October 27, 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 1, 2017.

Statement of Problem. The 100 year flood in Spring Creek along Puddington Road in College Township, Centre County, Pa has destroyed the bridge in the area.Heavy traffic flow is expected in the area since is is en route to the Mount Nittany Medical Center in State College, Pa. With the decommission of the bridge it has hindered and put many individuals in the area at risk who have had to take a longer commute. Worse, is that the medical assistance do have direct access to the area it hinders the safety and medical problems of the area.

Objective. Due to recent extreme flood events, PennDot has initiated an emergency to replace the bridge over Spring Creek with an economical and structural efficient designed bridge.

Design Criteria. PennDot District 2-0 requires the new bridge to include standard abutments, no piers (one span), deck material made of medium strength concrete, no cable anchorages, and designed to hold two AASHTO H20-44 trucks approximately weighing 225 kN. The deck elevation will be 20 meters and the deck span at 40 meters. One warren and one Howe bridge must be designed and proposed.

Technical Approach.

Phase 1: Economic Efficiency.

The Engineering Encounters Bridge Design 2016 software shall be used to determine the economic efficiency and will be based on requirements, constraints, and performance criteria. The bridge replacement has to be as low as possible and possibly within the $150,000 to $300,000.00 range. EEBD 2016 will perform systematic and iterative analysis to design a Warren and Howe through Truss bridge with maximum optimisation in low cost. The bridge should support its own weight (dead load), plus the weight of a standard truck loading. In both design projects there were difficulties to determine what material to use that was most cost efficient. The majority of the material used for the Warren truss bridge was carbon steel bars which is strong enough to hold the bridge yet very affordable. The Howe truss bridge is also made up mostly of carbon steel bars and tubes because of its cost efficiency without sacrificing to much strength. In our cost analysis the Howe Truss Bridge is about $48,000 dollars cheaper than the Warren Truss bridge. Further analysis are in attachment 1.

Phase 2: Structural Efficiency.

Using 60 popsicles sticks per bridge and Elmer’s Glue for prototype construction. Eight sticks out of the sixty were used for struts/ floor beams and hot glued on the day of load testing. The bridges were weighed out on a scale before hand. Both bridges were tested by placing a platform in the middle and slowly adding weight to the bridge. Weight was added until failure.The weights used were quantitatively recorded and the test was finalized. Finally, the different bridges were analyzed on the cause of the member(s) that failed and compared to other bridge designs.

Results.

Phase 1: Economic Efficiency.

Referencing from Attachment 1, In both design projects there were difficulties to determine what material to use that was most cost efficient. The majority of the material used for the Warren truss bridge was carbon steel bars which is strong enough to hold the bridge yet very affordable. The Howe truss bridge is also made up mostly of carbon steel bars and tubes because of its cost efficiency without sacrificing to much strength. In our cost analysis the Howe Truss Bridge is about $48,000 dollars cheaper than the Warren Truss bridge. Further analysis are in attachment 1.

Phase 2: Structural Efficiency.

The bridge’s structural efficiency was low compared to other design teams and both bridges failed due to failure of beam members. They has similar structural efficiency, and could be contributed to the fact the members were not completely dry in the prototype testing phase.Another flaw in the structure was how the sides did not match evenly and were not properly aligned in order to maximize the efficiency of the bridge.

Best Solution.

(i) The Economic Efficiency The total cost of the Howe through truss bridge is $249,857.22 opposed to the Warren through Truss bridge which is approximately $297,602.54. In terms of economic efficiency the Howe is slightly advantageous. Reference Tables 1 and 4 (Howe and Warren respectively) for the breakdown of the cost variables in the total.

(ii) The Structural Efficiency

Reference Tables 7 and 8 (Warren, and howe respectively) The Structural efficiency of the Howe Bridge is 175, while the Warren Truss bridge is 176. They are almost equivalent but the Warren bridge was one degree better than the Howe.

(iii) The Design Efficiency,

The design efficiency of Howe and warren respectively, was 1427.76 and 1690.92. Warren was more efficient in its design.

(iv) The Constructability

The Howe bridge is more efficient in terms of material and connection cost. The Howe Bridge materials cost $143,456.98 while the Warren was $196,402.54. Whereas the connection cost was $16,000 and $16,800 respectively. The Warren was more efficient in product cost with a total of $7,000. The Howe was $13,000.

Based off analysis from economic to structural the Howe bridge is quantitatively advantageous. The Howe bridge is about $48,000 dollars cheaper economically and its structural efficiency is basically equivalent to that of the Warren. The Materials cost is also lower by about $50,000 and a cheaper connection cost. Where the Warren is advantageous in factors such as design efficiency and product cost, it was not a large enough difference to be superior in comparison to the Howe.

Conclusions and Recommendations.

