EXPERIMENTAL ANALYSIS OF COLD- FORMED STEEL MEMBERS SUBJECTED TO TENSION LOAD

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 6, June 17, pp , Article ID: IJCIET_8_6_67 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed EXPERIMENTAL ANALYSIS OF COLD- FORMED STEEL MEMBERS SUBJECTED TO TENSION LOAD Paul Makesh A Assistant Professor of Civil Engineering, Dr. M.G.R Educational and Research Institute University, Chennai, India Arivalagan S HOD of Civil Engineering, Dr. M.G.R Educational and Research Institute University, Chennai, India ABSTRACT Cold-formed steel members with bolted end connections are frequently used in a variety of structures such as trusses, transmission, towers etc. This research work deals with the details of an Experimental and Numerical Analysis of shear lag on cold-formed steel section subjected to tension. This analysis carries single angle sections of 2 mm and double angles sections of 2 mm under plain (without ped) and with ped conditions subjected to tension. The papers present the load carrying capacity of single angles lipped section increases by 21% and double angles by 24% compare with plain angles. Key words: Tension Members; Cold-Formed Angles; Net Section, Block Shear; Shear Lag Effect. Cite this Article: Paul makesh A and Arivalagan S Experimental Analysis sf Cold- Formed Steel Members Subjected to Tension Load. International Journal of Civil Engineering and Technology, 8(6), 17, pp INTRODUCTION In India the use of cold formed steel sections is growing significantly, which is primarily used in storage racks, bracing members, hangars for roofs and trusses. Angle tension members are frequently encountered as principal structural members in trusses and lateral bracing system in general construction. The efficiency of angle tension members is reduced due to the coupled effects of connection eccentricity, stress concentration and shear lag. Sonal Banchhor et al [1] (16) were reported behavior of cold formed steel bolted angle tension members. The main objective of this study is to investigate the behavior of cold steel single and double angle subjected to tension. Experimental and theoretical investigations were editor@iaeme.com

2 Paul Makesh A and Arivalagan S carried out for single angle, double angle connected to opposite sides of gusset plates and double angle connected to same side of gusset plates and the whole cross-section may not be fully utilized which causes a reduction in the net section efficiency. This loss of efficiency of the section is due to shear lag. Padma Priya [2] (15) conducted experimental work on Sixteen single plain and lipped angle specimens and thirty two numbers of double angle specimens connected to the same side and opposite side of the gusset plate. The experimental loads are compared with ultimate load calculated using BS 595 (Part V)-1998, and AS/NZS 46:5. Most of the single and double angles failed by net section fracture failure and the outstanding leg are subjected to local bend due to shear lag effect. RajaRathinam et al., [3] (15) examine the main objective of this research is to understand the behavior and strength of cold formed steel HAT sections connected at ends only through gusset plate, causing shear lag at the end connections and thus develop a method for evaluating the net section rupture strength of such members. H. The [4] et al.,(13) presents paper to examines the accuracy of equations specified by the North American and Australasian steel structures codes for determining the net section tension capacity of a channel brace. They points out that there are three distinct factors affecting the net section efficiency of a coldformed steel channel brace bolted at the web. Chi-Ling Pan [5] (4) carried experimental work on cold form channel section to study the effect of connection length, bolt arrangement and tested a series of bolted cold-formed channel sections to study the shear lag effect. Pan concluded that the ratio of connection eccentricity to connection length, x /L, and the ratio of unconnected elements to connected elements, Wu/Wc, might be the two factors which can mainly influence the tensile strength of channel sections. This paper presents the effect of shear lag on the tensile capacities of cold formed angles. Practically angles are connected with gusset plates through one leg and due to this there will be non- uniform stress distribution due to eccentrically applied load. The unconnected portion of a section is not fully effective in carrying the applied load. Thus, the whole cross-section may not be fully utilized, which causes a reduction in the net section efficiency. Shear lag phenomenon is illustrated the unequal stress distribution, near to the connection region when subjected to tension. To simplify the design procedure of tension members, considerable amount of research has been carried out and some of their results are already incorporated in various international codes of practice. All the above investigations were made for the hot rolled double angle sections. There were only limited investigations for cold-formed steel members. The present investigation aims to study the behavior of cold-formed steel angle members. 2. EXPERIMENTAL INVESTIGATION A totally thirty six experiments were conducted on single and double angle specimen of 2 mm thickness which were connected to the gusset plate under eccentric tensile loads. The specimens were fabricated from 2 mm thickness cold- formed steel sheets of grade ST by bending and press breaking operations. The tensile coupon test as per ASTM A37-3a specification shown in Fig 1, to determine the material properties of the steel plate specimen and the stress Vs strain curve was plotted as shown in Fig 2. The reading were tabulated of yield stress, ultimate stress, modulus of elasticity and elongation obtained for these thicknesses of cold formed steel sheets as given in Table editor@iaeme.com

