(Revised 7/16/02)

C.H. Jenkins and S.K. Khanna

1. INTRODUCTION
1. Introduction
2. Motivational problems
3. Linkage between mechanics and materials science
4. Overview of structures
5. Overview of materials
6. MechanicsÛ materials link: partition of structural function
7. References
8. Key points to remember
9. Problems

2. TOTAL STRUCTURAL DESIGN
1. Introduction – the design space
2. Total structural design
3. The generalized design template
4. Methods of structural analysis
5. Failure mechanisms in materials
6. Material selection in structural design
7. MechanicsÛ materials link: probabilistic structural analysis
8. References
9. Key points to remember
10. Problems
3. DESIGN OF AXIAL STRUCTURES
1. Introduction (r , E_t, E_c, S_t, S_c, A, u)
2. Equilibrium and deformation: axial loading; normal stress and strain
3. Constitution: density and weight; 1-D elastic material in tension and compression
4. MechanicsÛ materials link: the tension test
5. MechanicsÛ materials link: the compression test
6. Energetics
7. Analysis of simple tensile structures
8. Materials selection in axial structures
9. Design of tensile axial structures
10. Analysis of compact compressive structures
11. Design of compact compressive axial structures
12. Analysis of complex axial structures
13. Design of complex axial structures
14. References
15. Key points to remember
16. Problems
4. DESIGN OF TORSION STRUCTURES
1. Introduction (G, S_s, J, b , f )
2. Equilibrium and deformation: torsion loading; shear stress and strain
3. Constitution: 1-D elastic material in shear
4. MechanicsÛ materials link: the shear test
5. Energetics
6. Analysis of static torsion structures: shear flow; torsional shape factor; torsion element
7. Material selection in static torsion structures
8. Design of static torsion structures
9. References
10. Key points to remember
11. Problems
5. DESIGN OF FLEXURAL STRUCTURES
1. Introduction (I, S_f, E_f, v)
2. Equilibrium and deformation: flexural loading; moment of inertia I; bending stress and strain, shear stress and strain
3. Constitution: 2-D elastic material, flexural strength S_f, and flexural modulus E_f
4. MechanicsÛ materials link: the flexural test
5. Energetics
6. Analysis of flexural structures
7. Materials selection in flexural structures
8. Design of flexural structures
9. References
10. Key points to remember
11. Problems
6. DESIGN FOR COMBINED STATIC LOADING
1. Introduction (n )
2. Equilibrium and deformation: combined loading; multiaxial stress and strain
3. Constitution: 3-D elastic material
4. MechanicsÛ materials link: the combined loading test
5. Energetics
6. Analysis for combined loading
7. Materials selection for combined loading
8. Design of structures under combined loads
9. References
10. Key points to remember
11. Problems
7. DESIGN FOR DYNAMIC LOADING (Cs , S_N)
1. Introduction
2. Equilibrium and deformation: fatigue loading; stress concentration Cs
3. Constitution: fatigue strength S_N
4. MechanicsÛ materials link: the fatigue test
5. Energetics
6. Analysis of cyclic torsion structures
7. Materials selection in cyclic torsion structures
8. Design of cyclic torsion structures
9. References
10. Key points to remember
11. Problems
8. DESIGN FOR YIELDING (S_u)
1. Introduction to plasticity
2. Equilibrium and deformation: limit loads, small strain plasticity
3. Constitution: elastic-perfectly plastic material response
4. MechanicsÛ materials link: hysteresis, strain hardening
5. Energetics
6. Analysis for yielding
7. Materials selection for yielding
8. Design of structures for yielding
9. References
10. Key points to remember
11. Problems

