STRUCTURAL STABILITY

LET’S PLAY

YOU CAN’T

MAKE IT

BALANCE

Stability

• Stability is the ability of a structure to remain stable or to return to a stable and balanced position when forces act on it
• when designing structures, we try to increase the stability
• adding braces at the correct locations can increase the stability

FORCE

UNSTABLE

(#Fail)

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Stable vs Unstable

explain why the braces increase the stability of the structures

FORCE

FORCE

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Stable vs Unstable

What is another way that the structure can be made more stable?

FORCE

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Centre of Gravity

• the centre of gravity is the point at which an object’s mass is equally balanced
• when an object is placed on it’s center of gravity, it will balance easily

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Centre of Gravity

• the center of gravity of most solid objects is located within the object
• the center of gravity of frame-type objects is often located outside of the object

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Stability

• the stability of a structure is determined by its centre of gravity and the width of the support base

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WILL IT TOPPLE?�Plumb Lines

PREDICT

OBSERVE

EXPLAIN

Will it Topple?

• to determine if a structure will topple over, we draw a plumb line straight down from the center of gravity

PREDICT

OBSERVE

EXPLAIN

COG

NO IT �WILL NOT!

if the plumb line lands within the support base, the structure is stable

WILL IT TOPPLE?

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COG

OVER SHE

GOES

if the plumb line lands outside of the support base, the structure is unstable and will topple over

WILL IT TOPPLE?

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Increase Stability

• this means we can increase the stability of structures by
• lowering the center of gravity
• (accomplished by concentrating the mass lower on the object)
• increasing the width of the base

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COG

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