3 Experimental Analysis of Cold-Formed Steel Members Subjected to Tension Load Fig 1 Tensile coupon test specimen Fig 2. Stress Vs. strain graph and tensile coupon specimen diagram Table 2 Value of test result of steel member Thickness of steel sheet 2mm Yield Stress in MPa (f y) 2N/mm 2 Ultimate Stress in MPa (fu) 252N/mm 2 Modulus of Elasticity 2.3x 5 N/mm 2 fu/fy 1.14 Percentage elongation % The specimens were tested as two different section configurations namely single angles and double angles. The single angle specimens were connected with their larger leg to end gusset plates of mild steel of 8mm thickness. Ordinary black bolts of mm diameter are used as connectors for specimens made from 2mm. In case of specimens fabricated from 2mm thickness sheet mm diameter bolts were used. The double angle specimens were connected with their larger leg with two mild steel gusset plates of 8mm using ordinary black bolts of mm diameter. The gusset plates were not reused for single angle specimens and were reused for double angle specimens. The required numbers of bolts are calculated for all specimens and were provided according to the design procedures. All the specimens were fabricated for a length of 5mm. The width of the gusset plate was kept mm more than the width of the connected leg. The length of gusset plate was provided according to the requirement of pitch and edge distance as per Indian code of practice. All the members were connected with gusset plate to the larger side by means of bolts. The details of the fabricated single plain angle with and without are present in Fig 3(a) and 3(b).The double angle on same side and opposite side specimens are present in Fig 3(c) and 3(d).The cold formed steel sheet and sheet cutting machine are shown in Fig 4(a). Marking the Specimen with Dimension and Cold formed steel angles after putting holes are shown in Fig 4(b).The experimental set up is in universal testing machine are testing specimen arrangement in single plane angle and back to back on same side of double angles are shown in Fig 4(c), and Fig 4(d) shows testing specimen and guest plate. The specimens were tested in Universal Testing machine of 4kN and KN capacity. The specimens were fixed vertically by gripping the gusset plates. The load was applied eccentrically through the gusset plates. Demec gauge was used for measuring the elongation for a gauge length of mm. The load is gradually applied with suitable increments from control panel and at each increment of loads corresponding elongation was taken. The yield, ultimate and breaking loads were also observed. The distance of separation between gusset plate and test specimens was also recorded. The procedure is repeated till the failure stage is reached in all specimens. The observed yield load and ultimate load of the specimens tested are recorded editor@iaeme.com

4 Paul Makesh A and Arivalagan S Figure 3 (a) Single angle without Figure 3 (b) Single angle with Figure 3(c) Double angle on same side without Figure 3(d) Double angle on opposite side without Figure 4 (a) Cold formed steel sheet Figure 4 (b) Marking the Specimen with Dimension Figure 4 (c) Angles fixed in universal testing machine (UTM) Figure 4 (d) Guest Plates Figure 5 Single angle without 5x5x2 (Ansys) editor@iaeme.com

