587

0.0660

0.0733

0.0807

0.0880

0.0953

0.1027

0.1100

0.1173

0.0000

0.0073

0.0147

0.0220

0.0293

0.0367

0.0440

0.0513

0.0587

0.0660

0.0733

0.0807

0.0880

0.0953

0.1027

0.1100

0.1173

Fig 22: Comparison Graph between stress and strain for SMPL-2 with 2mm thick Stiffener/Packing plate

All Five 1.5 mm Thick channel Samples

without stiffener plate

400.00 With 2mm stiffener plate

350.00	with 4mm stiffener plate With 5mm stiffner plate	80.00
300.00		70.00
250.00		60.00
200.00 150.00 100.00 50.00 0.00 Fig 23	Strain : Comparison Graph between Force and	50.00 40.00 30.00 20.00 10.00 0.00

350.00	with 4mm stiffener plate With 5mm stiffner plate	80.00
300.00		70.00
250.00		60.00
200.00 150.00 100.00 50.00 0.00 Fig 23	Strain : Comparison Graph between Force and	50.00 40.00 30.00 20.00 10.00 0.00

with 3mm stiffener plate

Table-6 Results of All the 1.2mm Thick Channel Specimen

Specimen No	Net Section Area	Ultimate Tensile Strength	Thickness of Stiffener /Packing plate	Elongation at Peak Load	%of increase in strength
	mm2	kN	mm	mm	%
SMPL-1	169.5	42.40	–	42.80	0.00
SMPL-2	169.5	44.90	2	43.20	4.90
SMPL-3	169.5	46.90	3	45.40	9.50
SMPL-4	169.5	48.80	4	48.80	14.0
SMPL-5	169.5	50.40	5	53.60	20.00

Specimens of Series C (1.5 mm Thick Channel Specimen with single Bolt at the Joint)

Sample -A

Stress N/mm2

Stress N/mm2

N/mm2

N/mm2

50x40x1.5 without stiffner plate

0.00

3.40

6.80

10.20

13.60

17.00

20.40

23.80

27.20

30.60

34.00

37.40

40.80

44.20

47.60

51.00

54.40

57.80

61.20

64.60

0.00

3.40

6.80

10.20

13.60

17.00

20.40

23.80

27.20

30.60

34.00

37.40

40.80

44.20

47.60

51.00

54.40

57.80

61.20

64.60

Stress

Stress

0.0000

0.0096

0.0192

0.0288

0.0383

0.0479

0.0575

0.0671

0.0767

0.0862

0.0958

0.1054

0.1150

0.1246

0.1342

0.1438

0.0000

0.0096

0.0192

0.0288

0.0383

0.0479

0.0575

0.0671

0.0767

0.0862

0.0958

0.1054

0.1150

0.1246

0.1342

0.1438

Sample -A

Elongation for all the five samples

Increase in Ultimate Tensile strength

52.00

Strain

Fig 25: Graph 6.46: Between Force and Elongation for specimen SMPL-A without Packing plate

Sample -A & B

50.00

Force kN

Force kN

48.00

46.00

44.00

42.00

40.00

Ultimate strength

120.00

100.00

N/mm2

N/mm2

80.00

Stress

Stress

60.00

40.00

50x40x1.5 with 4mm stiffner plate

38.00

0 2 3 4 5

Thickness of Packing Plate mm

20.00 Sample -A

4mm stiffner

0.0000

0.0124

0.0249

0.0373

0.0497

0.0621

0.0746

0.0870

0.0994

0.1119

0.1243

0.1367

0.1491

0.1616

0.1740

0.1864

0.0000

0.0124

0.0249

0.0373

0.0497

0.0621

0.0746

0.0870

0.0994

0.1119

0.1243

0.1367

0.1491

0.1616

0.1740

0.1864

0.00

Fig 24: Graph between Thicknesses of the Stiffener/Packing Plate to ultimate Strength

Strain

Fig 26: Graph 6.46: Between Force and Elongation for specimen SMPL-B with 4mm packing plate

Table-7 Results of 1.5mm Thick Channel section with single bolt at joint

Specimen No	Net Section Area	Ultimate Tensile Strength	Thickness of Stiffener /Packing plate	Elongation at Peak Load	% of increase in strength
	mm2	kN	mm	mm	%
SMPL-1	136.32	12.85	–	24.00	0.00
SMPL-2	136.32	17.40	4	28.00	35.40

20.00

18.00

Utlimate Force kN

Utlimate Force kN

16.00

14.00

12.00

10.00

8.00

6.00

4.00

2.00

0.00

Increase in Ultimate strength

Ultimate strength

0 4

Thickness of stiffner plate

Bearing + Rupture Failure Observed With 2mm Thick Packing Plate for 1.2, and 1.5mm thick specimen sample

Fig 27: Graph between Thicknesses of the Stiffener/Packing Plate to ultimate Strength

