FINAL PROJECT

PHYSICS 1401

JEFFERY DING

ALAN JONES

TRUSSES

• TRUSSES ARE USED IN NUMEROUS MANNERS.

• BRIDGE TRUSSES• ROOF TRUSSES • CONVEYOR FRAME TRUSSES• CRANE BOOM TRUSSES

COMMON TYPES OF TRUSSES

• TRUSSES WERE COMMONLY NAMED AFTER THE PERSON WHO DEVELOPED THEM

• EXAMPLES ARE AS FOLLOWS• King Post• Warren• Howe • English• Pratt• Fink • Parker

KING POST

WARREN

HOWE

ENGLISH

PRATT

FINK

PARKER

COMMON TYPES OF TRUSSES

• SOME WERE NAMED AFTER THE SHAPE OR CITY IN WHICH THEY WERE FIRST USED

• Bowstring• Baltimore• Pettit

BOWSTRING

BALTIMORE

PETTIT

TRUSSES

• Trusses 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.

TRUSSES

• Bridge 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.

TRUSSES

• Other 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 TRUSS

• Basic Shape and Construction• Truss was constructed from Popsicle sticks• Truss configuration was a three section Warren

truss.• Basic bridge dimensions are 13.5 inches long, 3.5

inches tall, and 2 inches wide.

TRUSS DRAWING

1

2 3

4

567

8 910

11

TRUSS DRAWING

TRUSS DRAWING

TRUSS DRAWING

TRUSS DRAWING

Predicted Weakness/Strength

• The 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 Inches

• Ultimate Shear Strength in psi for white pine is 860 psi

Shear Force= 860psi/.02347375 sq in

THEORETICAL STRENGTH

• Shear Force= 20.16 lbs per side• Two sides under common load=Total load of

20.16lbs.times 2= 40.32 lbs.• Maximum Load= 40.32 lbs.

20.1 LBS

7.07 LBS 7.07 LBS

7.07 LBS7.07 LBS 7.07 LBS

14.2 LBS14.2 LBS 14.2 LBS 14.2 LBS14.2 LBS 14.2 LBS

DESIGN LOADS/SIDE

TEST BREAKS

• TEST 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 BREAKS• TEST MEMBER POUNDS MISSING

• 11 26.4 lbs.

• 2 20.0 lbs. • 9 25.8 lbs.

TRUSS TEST

1

2 3

4

567

8 910

11

40 LBS

NO MEMBERS MISSING

TRUSS TEST

1

2 3

4

567

8 910

11

15.6 LBS

MEMBER THREE MISSING

TRUSS TEST

1

2 3

4

567

8 910

11

19.0 LBS.

MEMBER SIX MISSING

TRUSS TEST

1

2 3

4

567

8 910

11

32.0 LBS

MEMBER TEN MISSING

TRUSS TEST

1

2 3

4

567

8 910

11

26.6 LBS

MEMBER FOUR MISSING

TRUSS TEST

1

2 3

4

567

8 910

11

36.2 LBS.

MEMBER SEVEN MISSING

TRUSS TEST

1

2 3

4

567

8 910

11

40 LBS.

MEMBER EIGHT MISSING

TESTING ERROR

TRUSS TEST

1

2 3

4

567

8 910

11

26.4 LBS

MEMBER ELEVEN MISSING

TRUSS TEST

1

2 3

4

567

8 910

11

20.0 LBS

MEMBER TWO MISSING

TRUSS TEST

1

2 3

4

567

8 910

11

25.8 LBS

MEMBER NINE MISSING

TEST RESULTS• Number 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 REUSLTS• Number 10 missing, the

bridge could withstand more load since the force was transferred to member 9 until it became overloaded and failure occurred

• Number 4 missing, the load was carried by the majority of the truss until the bending of member 5 failed.

TEST RESULTS• Number 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 RESULTS• Number 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 RESULTS

Number 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.

CONCLUSION

• The 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.

CONCLUSION• It is very important to make sure that the

same amount of glue is used at each connection point.