5 Experimental Analysis of Cold-Formed Steel Members Subjected to Tension Load 3. RESULT AND DISCUSSION 3.1. Ultimate Load-Carrying Capacity A total of thirty six specimens have been tested by varying the angle sizes, number of bolts and the bolt pitch distance. All the specimens have been designed to undergo net section rupture failure. The specimens are equal angles of dimensions 5x5mm, 6x6mm and 7 x 7 mm and they have equal length 5mm and thickness 2 mm and unequal angle of 5x25mm, 6xmm and 7x3 mm and they have equal length 5mm and thickness 2 mm respectively. The experimental ultimate loads for all the cold-formed steel single angles are presented in Table 3. It is observed that in the case of single equal lipped angles the average increase in ultimate load is 1. times greater than that of single equal plain angles. In the case of single unequal lipped angles the average increase in ultimate load is found to be 1.24 times greater than that of single unequal plain angles. The average increase in ultimate load for double equal lipped angles connected to opposite side of the gusset plate is 1. times greater than that of double equal plain angles connected to the same side of the gusset plate. In the case of double unequal lipped angles connected to opposite side of the gusset plate the average increase in ultimate load is 1.24 times greater than that of double unequal plain angles connected to the same side of the gusset plate. From this research observed that when the cross-sectional area increases, the load carrying capacity increases. Table 3 Ultimate Load-Carrying Capacity Equal angles Un Equal angles S.No Description Single angle without Single angle with Double angle on opposite side without Double angle on opposite side with Double angle on same side without 6 Double angle on same side with Size of specimen ( bxdxt) Yield Load (Pyl) kn Ultimate Load (PUl) kn Design Strength ( (PDS) Size of Specimen ( bxdxt) Yield Load (Pyl) kn Ultimate Load (PUl) kn 5Design Strength ( (PDS) 5x5x x25x x6x xx x7x x35x x5x x25x x6x xx x7x x35x x5x x25x x6x xx x7x x35x x5x x25x x6x xx x7x x35x x5x x25x x6x xx x7x x35x x5x x25x x6x xx x7x x35x editor@iaeme.com

6 Paul Makesh A and Arivalagan S 3.2. Load vs Deflection The typical load versus deflection has shown in Fig 5(a) to 5(f) to Fig 18 shows the behavior for single angles with and without lips and double angles. From the graphs, it is observed that the ultimate load carrying capacity increases as the cross-sectional area and number of bolts in the connection increases. It is also observed that when the rigidity of the connection increases the stiffness of the member also increases. Load KN x5x2 6x6x2 7x7x2 Load KN x25x2 6xx2 7x35x2 Figure 5 (a) Load vs Deflection behavior of single plain angle specimen without Figure 5 (b) Load vs Deflection behavior of Double angle same side specimen -without Load KN x25x2 4 6xx2 7x35x2 Load KN 5 5X5X2 6X6X2 7X7X2 Figure 5 (c) Load vs Deflection behavior of unequal single plain angle specimen - without Figure 5 (d) Load vs Deflection behavior of Double angle opposite side specimen - with lip x25x2 6xx2 7x35x x25x2 6xx2 7x35x2 Figure 5 (e) Load vs Deflection behavior of unequal single plain angle specimen - with lip Figure 5 (f) Load vs Deflection behavior of unequal double angle specimen - with lip editor@iaeme.com

7 Experimental Analysis of Cold-Formed Steel Members Subjected to Tension Load 3.3. Modes of Failure The modes of failure of all single and double angle specimens were noticed during testing. Generally tearing failure, block shear failure, net section fracture failure were observed as in Figure 6(a) to 6(d).As the load was being applied, the corners of the angle at the two ends gradually separated from the gusset plates for both single and double angle members. Thus, a gap was formed between the corner of the connected leg and the gusset plate. This is referred as local bending. The mode of failure depends upon the cross section and rigidity of connection. During the loading process, the gusset plates of double angle members remained straight. However, in the case of single angles the gusset plate and the angles bent during loading. This is due to eccentrically applied load. This kind of bending is referred as global bending. As the load is applied, the angle and plate can be seen deforming; the plate edges bend over and the bolt hole undergo plastic deformation. Finally, the plate tears along a horizontal line that is coincident with the widest point of the bolt hole in tearing failure. The design strength of tension members are not always controlled by factor of safety or by the strength of the bolts or welds with which they are connected. After necking, the critical cross-section was torn out from the edge of the connected leg to the hole then to the corner of the angle. The specimens carried some amount of load beyond the ultimate load and until failure. It was noted that all the bolts were still tight after completion of the tests. This indicates that the bolts were not highly stressed during the tests. The outstanding leg which is subjected to compression experiences, local buckling nearer to the supports. Mode of failure as shown in Table 4. Table 4 Mode of Failure S. No Description 1 Single angle without 2 Single angle with 3 4 Double angle on opposite side without Double angle on opposite side with Size Equal angles Mode of failure angles Size Unequal Angles Mode of failure angles 5x5x2 Net Section 5x25x2 Net Section 6x6x2 Block Shear 6xx2 Block Shear 7x7x2 Net Section 7x35x2 Block Shear 5x5x2 Block Shear 5x25x2 Net Section 6x6x2 Net Section 6xx2 Block Shear 7x7x2 Net Section 7x35x2 Net Section 5x5x2 Block Shear 5x25x2 Net Section 6x6x2 Block Shear 6xx2 Block Shear 7x7x2 Net Section 7x35x2 Net Section 5x5x2 Block Shear 5x25x2 Net Section 6x6x2 Block Shear 6xx2 Net Section 7x7x2 Net Section 7x35x2 Net Section 5 6 Double angle on same side without Double angle on same side with 5x5x2 Block Shear 5x25x2 Block Shear 6x6x2 Net Section 6xx2 Net Section 7x7x2 Block Shear 7x35x2 Block Shear 5x5x2 Net Section 5x25x2 Block Shear 6x6x2 Block Shear 6xx2 Net Section 7x7x2 Net Section 7x35x2 Block Shear editor@iaeme.com

