Dhushy Sathianathan, Head



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Oct 21, 2016

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 structurally deficient bridge at Spring Creek along Puddingtown Road in College Township, Centre County, PA was destroyed by a local flooding from a recent 100-year flood. This bridge was heavily traveled upon and used to serve most traffic bound to the Mount Nittany Medical Center in State College, PA. Vehicular access to the Mount Nittany Medical Center has been restricted by the destruction of the bridge.

Objective. The Pennsylvania Department of Transportation (PennDOT) of Engineering District 2-0 has initiated a fast-track project to expedite the design a new vehicle bridge over Spring Creek to replace the bridge destroyed by the recent extreme flood event.

Design Criteria. The design criteria for the reconstruction of the bridge include: standard abutments, no piers (single span), deck material being medium strength concrete, having no cable anchorages and being designed for the load of two AASHTO H20-44 trucks (weighing 225kN each).

Technical Approach.

Phase 1: Economic Efficiency. The original idea in making the bridge designs economically efficient involved maintaining structural member consistency and substituting cheaper versions of structural members who did not experience maximum safe levels of compression and tension.

Phase 2: Structural Efficiency. In making the bridge designs structurally efficient, length consistency was followed through, resulting in the camelback design present on both Howe and Warren Truss bridges. This configuration evenly distributed stress on all members.

Results.

Phase 1: Economic Efficiency. The largest cost cutter was using hollow tubes made of quenched and tempered steel at the smallest load-allowing size as it provided large amounts of strength while keeping costs low. Additionally, the top chord was made arched which allowed the bridge to be made of similar sized members across due to evenly spread the forces.

Phase 2: Structural Efficiency. The hollow tube design cut down on weight while keeping structural integrity at a safe standard, this gives the highest possible structural efficiency. The strength of the cord in testing was never the greatest issue, making sure the chord was perpendicular the loading platform was the greatest concern since every prototype failed due to leaning.

Best Solution. The “Best Solution” based on economic efficiency, structural efficiency, design efficiency, and constructability is by far the Warren.

The Economic Efficiency of the warren was the best coming in at $198,565, while the Howe

was $206,065.

The Structural Efficiency(SE) of a warren bridge was superior to a Howe bridge based off of the average and maximum SE. The average value for the warren SE was 360 whereas the average Howe SE was 244. The maximum SE for a Howe was only 331, whereas the Warren came in at a staggering 641.

The Design Efficiency, of the Warren Truss bridge was $463/unit of structural efficiency while the design efficiency of the Howe Truss bridge was $622/unit of structural efficiency.

The Constructability of Warren bridge was better overall compared to the Howe bridge. It only contained 9 different materials whereas the Warren had 12. The Howe did one less joint the Warren however with 20 joints, saving four hundred dollars. The Warrens material cost, about ninety thousand dollars, was around five thousand dollars less than the Howe’s.

Conclusions and Recommendations. It is recommended that the Warren Truss Bridge be used to replace the bridge destroyed by the recent extreme flood event. Since the Warren bridge is better in all categories, PennDOT should proceed with the production of a Warren Truss bridge.

Respectfully,

|Jared Bunch |CJ Solt |

|Engineering Student |Engineering Student |

|EDSGN100 Section 001 |EDSGN100 Section 001 |

|Design Team 7 |Design Team 7 |

|Design Team BOST Industries |Design Team BOST Industries |

|College of Engineering |College of Engineering |

|Penn State University |Penn State University |

| | |

|Zachary Timothy |Jerome Orji |

|Engineering Student |Engineering Student |

|EDSGN100 Section 001 |EDSGN100 Section 001 |

|Design Team 7 |Design Team 7 |

|Design Team BOST Industries |Design Team BOST Industries |

|College of Engineering |College of Engineering |

|Penn State University |Penn State University |

ATTACHMENT 1

Phase 1: Economic Efficiency

Howe Truss. As shown in Table 1, the total cost of the Howe Truss bridge was $206,065.80 which is comprised of the material costs, connection costs, product costs, and site costs. The greatest way in which economic efficiency was achieved was by using thin hollow tubes made of quenched and tempered steel. This gave the greatest strength per dollar for the bridge in most situations. Table 1 shows that any variation in the size or type of material used adds $1,000 to the total costs. Therefore, efforts were made to keep the size and type of material consistent. For example, as seen in Figure 2, the bridge deck was made out of only two different sized members. Additionally, wherever there was similar tension and compression in members, they were made the same size to reduce the costs as seen in Table 2. Another way costs were reduced was to have the smallest size possible for the stress of a member without failure. This is exemplified in member 31 as shown in Table 3 which has the highest force to strength ratio.

