Trusses

FINAL PROJECTPHYSICS 1401JEFFERY DINGALAN JONES

TRUSSESTRUSSES ARE USED IN NUMEROUS MANNERS.BRIDGE TRUSSESROOF TRUSSES CONVEYOR FRAME TRUSSESCRANE BOOM TRUSSES

COMMON TYPES OF TRUSSESTRUSSES WERE COMMONLY NAMED AFTER THE PERSON WHO DEVELOPED THEMEXAMPLES ARE AS FOLLOWSKing PostWarrenHowe EnglishPrattFink Parker

KING POST

WARREN

ENGLISH

PARKER

COMMON TYPES OF TRUSSESSOME WERE NAMED AFTER THE SHAPE OR CITY IN WHICH THEY WERE FIRST USEDBowstringBaltimorePettit

BOWSTRING

BALTIMORE

PETTIT

TRUSSESTrusses act as long ,deep girders with the cutout webs.Roof trusses not only carry their own weight and the weight of the roof framing but also wind loads, snow loads, suspended ceilings and equipment, and a live load during construction and maintenance, and repair.

TRUSSESBridge trusses have to support their own weight and that of deck framing and deck live loads from traffic (automobiles, trucks, railroad trains, pedestrians, etc.) and forces caused by live loads.

TRUSSESOther uses of trusses are for conveyor frames in the material handling systems. Conveyors are uses to transport material, without the use of mobile equipment. Trusses in the material handling can reach spans in excess of 100 feet.Crane Booms are constructed of trusses, in order to give them the ability to lift large amounts of weight with smaller lighter steel members.

EXPERIMENTAL TRUSSBasic Shape and ConstructionTruss was constructed from Popsicle sticksTruss configuration was a three section Warren truss.Basic bridge dimensions are 13.5 inches long, 3.5 inches tall, and 2 inches wide.

TRUSS DRAWING1234567891011

TRUSS DRAWING

Predicted Weakness/StrengthThe quality of the wood used in the Popsicle stick may very greatly and therefore lead to the failure of a member prematurely.The glue used at the connections may not be of equal amounts at each point, this would cause one joint to fail prior to the wood member failing.The Warren truss, although simple in design, is one of the more common trusses used in the construction industry to span a distance with the use of smaller members.

THEORETICAL STRENGTH

Material of Construction Popsicle Stick Cross-Sectional Area (3/8 inch x 1/16 inch) .02347375 Square InchesUltimate Shear Strength in psi for white pine is 860 psi Shear Force= 860psi/.02347375 sq in

THEORETICAL STRENGTHShear Force= 20.16 lbs per sideTwo sides under common load=Total load of 20.16lbs.times 2= 40.32 lbs.Maximum Load= 40.32 lbs.

20.1 LBS7.07 LBS7.07 LBS7.07 LBS7.07 LBS7.07 LBS14.2 LBS14.2 LBS14.2 LBS14.2 LBS14.2 LBS14.2 LBSDESIGN LOADS/SIDE

TEST BREAKSTEST MEMBER POUNDS MISSING None Missing 40.0 lbs. 3 15.6 lbs. 6 19.0 lbs. 10 32.0 lbs. 4 26.6 lbs. 7 36.2 lbs. 8 40.0 lbs. error in testing due to string stretching

TEST BREAKSTEST MEMBER POUNDS MISSING 11 26.4 lbs. 2 20.0 lbs. 9 25.8 lbs.

TRUSS TEST123456789101140 LBSNO MEMBERS MISSING

TRUSS TEST123456789101115.6 LBSMEMBER THREE MISSING

TRUSS TEST123456789101119.0 LBS.MEMBER SIX MISSING

TRUSS TEST123456789101132.0 LBSMEMBER TEN MISSING

TRUSS TEST123456789101126.6 LBSMEMBER FOUR MISSING

TRUSS TEST123456789101136.2 LBS.MEMBER SEVEN MISSING

TRUSS TEST123456789101140 LBS.MEMBER EIGHT MISSINGTESTING ERROR

TRUSS TEST123456789101126.4 LBSMEMBER ELEVEN MISSING

TRUSS TEST123456789101120.0 LBSMEMBER TWO MISSING

TRUSS TEST123456789101125.8 LBSMEMBER NINE MISSING

TEST RESULTSNumber 3 missing, the horizontal force that number three should have had resulted in to much force at the connection on members 10, 11, 6, and 5 thereby causing failure.Number 6 missing caused the bridge to rotate around the load point causing failure.

TEST REUSLTSNumber 10 missing, the bridge could withstand more load since the force was transferred to member 9 until it became overloaded and failure occurredNumber 4 missing, the load was carried by the majority of the truss until the bending of member 5 failed.

TEST RESULTSNumber 7 missing, the truss could withstand the greater load until the connection at members 1, 8, and 2 failed.Number 8 missing, test procedure error occurred on this test but the results would be approximately the same as if member 11 was missing.

TEST RESULTSNumber 11 missing, the loading of the bridge had reached its maximum point at which failure occurred at member 5 due to shear forces.Number 2 missing, the results would be the same a number 3 missing but due to the difference in the wood quality and amount of glue applied at the joints the resultants loads were slightly different.

TEST RESULTSNumber 9 missing, this test would have the same results as if member 10 was missing, but due to the different quality of wood and the amount of glue used in the connections, the final result of maximum loads were different.

CONCLUSIONThe full truss tested very close to the theoretical value 40 lbs vs. 40.32 lbs.Removing a single member greatly reduced the amount weight that the bridge could hold.The fact that the unit was a truss allowed for a value of greater than 20.16 lbs when a single member was missing.Some of the failures occurred because of the inconsistency of the type of wood product.

CONCLUSIONIt is very important to make sure that the same amount of glue is used at each connection point.

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Trusses