Failure Patterns

Bearing + Rupture Failure Observed

Bearing + Rupture Failure Observed With 3mm Thick Packing Plate for 1.2, and 1.5mm thick specimen sample

Vertical Shear Failure of 1.5mm Thick Sample Specimen using 4mm thick Stiffener/packing plate

Block Shear Failure of 1.5mm Thick Sample Specimen using 5mm thick Stiffener/packing plate

Buckling of Stiffener/Packing plate used 1.5mm Thick Sample Specimen

Bearing + Shear Failure Observed for 1.5mm thick specimen sample with single bolted connection

Discussions and Conclusions

Table-8 Results of 1.2mm Thick Channel section with 3 bolts at the Joints

Size of the Specimen	Thickness of Stiffener /Packing Plate	Ultimate Tensile Strength	% of increase in Strength	Types of Failure observed
mm	mm	(kN)	%
50X40X1.2	–	34.16	0.00	Bearing + Rupture
50X40X1.2	2	35.90	4.60	Bearing + Rupture
50X40X1.2	3	37.50	7.15	Bearing + Rupture
50X40X1.2	4	40.90	19.6	Bearing + Rupture
50X40X1.2	5	43.50	26.9	Bearing + Rupture

Table-9 Results of 1.5mm Thick Channel section with 3 bolts at the Joints

Size of the Specimen	Thickness of Stiffener /Packing Plate	Ultimate Tensile Strength	% of increase in Strength	Types of Failure observed
mm	mm	(kN)	%
50X40X1.5	–	42.40	0.00	Bearing + Rupture
50X40X1.5	2	44.90	4.90	Bearing + Rupture
50X40X1.5	3	46.90	9.50	Bearing + Rupture
50X40X1.5	4	48.80	14.00	Vertical shear
50X40X1.5	5	50.40	20.00	Block shear Failure

Table-10 Results of 1.5mm Thick Channel section with single bolt at joint

Size of the Specimen	Thickness of Stiffener /Packing Plate	Ultimate Tensile Strength	% of increase in Strength	Types of Failure observed
mm	mm	(kN)	%
50X40X1.5	–	12.85	0.00	Bearing + Shear
50X40X1.5	4	17.40	35.40	Bearing + Shear

1. It is observed from the above Tables by the use of packing plates the load carrying capacity of the joint increases. As the thickness of the light gauge section increases the variation in increase of joint strength reduces for

   various thicknesses of Stiffener/packing plates.

2. For 1.2mm thick channel section it is observed that all failures are due to rupture with 3 bolts connection, and also for 1.5mm thick channel section up to 3mm thick Stiffener/Packing plate failure are due to rupture and for 4mm thick Stiffener/packing plate the failure is due to vertical shear failure along the line of vertical connection. With use of 5 mm thick Stiffener/packing plates the failure is due to block shear failure.

3. Hence with the use of thicker plates, bearing failure can be avoided. The increase in the tensile strength for change in each thickness of the Stiffener/packing plate is shown in Table 8 and 9.

4. By the use of lesser thickness of the Packing plate it is observed that the plate buckles along with the plate.

5. For 1.5mm thick channel section with single bolt at 3d end distance, it is observed that the failure is due to bearing and shear failure and the percentage of increase in tensile strength with 4mm thick Stiffener/packing plate is 35.40%.

References

1. Ed.Chaen Wai-Yu, W.W.Cold formed steel Structures Structural engineering Hand Book.

2. By, Xiao-Ling Zhao Tim Wilkinson and Gregory Hancock Cold Formed Tubular Members And Connections January 2005.

3. Experimental Studies on Cold-Formed Steel Angle Tension Members By

   Prabha P, Saravananm, Marimuthu V, and Arulayachandran.

4. Testing of bolted cold formed steel connections in bearing (with and without washers) By James A. Wallace.

5. ColdFormed Steel Frame with

   Bolted Moment Connections By, Bayan Anwer Ali, Sariffuddin Saad, Mo hd Hanim.

6. Cyclic Testing of Cold-Formed Steel Special Bolted Moment Frame Connections By Jong-Kook Hong, Atsushi Sato, Chia-Ming Uang, and Ken Wood.

7. Riveted and bolted jointsBy Munse and Chesson [1] in 1963.

8. Shear lag in bolted angle tension members By Kulak and Wu [7] in 1997.

9. Pan [11] in 2004 studied the prediction of the strength of bolted cold-formed channel sections in tension.

10. Barth et al. [9] in 2002 studied Behavior of steel tension members subjected to uniaxial loading.

11. Bouchair et al. [16] In 2008 studied Analysis of the behavior of stainless steel bolted connections.

12. Failure Modes of Bolted Sheet Steel By Colin A Rogers, Gregory J Hancock.

13. Bolted connections by Prof. S.R.Satish Kumar and Prof. A.R.Santha Kumar.

14. Failure mode of steel in tension member due to change in connection eccentricity and connection length by Diwakar Kumar.