Timber and Steel Design. Lecture 13. Welded Connections I

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1 Timber and Steel Design Lecture 13 Welded Connections I Advantages of Welding Types of Welding Welding Symbols Groove & Fillet Welds Allowable Strength of Welds Slot and Back Welds S U R A N A R E E UNIVERSITY OF TECHNOLOGY Mongkol JIRAVACHARADET INSTITUTE OF ENGINEERING SCHOOL OF CIVIL ENGINEERING

2 Advantages of Welding - Economic : save gusset and spice plates - Applicability : such as connection of steel pipe column - Rigidity & Continuity : strong joint makes one-pieces construction - Easier to make changes during construction - Relative silence Disadvantages of Welding - Fatique - Inspection Cost

3 Welding Process Electric arc produces 3600 o C between section to be welded and the electrode. Filler and Base metal are melt in a weld pool and join into one homogeneous solid Arc is shielded by slag to protect molten metal from air

4 Welding Inspection 1. Visual inspection 2. Liquid penetrants 3. Magnetic particles 4. Ultrasonic testing 5. Radiographic procedures

5 Classification of Welds Types of welds made: Fillet welds Groove welds Slot welds Plug welds Fillet welds

6 Classification of Welds Positions of welds: Vertical weld Horizontal weld Overhead welds Flat weld

7 Types of joint: Lap Butt Tee Edge Corner

8 Throat size F I L L E T W E L D Troat size = Leg size Root Leg size Leg Root Weld face Theoretical face Theoretical throat Leg Weld face Theoretical throat (a) Convex (b) Concave

9 ก ก ก ก T S(E) F A R ก L-P ก

10 Reference line & Arrow Arrow side & Other side below=arrow and above=other arrow side other side Weld-all-around The open circle at the arrow/reference line junction

11 ก & ก ก ก ก

12 Fillet Welds - For lap joints, corner joints and T joints - Triangular in cross-section Transverse fillet weld Longitudinal fillet weld

13 Example of Fillet Welds 8 mm 8 8 mm Symbol As built 10 mm 6 x 10 6 mm Symbol As built

14 Example of Fillet Welds mm 8 mm 15 cm Symbol As built 6 mm mm 5 cm 10 cm Symbol As built

15 Groove Welds - Commonly used to make edge-to-edge joints 8 mm max. (a) Reinforcement (b) (c) Reasons for having reinforcement: (a) To take care of pits and other irregularities (b) Too difficult to make weld surface equal to material Land (a) (b) Spacer (c) (d)

16 Types of Groove Weld Square groove weld "groove" is created by either a tight fit or a slight separation of the edges. The amount of separation, if any, is given on the weld symbol. 3 mm 3 V-groove weld, in which the edges of both pieces are chamfered, either singly or doubly 3 60 o 60 o 60 o 60 o 3 mm

17 If the depth of the V is not the full thickness--or half the thickness in the case of a double V--the depth is given to the left of the weld symbol o o 60 o 6 mm 60 o 10 mm 10 mm 60 o The bevel groove weld, in which the edge of one of the pieces is chamfered and the other is left square. 40 o 40 o

18 15 60 o The U-groove weld, in which the edges of both pieces are given a concave treatment. 15 mm 60 o The J-groove weld, in which the edge of one of the pieces is given a concave treatment and the other is left square o 40 o 15 mm

19 The flare-v groove weld, commonly used to join two round or curved parts. The intended depth of the weld itself are given to the left of the symbol, with the weld depth shown in parentheses. 25 (16) The flare bevel groove weld, commonly used to join a round or curved piece to a flat piece. 20 (10) 20 mm 10 mm 20 mm 10 mm

20 Plug & Slot Welds - Used to join overlapping members, one of which has holes in it. - Weld metal is deposited in the holes and penetrates and fuses with the base metal (3) (2) Det. B 25 Det. B 8 cm mm 12 cm 25 mm 8 cm 15 mm Section thru plug Section thru plug

21 ก 45 o P Throat = leg P (a) (b) ก

22 ก Leg Throat 45 o For equal leg fillet weld: Throat = Leg sin 45 o = Leg Leg : F v = 0.30 F u ก : P = F v (0.707) ( E60: F u = 60 ksi = 4,200 kg/cm 2 E70: F u = 70 ksi = 4,900 kg/cm 2

23 13.3 ก (ก.ก./.) (..) E E E70 leg 5 mm: (0.5) (0.3) (4,900) = 520 kg/cm

24 ก 1) Min. length of fillet weld 4 leg size 2) Max. weld size : - t 6 mm, weld size = t x 4 x t = Material thickness - t > 6 mm, weld size = t - 2 mm Weld size 3) Min. weld size : Material thickness t 6 mm Min. size 3 mm 6 mm < t 12 mm 5 mm 12 mm < t 19 mm 6 mm t 19 mm 8 mm

25 ก ( ) 4) End return length 2 weld size P End Return P 5) Longitudinal fillet: weld length weld distance weld distance 20 cm Weld distance P Weld length 6) Min. lap joint 5 thickness 25 mm P t P

26 13-1 ก A36, E70 ก cm PL 2 x 20 P 20 cm P 10 mm ก 10.. = 1,040 กก./. = ( )(1,040)/1,000 = 52 ก = (2 x 20)(0.60 x 2.5) = 60 P = 52

27 13-2 ก A36 E70 ก ก ก ก ก 1 x 10. PL 1 x 10 P P P = (1.0)(10)(0.6)(2.5) = 15 = 10 2 = 8., ก = ก = 830 กก./. ก = 15(1,000)/830 = 18. ก ก 2 x 0.8 = 1.6. ( 2.) = 18/2-2 = 7.0. ( 10.)

28 Slot and Back Welds when welds length not sufficient L= load (width)(allowable stress) ก ก : 1 1. ก ก ก ก 8. ก 2 2. ก ก 16., ก ก ก ก 16., ก ก ก ก P Weld on back of channel L 15 cm Slot weld 4 P

29 13-3 ก ก C380x54.5 ก ก ก ก 80 E70 ก 15. ก ก C380x54.5 (t w =10.5 mm) Slot weld 80 t 80 t ก ก Weld on back of channel 15 cm =t w 2 = = 8.5. ( 8..) ก 8. = 830 กก./. ก = 80(1,000)/830 = 96. > 68.

30 ก = = ก ก = 2 1/4 x = (2.25)(t w ) = 2.25(10.5) = 24. ( 25.) ก ก 8.=(830)( )/1,000=54.4 ก ก = = 25.6 ก = 25.6/(2.5 x 0.30 x 4.9) = 7.2. ( 7.5.) ก = 10(1.05) = > 7.5. OK 2.5 x 7.5.