Mass Supported by King-post and Queen-post Truss Designs
Researched by Aaron J. 1999-2000	PURPOSE  HYPOTHESIS  EXPERIMENT DESIGN  MATERIALS  PROCEDURES  RESULTS  CONCLUSION  RESEARCH REPORT  BIBLIOGRAPHY  ABOUT THE AUTHOR

PURPOSE

The purpose of this experiment was to test which truss design would support the most mass without caving in.

This project excited me because of houses and buildings caving in because of the snow in the year 1996, due to bad truss designs.  I want to find the better truss design so there will not be as many roofs caving in.

The information gained from this experiment will lead to better truss designs so peopleís houses or company buildings will not cave in because of snow so often.  This experiment will also help engineers and architects design better trusses, knowing what the better truss designs are. 

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My hypothesis is that the Kingpost w/ struts design will be more successful by holding more mass, than the Queenpost, or Kingpost designs.

I base my hypothesis on the structure of the truss designs, and the book, Timber Frame Construction.  Also by the fact that the Kingpost w/ struts model spreads the weight (load) from the top and sides of the truss. 

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The constants in this study were the: 
* same type of wood 
* type and amount of glue 
* same crushing device 
* span of truss 
* Same method of building them 
 

The manipulated variable is the design of each truss, and also the size of wood.

The responding variable is the mass each truss can hold until collapsing. 

To measure the responding variable I put my trusses one at a time on a scale, built a top that fit over the trusses and put pressure on the truss top until the truss collapsed. 

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1.   Gather all materials. 
1.   Buy 5, 4.6mm by 6.3mm, by 3-ft. strips of balsa wood. 
2.   Buy 4, 6.3mm by 6.4mm, by 3-ft. strips of balsa wood. 
3.   Measure each length of each line forming Kingpost w/ struts model in Timber Frame Construction page 26. 
4.   Multiply lengths of each line by 4 to make my model bigger.
5.   Put pieces together using straight pins to see if they fit together. 
6.   Take pins out if they do. 
7.   Glue pieces together with 1 drop of Elmers wood glue. 
8.   Fill in weak spots of truss using glue spread by toothpicks.
9.   Put straight pins in to hold glued pieces together to dry.
10. When dry take pins out. 
11. Repeat  steps 3-10 for Queenpost model. 
12. Repeat  steps 3-10 for Kingpost model. 
13. Cut piece of plywood to fit over Kingost model in V shape with flat top. 
14. Support plywood top on the top of the Kingpost model. 
15. Place truss on scale. 
16. Place plywood truss top, over truss. 
17. Put light pressure on truss top slowly and evenly. 
18. Continue adding pressure on truss top. 
19. Record the amount of weight  on screen as truss collapsed.
20. Record data. 
21. Repeat steps 13-20 with Queenpost model. 
22. Repeat steps 13-20 with Kingpost model. 
23. Record data. 
24. Repeat steps 5-23 for trail #2. 
25. Compare the results to one another.

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The original purpose of this experiment was to see what truss design holds the most mass before collapsing.
 

The results of the experiment was that the Kingpost w/ struts design held the most mass, the Kingpost design held the second most mass, and the Queenpost  design was the weakest
 

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My hypothesis was that the Kingpost w/ struts design would be the most successful by standing the most weight.

The results indicate that my hypothesis should be excepted.

Because of the results of this experiment, I wonder if I made my joints on my trusses better, that I might have better results, by the closer amount of Kilograms it took to break the certain truss designs for both trials.

If I were to conduct this project again I would have measured the pieces of the trusses lengths 3 times and cut them once to get a better angle. Also I would have bought a surplus of wood.  I would have made more trusses to test, and would have tried harder to use the same amount of glue.

