School of Architecture, Building & Design Research Unit for Modern Architecture Studies in Southeast Asia Bachelor of Science (Honours) (Architecture) Building Structures [ARC 2523]
Project 1:
Fettuccine Truss Bridge
Tutor:
Mr. Mohd. Adib Ramli
Group member: Tan Wei How
0310707
Teh Xue Kai
0317021
How Pei Ngoh
0316929
Ang Jia Pin
0315506
Lucas Wong Kok Hoe
0309421
Wong Kah Voon
0317510
Content 1. Introduction 1.1 Objective of project 1.2 Project requirement 1.3 Project schedule 2. Precedent studies 2.1 Navajo 1995 Bridge 2.2 Pratt Truss Bridge 3. Equipment and material study 3.1 Types of fettuccine 3.2 Adhesive test 3.3 Layering test 3.4 Clear span test 3.5 Joint test 4. Design process 4.1 Design 1 4.2 Design 2 4.2.1 4.2.2 4.2.3
Initial design Modified design Final design
5. Structural analysis of final design 5.1 Comparison between final design and modified design 5.2 Internal forces 5.3 Reflection 6. Reference 7. Appendix 7.1 Structural analysis of Final Design 7.2 Case Study 1 7.3 Case Study 2 7.4 Case study 3 7.5 Case study 4 7.6 Case study 5 7.7 Case study 6
1.0 Introduction 1.1 Objective of Project: To design a fettuccine truss bridge using understanding on tension, compression and force distribution in a truss.
1.2 Project Requirements: Design and construct a fettuccine bridge with 750mm clear span, maximum weight of 200g and high efficiency. 2 Maximum Load Efficiency, E
Weight of bridge
1.3 Project Schedule Date 23/03/2015 26/03/2015 31/04/2015 04/04/2015 08/04/2015 10/04/2015 15/04/2015 17/04/2015 20/04/2015 24/04/2015 25/04/2015 26/04/2015 27/04/2015
Task Precedent studies on truss bridge Discussion on precedent studies Preparing materials Equipment and material study, eg. adhesive test Building of Prototype Bridge 1 Testing of Prototype Bridge 1 Building of Prototype Bridge 2 Testing of Prototype Bridge 2 Building of Prototype Bridge 3 and 4 Testing of Prototype Bridge 3 and 4 Building of Parts for Final Bridge Design Assembling of Final Bridge Model Final testing of Final Bridge Model
2.0 Precedent Studies 2.1 Navajo 1995 Bridge
Figure 1 shows Navajo 1995 Bridge perspective view.
Navajo Bridge crosses the Colorado River's Marble Canyon near Lee's Ferry in the US state of Arizona. It carries U.S. Route 89A. Spanning Marble Canyon, the bridge carries northbound travellers to southern Utah and to the Arizona Strip, the otherwise inaccessible portion of Arizona north of the Colorado River.
The Navajo 1995 bridge is 143 meters height above the Colorado River. It has 11 spandrel panels within the main span, which is 221 meters span. Each panel is 10 meter from each other. (Godaddy software, 2010)
Figure 2 illustrates Navajo 1995 Bridge Elevation (Deck Arch Bridge).
LOAD
Figure 3 illustrates reaction force in Navajo Bridge. Compression Tension
4
5
6
7
4 5 6
7
Figure 4 shows how bracings are connected to curved-base chord. Figure 5, 6 show joints of Navajo Bridge. Figure 7 shows connection point of the bridge to the ground.
8
9
10 11
Figure 8, 9, 10 & 11 show arrangement of diagonal members, truss and connection parts.
2.2 Little Walnut River Pratt Truss Bridge
Figure 12 shows Little River Pratt Truss Bridge elevation.
The Little Walnut River Pratt Truss Bridge is a Pratt truss bridge. It was constructed shortly after 1885, in Bois d'Arc, Kansas. The bridge was constructed by the Kansas City Bridge and Iron Company as a carriage, horse and pedestrian bridge over the Little Hickory Creek. The bridge connects the Walnut River in southern Butler County. It was added to the National Register of Historic Places in the year 2003. The height limitation of the bridge is 6 feet and 6 inches. Consisting of two distinct spans, one span of 102 feet and the other 75 feet in length, using the Pratt Truss bridge design. The bridge is iron manufactured by the Carnegie Steel Company. The road surface is made of heavy timber. The total length of the bridge is 196.8 feet and the width of the deck is 13.4 feet.
Figure 13 illustrates elevation of Little Walnut River Pratt Truss Bridge, 1885.
LOAD
Figure 14 illustrates reaction force.
