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Nov 7, 2014 Kevin R. Kline, PE, District Executive PennDOT Engineering District 2-0 1924 Daisy Street - P.O. Box 342 Clearfield County, PA 16830 Dear Mr. Kline:

Reference. PennDOT Engineering District 2-0, Statement of Work, subj: Concept Design for Vehicle Bridge over Spring Creek along Puddintown Road in College Township, Centre County, PA, revision #1, dated February 10, 2014.

Statement of Problem. A flood has destroyed a bridge located over Spring Creek along

Puddingtown Road in Collge Township, Centre County, PA. The bridge was a heavily traveled

road for many citizens in the area as well as a vital route to the Mount Nittany Medical Center.

Due to the collapse of the bridge, vehicles must be re-routed about 10 miles around the bridge

which is disruptive to residential traffic flow, local commerce, and puts the safety of State

College residents at risk due to not having an easy access to the medical center.

Objective. To facilitate the design of a new vehicle bridge over Spring Creek to replace the

bridge destroyed by the recent extreme flood event.

Design Criteria. The replacement bridge should include: standard abutments, no piers (one

span), deck material shall be medium strength concrete (0.23 meters thick), no cable anchorages

and designed for the load of two AASHTO H20-44 trucks (225kN) with one in each traffic lane.

The bridge deck elevation shall be set at 20 meters and the deck span shall be exactly 40 meters.

Both a Warren through truss bridge and a Howe through truss bridge shall be analyzed.All other

design criteria, such as: steel member type, steel cross section type, and steel member size shall

be selected by each EDSGN100 design team.

Technical Approach.

Phase 1: Economic Efficiency. To determine Economic Efficiency the constraints, performance,

and requirements are factors in determining the cost of the bridge. The cost of the bridge should

be as low as possible and be able to support its own weight plus the weight of a standard truck.

School of Engineering Design, Technology and Professional Programs 213 Hammond Building

University Park, PA 16802-2701

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Phase 2: Structural Efficiency. For the two prototypes of bridges we built (Howe and Truss),

each bridge was allowed a maximum of sixty (60) of the standard (4-1/2 x 3/8 x 1/12 inch)

wooden (white birch) Popsicle (craft) sticks and Elmer’s white glue only. Eight (8) of the

popsicle sticks had to be used for the struts/floor beams and those were attached by using only

hot glue. In order to make our bridges structurally efficient, we made sure that all of our popsicle

sticks were level with one another. This ensures that the bridge is level which will allow it to

withstand more weight without swaying one direction, which would ultimately lead to the bridge

collapsing.

Results.

Phase 1: Economic Efficiency. We concluded that the Warren Truss Bridge was more

structural efficient, as well as less expensive than the Howe Truss Bridge. On West Point Bridge

Designer (WPBD), our final total for the Warren bridge was $246,962.39 while our total for the

Howe bridge was $273,700.49. We lowered the prices by testing different materials, making less

expensive materials stronger, and trying to make our bridge smaller but still making sure that the

truck can get across the bridge.

Phase 2: Structural Efficiency. We concluded that the Warren Truss was more structurally

efficient than the Howe Truss. We came to this conclusion by making a prototype of each bridge.

We were allowed a total of 60 popsicle sticks for each bridge and we used Elmer’s white glue

and allowed curing time so that the bonds keeping the popsicle sticks together would be strong.

We tried our best to make sure that all sticks were level with one another so that when we load

the bridges, the weight will distribute evenly across the bridge. When testing the loading, our

Warren bridge was able to withstand about 43.6 pounds while our Howe Truss could only

withstand 33.4 pounds.

Best Solution. Based on our data we collected, we recommend the Warren bridge as the best

solution. Not only is it more economically efficient, but it is also more structural efficient. The

Warren bridge is about $26,738.1 cheaper than the Howe truss. In addition, with our prototypes,

we discovered that the Warren bridge can also withhold more weight than the Howe bridge. By

looking at our data, the Howe bridge could only withstand 33.4 pounds while the Warren Bridge

could withhold 43.6 pounds, which is about a 10 pound difference.

