Welds in Shear, Bending, Torsion and Axial Loading

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1 Welds in Shear, Bending, Torsion and Aial Loading User Notes or The Analsis & Design o Weld Groups Subjected to Simultaneous Shear, Bending, Torsion and Aial Loading WeldCalc b Dr Shaiq U.R. Khan BEng (Civil), MEng, PhD, PE, CEng, FStructE Februar 010 ntroduction WeldCalc analses an coniguration o multi-linear weld lengths in an X-Y plane. The loads can be shear, moment, torsion and aial applied simultaneousl. WeldCalc calculates the induced stress at each node and identiies the node most highl stressed. t also calculates the magnitude o load resisted b each length o weld in the, and direction. n order to asses adequac o the weld proiles subjected to stresses in 3 directions, WeldCalc oers 3 options or calculating the resultant equivalent stress. The 1st option calculates the equivalent stress in shear, the nd in aial tension or compression and the 3rd a vector sum SRSS. A weld group can have up to 30 Nodes or 9 weld lengths. The line o weld lengths can be continuous or discontinuous. Each continuous series o weld lengths is termed as a Part and is given a reerence number starting rom 1 onwards. A weld group can have up to 15 parts connecting 30 nodes in an multi-linear pattern. Loading the Template on to our Computer WeldCalc is supplied as an Ecel Template, having.xlt as its ilename etension. You can use WeldCalc b opening its ile directl or coping it into the Microsot Oice older or its Templates. Consult Microsot Oice documentation or the path to this older. When opening the WeldCalc ile, Ecel issues a routine Warning about running Macros and prompts whether or not to load them. Answer YES to Load and Enable Macros. WeldCalc incorporates VB Macros and to allow our computer to use them is vital or its operation. Codes o Practice WeldCalc is a weld analsis program or nternational use. t is not dependent on the use o an speciic code o practice. However, to illustrate the use o WeldCalc and to discuss various weld details or design purposes,reerence has been to the British Standard Code o Practice BS : 000 Part 1, Structural Use o Steelwork in Building1. File: WeldCalc Tab: Notes Page 1/8 Date Printed: 16/05/010

2 Welds in Shear, Bending, Torsion and Aial Loading Using WeldCalc n addition to Job normation in the heading part, describe Applied Loads, Design Strength and details or each weld length. The applied loads can be actored or unactored depending upon the speciied design strength o welds. The weld details required are: part-number, coordinates and and throat thickness at each node. WeldCalc also incorporates a data store acilit. normation or up to and more than 10,000 weld groups is kept in the worksheet STORE. Clicking the "Store Eisting Data" command button in the top row, saves the current weld group data. Clicking the "Get Stored Data" button retrieves the previousl saved inormation. n order to save or retrieve a weld group inormation, the Template uses a Datastore Number. This number starting rom 1001 upwards must be speciied to store and or retrieve a weld group data. PLEASE NOTE that storing weld group data does not save the Ecel File. To ensure saving data to our hard disk, ou must use Ecel File, Save Pull Down Menu Option in the usual Windows procedure. Likewise, saving Ecel ile to hard disk does not store the eisting screen data into the worksheet "STORE". To do so, ou must use "Store Eisting Data" button beore saving the Ecel ile to hard disk. Database o Weld Group Details and Applied Loading: Worksheet STORE n each WeldCalc ile, weld connection details and applied loads can be stored or well ove 10,000 weld groups i required. Starting rom a minimum o 00 members, data rows are added and or deleted in multiples o 10 and up to 1000 rows at a time. The maimum limit is a storage o 10,000 weld groups in one ile. Each weld group is reerenced b a number in a range starting rom 1001 upwards. All inormation is kept in the worksheet STORE and is available to the user or use in the design process. A casual Ecel user generall does not need to tweak or amend the STORE worksheet. At the risk o upsetting this inormation, however, one can beneit b generating and using this inormation b Cop, Paste-Special-Values and Fill-Down commands o Ecel. t is strongl recommended that Cut Command o Ecel is not used on this worksheet; using this command aects the worksheet laout and can disrupt the working o WeldCalc. Similarl the use o Paste command (as opposed to Paste-Special-Values command) can override the helpul cell ormats. An eperienced Ecel User can emplo various Ecel eatures to tweak or manage this inormation. For eample, user reerence, title, design strength values can be generated via Cop, Paste-Special-Values and Fill Down eatures o the spreadsheet. Utilisation Ratio Limit and Values or Each Weld Proile The data worksheet "Store" includes a column or displaing the utilisation ratio or each weld proile. The ratio values are calculated when a weld proile data is stored. The check limit or this ratio is generall 1 but it can be changed to an desired numerical value. The cell speciing this ratio limit is in row 1 at head o the ratio column. When the utilisation ratio or an weld proile eceeds this limit, the weld proile title and its value cell File: WeldCalc Tab: Notes Page /8 Date Printed: 16/05/010