Warren Truss. As shown in Table 4, the total cost of the Warren Truss bridge was $198,565.63 which is comprised of the material costs, connection costs, product costs, and site costs. The greatest way in which economic efficiency was achieved was by using thin hollow tubes made of quenched and tempered steel. This gave the greatest strength per dollar for the bridge in most situations. Table 4 shows that any variation in the size or type of material used adds $1,000 to the total costs. Therefore, efforts were made to keep the size and type of material consistent. For example, as seen in Figure 2, the top chord was arched which creates similar compression through all the members. This allowed for only two sized to be needed. Additionally, wherever there was similar tension and compression in members, they were made the same size to reduce the costs as seen in Table 5. Another way costs were reduced was to have the smallest size possible for the stress of a member without failure. This is exemplified in member 15 as shown in Table 6 which has the highest force to strength ratio.

ATTACHMENT 2

Phase 2: Structural Efficiency

Howe Truss.

Prototype Bridge. The prototype bridge was built out of 60 popsicle sticks. Every popsicle stick surface that would be in contact with another stick was sanded in order to increase the surface area that contacts the glue. While the glue was curing, binder clips were used to ensure the popsicle sticks remained in the proper positions. Finally, additional support was added where the bridge would experience the most stress. For example, as shown in Figure 3, the center top chord experienced the most force and was designed to be three popsicle sticks thick. Finally, the Truss’s were placed roughly at a perpendicular angle to counteract the tilt that the mass would have on the bridge.

Load Testing. As seen in table 7, the average structural efficiency for the Howe Truss Bridge was 244.73. The minimum value for the structural efficiency was 175.58, the maximum value was 331.07, the range was 155.48, and BOST’s design had the maximum structural efficiency at 331.07. In order for a bridge to be structurally efficient, it must hold large weights while remaining light.

Forensic Analysis. At failure, the bridge tilted which twisted members of the top and bottom chord causing them to break. This twisting motion was caused since the two truss’s were not oriented completely perpendicular to the table so they tilted as more weight was added. Gluing was not a problem since the popsicle sticks broke before the joint failed which indicated strong joints. The break occurred at the members which most of the weight rested on as shown in Figure 4.

Results. The results for the structural efficiencies of all of the Howe Bridges in the class can be seen in Figure 7.

Warren Truss.

Prototype Bridge. The prototype bridge was built out of 60 popsicle sticks. Every popsicle stick surface that would be in contact with another stick was sanded in order to increase the surface area that contacts the glue. While the glue was curing, binder clips were used to ensure the popsicle sticks remained in the proper positions. Finally, additional support was added where the bridge would experience the most stress. For example, as shown in Figure 5, the center top chord experienced the most force and was designed to be five popsicle sticks thick. Finally, extreme care was given to ensuring that each truss was perpendicular to the horizontal and parallel to the other truss.

Load Testing. As seen in table 8, the average structural efficiency for the Warren Truss Bridge was 360.47. The minimum value for the structural efficiency was 182.34, the maximum value was 641.7, the range was 459.36, and BOST’s design had the maximum structural efficiency at 428.57. In order for a bridge to be structurally efficient, it must hold large weights while remaining light.

Forensic Analysis. The cause of failure for the warren bridge was leaning. It began to tilt, then fell on its side causing the cross members and bottom cord to break. This could be due to the loading platform not being exactly level. An un-level platform causes bridges to have a lean initially, which when weight is added, gets emphasized ultimately causing failure.

