Basics of Bridge Construction

Build a Spaghetti Bridge Project

Photo Journal

Created By

**** ******

April 2008

Planning

• 8 Processes of Engineering 

• Identify the Problem This problem was given Build a bridge out of Spaghetti.

Span between 20 and 30 inches Wide enough to allow a 2 x 4 flat to pass unimpeded through all supports. Able to support 15 lbs at any point along deck• Research the Problem What makes a bridge strong

• Develop Possible Solutions

• Select Best Solution 

• Construct a Prototype

• Test and Evaluate 

• Redesign

• Communicate Solution

The Challenge

Challenge Research , design, build and

revise:• A bridge using only spaghetti

and hot glue• Bridge span should be

approximate 20 -30 inches• Bridge base must be smooth

enough for 2x4 to pass through unimpeded

• Bridge should support 15 lbs at any point on deck

Step 1 Research

Interactive lessons from PBS Building Big 1st Bridge Basics exerciseathttp://www.pbs.org/wgbh/buildingbig/bridge/basics.html

2nd The Bridge challenge http://www.pbs.org/wgbh/buildingbig/bridge/challenge/index.html

3rd Forces Lab Exercisehttp://www.pbs.org/wgbh/buildingbig/lab/forces.html

Watch History Channel/National Geographic True Story of the Bridge of River Kwai

Step 2 Design Bridge

• Choice Warren Truss bridge

• Looked Sturdy and seemed to be able to be built with Spaghetti and hot glue

• Need to calculate the length of the span, height of trusses, width of roadbed

• Decide on how many pieces of spaghetti would be used in one bridge section

Step 3 Begin Construction

Prototype 1

• Follow design and construct first truss

• Double check that all sections are right length and same number of spaghetti in each

• Place sections in triangles and begin gluing in proper places

• Do not use excessive amounts of glue

Prototype ConstructionThe trusses

Prototype 1

• Construct 1st truss

Prototype ConstructionThe trusses

Prototype 1

• Construct 2nd truss

Prototype ConstructionStep 4 begin construction of base

Prototype 1

• Measure lengths and count number of spaghetti pieces in each section

• Place longer sections on bottom and shorter sections on the top

• Glue and let sit to dry

Prototype Construction Step 5 Finish construction

• After all the different pieces of the bridge have finished drying its time to finish the prototype

• First you must place a road bed on the base

• Put the trusses on the base and glue and let set

• Then place the cross braces at the top of the trusses for a bit more support

• Let set for awhile

Step 5 Finish Construction

Completed Prototype

End view

Prototype ConstructionStep 5 Finish Construction

Completed Prototype

Side view

Step 6 Test Prototype for problems

After the glue has set, check the bridge for potential problems

• The trusses were not all the same height

• The base was not strong enough

• There was a noticeable curve

Step 7 Redesign Bridge

• When redesigning the bridge make sure that all the problems with the Prototype were fixed

• Decide if change needs to be made in order of construction

Final Product Construction

Step 8 Measure and Cut

Correcting my first error, not every piece of spaghetti is the same length

Correction

• Measure each piece of Spaghetti and cut to proper lengths

Final Product ConstructionStep 9 Trusses

• Correcting 2nd error; not all triangles were the same size

• When constructing the trusses measure out the points for all the triangles to meet the beams.

• Glue and let set

Final Product ConstructionStep 10 Base

Correcting 3rd error

Base was curved and did not lay flat

The glue on each piece must set and then be trimmed to allow bridge deck to be flat and level

Final Product ConstructionStep 11 2nd layer added to base

The bridge must hold 15 lbs at any point on the deck.

To give the deck added strength a complete layer of spaghetti was added to the base running perpendicular to the beams and future deck.

Final Product ConstructionStep 12 Assemble structure

Project Completion ( almost)

Now all that was left was to trim decking to square.

Project Completion

End View

Project Completion

Side view

Project Completion

Overhead view

Final Testing

Spanning 2 Chairs

Testing Bridge Strength

I borrowed 2 weights

from a local hardware

store

Testing Bridge Strength

10 lbs

No Problem!

Testing Bridge Strength

15 lbs

I did it!

Communication

Presentation of Photo Journal

Created using Microsoft Powerpoint

Piccasa 2 Photo Editor

Thanks to:

PBS: Build Big

Price Of Freedom : True Story of The Bridge on River

Kwai

Unschooler’s Engineering Club

2007 – 2008