Structures | J.E. Gordon

Summary of: Structures: Or Why Things Don’t Fall Down
By: J.E. Gordon

Introduction

In the book summary of ‘Structures: Or Why Things Don’t Fall Down’ by J.E. Gordon, we explore the fascinating world of biological and man-made structures, and how they withstand various forces acting upon them. You can expect to learn about the fundamental concepts of structures and their strength, the science of stress and strain, the roles of tensile and compressive forces, as well as the intriguing concept of fatigue in materials. The book summary serves as a comprehensive guide to understanding how structures have evolved in nature and among humans, the science behind their longevity, and the technological advancements used to build safe and reliable structures in our modern world.

The Strength of Structures

The design of an object’s structure is what keeps it together and withstands outside forces. Structures can be found in both the natural and man-made world, from muscle tissues to bridges. The study of structures began in the seventeenth century by Galileo, who contributed to the subject after leaving astronomy behind. Academics then began researching different materials and how they behave under heavy loads, leading to the discovery of how structures resist stresses through pushing back with equal force. The strength of a structure is determined by the force it can resist, and this is one of the fundamental concepts of structures.

The Physics of Stress and Strain

Stress and strain affect the degree and distance, respectively, that atoms are pushed apart by external forces within a solid material. Stress is measured by comparing the force to the area it’s acting on while strain is measured by the increased length compared to the original. These two factors help determine the stiffness of a material under stress, with some materials being far more elastic than others.

Understanding Tensile Forces

Tensile forces cause deformations in materials under pressure. When materials are pulled, atoms move and cause creep. Creep helps materials adapt to further stress. However, materials also contract laterally when pulled. Blood vessels counteract the effects of tensile forces by balancing longitudinal and circumferential stresses.

Have you ever wondered why a piece of rubber stretches when pulled? The answer lies in tensile forces. Unlike pushing forces, tensile forces pull atoms apart and cause deformation under pressure. Tensile forces are essential to pressurized structures like bladders, arteries, diving cylinders, and balloons. Materials under tensile stress experience creep, deforming under mechanical stress and redistributing the pressure. Creep is an adaptation mechanism that helps materials cope with structural changes over time.

However, materials do not just stretch out under tensile forces. They also contract laterally, causing them to keep their shape while under stress. Blood vessels, for instance, balance longitudinal and circumferential stresses, enabling them to retain their shape despite blood flow. Understanding tensile forces is crucial to engineering, as they play a critical role in many structural designs.

How Structures Endure

Structures can last for centuries due to compressive forces that push on them. Our ancestors intuitively built structures that avoided tensile forces and relied on compression. Stability in a structure requires even compressive pressure on its supporting elements. Ancient people understood these principles before the scientific era, enabling the creation of massive castles and churches. When a compression structure falls, it’s due to lack of stability, not lack of strength. Tension structures collapse due to high stress, whereas compression structures don’t. Understanding these principles is intuitive even for children playing with blocks.

Beams: The Ingenious Solution for Roof Stability

Engineers use beams to make roofs stable and safe instead of putting too much stress on walls. Beams channel the force of the roof downwards and away from the walls, supporting a load at a right angle to the length of the beam. They are even found in nature, where they make heavy and compressive structures more stable.

The two most important features of a building are its walls and its roof. While walls hold the structure together, a roof is what protects a building from the elements. However, designing a sturdy and safe roof is a daunting task for engineers. This is due to the challenges presented by triangular roofs, the weight of which puts a lot of stress on the walls and increases the risk of building collapse.

To overcome this problem, engineers came up with an ingenious solution – the beam. Beams channel the force of the roof downward and away from the walls, supporting the load at a right angle to the length of the beam. They provide stability to the structure without putting any horizontal force on the supporting elements. This technique, in turn, helps to reduce the stress on the walls, thus making roofs safer and more stable.

Interestingly, beams also occur naturally, and animals like horses use them to support their heavy bodies on thin legs. However, even with a beam, problems may still occur during the construction of a roof. In conclusion, beams are an essential component in the design of a reliable, secure roof that protects the building and its inhabitants from the outside world.

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