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Index ~~ Background ~~ Purpose ~~ Hypothesis ~~ Materials ~~ Earthquake Machine ~~ Modifications: Overlapping - Height - Buttresses - Base Isolators - Cross Braces - Roofs ~~ Resistant Buildings ~~ Problems ~~ Further Experimentation ~~ Bibliography

STRUCTURAL MODIFICATIONS:

BASE ISOLATORS AND STABILITY

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PROCEDURE

A flat box with a layer of marbles in it was used as a base isolator. Cubic, overlapped buildings of three, six and nine layers of blocks were placed in turn on top of the marbles and tested on the earthquake machine for stability. The handles of the earthquake machine were pulled back to the line then let go. When the machine had stopped shaking, the handles were pulled again and again until the building collapsed. Each pull of the machine was timed to last two seconds. Three trials were done. At the end of each trial, the building was rebuilt. The data for each trial was recorded.

Layer of marbles in a shallow box to act as base isolator

Marble base isolator

Nine layer building sitting on marbles in a box, acting as a base isolator

Nine layer overlapped building on

marble base isolator

RESULTS

BASE ISOLATOR AND STABILITY
BUILDING WITH OVERLAPPED BLOCKS
	3 LAYER		6 LAYER		9 LAYER
	No Base Isolator	Base Isolator	No Base Isolator	Base Isolator	No Base Isolator	Base Isolator
	4	8			10	28
	6	8	6	20	14	28
	6	8	8	22	16	24
Average	5.3	8	8	20.7	11.3	26.7
	% Improved stability	51		159		136

CONCLUSION

A marble base isolator made a lot of difference to the stability of the buildings. It works because the marbles absorb the energy made when the earthquake machine vibrates and release it by rolling around. Without the base isolator, the bottom of the building sways faster than the top of the building. With the base isolator, the entire building moves as one unit and moves more slowly than the base isolator.

The base isolator improved the stability of the three layer building by 51%, the six layer by 159% and the nine layer building by 136%. This was unexpected because the nine layer building should increase the stability more than the six layer. This may be because it is already more stable because of its weight and the base isolator can't improve it much more.

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