Aluminium Design and Construction John Dwight

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where � 1 is again found from equation (7.5), or Figure 7.6, but now putting: (7.13) If an element has edge welds, a reduced thickness k z t is taken in each HAZ region in the same way as for uniform compression (i.e. the areas X in the figure are removed). 7.3.4 Outstands under strain gradient, general description Now we turn to outstands, for which there are two possible cases of strain gradient (Figure 7.12): Case T peak compression is at the tip; Case R peak compression is at the root. In either case, the more heavily compressed edge is called edge 1 as before. And again we use � (=e 2 /e 1 ) to specify the degree of strain gradient. The buckling of an outstand is mainly governed by what happens at the tip. Therefore, case T is only slightly more favourable than uniform compression, since the effect of � is merely to decrease the stress in the relatively stable material close to the supported edge. But case R is clearly more favourable, because � now directly affects the tip stress which is what matters. The elastic critical stress � cr (occurring at edge 1) for a simply supported outstand under strain gradient may be found from the standard equation (7.2), taking a suitable value for K. Figure 7.13 shows how K varies with � for the two cases, the curves being plotted from the following empirical expressions which give a good approximation to the rigorous values: Case T K=0.41 for 1 > � > 0.5 =0.50–0.18� for � < 0.5 (7.14a) Case R K=0.41+1.3(1-�) 4 (7.14b) Figure 7.12 Outstands under strain-gradient. Cases T and R. Copyright 1999 by Taylor & Francis Group. All Rights Reserved.
Figure 7.13 Outstands under strain-gradient, elastic buckling coefficient K. 7.3.5 Outstands under strain gradient, case T For an outstand under case T loading, it is reasonable in design to ignore the slight improvement in performance as compared with uniform compression. The value of ß f or ß s needed for classification, and likewise the effective block width b eo when the element is slender, may thus be taken using the data already provided for the case �=1 (Sections 7.2.2 and 7.2.4). 7.3.6 Outstands under strain gradient, case R With case R loading, the above approach would be unduly pessimistic. Instead we follow BS.8118 and introduce the parameter g given by: 1 > � > -1 g=0.7+0.3� (7.15a) (7.15b) Classification then consists of comparing ß (= b/t) with modified values of ß f and ß s obtained by dividing the uniform compression values (Table 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
Page 105 and 106: Nominal loading. Nominal loads are
Page 107 and 108: 2. Material factor (� m ). In the
Page 109 and 110: design does not, because stress at
Page 111 and 112: Table 5.2 Summary of limiting stres
Page 113 and 114: Figure 5.4 Plastic strain at workin
Page 115 and 116: example, a reduced value might be t
Page 117 and 118: The parameter � depends purely on
Page 119 and 120: CHAPTER 6 Heat-affected zone soften
Page 121 and 122: area of softening. With 7xxx-type m
Page 123 and 124: Figure 6.3 Typical hardness plots a
Page 125 and 126: 6.4 SEVERITY OF HAZ SOFTENING 6.4.1
Page 127 and 128: Figure 6.6 Categories of welded joi
Page 129 and 130: Figure 6.10 One-inch rule, extent o
Page 131 and 132: e allowed for in design by replacin
Page 133 and 134: Figure 6.13 Predicted area (A z ) o
Page 135 and 136: Figure 6.15 Overlapping HAZs. nomin
Page 137 and 138: In determining A zp , an appropriat
Page 139 and 140: failure plane in the HAZ, close to
Page 141 and 142: With MIG welding, an electrode-posi
Page 143 and 144: CHAPTER 7 Plate elements in compres
Page 145 and 146: (a) Compression member elements The
Page 147 and 148: Table 7.1 Classification of element
Page 149 and 150: Figure 7.4 Slender internal element
Page 151 and 152: Figure 7.7 shows curves of � ° p
Page 153 and 154: (7.9a) (7.9b) The strain gradient c
Page 155: (through the centroid) for ß S . F
Page 159 and 160: Figure 7.15 Reinforced elements. Th
Page 161 and 162: Figure 7.18 Stiffener location for
Page 163 and 164: Figure 7.20 Slender reinforced inte
Page 165 and 166: CHAPTER 8 Beams 8.1 GENERAL APPROAC
Page 167 and 168: 8.2.2 Section classification The di
Page 169 and 170: that for the gross section. It woul
Page 171 and 172: the usual manner. Line 1 in the fig
Page 173 and 174: 1. Fully compact sections. The limi
Page 175 and 176: Figure 8.8 Transverse and longitudi
Page 177 and 178: 8.3.4 Shear resistance of bars and
Page 179 and 180: Figure 8.12 Tension-field action. i
Page 181 and 182: Figure 8.14 Moment/shear interactio
Page 183 and 184: 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
Page 195 and 196: post (Section 8.6.4) or by some oth
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
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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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where b, t=element width and thickn
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10.5.3 Evaluation of warping When t
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For sections where the position of
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(10.31) where: e=distance that S li
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10.5.9 Asymmetric sections Before s
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CHAPTER 11 Joints This chapter cons
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the use of limiting stresses taken
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and the summation is made for all t
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Figure 11.3 Interaction diagram for
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k in order to give a fair compariso
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3. The design is satisfactory if fo
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When the method of surface preparat
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11.3.3 Weld force arising In many c
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Table 11.6 Limiting stress p w (N/m
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where p a =limiting stress for unwe
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Figure 11.11 Interaction diagram fo
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Manufacturers of structural adhesiv
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11.4.6 Creep Shear strength figures
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Figure 11.15 Effect of glue-line th
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Table 11.7 and Figure 11.17 provide
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11.4.11 Resistance calculations for
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high value reflects the various unc
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therefore usually presented in term
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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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