Structures or Why things don’t fall down - Book Summary Notes
Updated: Feb 12, 2022
Here we have the conversation in the unbuttoned mood of a learned engineer with wide sympathies about his art, its history, its range, and the silly things which happen. It reads easily and has immense charm.--Architect's Journal
It is really, really good if you want a primer on the structural design.--Elon Musk
Rich and readable...personal, witty, and ironic.--Scientific American
CHAPTER 1: The structures in our lives
p18. Can engineers learn from natural structures? What can doctors and biologists and artists and archaeologists learn from engineers?
p20. (the living structure) Trees are the most durable living structures (max height of 110 meters)
p22.(the technological structure) Limitation of material resources made the engineer turn to technology which was the primary approach to solving this problem.
p23. Pneumatic tire: (John Boyd Dunlop) A pneumatic, or air-filled, the tire is made of an airtight inner core filled with pressurized air. A tread, usually reinforced with steel belting or other materials, covers this inner core and provides the contact area with the road. John Boyd Dunlop
p25. (structures and aesthetics) relating the appearance to the structure of their products.
CHAPTER 2: Why structures carry a load
p38. All materials and structures deflect, although to greatly varying extents, when they are loaded.
CHAPTER 3: The invention of stress and strain
p50. Hooke's law: properties of material & behavior of the structure.
p52. E= Youngs Modulus = elastic modulus = stiffness - fundamental knowledge of stress and strain
p55-56. The strength of a Structure is simply the load (N or kg) that will just break the structure. Known as breaking load.
Strength of Material: is the stress (MN/m2) required to break a piece of the material itself.
The object of many strength calculations is to predict the strength of a structure from the known strength of its material.
CHAPTER 4: Designing for safety
p66. Stress trajectories in a bar are uniformly loaded in tension with and without a crack.
p68. Stress at the tip of the crack may well be a hundred or even a thousand times higher than the stress elsewhere in the material.
CHAPTER 5: Strain energy and modern fracture mechanics
p71. Information about local vs breaking stress
p74. Every elastic material which is under stress contains strain energy, and it does not make much difference whether the stress is tensile or compressive.
p92. The commonest arrangement to absorb energy is bending.
To break any material in tension a crack must spread right across it.
p94. The quantity of energy required to break a given cross-section of a material defines its toughness - fracture energy.
CHAPTER 7: Joints, fastenings, and people
P132-147 important pages.
p133. The design of a structure is influenced much more by its stiffness than by its strength. Where the need is for rigidity rather than strength, the whole problem becomes very much easier and cheaper.
p148. Creep : [definition] is why old shoes are more highly stressed than new ones.
CHAPTER 8: Soft materials and living structures
p151. emulsion [definition] : Two liquids can form different types of emulsions. An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable).
p156. Arteries are under constant stress n strain.
p158. In a cylindrical vessel (always) :
longitudinal stress: p
Circumferential stress: 2p
p159. Poisson ration [definition] : elastic effect behavior.
p161. Membranes stretch with no thickness deformation: constant stress.
p171. Our ancestors generally avoided tension structures as far as they could and tried to use constructions in which everything was in compression.
p174. What kept a building from tipping up and collapsing was not so much strength of the stones and mortar as the weight of the material acting in the right places.
p181-183. Thrust line: The line of thrust is the locus of the points, through which forces pass in a retaining wall or an arch. It is the line, along which internal forces flow.
In a stone structure, the line of thrust is a theoretical line that through the structure represents the path of the resultants of the compressive forces. For a structure to be stable, the line of thrust must lie entirely inside the structure
p182. Oblique loading [definition]: the loading that deflects the thrust line in this kind of way.
p184. Where there is a crack, there must once have been tension stress.
walls, masonry dams usually fail not from lack of strength but from lack of stability.
p186. Heavy masonry can be regarded as a structure that is ‘ pre-stressed’ conditions.
p188. Definition of an Arch.
p188-191. Useful information about arches.
p192. Sealing up of structures (interesting to read)
The square-cube law (or cube–square law) is a mathematical principle, applied in a variety of scientific fields, which describes the relationship between the volume and the surface area as a shape's size increases or decreases. It was first described in 1638 by Galileo Galilei in his Two New Sciences as the "...ratio of two volumes is greater than the ratio of their surfaces”.
-unlike most other structures, buildings fail because they become unstable and tip-up.
CHAPTER 10: Something about bridges
p200. The facts of life are that the rise of the arch must be about half its span.
p201. Cast iron is very brittle. It resembles stone in being strong in compression but weak and unreliable in tension, and so, in building construction, it has to be treated rather like masonry.
p202. Vibrations of the trains would crack the brittle cast iron.
p205. James Fin