8 Paul Makesh A and Arivalagan S Figure 6 (a) Single Plain angle with (Tearing-Local bucking) Figure 6 (b) Double Angle on same side with out (Global buckling) Figure 6 (d) Single Plain angle without (Local Buckling-Net section) Figure 6 (d)block shear Failure 4. CONCLUSIONS The presence of lip increases the load carrying capacity of single angles by 21% and increases by 24% for double angles. From this study it was recorded as the load carrying capacity increases for connected to the opposite side of the gusset than the connected to same side REFERENCES [1] AISI commentary (7), Design of Cold-formed Steel Structural Members, North American Specification. [2] AS/NZS: 46 (5), 'Cold-formed Steel Structures', Australia / New Zealand Standard. [3] BS: 595-Part 5 (1998), Structural Use of Steelwork in Building-Code of practice for design of cold-formed thin gauge sections', British Standards Institution. [4] Chi - Ling pan, (4), Prediction of the strength of bolted cold - formed channel sections in tension, Thin walled structures, Volume 42, pp [5] Chi-Ling Pan,(6),Shear Lag Effect on Bolted L-Shaped Cold-Formed Steel Tension Members, Eighteenth International Specialty Conference on Cold-Formed Steel Structures Orlando, Florida, U.S.A, October 26 & 27, pp [6] Gupta L.M and Mohan Gupta, (4), "Evaluation of stress distribution in bolted steel angles under tension", Electronic Journal of Structural Engineering, Vol.35, Issue 4, pp 17-. [7] Gupta L.M and Mohan Gupta (5), "Limit state design of bolted steel angles under tension", Journal of Structural Engineering, Vol.31, No.4, pp [8] H. Teh, and Benoit P. Gilbert, (13), Net Section Tension Capacity of Cold-Reduced Sheet Steel Channel Braces Bolted at the Web, Journal of Structural Engineering, 139(3), pp [9] H. Teh and Benoit Gilbert, (14), Net section tension capacity of equal angle braces bolted at different legs, Journal of Structural Engineering, 14 (6), pp [] Prabha P, Saravanan M, Marimuthu V And Arul Jayachandran S,(11), Experimental Studies on Cold-Formed Steel Angle Tension Members, Journal of Recent Researches in Geography, Geology, Energy, Environment and Biomedicine,Vol.1, Issue. 4, pp editor@iaeme.com

9 Experimental Analysis of Cold-Formed Steel Members Subjected to Tension Load [11] Palden Humagai, Pavan Kumar Peddineni and C. Raja Mallu, Manual Analysis and Design of Post Tensioned Pre-Stressed Concrete T-Beam Segment Bridge Using Proto- Type Model. International Journal of Civil Engineering and Technology, 8(4), 17, pp [12] Kamal Padhiar, Dr. C.D. Modhera and Dr. A. K. Desai, Comparative Parametric Study for Post-Tension Flat Slab and Flat Slab with Drop System. International Journal of Civil Engineering and Technology, 8(5), 17, pp [13] Jaghan S and Padmapriya R, (15), Behavior of Bolted Cold Formed Steel Channel Tension Members, Asian Journal of Civil Engineering (BHRC), 17 (1), pp [14] Kulak, G. and Wu, E. (1997). "Shear Lag in Bolted Angle Tension Members, Journal of Structural Engineering, Volume 123, Issue 9, pp editor@iaeme.com