Results. The results for the structural efficiencies of all of the Howe Bridges in the class can be seen in Figure 8. On average, the efficiencies of the warren bridge exceeded those of the Howe bridge.

TABLES

|Type of Cost |Item |Cost Calculation |Cost |

|Material Cost (M) |Carbon Steel Hollow Tube |(1234.8 kg) x ($6.30 per kg) x (2 |$15,558.47 |

| | |Trusses) = | |

|  |Quenched & Tempered Steel Hollow Tube |(5526.5 kg) x ($7.70 per kg) x (2 |$85,107.34 |

| | |Trusses) = | |

|Connection Cost (C) |  |(20 Joints) x (400.0 per joint) x (2|$16,000.00 |

| | |Trusses) = | |

|Product Cost (P) | 6 - 90x90x4 mm Quenched & Tempered Steel |($1000 per Product) = |$1,000.00 |

| |Tube | | |

|  | 1 - 100x100x5 mm Quenched & Tempered Steel|($1000per Product) = |$1,000.00 |

| |Tube | | |

|  | 2 - 110x110x5 mm Quenched & Tempered Steel|($1000 per Product) = |$1,000.00 |

| |Tube | | |

|  | 2 - 120x120x6 mm Carbon Steel Tube |($1000 per Product) = |$1,000.00 |

|  | 2 - 140x140x7 mm Carbon Steel Tube |($1000 per Product) = |$1,000.00 |

|  | 2 - 150x150x7 mm Quenched & Tempered Steel|($1000 per Product) = |$1,000.00 |

| |Tube | | |

|  | 2 - 160x160x8 mm Carbon Steel Tube |($1000 per Product) = |$1,000.00 |

|  | 2 - 170x170x8 mm Quenched & Tempered Steel|($1000 per Product) = |$1,000.00 |

| |Tube | | |

|  | 8 - 180x180x9 mm Quenched & Tempered Steel|($1000 per Product) = |$1,000.00 |

| |Tube | | |

|  | 2 - 190x190x9 mm Quenched & Tempered Steel|($1000 per Product) = |$1,000.00 |

| |Tube | | |

|  | 3 - 200x200x10 mm Quenched & Tempered |($1000 per Product) = |$1,000.00 |

| |Steel Tube | | |

|  | 5 - 220x220x11 mm Quenched & Tempered |($1000 per Product) = |$1,000.00 |

| |Steel Tube | | |

|Site Cost (S) |Deck Cost |(10 4-meter panels) x ($4,700.00 per|$47,000.00 |

| | |panel) = | |

|  |Excavation Cost |(19,400 cubic meters) x ($1.00 per |$19,400.00 |

| | |cubic meter) = | |

|  |Abutment Cost |(2 standard abutments) x ($5,500.00 |$11,000.00 |

| | |per abutment) = | |

|  |Pier Cost |No pier = |$0.00 |

|  |Cable Anchorage Cost |No anchorages = |$0.00 |

|Total Cost |M + C + P + S |$100,665.80 + $16,000.00 + |$206,065.80 |

| | |$12,000.00 + $77,400.00 = | |

| | |Table 2 | |

| | |Load Test Results Report from Bridge Designer 2016 for the Howe Truss Bridge | |

|# |Material Type |Cross Section |Size (mm) |

|Material Cost (M) |Carbon Steel Hollow Tube |(1554.4 kg) x ($6.30 per kg) x (2 Trusses) = |$19,585.21 |

|  |Quenched & Tempered Steel Hollow |(4920.8 kg) x ($7.70 per kg) x (2 Trusses) = |$75,780.42 |

| |Tube | | |

|Connection Cost (C) |  |(21 Joints) x (400.0 per joint) x (2 Trusses)|$16,800.00 |

| | |= | |

|Product Cost (P) | 2 - 100x100x5 mm Carbon Steel |(%s per Product) = |$1,000.00 |

