Aircraft Structures

Front Matter......Page 1
Preface......Page 3
Table of Contents......Page 4
1.1 Equations of Equilibrium......Page 5
1.2 Two-Force Members......Page 6
1.3 Truss Structures......Page 11
1.4 Truss Analysis by Method of Joints......Page 13
1.5 Truss Analysis by Method of Sections......Page 15
1.6 Truss Analysis - Graphic Method......Page 16
1.7 Trusses Containing Members in Bending......Page 20
2.1 Equations of Equilibrium......Page 24
2.2 Moments and Couples......Page 25
2.3 Analyses of Typical Space Structures......Page 27
2.4 Torsion of Space Frameworks......Page 36
2.5 Wing Structures......Page 40
References......Page 49
3.1 Pure Translation......Page 50
3.2 Inertia Forces on Rotating Bodies......Page 58
3.3 Load Factors for Translational Acceleration......Page 69
3.4 Load Factors for Angular Acceleration......Page 74
4.1 Centroids......Page 77
4.2 Moment of Inertia......Page 78
4.3 Moments of Inertia about Inclined Axes......Page 86
4.4 Principal Axes......Page 88
4.5 Product of Inertia......Page 89
4.6 Mohr's Circle for Moments of Inertia......Page 92
4.7 Mohr's Circle for Combined Stresses......Page 96
Reference......Page 103
5.1 Shears and Bending Moments......Page 104
5.2 Relations between Load, Shear, and Bending Moment......Page 107
5.3 Bending Moment as Area of Shear Diagram......Page 108
5.4 Members Resisting Noncoplanar Loads......Page 113
6.1 Flexure Formula......Page 117
6.2 Beam Shear Stresses......Page 119
6.3 Direction of Shear Stress at a Free Surface......Page 126
6.4 Shear Flows in Thin Webs......Page 127
6.5 Shear Center......Page 129
6.6 Torsion of Box Sections......Page 136
6.7 Shear Flow Distribution in Box Beams......Page 137
6.8 Tapered Beams......Page 145
6.9 Beams with Variable Flange Areas......Page 151
7.1 Bending about Both Principal Axes......Page 157
7.2 General Equations for Bending Stress......Page 160
7.3 Unsymmetrical Beams Supported Laterally......Page 166
7.4 Beams with Three Concentrated Flange Areas......Page 171
7.5 Shear Flows in Unsymmetrical Beams......Page 173
7.6 Beams with Varying Cross Sections......Page 176
7.7 The Choice of Wing Reference Axes......Page 178
7.8 Correction of Wing Bending Moments for Sweepback......Page 181
Reference......Page 184
8.1 Distribution of Concentrated Loads to Thin Webs......Page 185
8.2 Loads on Fuselage Bulkheads......Page 190
8.3 Analysis of Wing Ribs......Page 195
8.4 Shear Flow in Tapered Webs......Page 201
8.5 Cutouts in Semimonocoque Structures......Page 206
References......Page 216
9.1 General Considerations......Page 217
9.2 Wing Vortex Systems......Page 219
9.3 Fundamental Equations for Obtaining Downwash Velocities......Page 223
9.4 Wing with Elliptical Planform......Page 226
9.5 Approximate Lift Distribution for Untwisted Wings......Page 228
9.6 Approximate Lift Distribution for Twisted Wings......Page 230
9.7 Spanwise Lift Distribution Obtained by Fourier's Series Method......Page 237
9.8 Evaluation of Fourier Series Coefficients......Page 240
9.9 Evaluation of A_n Coefficients......Page 243
9.10 Spanwise Distribution of Induced Drag......Page 246
9.11 Other Factors Affecting Distribution of Air Loads......Page 250
9.12 Limitations of Lifting Line Theory......Page 251
References......Page 253
10.1 General Considerations......Page 254
10.2 Basic Flight Loading Conditions......Page 255
10.3 Aerodynamic Data Required for Structural Analysis......Page 260
10.4 Balancing Tail Loads......Page 261
10.5 Velocity - Load-Factor Diagram......Page 262
10.6 Gust Load Factors......Page 265
10.7 Numerical Example of Air-Load Calculations......Page 268
References......Page 274
11.1 Stress-Strain Diagrams......Page 275
11.2 Designations for Metal Materials......Page 278
11.3 Strength-Weight Comparisons of Materials......Page 281
11.4 Sandwich Materials......Page 284
11.5 Typical Design Data for Materials......Page 287
11.6 Equations for Dimensionless Stress-Strain Curves......Page 289
11.7 Safety Factors and Margins of Safety......Page 290
References......Page 293
12.1 Introduction......Page 294
12.2 Bolted or Riveted Joints......Page 295
12.3 Standard Parts......Page 300
12.4 Accuracy of Fitting Analysis......Page 306
12.5 Eccentrically Loaded Connections......Page 312
12.6 Welded Joints......Page 315
Reference......Page 319
13.1 Tension Members......Page 320
