Aluminium Design and Construction John Dwight

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provided, to which the equation is (valid for a > r): 0.1 < r/b < 1 K=1.2 {1+ (1-e -0.7a/r )(1-r/b) 2 } r/b > 1 K=1.2 (12.2) Other non-linear effects which become significant in fatigue are the secondary stresses in trusses, due to joint fixity, and the effects of shear lag, distortion and warping in plated structures. The increased stress levels resulting from these must be allowed for. 12.4.2 Method B This is used for fillets and partial penetration butt welds transmitting load from one plate to another. A notional value is assumed for f obtained as follows: (12.3) where F – =force transmitted per unit length of joint at the position considered, g=nominal throat dimension (Figure 11.7), and n=number of welds. Here F – can be a force transverse to the weld, a longitudinal one, or a vectorial sum of the two. It is normally found in the same general way as for P – when considering static resistance (Section 11.3.3), except that we are now considering the force transmitted under nominal, and not factored loading. When a single weld suffers bending about its longitudinal axis, f should be taken as the elastic flexural stress at the root, based on a linear stress distribution through the (nominal) throat. If necessary, this component of f should be added vectorially to the value found using equation (12.3). Table 12.2 Classification of fatigue details (non-welded) Notes. 1. Use K for cases 2, 3, 4. 2. An open hole having d/t in the range 2–3 may be treated as either case 4 (using actual stress concentration factor K), or case 5 (putting K=1). Copyright 1999 by Taylor & Francis Group. All Rights Reserved.
12.5 CLASSIFICATION OF DETAILS 12.5.1 The BS.8118 classification An essential step in any fatigue calculation is to classify the form of the detail at the position being considered, so that the relevant endurance curve can be selected. British Standard BS.8118 distinguishes nine such classes, the reference number for each being the value of fr (in N/mm2 ) corresponding to a predicted endurance (N) of 2 million cycles. The class numbers thus defined are 60, 50, 42, 35, 29, 24, 20, 17, 14. The class for a given detail may be found by referring to the relevant table, based on BS.8118: Table 12.2 non-welded details; Table 12.3 welded details, crack propagation through parent metal; Table 12.4 welded details, crack propagation through the weld. Table 12.3 Classification of fatigue details (arc-welded) —propagation through parent metal Notes. 1. For cases 26–30, avoid weld returns around lap. 2. l=length of connected part in direction of f r . Copyright 1999 by Taylor & Francis Group. All Rights Reserved.
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Aluminium Design and Construction C
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First published 1999 by E & FN Spon
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2.2.1 Rolling mill practice 2.2.2 P
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5 Limit state design and limiting s
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8.2.6 Use of interpolation for semi
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10.3.2 Inertias for a section with
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Preface Aluminium is easily the sec
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List of symbols The following symbo
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uu, vv principal axes w effective s
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1.1.3 The industrial metal It is on
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where A is the section area (mm 2 )
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1.3.1. The good points about alumin
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Deflection Because of the lower mod
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1.4.4 Establishment of the alloys I
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1.5.2 New technology Most of alumin
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large span, where self-weight is a
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These tend to be in all-aluminium c
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Close-up of the M-dec system, which
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Aluminium glazing system for commer
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Nat West Media Centre, Lords Cricke
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The main requirements for the produ
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in which t and w are in mm. These a
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Figure 2.1 Extrusion process (direc
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Figure 2.2 Typical extrusion die. t
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Figure 2.6 ‘Semi-hollow’ profil
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especially the stronger alloys in t
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Figure 2.9 Conventional profiles. 2
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2.4 TUBES By tubes we mean hollow s
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CHAPTER 3 Fabrication 3.1 PREPARATI
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Figure 3.1 Alternative designs for
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Figure 3.2 Thread insert. a coil-sp
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3.3 ARC WELDING 3.3.1 Use of arc we
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adjusted. The technique is claimed
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For welds of minimum or fatigue qua
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Figure 3.5 Friction-stir welding: s
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are, and the designer/fabricator mu
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cartridge, and mixing takes place a
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3.7.4 Painting Alloys having durabi
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Where a range is given, as for the
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will be only slightly above that fo
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heating the metal to a temperature
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Table 4.4 Characteristics of differ
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softening in the heat-affected zone
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60 alloys, are: BSEN.485 plate and
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Firure 4.3 Nominal composition and
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popular alloys in the series are: 6
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Figure 4.6 Variation of tensile str
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undercarriages of aircraft. They ar
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Figure 4.11 Minimum stress-strain c
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AC.51400 This is another non-heat-t
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times that of the actual pits) prod