| |Tube | | |

|  | 4 - 110x110x5 mm Carbon Steel |(%s per Product) = |$1,000.00 |

| |Tube | | |

|  | 4 - 120x120x6 mm Carbon Steel |(%s per Product) = |$1,000.00 |

| |Tube | | |

|  | 4 - 130x130x6 mm Quenched & |(%s per Product) = |$1,000.00 |

| |Tempered Steel Tube | | |

|  | 4 - 140x140x7 mm Carbon Steel |(%s per Product) = |$1,000.00 |

| |Tube | | |

|  | 2 - 140x140x7 mm Quenched & |(%s per Product) = |$1,000.00 |

| |Tempered Steel Tube | | |

|  |10 - 180x180x9 mm Quenched & |(%s per Product) = |$1,000.00 |

| |Tempered Steel Tube | | |

|  | 2 - 200x200x10 mm Quenched & |(%s per Product) = |$1,000.00 |

| |Tempered Steel Tube | | |

|  | 7 - 220x220x11 mm Quenched & |(%s per Product) = |$1,000.00 |

| |Tempered Steel Tube | | |

|Site Cost (S) |Deck Cost |(10 4-meter panels) x ($4,700.00 per panel) =|$47,000.00 |

|  |Excavation Cost |(19,400 cubic meters) x ($1.00 per cubic |$19,400.00 |

| | |meter) = | |

|  |Abutment Cost |(2 standard abutments) x ($5,500.00 per |$11,000.00 |

| | |abutment) = | |

|  |Pier Cost |No pier = |$0.00 |

|  |Cable Anchorage Cost |No anchorages = |$0.00 |

|Total Cost |M + C + P + S |$95,365.63 + $16,800.00 + $9,000.00 + |$198,565.63 |

| | |$77,400.00 = | |

Table 5

Load Test Results Report from Bridge Designer 2016 for the Warren Truss Bridge

|# |Material Type |

|Design Team No. |Actual Bridge Weight (grams) |Actual Bridge Weight (lbs.) |LOAD at Failure (lbs.) |Structural Efficiency |

|1 |71.9 |0.158 |48.1 |303.45 |

|2 |83.7 |0.184 |32.4 |175.58 |

|3 |81.4 |0.179 |32.6 |181.66 |

|4 |81 |0.179 |47.8 |267.68 |

|5 |60.7 |0.133 |40.3 |301.15 |

|6 |70.4 |0.158 |32.4 |208.76 |

|7 |73.3 |0.162 |53.5 |331.07 |

|8 |77.5 |0.171 |32.2 |188.46 |

| | | |minimum |175.58 |

| | | |maximum |331.07 |

| | | |range |155.48 |

| | | |average |244.7250329 |

Table 8 Load Testing Results for the Warren Truss Bridge

|Design Team No. |Actual Bridge Weight |Bridge Weight (lbs.) |LOAD at Failure (lbs.) |Structural Efficiency |

| |(grams) | | | |

|1 |85.1 |0.188 |40.2 |214.27 |

|2 |78.6 |0.173 |63.3 |365.3 |

|3 |77.2 |0.170 |58.8 |345.48 |

|4 |76.2 |0.168 |107.8 |641.7 |

|5 |75 |0.165 |74.5 |450.57 |

|6 |85.2 |0.188 |48 |255.55 |

|7 |87 |0.192 |82.2 |428.57 |

|8 |80.6 |0.178 |32.4 |182.34 |

| | |minimum |182.34 | |

| | |maximum |641.7 | |

| | |range |459.36 | |

| | |average |360.4709342 | |

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FIGURES

Figure 1.  Howe Truss Bridge Model from Bridge Designer 2016

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Figure 2.  Warren Truss Bridge Model from Bridge Designer 2016[pic]

Figure 3.  Howe Truss Bridge Prototype before Load Testing

Figure 4.  Howe Truss Bridge Prototype Failure after Load Testing

Figure 5.  Warren Truss Bridge Prototype before Load Testing

Figure 6.  Warren Truss Bridge Prototype Failure after Load Testing

Figure 7. Howe Truss Bridge Structural Efficiencies

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Figure 8. Warren Truss Bridge Structural Efficiencies

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School of Engineering Design, Technology and Professional Programs

213 Hammond Building

University Park, PA 16802-2701

Table 1

Cost Calculation Report from Bridge Designer 2016 for the Howe Truss Bridge

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