Research
Research was done mostly by simply testing different materials and widths of the beams in the software. I found that hollow tubes worked better that the solid beams and could actually withstand more force and were much cheaper than the solid beams.
Brainstorming
I created a few simple sketches but when I tried them in the software they failed right away so I knew I would have to create much more complex designs.
Modifications
My design started out very simple and was made of solid tubes. The bridge failed before the truck even touched it so I added more members and a second layer of members. With all the solid tubes the bridge was well over the $400,00 limit so I changed most of the members to hollow tubes. After adding many members the truck was able to go on the bridge but it would still fail. Using the reports I pinpointed where the failure was occurring and strengthened them by making them thicker. Then the truck was able to cross the bridge with causing the bridge to fail.
I would provide photos of the modifications but the software refused to allow me to view the previous iterations of the design.
I would provide photos of the modifications but the software refused to allow me to view the previous iterations of the design.
Final Bridge Design
Cost Report
Load Report
Final Bridge JustificationI used Carbon Steel because it seemed to be the strongest material, as well as the cheapest, when I was testing material during modifications. I came upon the design I used by creating as many triangles as I could and using hollow bars to be cheaper but still dependable. I tried to keep the bridge symmetrical for aesthetic reasons and for overall strength.
I made the longer members thicker to be more dependable and less likely to break under tension or compression forces. ReferencesI did not use any references
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Material Report |
Conclusion Questions
Q: How does the type and direction of stress applied affect the selection of the material type and the cross-sectional area?
A: For members that undergo tension you would want materials that are more ductile and capable of stretching so that they wouldn't simply snap under the force. However if it is under compression you might want to use a material that is strongest and resists deformation the most. Also by changing the cross sectional area you can strengthen the material to perform better in tension and compression.
Q: How can the forces of tension and compression work together to make a stronger bridge?
A: By having members that are affected by tension and compression the forces of the load are spread out so that all the force isn't focused on one point. If the members weren't under any force at all the bridge would fail. The tension and compression forces act against each and balance out the forces acting on the bridge so that the joints wont fail.
A: For members that undergo tension you would want materials that are more ductile and capable of stretching so that they wouldn't simply snap under the force. However if it is under compression you might want to use a material that is strongest and resists deformation the most. Also by changing the cross sectional area you can strengthen the material to perform better in tension and compression.
Q: How can the forces of tension and compression work together to make a stronger bridge?
A: By having members that are affected by tension and compression the forces of the load are spread out so that all the force isn't focused on one point. If the members weren't under any force at all the bridge would fail. The tension and compression forces act against each and balance out the forces acting on the bridge so that the joints wont fail.