3 Welds in Shear, Bending, Torsion and Aial Loading utilisation ratio or an weld proile eceeds this limit, the weld proile title and its value cell changes to red. Hence all overstressed weld proiles become visible at a glance. Auto Analsis o Weld Groups Use this acilit to analse and or print all weld groups b a single click o Auto Analse/Print Button in the top right corner o the screen. To use this acilit, two columns coloured in ellow to the right o the Store worksheet are provided. One column is headed Analse Y? and the other as Print?. The Auto Analse/Print Button is located at the top o these two columns in the Worksheet Store. Entering Y in these two columns, signiies that the respective weld group in a given row need to be analsed and or printed. Leaving the cells blank signiies that respective weld groups are not to be analsed or printed. Auto Analsis acilit is useul when all or a selected ew weld groups are to be analsed and or printed ater updating the weld group details and loading in the STORE worksheet. Design o Fillet Welds The vector sum o the design stresses due to all orces and moments transmitted b the weld should not eceed the design strength. When this design strength is shear, the valid option or the equivalent stress is Von Mises Shear", When using BS 5950 the design strength pw under actored loads is 0.0 kn/mm or S75 Grade, 0.50 kn/mm or Grade S355 and 0.80 kn/mm or Grade S460 (Table 37, Cl 6.8.5). As these design values are about 0.6 times the applicable weld ield stresses, BS 5950 strength appear to represent the weld strengths in shear. Throat Thickness The sie o the illet is epressed b the length o the leg o the largest isosceles right angle triangle that can be inscribed on the outline o the weld. The weld usuall has equal legs, but conditions ma require the use o weld with unequal legs. Thickness o the weld is measured b the perpendicular drawn rom the intersection o the legs on to the hpotenuse, as shown in the igure. This is called the throat thickness or simpl Throat o the illet weld. The strength o the illet welds is related to the throat thickness and depends upon the angle between the usion aces. This relationship between the leg length s and the throat thickness a or various angles between usion aces is given as ollows: 60 o to 90 o, a = 0.7 s 91 o to 100 o, a = 0.65 s 101 o to 106 o, a = 0.6 s 107 o to 113 o, a = 0.55 s 114 o to 10 o, a = 0.5 s Sign Convention Weld sie s Penetration a, throat thickness M F, M M F, +ve values F, Sign Convention The sign convention is shown on the screen and in the printed output via sketch as shown. The applied point loads F, F and F are positive when acting in the direction o aes. File: WeldCalc Tab: Notes Page 3/8 Date Printed: 16/05/010

