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March 31, 2017 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, dated September 2, 2016.

Statement of Problem. A 100-year flood event destroyed a vehicle and pedestrian bridge over Spring Creek along Puddintown Road in College Township, Centre County, PA. The road that accessed the bridge is heavily travelled and is access to the Mount Nittany Medical Center, without the bridge traffic is rerouted a few miles around the bridge which disturbs residential traffic flow, school bus routes and exposes the residents of State College to severe risk since first responder vehicles do not have direct access to that area.

Objective. Pennsylvania Department of Transportation of (PennDOT) Engineering District 2-0 has initiated an emergency, fast track project to expedite the design of a new vehicle bridge over Spring Creek to replace the old bridge that was destroyed by the flood event.

Design Criteria. The replacement bridge should include: standard abutments, no piers (one span), deck material will be medium strength concrete (.23 meters thick), no cable anchorages and designed for the load of two AASHTO H20-44 trucks (225 kN) with one in each traffic lane. The bridge deck elevation will be set at 20 meters and the deck span will be 40 meters. Concept designs for both a Warren through truss bridge and a Howe through truss bridge will be performed by each design team. All other design criteria, such as: steel member type, steel cross section type, and steel member size, etc., will be selected by each design team.

Technical Approach.

Phase 1: Economic Efficiency. Cost was determined by using the Engineering Encounters Bridge Design 2016 (EEBD 2016) software and meeting all requirements. The design objective is to use EEBD 2016 to design a stable Warren and Howe through truss bridge that keeps the cost as low as possible, well below $300,000. As well as keeping the cost very low, the

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design had to ensure that the replacement bridge can safely support its own weight in addition to the weight of a standard truck loading (live load).

Phase 2: Structural Efficiency. Two bridges are built as scale models, one a Warren through truss bridge and the other a Howe through truss bridge. Each bridge was load tested in the lab to catastrophic failure. This testing will then prove one of the truss bridge types to exhibit the best structural efficiency. Structural efficiency is the ability of the truss bridge to safely dissipate live loads. The Structural Efficiency (SE) is calculated by dividing the load the bridge supports at catastrophic failure by the weight of the prototype bridge. The objective is to report which prototype, Howe through truss bridge or Warren through truss bridge, design is more effective at dissipating the force of a load. One prototype of the Howe through truss bridge and one prototype of the Warren truss bridge must be constructed out of standard (4-½ x ⅜ x 1/12 inch) wooden (white birch) popsicle (craft) sticks and Elmer’s white glue only. Hot glue may be used to attach the final 8 popsicle sticks (no more than 8) that act as the struts/floor beams between the two adjacent truss sections. For all teams to have consistent results, each prototype bridge should have a maximum of 60 popsicle sticks, with final dimensions of about 13.5 inches in length, 4 inches in height, and 4.5 inches in width. All materials used in the prototypes will be provided by PennDOT District 2-0. Each prototype (2 per design team) will be tested in the lab to catastrophic failure by test loading the top cord of the truss with a loading block attached to a dead load suspended from the block. Teams will estimate the weight of their bridges based on the weight study of typical bridge members. All prototype bridges shall be accurately weighed and measured prior to the load testing and this data will be recorded. The load at failure of each prototype will be accurately measured, with witnesses, and recorded. Once the bridge fails, an investigation will be conducted to determine exactly what part of the bridge failed and why. The investigation will be documented with photographs. The typical markings for identifying members and joints are shown in Figure 10. The failures would then be noted using these labels to note where the failure(s) occurred. A suggestion on how to improve the design or construction of the bridge will also be provided.

Results.

Phase 1: Economic Efficiency. The design process was difficult for both bridges when trying to keep the cost low, but structural efficiency high. The Warren Truss Bridge was constructed of about an equal mix of both carbon steel (least expensive, lowest strength) and quenched and tempered steel (most costly, highest strength). The Howe Truss Bridge was constructed of quenched and tempered steel, but manipulated so less total material would be used to reduce the cost. More details of the results can be reviewed in Attachment 1

Phase 2: Structural Efficiency. The structural efficiency of the Warren bridge was not

equal to the structural efficiency of the Howe bridge, although they were close. Both bridges had the same load at failure, but the Howe bridge prototype had a slightly smaller mass. For this reason, the structural efficiency of the Howe bridge was 416 while the structural efficiency

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of the Warren bridge was 379. This was partially due to the use of poor sticks on the Warren bridge, because it was intended to support a larger load. The Warren bridge had a larger mass because it was possible to double the popsicle sticks on the diagonals, whereas that was more difficult on the Howe bridge because of the need for horizontal popsicle sticks as well. Because of this limitation, the Howe bridge could not have as many reinforcements, yet in our personal case the loads at failure were the same, but this was not a theme overall as seen in class data. More information concluding the results of the prototype bridges can be found in Attachment 2.