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RESEARCH REPORT     INTRODUCTION A truss is a structure used like a beam, in roof or bridge building. The design of trusses is based on the principle that a triangle is a rigid configuration that cannot collapse, or change its shape. HOW TRUSSES HELP SUPPORT The kinds of trusses are called Simple, King-post, and Queen-post where there is a beam or post supporting the peak of a truss.  Also the Kingpost with struts design, which is the same as the Kingpost design but there are horizontal struts going out from the middle of the bottom of the truss to support the sides.  Another kind of truss is the Queen-post design where there are two posts going diagonally up and supporting the sides of the triangle shape, and then extending across the middle where they join.  One more kind is called Hammer Beam, which is more sufisticated than the others are, and is used in larger houses, or buildings.  Simple trusses are braced triangle frames that always used on roofs.  But more complicated designs of trusses have several triangular structures that form a unit that support roofs.  The connection pieces that make up the top and bottom lengths of trusses are called chords.  The pieces that form the triangle between chords are refered to as the web.  Trusses may consist of either steal or wood parts that form triangles.  One of the simplest truss designs may consist of three parts fastened together to form a triangle.  Trusses are used for railroad bridges, truss bridges, and buildings like houses, skyscrapers, aircraft fuselages, and automobile frames.  Today’s wooden trusses are made with steel connector plates, with bolted connections.  The principal of triangulation is attaching a horizontal tie beam at the bottom ends to two peaked rafters.  If the span of a roof is wide the more complicated the structure supporting the roof is, and the narrower the range of well chosen materials.  In these days most timber frame buildings, trusses are not needed.  With trusses as span increases diagonal members called struts are added, usually 2 struts are added.    TRUSS BRIDGES  Steel truss construction has been used a lot over time because of its low cost.  In some situations engineers chose to build truss bridges, rather than girder bridges, because they require less material than the girder bridges.  Yet sometimes they choose to build girder type bridges because they are more attractive, easier to maintain, and also they are easier to build.   One example of a truss bridge is the Lendenthals Sciotoville Bridge that crosses the Ohio River and has a truss of 1550 feet long with two long spans of 775 feet each.  Another example of a truss bridge is the Astoria Bridge, which was built over the Columbia River, in Oregon and was the longest continuous truss bridge with a 1232-foot span.  A continuous truss bridge is a bridge that each truss must have 3 or more supports, like piers.  The Lendenthal Sciotoville Bridge is a simple span truss bridge where it expands between two piers.  The main types of bridges are Beam bridges, girder bridges, Truss bridges, Arch Bridges, Suspension bridges, and Moveable bridges.  Such bridges are used over usually just canyons, and rivers.  Truss bridges are mainly used over long spans. Trusses are always triangle shaped.  In Truss bridges trusses are added as a structural member, and put with other members of structure bridges get really strong, and provide structural strength and support over long spanned.  The first Truss bridges were make of wood, and had spans ranging up to 360 feet.  Iron and steel came into bridge use in the late 1800’s.  Now days modern Truss bridges can have spans up to 800 feet.  FOUNDATION OF TRUSSES  Buildings have two main parts.  The substructure, which is the part of the building below ground, and the superstructure, the part of the building above ground level.  Usually the superstructure is referred to as the foundation, which includes the basement walls, even though the part of the building may be below ground level.  Beams, girders, and columns form the superstructure, which include trusses.  Although beams and girders run horizontally.  Both the substructure and the superstructure help to support the weight of the building.  The dead load is the total weight of all its parts like the roof, furniture, and any pressure.  Wind pressure is part of the dead load and is called the wind load.  Other kinds of loads are the snow load, and earthquake shock.  These kinds of loads are important for a building to stand up to.  There are 4 kinds of foundations.  The spread foundations, which are long rectangular slabs of reinforced concrete, extend beyond outer edges of buildings.  These are not as firm as Pier foundations, which are columns of concrete that go through the topsoil to a bed of firm rock or clay.  Pile foundations are long slender columns of steel, concrete, or wood, are pounded into the ground by machines called Pile drivers. Another type of foundation is called the Mat foundation, or sometimes called Raft foundations.  They consist of thick slabs of reinforced concrete that span the whole area under a building.  These Mat/Raft foundations are usually used in poor soil conditions when it is not really possible to drive the piers or piles down to good supportive rock, or soil. HISTORY  In the 18th Century mathematics learned how to apply their science to the behavior of structure and making it possible to determine the amounts of the stresses in deferent places in buildings.  This info led to the development of space frames, which are trusses, or other parts arranged three-dimensionally.  The Romans were on of the first to come up with building trusses.  They made them to span large open spaces in buildings that use post and lintel construction.  Also in Rome truss descriptions were made by roman Architect, Vitrivius De Architura.  During the 19th Century cast iron, wrought iron, and also steel became the preferred truss material, because of how strong and supporting steel, and other metals are.       SUMMARY Trusses are used to support building roofs. They are triangle shaped and have posts that are in the triangular shape that supports the truss from the sides. Some of the types of trusses are called the Kingpost, Simple, Kingpost w/ struts, Queenpost, and Hammer Beam. Truss bridges are used to span long distances; for example the Astoria Bridge which has a 1232-foot span and is the longest continuous truss bridge has 3 or more supports, or piers. There are two kinds of foundation. The superstructure and the substructure.  The superstructure is the part of foundation above ground level. The substructure is the foundation below ground level.  Basements are considered part of the superstructure. In the 18th Century mathematics learned how to apply their science to the behavior of structure and making it possible to determine the amounts of the stresses in buildings. Back to top

BIBLIOGRAPHY   ‘Construction Building’, World Book Encyclopedia, 1997, T,B ‘Truss’ Microsoft Encarta 2000 http://www.samyoder.com/products.html JMP Pannell, "An illustrated History of Civil Engineering", 1965, Fredrick Ungar Publishing Co. New York ‘Truss’ Microsoft Encarta 1995 Soben, Jack and Schroeder,  Roger  "Timber Frame Construction" "The Builders Marvels of Engineering", National Geographic Society, 1992 "The New Book of Popular science", 1978, Grolier international, inc. Truss, Microsoft Encyclopedia, 1998  Truss, Grolier 1998 Back to top

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