4 Welds in Shear, Bending, Torsion and Aial Loading The applied moments M, M and M are positive Anti-clockwise when viewed looking into the origin. Properties o Fillet Welds The shape o illet welds is usuall triangular. As shown in the sketch, the outer surace o a weld is reinorced, i.e. made conve, but in strength calculations this reinorcement is ignored. The ailure o welds usuall occurs in the throat section. This area is thereore used in strength calculations o welded joints. t is equal to the summation o the throat thickness multiplied b the weld length. Other weld properties are also based on the throat area o welds. These properties are, and. The origin or these properties is at centroid o the welds and the are calculated b using, coordinates and the throat thickness deined b the user or each node. Formulae or Stress Components At each node, the components o stress in, and direction are calculated b elastic analsis, given b: F M = A F M + M = A Formulae or nduced Maimum Design Stress At each node, the equivalent stress e is calculated using component stresses and in shear and in aial tension or compression. The maimum o these e values is then chosen and placed in the bottom cell. The equation used or calculating e depends upon the method selected b the user via a pull down menu. Three options are available described in the adjacent. Option 1 Von Mises Shear is generall meant or comparing the design strength in shear. The calculated equivalent stress represents a stress value in shear. n general, the design strength relevant to this case roughl equal to p/sqrt(3). For eample, a value o 0.55 Us in BS5950-1:000, which implicitl assumes that the weld stress is in shear. When designing illet welds to BS5950, the design weld stresses happen to be: p = 0 N/mm or S75, p = 50 N/mm or S355 and p = 80 N/mm or S460. Option Von Mises Aial is generall meant or comparing the design strength in tension or compression. The calculated equivalent stress represents a stress value in tension or shear. n general, the design strength relevant to this case roughl equal to the ield stress p. Designing o illet welds to Eurocode 3 involves the use o equation emploed in this option. Option 3 SRSS F M = + A p p e e e + Option = Option = Option = M 1 : 3 ( + + M Von + SRSS + Mises ) : Von Mises 3 : Shear Aial File: WeldCalc Tab: Notes Page 4/8 Date Printed: 16/05/010

5 Welds in Shear, Bending, Torsion and Aial Loading Option 3 SRSS represents square root o the sum o square values. This option simpl calculates the resultant stress based on, and stress components. Detailing Requirements or the Design o Welds The ollowing requirements are based on recommendations contained in Cl 6.7. BS : The are intended or guidance onl. A user ma emplo another code o practice or such requirements. End Connections Where the ends o an element is connected onl b a longitudinal illet, the length o each weld should be, L >= T w, the transverse spacing Eective Length The eective length o a run o illet weld should be taken as the over all length less one leg length, s, or each end which does not continue round the corner or a length o s, as shown in the sketch. The eective length should be: L >= 4 s End returns Welds terminating at the ends or sides should be returned continuousl around the corners or a distance >= s (the weld leg length), wherever it is practicable. This detail is particularl important or welds in tension due to bending. Lap Joints Minimum lap should be: L >= 4t, where t is thickness o the thinner part. Single illet weld should onl be used where parts are restrained to prevent opening o the joint. Weld end return >=s L >=Tw L >=4 t L >=4 s 1 1 L >=Tw L >=4t L >=4s s, leg length Length s ignored in eective length L s, ignored in L Tw transverse weld spacing Welded end connection showing End Returns Lap & Eective Length Requirements Section 1-1 t Maimum Fillet Weld Sie The maimum leg length or a illet weld is to be limited to the plate thickness less mm. Hence i the plate thickness is 1 mm, the maimum illet weld sie would be 10 mm. This limit helps ensure that edge o the plate being welded is not burned and provides a visual weld edge or checking its thickness. Fillet Weld Sie or Full Strength Considering that the throat thickness controls the strength o illet welds, the required sie o two illet welds is * plate thickness. Hence i the plate sie is 15 mm, the leg length o two illet welds would be 0.707* 15 = mm. This provides a total throat thickness o *0.707* = 15 mm, which is equal to the plate thickness. File: WeldCalc Tab: Notes Page 5/8 Date Printed: 16/05/010