Best Solution. The best solution for a replacement bridge over Spring Creek would be the Howe through truss bridge. The solution is formed on the conclusions made from numerous factors regarding both the Howe and Warren through truss bridges. The factors consist of the economic efficiency, structural efficiency, design efficiency, and constructability of the Warren and Howe bridges. The Economic Efficiency

The total cost of the Warren through truss bridge is $199,134.72 while the total cost of the Howe through truss bridge is $210,731.30. The costs conclude that the Warren through truss bridge is $11,596.58 less expensive than the Howe through truss bridge. The final cost breakdowns and totals can be seen in Table 1 and Table 4. The Structural Efficiency

The structural efficiency (SE) of the bridges is determined by the calculation mass of load at failure divided by the mass of the bridge. The Warren through truss bridge has a SE of 379 compared to the 416 SE of the Howe through truss bridge. There are eight design teams who each created and tested their own Warren and Howe bridges. The data of the results conclude the means (371 vs 347), geometric means (384 vs 353), minimums (172 vs 125), maximums (571 vs 584), and ranges (399 vs 459) of the SE values for the Warren and Howe bridges. This data can be found in Tables 7 and 8. Through this data, it can be concluded that the Warren truss through bridge is slightly structurally efficient than the Howe through truss bridge.

The Design Efficiency The design efficiency is calculated by dividing the total cost of the bridge by the structural efficiency (SE) of the bridge. The smaller the number is, the more efficient the design is. The design efficiency of the Warren bridge is 525.42 ($/SE) whereas the Howe bridge is 506.57 ($/SE) The Constructability

The overall constructability cost of the Warren through truss bridge is $11,596.58 less expensive than the Howe through truss bridge. The cost of the materials for the Warren through truss bridge is $89,934.72 compared to $103,331.30 for the Howe through truss bridge. The Warren through truss bridge requires more joints, so its connection costs would be more expensive than that of the Howe through truss bridge: $16,800 vs $16,000. The production cost is determined by the number of different types of material, including their size and type of bar, that would be used in the structure of the bridge. The production cost of the Warren through truss bridge is $15,000 and the cost of production for the Howe through truss bridge is $14,000. The difference is due to the fact that the Warren bridge design switched between materials

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slightly more often than the Howe. The overall constructability of the Warren through truss bridge is $121,734.72 and the Howe through truss bridge is $133,331.30. The breakdown of costs are laid out in Table 3 and Table 4.

Conclusions and Recommendations. It is recommended that the replacement bridge be a Howe through truss bridge. In both EEBD 2016 and the prototype testing, the Howe through truss proved to be more efficient overall. Although the cost of the Howe bridge is slightly more expensive ($6,399.27), the Howe bridge is more structurally efficient and has a better design efficiency. Therefore, the cost difference is not enough to choose a bridge that did not perform as well in testing. The people’s safety is worth much more than the small difference in costs. The Howe through truss bridge has proved to have the necessary qualities desired for the replacement bridge and would be a great choice. To advance to the final design process please contact The Spectrum Co. for more details regarding this project. Respectfully, Peyton Bayer Engineering Student EDSGN100 Section 002 Design Team 4 Design Team: The Spectrum College of Engineering Penn State University

Greg Gavazzi Engineering Student EDSGN100 Section 002 Design Team 4 Design Team: The Spectrum College of Engineering Penn State University

Michael Creighton Engineering Student EDSGN100 Section 002 Design Team 4 Design Team: The Spectrum College of Engineering Penn State University

Madisyn Lloyd Engineering Student EDSGN100 Section 002 Design Team 4 Design Team: The Spectrum College of Engineering Penn State University

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ATTACHMENT 1

Phase 1: Economic Efficiency

Howe Truss. The bridge designed in EEBD 2016 went through many iterations to minimize cost while

also withstanding the test load. The most cost efficient bridge was made with thin, expensive vertical and horizontal beams in conjunction with less expensive, thicker diagonal beams. Most of the tubes were also hollowed to reduce use of material and lower the total cost. The final design can be seen in Figure 1, and the load test results can be observed in Table 2.