Conclusions and Recommendations Our recommendation would be to build a Warren

Bridge because it is the most structural and economic efficient. The initial step should be to

gather the necessary materials and build a primary deck and then build the sides of the bridge. Respectfully,

Luke Emerson

Engineering Student

EDSGN100 Design Team #6

College of Engineering

Penn State University

Anjana Setlur

Engineering Student

EDSGN100 Design Team #6

College of Engineering

Penn State University

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Jacqueline Chen

Engineering Student

EDSGN100 Design Team #6

College of Engineering

Penn State University

Julian Freedman

Engineering Student

EDSGN100 Design Team 6

College of Engineering

Penn State University

ATTACHMENT 1

. table 1

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Table 2

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table 3

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Figure 1

Table 4

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Table 5

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Table

6:

Figure 2

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ATTACHMENT 2

Phase 2: Structural Efficiency

Howe Truss. The results from the structural efficiency study showed that the Howe Bridge was

successful in being able to undergo the tension and compressional forces that were applied to the

bridge in testing. We used the West Point Bridge Design software in order to manipulate

different elements of the warren truss bridge. We concluded that the best method was to mainly

focus on decreasing the thickness of each member in order to get the force to strength ratio as

close to zero as possible. We implemented structural efficiency into our physical bridge by

creating a ranking system where the best Popsicle sticks were ranked as a 3 and the worst a 1.

Using this scale we were able to strategically place the Popsicle sticks in order to maximize the

efficiency of the design. We also made sure to sand each end of the Popsicle stick where it would

form a joint with another stick in order to help to strengthen the bond.

Prototype Bridge. For the Howe Bridge we first drew out a design then proceeded to build the

bridge sides and hold it in place with tape. After that we sanded and glued the pieces together

and held them in place with the clips that were provided.

Load Testing. Our team, team six, had the weakest bridge when load testing the Howe Bridge.

Compared to the other teams our bridge was ranked the lowest while the strongest Howe Bridge

was rated a 1.3. While our team was ranked the lowest, our bridge could still withstand a small

load.

Forensic Analysis. The Howe Truss Bridge failed due to structural errors. It failed at 33.4 lbs,

which was disappointing to say the least. The verticals would lean right with slight pressure to

the top. Not all the top struts were level as well. As a result, the weight of the load was not

distributed evenly, and the bridge almost instantly broke.

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Results.

Warren Truss. The results from the structural efficiency study showed that the warren bridge

was successful in being able to undergo the tension and compressional forces that were applied

to the bridge in testing. We used the West Point Bridge Design software in order to manipulate

different elements of the warren truss bridge. We concluded that the best method was to mainly

focus on decreasing the thickness of each member in order to get the force to strength ratio as

close to zero as possible. We implemented structural efficiency into our physical bridge by

creating a ranking system where the best Popsicle sticks were ranked as a 3 and the worst a 1.

Using this scale we were able to strategically place the Popsicle sticks in order to maximize the

efficiency of the design. We also made sure to sand each end of the Popsicle stick where it would

form a joint with another stick in order to help to strengthen the bond.

The structural efficiencies for the Warren Bridge with the estimated weight and the actual differ

because the estimated weight was a lot heavier therefore its structural efficiency is significantly

less than the actual bridge’s weight.

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Prototype Bridge. Just like the Howe Bridge we also first drew out a design then proceeded to

build the bridge sides and hold it in place with tape. After that we sanded and glued the pieces

together and held them in place with the clips that were provided.

Load Testing. Our Warren bridge, was rated a .5 on the structural efficiency scale. While this

rating is not the best compared to the other design teams, our bridge broke at the struts compared

to other teams were their sidings would break as well. When our team was load testing the

prototype bridge, we were pouring the sand at a more rapid rate, ensuring the bucket would not

sway.

Forensic Analysis. The Warren Truss Bridge fared better than our Howe Truss Bridge. It

failed at 43.6 lbs. The top struts were what failed this bridge. They were not level so the uneven

distribution of weight was too much too hold for the few struts that were level.

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