6 Welds in Shear, Bending, Torsion and Aial Loading throat thickness o *0.707* = 15 mm, which is equal to the plate thickness. Describing Weld Group Coniguration First estimate throat thickness or each length o weld in the joint and also select a convenient point as origin or deining coordinates. Weld group coniguration is then deined b giving part-no, -coordinate, -coordinate and throat thickness at each node. Start using part-no rom 1 onwards at irst node. When the line o welds becomes discontinuous or the throat thickness changes, increment the part-no b one or the node at net weld length. Si eamples are included in the worksheet STORE o this template. The can be viewed or recalled on the screen b giving their Datastore number rom 1001 to 1006 ater clicking Get Weld Group Data button. To illustrate data preparation, details o the irst 4 eamples are eplained below via sketches. Eample 1 This eample has 4 parts and 8 Nodes. t represents junction o a UB section welded at its top and bottom langes and on either side o its web. To describe illet weld legs o 8 and 6 mm, the throat thickness o the horiontal and vertical weld lengths are 5.6 and 4. mm respectivel. Weld Details: Part, Node, Coordinates & Throat Thickness Part1, Node 1: -86.6, 18.3, Throat 5.6 Part1, Node : +86.6, 18.3, Throat 5.6 Part, Node 3: -86.6, -18.3, Throat 5.6 Part, Node 4: +86.6, -18.3, Throat 5.6 Part3, Node 5: -5, +140, Throat 4. Part3, Node 6: -5, -140, Throat 4. Part4, Node 7: +5, +140, Throat 4. Part4, Node 8: +5, -140, Throat 4. Applied Loads: F = 88 o = 50 mm 88 kn 1 Part Part 3 Part Part Eample This eample represents a circular weld o 400 mm diameter and 8 mm illet weld. t has 1 Part and 5 Nodes. The irst and the last node numbers 1 and 5 are phsicall coincident. Onl selected nodes and part data have been shown below or brevit. Weld Details: Part, Node, Coordinates & Throat Thickness Part 1, Node 1: 0, 00, Throat 5.6 Part 1, Node 7: 00, 0, Throat 5.6 Part 1, Node 13: 0, -00, Throat 5.6 Part 1, Node 19: -00, 0, Throat 5.6 Part 1, Node 5: 0, 00, Throat 5.6 Applied Loads: F = 450 = 100 mm & = 50 mm 450 kn Node 19 Nodes 5, 1 50,000 knmm Node 7 File: WeldCalc Tab: Notes Page 6/8 Date Printed: 16/05/010

7 Welds in Shear, Bending, Torsion and Aial Loading 50,000 knmm F = 450 o = 100 mm & o = 50 mm M = 50,000 knmm N Node 13 Eample 3 This eample represents a closed trapeoidal weld o 5 mm illet weld. t has 1 Part and 5 Nodes. The irst and the last node numbers 1 and 5 are phsicall coincident. Weld Details: Part, Node, Coordinates & Throat Thickness Part 1, Node 1: 0, 170, Throat 3.5 Part 1, Node : 0, 0, Throat 3.5 Part 1, Node 3: 70, 0, Throat 3.5 Part 1, Node 4: 70, 100, Throat 3.5 Part 1, Node 5: 0, 170, Throat 3.5 Applied Loads: F = 49.5 o = 49.9 mm Nodes 1, kn Node 4 Eample 4 Node Node 3 This eample is an open trapeoidal 8 mm illet weld having a 5.6 mm Throat Thickness. t has thereore1 Part and 4 Nodes. As shown in the sketch below, the weld group represents a 1764 RSC (rolled steel channel) welded to the inside lange o a UC (universal column) section at an angle. Acting at Centroid o the RSC, the applied aial load o F = 300 kn has an eccentricit o Xo = 6.5 mm and Zo = 19.4 mm. The weld group is thereore subjected to direct shear, bending and torsion simultaneousl. 300 kn 300 kn 300 kn Section - Plan Node 300 kn Node 3 Node 1 Node 4 Weld Details: Part, Node, Coordinates & Throat Thickness Part 1, Node 1: 0, 0, Throat 5.6 Part 1, Node : 0, 180, Throat 5.6 Part 1, Node 3: 17, 60, Throat 5.6 Part 1, Node 4: 17, 0, Throat 5.6 Applied Loads: F = 300 o = 6.5 mm and o = 19.4 mm Reerences 1 BS 5950: Structural use o steelwork in building File: WeldCalc Tab: Notes Page 7/8 Date Printed: 16/05/010

8 Welds in Shear, Bending, Torsion and Aial Loading BS :000: Code o practice or design - Rolled and welded sections, 001 DD ENV : 199; Eurocode 3: Design o steel structures Part 1.1 General rules and rules or buildings Calc Dr Shaiq Khan, Techno Consultants L File: WeldCalc Tab: Notes Page 8/8 Date Printed: 16/05/010

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