# Bridges Quiz Review

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15 Νοε 2013 (πριν από 4 χρόνια και 6 μήνες)

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Bridges

Quiz Review

Quiz is Friday,
September 12

No need for calculators

Design Process

Describe the problem

Describe the results you want

Research, gather information

Define the constraints

Propose solutions by sketches

Build prototype

Design Process (cont)

Understand how our bridge building project
used the design process.

How is the
engineering design process

different than the one we used?

Iterative design

means many repetitive
efforts (as if we rebuilt the bridge several
times in order to improve its performance)

Types of Forces

Tension

Compression

Torque (or twisting)

Sheer (two forces in opposite directions)

Bending (opposite of beam loading)

Beam loading

And why do we care????

Be able to tell why engineers, designers,
manufacturers and constructors care about strengths
of materials….

Materials can become stronger if they are under
tension or compression (think about DIA and its roof)

When
nanotubes

are combined with polymers they
form super
-
strong
composites
, making projects like
the space elevator closer to reality.

How triangles react to loads

How do you account for small variations in the colors?

Types of Loads on Bridges

The weight of the structure itself

1.
Vehicles

2.
Soil adds a load because of
hydrostatic pressure

3.
Thermal load (heats up and cools down)

4.
Earthquake load

5.
Wind, snow, ice

Types of bridges do you need to know

Beam Bridge

How would your strengthen a simple beam bridge?

Why does that work?

Truss Bridge

How are these an improvement to beam bridges?

Suspension Bridge
When are these used? How do they work?

What part of a suspension bridge supports most of the weight

Arch Bridge

Why do they work? Is it due to compression or tension?

http://science.howstuffworks.com/bridge2.htm

Use this website to find answers

Terminology

When any structure breaks because of too much load, it
fails.

When a structure is under too much compression, it
buckles

When a structure is under too much tension, it

snaps

The length of a bridge is called the

span.

Know these types of connections we used:

Butt joint

Lap joint

Mitre joint

Drawing types you need to know:

Orthographic

Isometric

Perspective

Oblique

As
-
builts

Isometrics

These are used in engineering drawings because
they are easy to take measurements off of

They are easy to recognize because they have
120

degree angles in them

They do not account for distance like your eye or a
camera view would

Drawing Types

The figures on the left are
orthographic, or 2D

The figure on the right is an
isometric

What type of drawing?

This is
isometric
; the corner of the truck bed is at 120 degrees to
horizontal

What type of drawing?

This is a floor plan of a
bathroom.

It is really a “birds eye” view

It is 2D…

It is orthographic in nature

What type of drawing?

This is a diagram of how to
install drainage and venting in a
bathroom

Notice the angle of the pipes
that are on the ground.

They are at 120 degrees to
horizontal, therefore its

isometric

What type of drawing?

These are figures from a safety
manual for workers in a shipping
business

What type of drawing?

What types of drawing?

Notice how the perspective drawing shows lines converging, even
though they are parallel in real life.

Oblique drawings are useful, but are not true size, like isometric
drawings

Converging lines

True in the front, but
can’t measure the
length off this drawing.

Notice the 45 degree
note!

These are isometric

Figure on the right has circular parts, but look at the square
piece; it has a corner that is at 120 degrees to horizontal

What drawing type?

This is
oblique

(45 degrees to
horizontal)

These are

orthographic
; they are 2D

These are called
elevations

What drawing type?

This is a simple roof plan.

The roof slopes, but this is still
considered a 2D, and an
orthographic

projection or drawing.

Examples of Perspective Drawings,
Paintings

Measuring material strength

This is a UTM, or a Universal Testing Machine. There are common, and
would be found in many labs that test concrete, steel, etc.

Making sample concrete cylinders for
testing in the lab.

Nanotubes = hexagonal structure

A carbon nanotube has an extremely high
strength to weight ratio.

Carbon
nanotubes

are smaller than the eye
can see, yet stronger than steel

Measuring the strength of a
material….the MATH!

Bridge weight

Weight of load
at failure

Convert ounces
to pounds

Strength to
weight ratio

8 ounces

(.5 pounds)

80 pounds

4 ounces

200 pounds

16 ounces

158 pounds

Calculate these strength to weight ratios without using a calculator.

Which is the strongest bridge?

Measuring the strength of a
material….the MATH!

Bridge
weight

Weight of
load at
failure

Convert
ounces to
pounds

Strength to
weight ratio

8 ounces

(.5 pounds)

80 pounds

8 oz = .5
pounds

80/.5=40 so
S/W =
160

4 ounces

200 pounds

4 oz = .25
pounds

200/.25 =
800

16 ounces

158 pounds

16 oz = 1
pound

158/1=
158

The 4 ounce bridge is the strongest, express as
1:160

Struggling with the math?

If you struggle with division like 80 divided by .5…..

then convert the decimal to a fraction.

80
÷

.5

is the same as 80
÷

½

Invert that second fraction and multiply

Now you have 80 x 2, right? Because ½ inverted is 2/1, or 2

80/1 x 2/1

Multiply the tops

Multiply the bottoms

Now you have 160/1 or just plain old 160!