For future projects on a Howe Bridge we would want to look into the material’s quality and durability used in comparison with their cost. Also, investigation into improving the design efficiency where little maintenance will have to be done.

Respectfully,

Name Anna Macasinag

Engineering Student

EDSGN100 Section 002

Design Team 7

Design Team Overbuilt & Underpaid

College of Engineering

Penn State University

Name Aldo Ramirez

Engineering Student

EDSGN100 Section 002

Design Team 7

Design Team Overbuilt & Underpaid

College of Engineering

Penn State University

Name Bingxin Liu

Engineering Student

EDSGN100 Section 002

Design Team 7

Design Team Overbuilt and Underpaid

College of Engineering

Penn State University

Name Mahima Kania

Engineering Student

EDSGN100 Section 002

Design Team 7

Design Team Overbuilt and Underpaid

College of Engineering

Penn State University

ATTACHMENT 1

Phase 1: Economic Efficiency

Howe Truss.

After analyzing economic efficiency the Howe bridged was collaboratively the advantageous design. It was lighter and able to take more load. (Figure 5). Is the final prototype of the Howe Truss bridge. The individual and class load test results can be found Figure 5 and Table 7. In Bridge Designer 2016 the bridge was made economically efficient carbon steel tubes in areas of compression and solid bars in sections of tension. Also using smaller, cheaper material in areas where neither high amounts of compression or stress was beneficial in the economic efficiency. Most of the bridge was constructed using carbon steel and strategically either hollow tubes or a solid bar. However, in the areas of high compression or tension which was in two trusses the material was replaced in High strength Low Alloy Steel as seen in Table 1.

The Howe experienced the highest forces acting on it in members 26-29, and 32 as seen in Table 2. 26-29 are hollow tubes while member 32 is a solid member. They may have been a moment of high force but they were structurally safe. The cost could be in future projects be reduced in one type of material was used throughout and no mixture of solid and hollow because they caused a price increase. The hollow bars were more expensive too because of the craft required to carve out the bars. Reference Table 1 .

In the prototype testing of the bridges they were equivalent on structural efficiency(Table 7 and 8 Design group 7). The howe bridge overall was about $48,000 at an estimate of about $250,000 to build.

Warren Truss.

Ultimately, the Warren Bridge was eliminated when compared to our Howe design due to how it was just slightly more expensive and in perspective of materials was complex and overdone.The bridges weighed about the same and carried almost the same load in prototype testing.(Table 7 and 8). In the Bridge design software the warren truss experienced the most strain in member thirty (reference table 6) which was a hollow tube steel material.. After analyzing the bridge structurally and economically it was not as successful when compared to the other design teams. In future projects it would be best to improve the affordability of the bridge by analyzing the material cost more carefully.

Economically it was a more expensive bridge and in comparison to the Howe, Reference Table 4 for Warren, it was equivalent in load it was able to carry. It experienced the most force in member 30 (Table 6) which was a hollow tube. In prototype testing the bridge failed due to beam failure. Next time, the bridge should be designed and tested after the glue has completely dried. This bridge was priced at almost $300,000 dollars and was the m0st expensive design.

ATTACHMENT 2

Phase 2: Structural Efficiency

Howe Truss.

Structural efficiency is a function of the weight of the structure to the afforded ships strength in which the better quality of the bridge is defined by the higher number of the structural efficiency. The structure efficiency is calculated by the load at failure (lbs) divided by the actual weight of the bridge (lbs). In the attachment two, the results of the lab load testing and the results from the entire class of the Howe truss bridge shall be presented and discussed in the report.

Prototype Bridge.

We used Popsicle sticks to construct the Howe truss bridge, the number of Popsicle sticks that have been using is 60. The dimension of the bridge meets the minimum requirement of the design project, the height is 11.4cm, bottom length is 34.2cm, top length is 28.5cm and the width is 10cm. The total weight of this Howe truss bridge is 93g or 0.205 lbs. A photograph of the prototype Howe Truss bridge taken BEFORE load testing shall be included in Figure 5.

Load Testing.

The load at failure for our group is 36 lbs and the structure efficiency is calculated for the Howe truss bridge is 175, which is relatively low compared to the average results of all other EDSGN 100 design teams and the average is 278. The class minimum is 175, the maximum is 440 and the range in between is 265 for all the EDSGN 100 design teams. The Load at bridge failure results, bridge weights and calculation of structural efficiencies for all Howe truss bridges must be collected and presented as Table 8.

Forensic Analysis.

The main problem of our Howe truss bridge is the members in the middle and it is the main part that failed when doing the load testing. During the load testing, the bridge was collapsing toward the left side and after the load testing, some of the middle members broke and the joins fell out. The analysis of the failure is the following. Firstly, we did the load testing without the glue completely dry because we did the load testing right after we glued the two bridge together. Secondly, the Howe truss bridge we made are not perfect symmetry. In fact, we have two group members did each side of the Howe bridge and when we connected them together, we found that they are not perfectly matched. This could result in uneven bearing force when doing load testing and this is why the bridge collapsed towards one side. A photograph of the prototype Howe truss bridge taken AFTER failure load testing shall be included in Figure 6.