The beams mostly taking on tension forces seemed to fail easier than the beams taking on mostly compressive forces. To combat this problem, we used thin quenched & tempered steel beams that gradually thickened as you got further from the middle of the bridge. The majority of the vertical beams were also made hollow to cut down costs without taking away from the load strength.

The beams mostly being compressed did not need to be made up of as strong material as the other beams so we used a 50/50 split of quenched & tempered steel, and carbon steel. The most efficient way to use these materials was to make them thick but hollow. This gave us the cheapest outcome while also passing the load test. The combination of material used and their thickness aided in the cost efficiency of the bridge. All cost values can be seen in Table 1. Most of the earlier designs for the bridge failed in the center. To fix this we made the center beams thicker than the others around it and made it out of a higher-grade steel. One of these center beams can be seen in a detailed member report in Table 3.

Warren Truss. Economic efficiency was determined through the bridge designed in EEBD 2016.

Manipulating of the design was done until the bridge was the lowest possible cost while still being structurally efficient. This goal was met by choosing wisely where high and low cost material was used for the members.

The goal was to make a low-cost replacement that would still be a useful and successful bridge. When designing the bridge, it was important to only use the strong expensive materials in the parts of the bridge that serve most support. All other places used lower cost materials because they worked just as well and were more cost efficient. Where the higher cost material (quenched and tempered steel) was used, the member would be as thin as possible to keep costs low. This high strength material has the highest cost to weight ratio, but the best strength to weight. This relationship can be viewed in Table 4. The use of this material along with carbon steel was cost effective because it costs less due to the ability to create thinner members with less material. Cost of the different materials with their thicknesses can be viewed in Table 5. The use of different materials and thicknesses was determined by the compressions and tensions of each member. Members 11, 13,15, and 20-27 are all thick, but hollow members to reduce the amount of material, thus reducing the cost. All other thicknesses of the other members were chosen by trial and error, making sure the bridge was still structurally efficient and lower in cost. The highest load on members of the bridge can be seen in Table 6.

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ATTACHMENT 2

Phase 2: Structural Efficiency

Howe Truss. The Howe Truss bridge was constructed using popsicle sticks, Elmer’s glue, and a small

amount of hot glue. The final prototype can be seen in figure 3. The bridge had a total mass of 77.4 grams

(.171 pounds) and failed at a load of 71 pounds. The mass and failure load can both be viewed in Table 7.

The Truss bridge after the failure can be seen in Figure 4. The structural efficiency was calculated by

dividing the maximum load by the mass of the bridge. The structural efficiency of the bridge was 416,

which is above the class average of 329.

Prototype Bridge. The Howe Truss prototype bridge was constructed using 58 wooden

popsicle sticks. The dimensions of the bridge were 4 inches in height, 4.5 inches in width, and 13.5 inches

in length. The popsicle sticks were bonded together using white Elmer’s glue. The glue was given a

minimum of a week to cure, but most of the sections were given two week to cure. The hot glue was used

to connect the struts and floor beams. This prototype can be viewed in Figure 3.

Load Testing. The Howe Truss Prototype Bridges from all design teams were tested until

failure. The test was set up in a way in which a platform was suspended from the center of the bridge’s

top beam. Weights were added to the suspended platform until the bridge failed. Our bridge failed at 71

lbs. With a total mass 77.4 grams (.171 lbs), the structural efficiency of the bridge ended up at 416. This

was above the average of 329. The minimum structural efficiency was 125 and the maximum was 581.

Ours ended up significantly closer to the maximum than the minimum. These results can be seen in Table

7. Forensic Analysis. The bridge failed when the load reached 71 pounds. One of the top beams

broke away from the hot glue, which can be seen in Figure 4. The wooden stick did not snap, but broke

away from the hot glue that connected it to the rest of the bridge. This most likely occurred due to the

imbalance of the bridge as a whole and the fact that we did not give enough time for the hot glue to fully

cure. The imbalance of the bridge caused a disproportionate distribution of force. This most likely put too

much force on that specific beam, and when combined with the incomplete glue joint, the beam broke

free from the glue. This problem could have been prevented by matching each side better so that one side

of the bridge was bigger than the other and by letting the final glues joints to cure longer.