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The severity of bimetallic corrosio
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Nominal loading. Nominal loads are
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2. Material factor (� m ). In the
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design does not, because stress at
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Table 5.2 Summary of limiting stres
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Figure 5.4 Plastic strain at workin
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example, a reduced value might be t
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The parameter � depends purely on
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CHAPTER 6 Heat-affected zone soften
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area of softening. With 7xxx-type m
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Figure 6.3 Typical hardness plots a
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6.4 SEVERITY OF HAZ SOFTENING 6.4.1
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Figure 6.6 Categories of welded joi
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Figure 6.10 One-inch rule, extent o
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e allowed for in design by replacin
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Figure 6.13 Predicted area (A z ) o
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Figure 6.15 Overlapping HAZs. nomin
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In determining A zp , an appropriat
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failure plane in the HAZ, close to
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With MIG welding, an electrode-posi
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CHAPTER 7 Plate elements in compres
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(a) Compression member elements The
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Table 7.1 Classification of element
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Figure 7.4 Slender internal element
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Figure 7.7 shows curves of � ° p
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(7.9a) (7.9b) The strain gradient c
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(through the centroid) for ß S . F
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Figure 7.13 Outstands under strain-
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Figure 7.15 Reinforced elements. Th
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Figure 7.18 Stiffener location for
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Figure 7.20 Slender reinforced inte
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CHAPTER 8 Beams 8.1 GENERAL APPROAC
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8.2.2 Section classification The di
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that for the gross section. It woul
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the usual manner. Line 1 in the fig
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1. Fully compact sections. The limi
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Figure 8.8 Transverse and longitudi
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8.3.4 Shear resistance of bars and
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Figure 8.12 Tension-field action. i
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Figure 8.14 Moment/shear interactio
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depending on the estimated degree o
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where a is the stiffener spacing an
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plates (if fitted), p v =limiting m
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ending moment diagram. Two cases ar
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Figure 8.23 Sections covered in Tab
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where: I yy , I vv =inertia about m
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post (Section 8.6.4) or by some oth
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Figure 8.26 Components of deflectio
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9.1.2 Classification of the cross-s
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hole. Alternatively, it might fail
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Figure 9.2 Limiting stress p b for
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The determination of l involves a c
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Figure 9.6 Monosymmetric section. I
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Figure 9.9 Limiting stress p b for
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where s=� s /� t s =slenderness
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Figure 9.11 Type-R sections covered
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Figure 9.14 Four standardized profi
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9.7.2 Secondary bending in trusses
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Table 9.5 Necessary checks for memb
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Figure 9.18 Axial load with biaxial
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1. Tension members. The localized f
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Figure 10.1 Symmetric plastic bendi
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We now turn to monosymmetric sectio
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distance of its centroid from the n
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Figure 10.6 Elements of sections. I
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10.3.3 Product of inertia The produ
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Usually the conditions are such as
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Table 10.2 Torsion constant. Factor
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Figure 10.12 Warping. Conventional
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Page 243 and 244: 10.5.3 Evaluation of warping When t
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Page 251 and 252: CHAPTER 11 Joints This chapter cons
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Page 259 and 260: k in order to give a fair compariso
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Page 265 and 266: 11.3.3 Weld force arising In many c
Page 267 and 268: Table 11.6 Limiting stress p w (N/m
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Page 271 and 272: Figure 11.11 Interaction diagram fo
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Page 275 and 276: 11.4.6 Creep Shear strength figures
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Page 279 and 280: Table 11.7 and Figure 11.17 provide
Page 281 and 282: 11.4.11 Resistance calculations for
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Page 289 and 290: act on the structure. However, BS.8
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Aluminium Design and Construction John Dwight

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