Engineering Loads

Objectives

Identify and explain the differences between tension and compression.

Identify and provide examples of the 4 primary loads affecting structures.

Design and test bridges using West Point software.

Run simulations and manipulate bridge designs to optimize cost and strength.

Primary Structural Forces

Tension- pulling or elongation of materials.

Compression- pushing together or shortening of materials.

What are the implications of a bridge that has excessive tension or compression?

Talk with your neighbor about this

(30 seconds)

Equilibrium

The state in which there are no unbalanced forces acting on a body, balance of tension and compression.

x

y

F =0

F =0

©iStockphoto.com ©iStockphoto.com

Balanced Unbalanced

Structural Loads

The forces applied to a structure.

-With your neighbors (3 or 4 people) discuss a few examples of loads that are applied to everyday structures such as bridges and schools in Minnesota?

-Example loads on bridges and schools on the west coast of the United States?

Structures

A few considerations…

- size

- shape

- geographic location

- materials

- geotechnical

- structural loads to support

Various Structures

Designed dependent on their purpose

Engineers and architects must consider weight requirements

Must design around a structures safety factor

Safety Factor

The ratio of the breaking stress of a structure to the estimated maximum stress in ordinary use

A bridge may typically only carry passenger cars.

Will it support a fully loaded cement truck?

Most structures have a safety factor of 3.

Safety Factor Question

The city of Plymouth is proposing a new 4 lane bridge to be built on Peony Lane with a safety factor of 10. What issues might homeowners and taxpayers have with this proposal?

Take a minute and talk with someone nearby.

Dead Loads

Stationary or permanent parts of a structure.

Walls Floor Ceiling Essentially the weight of

the structure with nothing on or in it.

Live Loads

Weight that travels within or across a structure

A high school hallway

Cars on a bridge

Static Loads

Accumulate over time

It can become a dead load

A steady rain or snow

Cars backing up on a bridge due to an accident

Dynamic Loads

A sudden exertion of force on a structure

A strong gust of wind Earthquake Explosion Collision

Load Miscalculations

Engineers must take all loads into account

Consider….- What will be in or on

the structure- Who will use the

structure- Where is it located

geographically

Exit Question #1

This force shortens structural members.

A. Equilibrium

B. Tension

C. Dynamics

D. Compression

Question 2

This force lengthens or stretches structural members.

A. Statics

B. Tension

C. Safety factors

D. Compression

Question 3

This type of structural load occurs when there is a sudden exertion of force.A. StaticB. DynamicC. DeadD. Live

-List an example

Question 4

This type of structural load accumulates over time.A. StaticB. DynamicC. DeadD. Live -List an example

Question 5

This type of structural load is a permanent part of the structure.A. StaticB. DynamicC. DeadD. Live -List an example

Question 6

This type of structural load moves across or within a structure.A. StaticB. DynamicC. DeadD. Live -List an example

Question 7

This type of structural load is applied during the west point bridge builder simulation.A. StaticB. DynamicC. DeadD. Live