Design Portfolio – BRIDGE

Name ____________________________________

Design Brief (A description of the problem that needs solved) The objective of this project is to give each student the opportunity to apply and demonstrate their Math, Science and Technology knowledge and skills while designing and building the most efficient balsa wood bridge possible. The bridge will span a distance of 8” and can only be built from the materials provided; (15) pieces of 1/8 X 1/8 X 36” balsa wood and Elmer’s glue. The balsa wood MAY NOT be treated in any way to change its strength or appearance therefore, ONLY water &/or steam may be used to facilitate bending. The balsa wood MAY NOT be laminated together, therefore if two pieces are placed parallel to each other, no more than 2, there must be at least 1/8” gap between them. You may ONLY place 1 truss underneath the roadbed, which means the truss may be split in half to allow for the necessary ½” gap in the center of the roadbed. The instructor has the final say as to what is legal or illegal, safe or unsafe. Any entry deemed illegal or unsafe will be ineligible to participate in the testing portion of the project. Restrictions:

ELEMENT 1: Investigation & Analysis Bridge A structure built to span a valley, road, body of water, or some other physical obstacle with the purpose of providing a passage over the obstacles. Designs of bridges vary depending on the intended function, the nature of the terrain and the materials used to construct it Because the bridge tester limits what type of bridges can be tested on it, some of the following types may not be an option when designing Basic Parts of your Bridge Cords Horizontal girders that transmit the loads to the foundation Webs Connect the top and bottom cords 1

Beams Connect the cords of one side to the cords of the other Arch A bridge shaped like a curved arch with abutments (supports/anchors) at each end Arch bridges work by transferring the weight of the bridge and its loads partially in a horizontal manner, restrained by the abutments at either side

Beam A rigid horizontal bridge that rests on two piers, one at each end The weight of the bridge and any traffic on it is directly supported by the piers. The weight is traveling directly downward

Tension A bridge that carries the load in tension from the roadbed, to the top of the towers and back down to the ground to abutments all through steel cables (made of thousands of steel wires bound together) Math Measurement The process of using tools to layout and acquire sizes of materials and components You will make precise/accurate measurements with a ruler as well as use the provided drawings as templates to build from to insure accuracy Linear Measurement Measuring parallel to horizontal & vertical surfaces Aligned Measurement Measuring parallel to angled surfaces 2

Science Forces How mass is affected by mechanical stress such as a push or pull, which can cause a flexible object to deform or a nonflexible object to break The following forces will cause your bridge to deform and possibly break Dead Loads Loads that do not change or move These loads come from the materials used to build your bridge (balsa wood and Elmer’s Glue). Note; if more materials are used to construct your bridge the greater the dead load Live Loads Loads that change or move slowly These loads come from the loading block, bucket and sand Dynamic Loads Live Loads that change quickly such as a gust of wind You may choose to apply the sand (live load) quickly, requiring your bridge to suspend the applied loads for a long period of time. Or you may choose to apply the sand (live load) slowly, requiring your bridge to suspend the applied loads for a longer period of time Stress The measurement of the amount of force placed on an object, measured in pounds per square inch, PSI Pay close attention for signs of the following stresses while testing your bridge. Your best viewpoint is to look at the bridge from one of its ends Compression To push or squash a piece of material Tension To pull apart a piece of material Shear When a piece of material is divided by two parallel but opposing compression forces and one part of the material slides past the other 3

Torsion Twisting a piece of material Bending When the top surface of a piece of material is in compression while the bottom surface of that same piece of material is in tension causing the piece of material to sag, resulting in bending Strain The distance a shape deforms while under stress Technology Construction The process of building Craftsmanship The practice of performing a craft with great skill Think of craftsmanship as the level of quality applied to your project throughout the construction process; poor, average or excellent Tools A device, such as a saw, used to perform or facilitate manual or mechanical work. There are several tools to choose from when manipulating materials. Be sure to choose the proper tool to ensure easy and proper manipulation of your materials. Always follow manufacturer’s and instructor’s safety procedures when using tools! Fixture A tool used to hold your material while it’s manipulated The foam block you use to build your project on will act as a fixture Jig A tool used to hold and guide your material while it’s manipulated

