Ladder Failures

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Ladder Failures Per Reinhall

description

Ladder Failures. Per Reinhall. Ladder cases. More than half a million people in the United States suffer ladder-related injuries every year More than 300 people die each year in the U.S. from ladder injuries - PowerPoint PPT Presentation

Transcript of Ladder Failures

Page 1: Ladder Failures

Ladder Failures

Per Reinhall

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Ladder cases• More than half a million people in the United

States suffer ladder-related injuries every year • More than 300 people die each year in the U.S.

from ladder injuries • The principles of product liability hold

manufacturers, distributors, suppliers and retailers responsible for injuries caused by their products. A product liability claim is usually based on design defects, manufacturing defects of insufficient warning documentation, often termed as "failure to warn."

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•Federal Reform Attempts

The closest the U.S. Congress has ever come to enacting broad-scope product liability reform was in 1998. In that year, Congress passed the Federal Product Liability Fairness Act. This bill would have limited punitive damage awards to the greater of $250,000 or twice compensatory damages.

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It would have also:

• Required plaintiffs to present a stronger case by raising the standard of evidence to "clear and convincing" from the current "preponderance of the evidence.“

• Required plaintiffs to show that a manufacturer acted with a "conscious and flagrant indifference to the safety of others" in order to prevail.

• Abolished the application of "joint and severable liability," thus ending the practice of suing "deep pocket" defendants with little or no liability.

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Design Flaws– A single motion of the release bar can unlock both

hinges at a joint while loaded– The release bar is shaped such that it can be kicked

by the user. This can cause collapse of the ladder by unlocking both hinges in a joint.

– A low level of force on the release bar can unlock both hinges in a joint even when the ladder is fully loaded.

– The release bar can snap into locked position with an audible noise without total engagement of the locking pins. It is therefore possible for a user to get the impression that a joint is properly locked when it is not.

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Zinc Hinge 1

0500

10001500200025003000350040004500

0 0.3 0.6 0.9 1.2 1.5 1.8

Displacement (inch)

Forc

e (lb

f)

Series1

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Steel Hinge 1

0500

10001500200025003000350040004500

0 0.3 0.6 0.9 1.2 1.5 1.8

Displacement (inch)

Forc

e (lb

f)

Series1

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LADDER SATISFYING THE ANSI A14.2 STANDARD

WITH ONE MIDDLE HINGE UNLOCKED

Torque=11,000 in-lb1000 lb

75.5 degrees

Torque=11,000 in-lb 355 lb

52 degrees

CONCLUSION

A ladder satisfying the ANSI A14.2 standard can easily support the weight of a 230 lb person when the ladder is at 52 degrees and one middle hinge unlocked

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THE SUBJECT LADDER

WITH ONE MIDDLE HINGE UNLOCKED

Torque=5,805 in-lb

518 lb

75.5 degrees

Torque=5,805 in-lb187 lb

52 degrees

CONCLUSION

The subject ladder cannot support the weight of a 230 lb person when the ladder is at 52 degrees and one middle hinge unlocked

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Moment in Middle Hinge While Climbing

0

2000

4000

6000

8000

10000

12000

0 1 2 3 4 5 6 7 8 9

RUNG

Mom

ent (

lb in

)

Moment While ClimbingStrength Specified by StandardKrause Multimatic (Zinc)

ANSI Standard

Krause Multimatic