Results. The results of the Howe Truss Bridge Prototype that we built can be seen in Figure 7

and Table 7. It has a structural efficiency of 416 which was above the 329 average. Group 2 had the

highest structural efficiency which was 581. Our bridge hd the second highest structural efficiency out of

the 8 groups.

Warren Truss. The Warren Truss Bridge Prototype was constructed using popsicle sticks, Elmer’s

glue, and a small amount of hot glue. The Warren bridge prototype can be viewed in Figures 5 and 6. The

prototype had a mass of 84.9 grams (.187 pounds) and held a load of 71 pounds. The structural efficiency

was calculated by dividing the maximum load by the mass of the bridge. The bridge had a structural

efficiency of 379 which was slightly above average of 371. These statistics can be viewed in Figure 8 and

Table 8.

Prototype Bridge. The prototype of the Warren through truss bridge consisted of 58 popsicle

sticks that were bonded together with Elmer’s white glue. The glue was given at least seven days to cure,

but most joints were given fourteen days to cure. The bridge had dimensions of 4 inches in height, 4.5

inches in width, and 13.5 inches in length. An image of the prototype can be viewed in Figure 5.

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Load Testing. The prototype bridge was load tested by placing a wooden block on the center

of the top chord of the bridge that was attached to a platform that held increasing weights. The prototype

failed when the load was 71 pounds. This load at failure resulted in a structural efficiency of 379. The

mass of the bridge and maximum load are displayed in Table 8. By viewing the table, it can be concluded

this prototype had an average performance compared to the other prototypes. The average structural

efficiency of the table is 371 compared to 379 of our prototype. The range for all design teams was 172 -

571 pounds. Our prototype fell in between the minimum and maximum loads. The broad range of

structural efficiencies exhibits the different designs and use of given materials, which resulted in various

results from each design team.

Forensic Analysis. An image of the Warren truss through bridge prototype after failure can be

viewed in Figure 6. The picture is hard to interpret but the top right joint between the top chord and

diagonal failed, possibly because a popsicle stick split on the bottom chord. The prototype was successful

until the load reached 71 pounds. This resulted in the splitting of a popsicle stick and the detachment of

one of the joints. The stick was weak and was not correctly placed because there was too much stress on

the location where it was placed (toward the center of the bottom chord). The failure may have also been

a result of the glue at the joint. It is also possible both failures occurred together. The glue may have not

seeped into the popsicle sticks, which would have made the bond too weak for a heavy load. Regardless,

the bridge failed due to glue error or placement of weak popsicle stick, which is not a result of a design

flaw.

Results. The Warren Through Truss Bridge results can be viewed in Table 8 and Figure 8. The

structural efficiency was above average at 379 compared to 371. The results were successful, and

although it is ranked in the bottom four of the eight teams, our efficiency is above the mean and sufficient

for its purpose. The design had negligible impact on the outcome of the load or structural efficiency. The

failure was due to the construction of the bridge. Other teams had similar designs with better or worse

results, proving that construction of the bridge prototypes was a major factor in the success of the bridge.

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TABLES

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Table 1 Howe Truss Bridge

Cost Calculation Report from Bridge Designer 2016

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Table 2 Howe Truss Bridge

Load Test Results from Bridge Designer 2016

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Table 3 Howe Truss Bridge

Member Details Report from Bridge Designer 2016 Member with Highest Compression Force/Strength Ratio

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Table 4 Warren Truss Bridge

Cost Calculation Report from Bridge Designer 2016

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Table 5 Warren Truss Bridge

Load Test Results from Bridge Designer 2016

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Table 6 Warren Truss Bridge

Member Details Report from Bridge Designer 2016 Member with the Highest Tension Force/Strength Ratio

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Table 7 Load Testing Results for the Howe Truss Bridge

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Table 8 Load Testing Results for the Warren Truss Bridge

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FIGURES

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Figure 1. Howe Truss Bridge from Bridge Designer 2016

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Figure 2. Warren Truss Bridge from Bridge Designer 2016

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Figure 3. Howe Truss Bridge Prototype Before Load Testing

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Figure 4. Howe Truss Bridge Prototype Failure After Load Testing

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Figure 5. Warren Truss Bridge Prototype Before Load Testing

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Figure 6. Warren Truss Bridge Prototype After Load Test

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Figure 7. Howe Truss Bridge Structural Efficiencies

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Figure 8. Warren Truss Bridge Structural Efficiencies