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Materials Any substance made of matter; hydrogen, air and water When designing and building projects pay close attention to your choice of materials and their characteristics; strength, weight, flexibility, etc… Arches A strong shape because it supports loads at any point along its curve. The load being supported is transmitted entirely in compression along the arch to the ground. One disadvantage is that it requires strong abutments (supports/anchors at the ends) to prevent it from spreading out Even though the material is very flexible, if not treated properly (with steam or water) or if the arch is to tight/small, the material will break while forming it Triangles A strong shape because one side is always in tension when a load is applied Glue Joint The area on a piece of material where glue is applied so it can be attached to another piece of material Butt Two pieces of material joined end to end or end to side One of the simplest joints yet weakest glue joints Miter Beveled pieces of material joined at an angle, to form a corner The ends of the pieces of material are cut at angles Notch One or both pieces of material carved out to receive the other Strong glue joint because the pieces of material interlock and because the gluing surface is increased

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Lap One piece of material laid over another One of the simplest yet weakest glue joints Lamination Two or more pieces of material glued together in parallel fashion The purpose is to make one piece of material twice as thick Thrust Lines Imaginary lines of force caused by loads. They are transmitted through all parts of the structure to the ground These imaginary lines will help you design your project by determining where and how many braces your bridge should have

OUTSIDE RESEARCH (List All Resources (books, magazines, web sites, etc…) & a Brief Description of how each resource was helpful) 1.

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3. Grade for OUTSIDE RESEARCH ________ / 15pts 6

ELEMENT 2: Developing & Refining Ideas (complete all drawings) The best way to initiate creative thinking is to look at existing designs that were created to solve the same problem. You can look on the internet, in books, magazines, etc… and you may also ask for design tips and ideas from family, friends, neighbors, peers and engineering and construction professionals. Once, you’ve completed your research it is now time to begin developing your own ideas. Begin by utilizing the simplest form of drawing and the fastest way to put ideas into visual form, which is creating Freehand Sketches. The purpose of a freehand sketch is the same as a mechanical drawing, which is to communicate ideas for both picture and construction purposes. A freehand sketch is not drawn to exact size or shape however, it should be drawn proportionately. No two people will make identical freehand sketches therefore everyone will have their own style while maintaining the intent of it.

Thumbnail Sketches – Create 2 Thumbnail Sketches, on a plain piece of paper GRADE for SKETCHES ________ / 15PTS

Mechanical Drawings – (5pts-title block / 5pts-centered / 20-accurate (must resemble your sketch) / 5pts-line types & weights) Create your Mechanical Drawings using AutoCAD. Print two copies of each drawing GRADE for MECHANICAL DRAWING ________ / 35PTS 7

ELEMENT 4: Construction ______ / 15pts Project was completed by due date (project must be completed by due date in order to participate in competition and in order to have the project graded for construction) ______ /15pts Student utilized all of the allotted class time to design build & test project ______ / 15pts Project was built within restrictions ______ / 15pts Overall Craftsmanship was EXCELLENT Grade for CONSTRUCTION ________ / 60pts

EFFICIENCY

We want to compare how many grams of weight your project supported for every gram of its own weight. To do this, utilize the formula below. EFFICIENCY = Load/Maximum Weight Supported Weight of Project Example: If your Project held 25lbs and weighted 15g what would its efficiency be? Note: 453.6 grams = 1 pound Efficiency = (25lbs) (453.6g) = 11340g = 756g per 1g of Project weight 15g 15g Conclusion: The higher the resultant answer the more efficient your Project because each gram of Project weight supported more grams of applied weight.

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