Compression Tension
15
16
17
18
Figure 15, 16, 17 & 18 show connection parts and truss members of Little Walnut River Pratt Truss Bridge.
3.0 Equipment and Material Study
Average thickness: 10 mm
Figure 19 shows average thickness of a single fettuccine is 10 mm.
Average length: 250 mm
Figure 20 shows fettuccine comes in different length with an average of 250 mm.
3.1 Types of Fettuccine Constant Manipulated Responding Brand Kimball
Length = 60mm, clear span = 40mm, no. of layers = 2, adhesive Brand Ability to withstand load for 10 seconds. Load withstand/g Cross-section of fettuccine 200
San Remo
165
Barilla
105
Conclusion: Barilla fettuccine is the strongest, but San Remo is the most suitable for bridge making as it has flatter surface which enables larger contact adhesive surface.
Figure 21 illustrates how surface condition influences strength of fettuccine.
3.2 Adhesive Test
Figure 22 shows how test is being carried out. Constant Length = 60mm, clear span = 40mm, no. of layers = 2 Manipulated Adhesive Responding Ability to withstand the load for 10 seconds *Remark: V=vertical, H=horizontal, load [= water + 150g (container + hook + thread)] Water /g Adhesive 300 800 1300 V H V H V 3-seconds √ √ √ √ √ Bossils √ √ √ √ √ Dunlop x x √ √ √ PVC x x √ √ √ Super glue √ √ √ √ √ UHU x √ √ √ √ White glue x x √ √ √ 3s+Dunlop √ √ √ √ √ 3s+PVC √ √ √ √ √ 3s+UHU √ √ √ √ √ Bossils+Dunlop √ √ √ √ √
H √ x x x x x x x x x x
Bossils+PVC x x √ √ √ √ Bossils+UHU x √ √ √ √ √ Conclusion: 3-seconds glue is the most effective glue. White glue is water-based glue so it actually softens fettuccine by a certain degree and makes its joints weak. Constant Length = 255mm, clear span = 110mm, no. of layers = 4, water = 500g Manipulated Adhesive *Remark: V= vertical, H= horizontal Adhesive V H 3s √ √ 3s+Dunlop x √ 3s+UHU x x Conclusion: 3-seconds glue performs well even in longer clear span.
3.3 Layering Test Constant Adhesive= 3-seconds, load (water= 500g), length = 255mm Manipulated No. of layers *Remark: V=vertical, H=horizontal Clear span /mm No. of layers 110 130 150 170 190 210 V H V H V H V H V H V H 2 x x x x x x x x x x x x 3 x x x x x x x √ √ √ √ √ 4 x x x √ √ √ √ √ √ √ √ √ 5 x x √ √ √ √ √ √ √ √ √ √ Conclusion: Number of layers needed increases as clear span increases.
230 V x x x √
H x x x √
3.4 Clear Span Test Constant Adhesive= 3-seconds, load (water= 500g), length= 255mm, no. of layers= 4 Manipulated Clear span *Remark: V=vertical, H=horizontal Clear Span /mm V H 70 √ √ 90 √ √ 110 √ √ 130 √ √ 150 √ √ 170 √ √ 190 √ √ 210 x √ 230 x x
3.5 Joint test
Butt Joint
Lap Joint
Mortise and Tenon
Figure 23 shows three different types of joint. They are commonly used in timber construction and fettuccine comes in shape similar to timber. No fixture is required for these joint thus damage to fettuccine is avoided.
Figure 24 shows how test is being carried out using frame, strap with chain and plastic bag filled with water. Water is weighed using electric balance. Constant Dimension of frame = 50 x 50 mm, no. of layers = 3, adhesive = 3-seconds Manipulated load [= water + 80g (plastic bag + strap)] Responding Ability to withstand the load for 10 seconds *Remark: fettuccine frame is tested vertically, load [= water + 80g (plastic bag + strap)] Load /g Joint 500 1100 1500 2000 2400 Butt
√
X (2.60s)
X
X
X
√
√
√
√
X (1.00s)
√
√
√
X (3.93s)
X
Lap
Mortise and tenon
Conclusion: strongest.
Lap joint has less contact adhesive surface than mortise and tenon but it is the
4.0 Design Process 4.1 Design 1 750 750
100 100
100 100
60
Top View
40 140
Force Front View
Figure 25 shows the reaction force diagram of the bridge. Inspiration of this design is taken from Navajo Truss Bridge. Compression Tension
Figure 26, 27 & 28 show testing of Design 1.