9. DESIGN FOR FRACTURE (K_I)
1. Introduction to fracture mechanics
2. Equilibrium and deformation: crack mechanics
3. Constitution: brittle materials
4. MechanicsÛ materials link: stress intensity factor K_I
5. Energetics
6. Analysis for fracture
7. Materials selection for fracture
8. Design of structures for fracture
9. References
10. Key points to remember
11. Problems
10. DESIGN OF SLENDER COMPRESSIVE AXIAL STRUCTURES
1. Introduction (P_cr,, L_eff)
2. Equilibrium and deformation: compressive loading
3. Constitution: 1-D elastic material in compression
4. MechanicsÛ materials link: buckling tests
5. Energetics
6. Analysis of slender compressive structures
7. Materials selection in slender compressive structures
8. Design of slender compressive axial structures
9. References
10. Key points to remember
11. Problems
11. DESIGN FOR THERMAL LOADS
1. Introduction to thermoelasticity (a )
2. Equilibrium and deformation: Thermal loads, stress, and strains
3. Constitution: coefficient of thermal expansion a
4. MechanicsÛ materials link: temperature dependency of materials
5. Energetics
6. Analysis for thermal loads
7. Material selection for thermal loads
8. Design of structures for thermal loading
9. References
10. Key points to remember
11. Problems
12. ADVANCED DESIGN CONSIDERATIONS
1. Load paths
2. Optimization
3. Heat and surface treatments
4. Residual stress
5. Interfaces and joining
6. Environment
7. Impact and dynamic loading
8. Time dependency and aging
9. Geometric nonlinearity
10. Material nonlinearity
11. References
12. Key points to remember
13. Problems

1. Fundamental mechanics concepts
2. Fundamental materials science concepts
3. Free body diagrams
4. Systems of units
5. St. Venant’s principal
6. Coordinate transformation

1. Material properties
2. Material property charts
3. Singularity of the stiffness matrix and other issues
4. Stress concentration factors

This text is concerned with two interconnected activities:

• Bridging the divide in teaching the art and science of structural design

• Bridging the divide between applied mechanics and materials science

First, a few words about structures and structural design are in order. A structure is any physical body that must carry loads, and hence develops stresses and strains. The primary engineering disciplines that design structures are aerospace, civil, and mechanical engineering. It is somewhat unfortunate that in the practice of engineering, the name structural engineer is often taken to mean someone involved only in the design of civil structures. Aerospace structural engineers design airplanes, rockets, satellites, and the like. Civil structural engineers design buildings, highways, and bridges. Mechanical structural engineers design machinery, vehicles, and consumer products. From a structures perspective, there is much more in common in what aerospace, civil, and mechanical structural engineers do than there is different. A structure is a structure is a structure …

This text attempts to provide a unifying treatment of structural design, and should prove useful to any engineer involved in the design of structures. We consider structural engineering in the broadest and most general sense, and it is important that the structural engineering student learn from the design of structures in all applications, in or out of their discipline. A wing truss, bridge girder, or overhead crane trolley are all close relatives of the same family of structures. Certainly the design practices of the specific discipline must by learnt, but early on it is much more important to design structures generally. To become a great painter, we don’t want to always just paint bowls of fruit!

The other divide to be bridged is that between applied mechanics and materials science. In an earlier time, perhaps there was much less gap to be closed. The onset of specialization and the rapid rise of technology, however, have created separate disciplines concerned with the deformation of solid materials. At the expense of over simplifying, mechanics has roots in physics, where materials science derives from chemistry. But in the deformation of a real body, both the macroscopic loads and geometry interact with the material microstructure – any separation is ours alone, not natures!

The typical undergraduate engineering curriculum follows along this schism. An introductory course in "mechanics of materials" is taught by mechanics faculty, whereas an introductory course in "property of materials" is taught by science faculty. Mostly, such courses are taught in isolation from one another, both philosophically (in different languages and points of view) and physically (in different buildings). (That the faculty are competent in their respective disciplines and teach their courses well is assumed.) But such a separation is purely artificial, and the student misses out in never seeing the intimate connection between the macroscopic and microscopic domains of the problem. Society loses out on having at their service efficient, high-performance material/structural systems.

We follow a very methodological process to introduce mechanics, materials, and design issues continuously throughout the text. We engage the actual design of structures very early by first providing a generalized design template, which can be followed and specified for various structural applications. Every chapter emphasizes a link between mechanics and materials quantities. A thematic example problem is continued throughout the text, both for continuity and so that students may get a sense of how a real complex structure is designed. Problems are provided from aerospace, civil, and mechanical applications, and include both deterministic and design-type problems. Various links to websites are provided. A CD-ROM is provided with graphics, virtural labs, and other supporting materials.

The course material presented here is suitable for a first course that encompasses, but replaces, the traditional mechanics of materials and properties of materials courses. At many institutions, however, such a replacement will be exceedingly difficult, due to a wealth of factors. Thus the text is also appropriate for a follow-on course in design of structures, which would precede the typical introductory mechanics and properties courses. In this latter case, one would in essence be "putting the pieces back together."