Book SummaryStructures, by J. E. Gordon

1-Page Summary1-Page Book Summary of Structures

What is structural integrity? According to scientist and engineer James Edward Gordon, it’s how much force a structure can withstand without losing its form or collapsing. He explains that all structures, both natural and man-made, are subjected to external forces that they must withstand to maintain their form and stability. For example, trees must counter forces such as wind and heavy rain, while buildings must withstand the weight of furniture and people. In Structures, Gordon examines the factors that make some objects sturdy while others are vulnerable to failure. (Shortform note: Structures was originally published in 1978. This guide is based on the 2003 updated edition.)

Gordon was a pioneering materials scientist who bridged the gap between theoretical physics and practical engineering. He served as head of plastic structures research at the Royal Aircraft Establishment and professor of materials technology at the University of Reading. In addition to Structures, he authored several other books on engineering, including *[The Science of Structures and...

Structures Summary Principle 1: Material Properties

According to Gordon, a structure is only as stable as the materials it’s made of. Therefore, to understand how a structure can withstand external forces, you first need to grasp how its individual materials respond to forces. Gordon suggests that three key properties determine how a material responds to external force: elasticity, energy storage, and strength. Let’s explore each of these in detail.

Material Property #1: Elasticity

A material’s elasticity is its ability to return to its original shape after being misshapen by an external force. Gordon explains that every material has a given internal molecular structure—the bonds between its molecules are organized in a specific way. When a force acts on a material, its internal molecular structure shifts as the bonds between molecules stretch. This may or may not impact the material’s visible shape, depending on the material itself and the amount of force applied. In any case, elasticity is the material’s ability to recover its original molecular structure after being subjected to force. (To picture elasticity on a larger scale, think of how a spring compresses when you squeeze it and expands when you release...

Structures Summary Principle 2: Force Distribution

We’ve just explained the properties that determine how individual materials respond to force: elasticity, energy storage, and strength. Since structures tend to be composed of different materials, each with its own molecular composition, we’ll now explore how the combination of different materials impacts a structure’s ability to withstand force and maintain structural integrity.

Structures composed of multiple materials respond collectively to force. Gordon explains that applying force to a structure doesn’t just affect each constituent material in isolation. Rather, the energy of the force moves through all the materials that make up the structure, triggering complex interactions between them. How a structure responds to this moving energy depends on two key factors:

1. Each material’s capacity for energy storage
2. The structure’s shape

Let’s examine how each of these factors impacts a structure’s response to force.

Factor #1: Each Material’s Capacity for Energy Storage

As we’ve established, applying force to a material causes the material’s molecular bonds to stretch and absorb the energy carried by a force. Gordon explains that in a structure made of...

Structures Summary Principle 3: Time Effects

Until now, we’ve been discussing the immediate effects of force on materials and structures. Now, we’ll examine how these effects can accumulate over time, impacting a structure’s long-term stability.

Gordon explains that the effects of force eventually add up, changing a material’s molecular structure. As we’ve discussed, when force impacts a material, its molecular bonds stretch and return to their original positions. When this happens frequently, the cycle of stretching and returning can cause these molecular bonds to settle into slightly different positions, permanently altering their internal structure and their ability to withstand force. Gordon explains that three conditions impact how a material’s internal structure changes over time:

1) Force variations: Consistent force (like the same weight on a floor) creates predictable stretch-return patterns that make it easier for molecular bonds to maintain their original structure. However, Gordon writes that variations in force (like abrupt spikes in weight) cause molecular bonds to stretch in unpredictable patterns. The more these stretching distances vary, the more difficult it becomes for molecular bonds to find...

Shortform Exercise: Consider How Structures Respond to Force

According to Gordon, three principles underpin the structural integrity of all materials and structures. This exercise will help you apply these principles to understand how the structures around you respond to force.

Think about a structure you interact with regularly—like a chair, a table, or a shelf. What forces act upon this structure during normal use? Consider both constant forces like gravity and variable forces like the weight distribution of objects placed atop the structure.