13.2 Plastic Bending......Page 321
13.3 Constant Bending Stress......Page 323
13.4 Trapezoidal Distribution of Bending Stress......Page 325
13.5 Curved Beams......Page 328
13.6 Torsion of Circular Shafts......Page 331
13.7 Torsion of a Noncircular Shaft......Page 333
13.8 End Restraint of Torsion Members......Page 337
13.9 Torsional Stresses above the Elastic Limit......Page 339
13.10 Combined Stresses and Stress Ratios......Page 341
References......Page 347
14.1 Beam-Deflection Equations......Page 348
14.2 Long Columns......Page 349
14.3 Eccentrically Loaded Columns......Page 351
14.4 Short Columns......Page 352
14.5 Column End-Fixity......Page 354
14.6 Other Short-Column Formulas......Page 357
14.7 Practical Design Equations......Page 359
14.8 Dimensionless Form of Tangent Modulus Curves......Page 365
14.9 Effect of Eccentric Loading on Ultimate Strength......Page 368
14.10 Buckling of Flat Plates in Compression......Page 372
14.11 Ultimate Compressive Strength of Flat Sheet......Page 375
14.12 Plastic Buckling of Flat Sheet......Page 381
14.13 Nondimensional Buckling Curves......Page 384
14.14 Columns Subject to Local Crippling Failure......Page 386
14.15 Curved Sheet in Compression......Page 391
References......Page 396
15.1 Elastic Buckling of Flat Plates......Page 397
15.2 Elastic Buckling of Curved Rectangular Plates......Page 399
15.3 Pure Tension Field Beams......Page 402
15.4 Angle of Diagonal Tension in Web......Page 407
15.5 Semitension Field Beams......Page 410
15.6 Curved Tension Field Webs......Page 416
References......Page 422
16.2 Strain Energy in an Axially Loaded Member......Page 423
16.3 Truss Deflections......Page 425
16.4 Strain Energy of Bending......Page 429
16.5 Beam-Deflection Equations......Page 430
16.6 Semigraphic Integration......Page 434
16.7 Angular Deflections of Structures......Page 436
16.8 Deflections Resulting from Torsional Deformations......Page 437
16.9 Relative Displacements......Page 441
16.10 Shearing Deformations......Page 443
16.11 Twist of Box Beam......Page 446
16.12 Accuracy of Analysis Methods......Page 447
16.13 Warping of Beam Cross Sections......Page 448
16.14 Maxwell's Theorem of Reciprocal Displacements......Page 451
16.15 Elastic Axis, or Shear Center......Page 452
16.16 Castigliano's Theorem......Page 455
Reference......Page 457
17.1 Degree of Redundancy......Page 458
17.2 Trusses with Single Redundancy......Page 459
17.3 Other Structures with Single Redundancy......Page 463
17.4 Trusses with Multiple Redundancy......Page 468
17.5 Other Structures with Multiple Redundancy......Page 473
17.6 Selection of Redundants......Page 478
17.7 Circular Fuselage Rings......Page 486
17.8 Irregular Fuselage Rings......Page 489
17.9 Redundancy of Box Beams......Page 493
17.10 Torsion of Multicell Box Beams......Page 495
17.11 Beam Shear in Multicell Structures......Page 497
17.12 Analysis of Practical Multicell Structures......Page 501
17.13 Shear Lag......Page 506
17.14 Spanwise Variation of Warping Deformation......Page 507
17.15 Numerical Example of Shear-Lag Calculations......Page 510
17.16 Ultimate Strength of Indeterminate Structures......Page 512
17.17 Method of Least Work......Page 514
References......Page 516
18.1 Area Moments......Page 517
18.2 Conjugate Beam Method......Page 519
18.3 Truss Deflections by Elastic Loads......Page 523
18.4 Beam Columns......Page 528
18.5 Superposition of Beam-Column Loadings......Page 532
18.6 Approximate Method for Beam Columns......Page 536
18.7 Beams in Tension......Page 537
18.8 Moment Distribution......Page 538
18.9 Practical Procedure for Moment Distribution......Page 544
18.10 Joint Displacement......Page 549
18.11 Moment Distribution for Axially Loaded Members......Page 553
18.12 Other Applications of Moment Distribution......Page 557
References......Page 559
Table A.1 Properties of Round Tubing......Page 560
Table A.2 Allowable Strength of Protruding Head Rivets in Single Shear, Lb/Rivet......Page 562
Table A.3 Allowable Strength of Flush Riveted Joints, 100° Head Angle, Lb/Rivet......Page 563
A......Page 564
B......Page 565
C......Page 567
E......Page 569
F......Page 570
G......Page 571
J......Page 572
L......Page 573
M......Page 574
P......Page 575
R......Page 576
S......Page 577
T......Page 579
V......Page 580
W......Page 581
Y......Page 582