# BridgeBuilding - Skyview Middle School

Urban and Civil

Nov 29, 2013 (4 years and 5 months ago)

96 views

TODAY

ADD LEGO rubric to end of your
lab write
-
up for LEGO NXT

Start a new lab write
-
up for
Bridge Building

Module 4

notebook at end of hour

keep
open to LEGO lab. Put name at
top of page.

Skyview Middle School

S.T.E.M

Bridge Building

Lab Write
-
Up

I. Title

MODEL BRIDGE BUILDING DESIGN

II. Purpose / Problem

Bridges must be built to withstand certain
amounts of forces. These forces include
gravity, compression, tension, waves, and
shear. I will design and build a model
bridge that works to withstand these forces.

Lab Write
-
up

III. Hypothesis

A bridge built on a miniature
scale, using similar construction
techniques from full
-
size
bridges, will be able to withstand
the compressional forces
imparted by extra weight. The
construction that best distributes
the weight evenly to the outside
edges and to the ground will be
most successful.

Lab Write
-
Up

IV. MATERIALS

Elmer

s White Glue

Toothpicks

cardboard

scrap paper

tape

Wax paper

weights

Lab Write
-
Up

V. Procedure

(step by step instructions)

1)
Decide bridge design and draw
simple outline on paper. Decide
how to attach crossbeams and
stabilizers.

2)
Keep going from here, be
precise

Lab Write Up

VI. Collection of Data and Results

1.

2.
Weight will be added to the bridge
center until catastrophic failure.

3.
Divide compressional weight (g) by
bridge weight (g) = Efficiency factor

VII. Conclusion.

Use these measurements!

Truss Bridge

Possible designs

Toothpick Bridge Designs

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.
Types of Bridges

Beam Bridge

constructed to
span short distances because of
its horizontal
beam

supported at
each end by
piers
.

Beam Bridge

Truss Bridge

constructed with
straight,
steel

bars in series of
triangles.
Rigid

arms extend from
both piers, diagonal steel tubes,
projecting from the top and
bottom of each
pier
, hold the
arms in place. The arms that
project toward the middle are
supported on one side.

Truss Bridge

Arch Bridge

built to squeeze
together, and this squeezing
force

is carried outward along
the curve to the supports at
each end. The supports, called
abutments, push back on the
arch and prevent the ends of the

Arch Bridge

Model Arch Bridges

Forces on Bridges

Suspension Bridge
-

hangs from
steel

cables
,
draped over
towers

and
secured by anchorages, on both
ends of the bridge. The force on
compression

on the towers
which support most of the
bridge's weight.

Suspension Bridge

Model popsicle bridges

Planning Construction

Sketch two different bridges with
a top, front, and side views.

Draw the outline of your bridge
design. Draw all of these lines
as single lines. It should be
drawn to the actual size.

Draw all of your cross members
to strengthen the bridge.

Planning Construction

overall length of the bridge span
is between 25cm to 35cm.

Find the center of the land by
drawing diagonal construction
lines from corner to corner.

This is where the force of
pressure will begin.

Planning Construction

Start the construction with the
outer support pieces.

Glue sticks together making a
beam long enough to support
from one side to the other.

Use only enough glue as
needed. A drop per connection
is all that is needed.

Planning Construction

Glue your pieces and let them
dry on WAX paper.

When the front is completely

Finally, add to the sides of the
bridge, this will keep the back
and forth shifting from breaking
the bridge.

Bridge joints

Lap Joint:

The lap joint is one of the
strongest. It strengthens by
stiffness. The lap joint

s one
drawback is the joint is only as
strong as the face of the wood.
That means that only one part of
your piece of wood is in contact
with the other.

End Joint:

The end joint is not a very
strong joint for tension
members. In tension, the two
pieces of wood will pull away
from each other. In
compression, this joint will allow
the piece to bend in a arc. The
lap joint holds the piece stiff,
which helps it to hold.

Forces

Compression:

Compression is a pushing force. If
you take the middle a straw and
squeeze, the straw flattens. If you
hold each end of a straw and push it
is harder to make the straw
compress, or flatten. The shorter a
piece of wood is, the more
compression it can hold.

Tension:

Tension is pulling. Wood has the
ability to resist tension. Tension may
be applied parallel to the grain of the
wood, but should be avoided
perpendicular to the grain. Wood is
very strong in tension parallel to the
grain, but extremely weak in tension
perpendicular to the grain.

Torsion:

Torsion is twisting. When you
wring out a cloth, you are
applying torsion to the cloth. If
you take a piece of licorice and
apply torsion to it, the licorice
will twist around several times
before it breaks.

Shear:

Shear occurs when there are two
opposing forces acting on the same
point. If a piece of wood is held with
both hands next to each other, and
one hand pushes up while the other
pushes down, you are applying
shear force. Shear usually occurs
horizontally, and not vertically.

Popsicle Bridge World Record
Holder