Results.

An EXCEL bar graph is included as Figure 8 comparing Structural Efficiencies as presented in Table 8.

Warren Truss.

Structural efficiency is a function of the weight of the structure to the afforded ships strength in which the better quality of the bridge is defined by the higher number of the structural efficiency. The structure efficiency is calculated by the load at failure (lbs) divided by the actual weight of the bridge (lbs). In the attachment two, the results of the lab load testing and the results from the entire class of the Warren truss bridge shall be presented and discussed in the report.

Prototype Bridge.

We used Popsicle sticks to construct the Howe truss bridge, the number of Popsicle sticks that have been using is 60. The dimension of the bridge meets the minimum requirement of the design project, the height is 11.6 cm, bottom length is 36 cm, top length is 28.5cm and the width is 10cm. The total weight of this Warren truss bridge is 93g or 0.205lbs. A photograph of the prototype Howe Truss bridge taken BEFORE load testing shall be included in Figure 3.

Load Testing.

The load at failure for our group is 36 lbs and the structure efficiency is calculated for the Howe truss bridge is 176, which is relatively low compared to the average results of all other EDSGN 100 design teams and the average is 249. The class minimum is 174, the maximum is 407 and the range in between is 233 for all the EDSGN 100 design teams. The Load at bridge failure results, bridge weights and calculation of structural efficiencies for all Howe truss bridges must be collected and presented as Table 7.

Forensic Analysis.

Similar to Howe truss bridge, the main problem of our Warren truss bridge is the members in the middle and it is the main part that failed when doing the load testing. During the load testing, the bridge was collapsing toward the left side and after the load testing, some of the middle members broke and the joins fell out. The analysis of the failure is the following. Firstly, we did the load testing without the glue completely dry because we did the load testing right after we glued the two bridge together. Secondly, the Howe truss bridge we made are not perfect symmetry. In fact, we have two group members did each side of the Howe bridge and when we connected them together, we found that they are not perfectly matched. This could result in uneven bearing force when doing load testing and this is why the bridge collapsed towards one side. A photograph of the prototype Howe truss bridge taken AFTER failure load testing shall be included in Figure 4.

Results.

An EXCEL bar graph is included as Figure 7 comparing Structural Efficiencies as presented in Table 7.

Enclosures.

Tables Nos. 1 through 7 and Figure Nos. 1 through 8 are attached.

TablesDesign Team 7

Table 1Howe Truss BridgeCost Calculations Report

Table 2Howe Truss bridgeLoad Test Results from Bridge Designer 2016

Table 3 Howe Truss Bridge Member Details Report from Bridge Designer 2016 Member with the Highest Compression Force/Strength Ratio

Table 4Warren Truss BridgeCost Calculation Report from Bridge Designer 2016

Table 5Warren Truss BridgeLoad Test Results Report from Bridge Designer 2016

Table 6 Warren Truss BridgeMember Details Report from Bridge Designer 2016 Member with the Highest Tension Force/Strength Ratio

Design Team No.

Actual Bridge Weight (grams)

Actual Bridge Weight (lbs)

LOAD at Failure (lbs)

Structural Efficiency

1

90.2

0.1988

81

407

2

87.8

0.1936

51

263

3

78.5

0.1731

36

208

4

93.6

0.2063

36

174

5

80.6

0.1777

36

203

6

85.4

0.1883

66

351

7

93

0.2050

36

176

8

77.4

0.1706

36

211

Minimum 174

Maximum 407

Range 233

Average 249

Geomean 238

Table 7

Loading Test Results for the Warren Truss Bridge

Design Team No.

Actual Bridge Weight (grams)

Actual Bridge Weight (lbs)

LOAD at Failure (lbs)

Structural Efficiency

1

80.2

0.1768

36

204

2

82.5

0.1819

36

198

3

84

0.1852

101

545

4

83.5

0.1841

81

440

5

63.9

0.1409

36

256

6

79.1

0.1744

36

206

7

93.3

0.2057

36

175

8

82.1

0.1810

36

199

Minimum 175

Maximum 440

Range 265

Average 278

Geomean 255

FiguresDesign Team 7

Figure 1. Howe Bridge Model from Bridge Designer 2016

Figure 2. Warren Bridge Model from Bridge Designer 2016

Figure 3. Warren Truss Bridge before Loading Test

Figure 4. Warren Truss Bridge after Loading Test

Figure 5. Howe Truss Bridge before Loading Test

Figure 6. Howe Truss Bridge after Loading Test

Figure 7: Warren Truss Bridge Structural Efficiency

Figure 8: Howe Truss Bridge Structural Efficiency