Aluminium Design and Construction John Dwight

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Figure 10.9 Basic torsion box for hollow section, thickness t of the element varies with distance s across its width, the contribution dI is taken as: (10.17) Hollow sections have a vastly increased torsional stiffness, as compared with non-hollow ones of the same overall dimensions. Even so, it is occasionally possible for them to fail torsionally, as when a deep narrow box is used as a laterally unsupported beam. To find � for a hollow section (Figure 10.9), we simply consider the basic ‘torsion box’ (shown shaded) and ignore any protruding outstands. � is then given by: (10.18) where A b =area enclosed by the torsion box measured to mid-thickness of the metal, s=distance measured around the periphery of the torsion box, and t=metal thickness at any given position s. The integral in the bottom line of equation (10.18) is evaluated all around the periphery of the torsion box. For a typical section, in which the torsion box is formed of flat plate elements, it can be simply obtained by summing b/t for all of these. 10.4.3 Torsion constant for sections containing ‘lumps’ The torsional stiffness of non-hollow profiles can be much improved by local thickening, in the form of liberal fillet material at the junctions between plates, or bulbs at the toes of outstands. To find � for a section thus reinforced we again split it up into elements and sum the contributions �� (Figure 10.8(b)). For a plate element, �� is bt 3 /3 as before; while for a ‘lumpy’ element, it may be estimated from data given below or else found more accurately using a finite-element program. Copyright 1999 by Taylor & Francis Group. All Rights Reserved.
Table 10.2 Torsion constant. Factors used in finding dI for certain types of section reinforcement Notes. 1. The table relates to expression (10.19). 2. Refer to Figure 10.10 for geometry and definition of N. Figure 10.10 Torsion. Section reinforcement covered by expression (10.19) and Table 10.2. 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
Page 185 and 186: where a is the stiffener spacing an
Page 187 and 188: plates (if fitted), p v =limiting m
Page 189 and 190: ending moment diagram. Two cases ar
Page 191 and 192: Figure 8.23 Sections covered in Tab
Page 193 and 194: where: I yy , I vv =inertia about m
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Page 197 and 198: Figure 8.26 Components of deflectio
Page 199 and 200: 9.1.2 Classification of the cross-s
Page 201 and 202: hole. Alternatively, it might fail
Page 203 and 204: Figure 9.2 Limiting stress p b for
Page 205 and 206: The determination of l involves a c
Page 207 and 208: Figure 9.6 Monosymmetric section. I
Page 209 and 210: Figure 9.9 Limiting stress p b for
Page 211 and 212: where s=� s /� t s =slenderness
Page 213 and 214: Figure 9.11 Type-R sections covered
Page 215 and 216: Figure 9.14 Four standardized profi
Page 217 and 218: 9.7.2 Secondary bending in trusses
Page 219 and 220: Table 9.5 Necessary checks for memb
Page 221 and 222: Figure 9.18 Axial load with biaxial
Page 223 and 224: 1. Tension members. The localized f
Page 225 and 226: Figure 10.1 Symmetric plastic bendi
Page 227 and 228: We now turn to monosymmetric sectio
Page 229 and 230: distance of its centroid from the n
Page 231 and 232: Figure 10.6 Elements of sections. I
Page 233 and 234: 10.3.3 Product of inertia The produ
Page 235: Usually the conditions are such as
Page 239 and 240: Figure 10.12 Warping. Conventional
Page 241 and 242: where b, t=element width and thickn
Page 243 and 244: 10.5.3 Evaluation of warping When t
Page 245 and 246: For sections where the position of
Page 247 and 248: (10.31) where: e=distance that S li
Page 249 and 250: 10.5.9 Asymmetric sections Before s
Page 251 and 252: CHAPTER 11 Joints This chapter cons
Page 253 and 254: the use of limiting stresses taken
Page 255 and 256: and the summation is made for all t
Page 257 and 258: Figure 11.3 Interaction diagram for
Page 259 and 260: k in order to give a fair compariso
Page 261 and 262: 3. The design is satisfactory if fo
Page 263 and 264: When the method of surface preparat
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
Page 269 and 270: where p a =limiting stress for unwe
Page 271 and 272: Figure 11.11 Interaction diagram fo
Page 273 and 274: Manufacturers of structural adhesiv
Page 275 and 276: 11.4.6 Creep Shear strength figures
Page 277 and 278: Figure 11.15 Effect of glue-line th
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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For example: The loading spectrum i
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act on the structure. However, BS.8
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Figure 12.4 Crack propagation: (a)
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12.5 CLASSIFICATION OF DETAILS 12.5
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i.e. a joint extending in the same
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when the design life is low or when
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Methods (2) and (3) are difficult t
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it reverts to line 1. The slope s o
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Aluminium Design and Construction John Dwight

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