School of Engineering Design, Technology and Professional Programs

213 Hammond Building

University Park, PA 16802-2701

March 31, 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. Flooding has completely destroyed the structurally deficient vehicle bridge above Spring Creek in College Township, Centre County, PA (PennDOT Engineering District 2-0). The destroyed bridge acted as a vital lifeline for access to the Mount Nittany Medical Center in State College, PA. Traffic now must be re-routed for an extra 10 miles in an area highly populated by local vehicles, thus disrupting residential traffic flow, local commerce, and risking the lives of residents in emergency situations. Objective. PennDOT Engineering District 2-0 initiated an emergency project expediting the design of a new vehicle bridge over Spring Creek to replace the bridge destroyed by the recent extreme flood event. Design Criteria. PennDOT District 2-0 requires the replacement bridge includes: standard abutments, no piers (one span), deck material of medium strength concrete (.23 meters thick), no cable anchorages, and hold load of one AASHto H20-44 truck (225 kN) in each traffic lane. Bridge deck elevation of 20 meters and a deck span of 40 meters. Both Warren and Howe through truss bridges shall be analyzed. Each EDSGN 100 design team selects all other design criteria: steel member type, steel cross section type, and steel member size. Technical Approach. Phase 1: Economic Efficiency. Cost efficiency is to be determined using the West Point Bridge Designer 2013 software. Use WPBD 2013 to design a stable Warren and Howe through truss bridge that has been optimized to keep the cost of the replacement bridge at a minimum while ensuring the bridge can support both a dead and live load.

Phase 2: Structural Efficiency. A prototype bridge of both a Warren and Howe through truss bridge shall be designed, built, and load tested until catastrophic failure (shown in Figures 8 and 9). The bridge that exhibits the best structural efficiency, or ability to safely dissipate live loads, will be determined through the prototypes. Each EDSGN 100 design team is to construct a prototype of the Warren and Howe through truss bridges using Elmer’s white glue and no more than 60 standard wooden Popsicle sticks per bridge. Out of the 60 Popsicle sticks, only 8 are to be used along with hot glue to attach struts/floor beams between the two adjacent truss sections. All materials will be provided by PennDOT District 2-0 and all bridges are to be approximately 13.5 inches in length, 4 inches in height and 4.5 inches in width. Examples of a Howe through truss bridge prototype can be found in Figures 2,3, and 4. Examples of a Warren through truss bridge prototype can be found in Figures 5,6, and 7. Results. Phase 1: Economic Efficiency. The West Point bridge design software helped us to be able to analyze the bridges and compare the cost. The Howe bridge we were able to get the price down to $216,643.91 while still being able to pass the load test. The Warren truss bridge was slightly cheaper with a cost of $208,919.62. We were able to get the Warren truss bridge cheaper mainly because it required less material to build with fewer members at higher tension or compression. See attachment 1 for further information regarding the economic efficiency. Phase 2: Structural Efficiency. In the load test the bridges were tested by using load applied to the center of the bridge. The Warren bridge was able to withstand a higher load than the Howe in the load testing. The Howe bridge failed in the bottom cord with one of the members breaking and caused the bridge to fall of the supports. The Warren failed at the top cord when one of the joints failed and caused all the struts to come off the bridge and lead the bridge to split apart. For further details see attachment 2. Best Solution. The Warren through truss bridge was more economically efficient design. Through the use of West Point bridge design software the Warren through truss bridge was $8,000 less than the Howe bridge. Through Structural test the Warren was able to carry a load almost double the weight of the Howe bridge. For economical and structural strength the Warren through truss bridge design was the most appropriate solution and should be considered to be used for this project. Conclusions and Recommendations. According to our structural efficiency tests and economical efficiency calculations the Warren through truss bridge would be best suited for the replacement bridge. The bridge will be able to provide the support needed to withstand vehicular traffic without the need of a pier in the middle of the creek. The Warren through truss bridge will be able to use fewer members leading to a shorter construction time and less materials and workers to replace the bridge. The next step would be to approve the Warren through truss bridge design which would allow us to start the project to help to minimize congestion in the shortest amount of time at the medical center. Respectfully,

Ryan McKay Engineering Student EDSGN 100 Design Team #6 College of Engineering Penn State University

Hamad Alkhoori Engineering Student EDSGN 100 Design Team #6 College of Engineering Penn State University

Lisa Argentina Engineering Student EDSGN 100 Design Team #6 College of Engineering Penn State University

ATTACHMENT 1

Phase 1: Economic Efficiency

Howe Truss. Figure 1

Table 1

Table 2

Table 3

We were able to lower the cost by going through each member and slowly reducing the size of the member. We also found that if you use the Hollow tubes for the members that are in compression they end up being stronger and reduce the cost of the bridge. It was also cheaper to buy the members in packages so if you increased the size of some of the members to get more of the same member it reduced the cost of the bridge while adding more strength to the bridge. We decided to use the Quenched Tempered steel was able to hold the most weight while being the cheapest option for the bridge. In table 1 the table shows the cost of different types of costs. The production cost was what we used to bring the price down at the end by buying things in bulk. In Table 2 the table reveals the strength of each individual member in bridge telling you where you need to work on because the member is too strong and not needed to be used. In table 3 the member #35 has the highest compressive force/strength ratio on the bridge. This member is used closest to the maximum strength it can support on the bridge. Warren Truss.

Figure 2 Table 4

Table 5

Table 6

The Warren through truss bridge was built at a lower cost than the Howe through truss bridge. The Warren through truss bridge required less members than the Howe through truss bridge. Through the use of the quenched and tempered steel we were able to get the most strength at the lowest cost. We also bought items in bulk when we were able to, to help reduce the production cost of the bridge. Table 4 reveals the cost by category for the Warren through truss bridge. Table 5 provides information on the compression or tension force on each member. Table 6 shows member 35 which has the value of compressive force/strength whose value is closest to 1. This shows that this member is well used and is not overbuilt for the design.

ATTACHMENT 2

Phase 2: Structural Efficiency

Howe Truss. The Howe Truss Bridge was able to hold 40.3 lbs. until it failed at one of the joints. The Howe was much weaker than the Warren although the Howe has more members attached diagonally and vertically. We were expecting the Howe to withstand more load before we started the load testing but at the end we saw that it was the opposite of our expectation. We estimated the Howe bridge weight to be 79g. The actual weight was 78.1g. Structural Efficiency for estimated weight= Load at Failure/Weight of Structure=18,415.85g/79g=233.11 Structural efficiency for actual weight=Load at Failure/Weight of Structure=18,415.85g/78.1g=235.8 Prototype Bridge. At the beginning of the project, we started by thinking of the best way to arrange the popsicle sticks that will give the strongest and most rigid structure. We separated the popsicle sticks for the bottom and top cords from the rest and we also kept the popsicle sticks for each bridge separate.Then we tried to put the popsicle sticks on each other without any gluing until we almost came up with the best design. After that, we drew the bridge design on a paper to make sure the popsicle sticks were placed correctly before gluing. Finally, we placed the top and bottom chords on the drawing on the paper and started by gluing them. After we finished with them, we started to glue the vertical members, and then we finally glued the diagonals. We clamped all the members to make sure the glue penetrates them and makes the members attached strongly. We used all 60 popsicle sticks for the bridge and the dimensions of the bridge were: height:3-3/4 in, width: 4-½ in, and length: 13-¼ in.

Figure 3

Load Testing. Table 7

Design Team No. Load at Failure (lbs.)

1 136.6

2 27.9

3 60.7

4 52.7

5 50.4

6 40.6

7 30.8

According to the table, we were the 5th among the other groups. The average load was 57.1 lbs. While our bridge was lower than the average the bridge collapsed mostly due to a joint failure. So the issue was not with the design but with inadequate glueing of the joint. Forensic Analysis.

Figure 4

The Howe truss bridge failed at the bottom cord where the members pulled away from the joint. The bridge started to lean and snapped one of the members causing the bridge to fail. The failure was mostly due to a force that caused the bridge to lean and put a stress on the member causing it to be in compression. This ended up snapping the member and causing the bridge to fail. Results.

Table 8

Design Team No. Structural Efficiency

1 816.35

2 171.71

3 373.58

4 474.29

5 301.20

6 235.80

7 179.34

Figure 7

Warren Truss. The Warren bridge was able to carry 83.3 lbs. until it failed at the top and bottom chords due to the detachment of one of the chords at the top which caused all of the others to move out of their place and detach. The Warren was able to carry a large amount of weight compared to the Howe despite the fact that the Howe has more vertical and diagonal members and looks like it can carry more weight. So, it was structurally efficient. It really exceeded our expectation and we see that it did good in the load testing. The estimated bridge weight was 80.5g and the actual was 77.7g. Structural Efficiency using estimated weight= 37784.24g/80.5g= 469.37 Structural Efficiency using actual weight= 37784.24g/77.7g= 486.28 Prototype Bridge.

At the beginning of the project, we started by thinking of the best way to arrange the popsicle sticks that will give the strongest and most rigid structure. We separated the popsicle sticks for the bottom and top cords from the rest and we also kept the popsicle sticks for each bridge separate.Then we tried to put the popsicle sticks on each other without any gluing until we almost came up with the best design. After that, we drew the bridge design on a paper to make sure the popsicle sticks were placed correctly before gluing. Finally, we placed the top and bottom chords on the drawing on the paper and started by gluing them. After we finished with them, we started to glue the diagonals. Then, we clamped all the members to make sure the glue penetrates them and makes the members attached strongly. We used all 60 popsicle sticks for the bridge and the dimensions of the bridge were: height: 4 in, width: 4-½ in, and length: 13-½ in.

Figure 5

Load Testing.

Table 9

Design Team No. Load at Failure (lbs.)

1 56.7

2 95.5

3 82.9

4 52.9

5 47.1

6 83.3

7 79.1

According to the table, we were the 2nd among the other groups. The average load was 71.07lbs. We did very well in this load testing. The Warren through truss bridge we built was well designed and mostly

failed when it started to separate from the joint which put extra pressure on one of the bottom cord members. This caused the member to snap and put extra stress on the bridge causing it to fail. The bridge failed at a decent load compared to the other designs and had no major flaws in the design.

Forensic Analysis.

Figure 6

The Warren truss bridge failed at the top cord where the joint did not hold the members. The joint was not properly glued causing the joint to fail and the truss to rotate. After the joint failed it snapped the member at the bottom cord at the point where it rotated about. Proper gluing of the joint would have helped to prevent this failure in the bridge. Results.

Table 10

Figure 8