Total Length
= 950mm
Clear Span
= 700m
Weight of Bridge
= 260g
Load Sustained
= 1600g
Efficiency
= 0.0098
Design 1 is inspired by the Navajo 1995 Bridge (Precedent Study), which is the deck arch truss. This design has high aesthetic value but it exceed the 200 grams to 260 grams. Problem Identification: 1. 2. 3. 4.
The bridge is over-weight, 260 grams. The bridge experienced twisting when load applied. The end of the bridge was not strong enough and it broke. The forces are not fully distributed to some of the members of the bridge as the joints are not connected properly. 5. Efficiency of bridge is not satisfied yet for us although there is improvement.
4.2 Design 2 42
58 60
`
60
75
100
950
Forces 100
950
Figure 29 illustrates the reaction force of the bridge. Compression Tension
Figure 30 shows testing of Design 2.
Total Length
= 950mm
Clear Span
= 700m
Weight of Bridge
= 200g
Load Sustained
= 6180g
Efficiency
= 0.1910
Design 2 used back the same design as Design 1, which is the deck arch truss with some improvement. Thus, its efficiency is getting higher compared to Design 1. However, its aesthetic value is still remained the same Improvement: 1. Decrease numbers of panel and layers of the tension members in order to decrease the weight of the bridge. (The weakness of design 1) 2. Add bracing of the top. (The weakness of design 1) 3. Strengthen the both the ends of the bridges, adding more layers to make it thinker. (The weakness of design 1) 4. Add three triangular members to the centre of the bridge to strengthen it. 5. Improve the way of connecting the joint by using mortise and tenon joint. (The weakness of design 1) Problem Identification: 1. The middle part of the bridge is still not strong enough to withstand the load. 2. Efficiency of bridge is not satisfied yet for us although there is improvement.
4.3 Design 3 - Space Truss
80
50 800
50 800
Figure 30 illustrates reaction force in Space Truss. Compassion Tension
Total length = 800mm Weight of bridge = 140g Efficiency = 0.0926 Clear span = 750mm Load sustained = 3.6kg Efficiency = 3.6 2/140 = 0.0926
Figure 31 shows testing of Design 3 – Truss Bridge.
Figure 32 shows failure of Truss Bridge.
Problem identified: 1. The joint of the bridge is not strong enough to withstand the load.
2. Mortise and Tenon joint method used is good for fixing the members together however the strength of the joint is low.
3. The members turned brittle and weak after 2 days
4. The height of the bridge is too high in relation to the width. 5. Uneven load distribution due to the top point of truss did not meet with another side and form a pyramid.
4.4 Final Design 1 60
55
Cross-section
55
980 55
Top View
Forces
60
980 55
Front View
Figure 33 illustrates reaction force of the bridge. Compression Tension
Problem Identified: The top chord was not properly glued to the members of the truss. Improvement suggested: 1. The height of the bridge is decreased. 2. Butt joint is used. 3. More layers are added to truss members and chord.
Final Design 2 60
55
Cross-section
55
980 55
Top View
Forces
60
980 55
Figure 34 illustrates reaction force of the bridge.
Front View
Compression Tension
Model Testing Two lanyards were used at two points of the top horizontal interconnecting member in the center between the two planar trusses of the bridge. Then the lanyards were tied to a pail. Starting at 530g (the weight of the pail) we poured in water to the pail our bridge re
Figure 35 shows testing of Final Model.
Total length /mm Clear span /mm Total weight /g Load withstand /kg Efficiency /kg2g-1 Time between completio n and testing / hr Crosssection
Modified Design 2 900
Final Design 2 980
750
750
160.0
216.0
8.100
5.75 0
8.12 / 160 = 0.4101
5.75 2 / 216 = 0.1531
48
3
Elevation
Adhesive medium added on top of base chord to increase contact adhesive surface.
Failure Analysis 1. Time between completion and testing of final bridge is too short. Fettuccine truss has lower load bearing when adhesive is still wet. 2. Base chord should be perpendicular to desk surface to ensure maximum surface area is used for load transfer. Diagonal base chord is due to poor workmanship. 3. Weight of 20cm fettuccine is 1.30g. 17 pieces of 5cm doubled-layer hanging member contribute to redundant members of approximately 11g. 4. Adhesive medium added to enable greater contact adhesive surface is not glued tightly to base chord. This is the paramount reason for lower truss efficiency.
Structural Analysis Our final fettuccine bridge model is designed based on a warren (with verticals) truss design. The reaction forces of the bridge were calculated and identified. The bridge was tested with multiple types of adhesive and joining methods. We obtained different levels of strength in different types of design. The result of the testings showed that fettuccine is strong against tension and weak against compression forces as fettuccine is higher in elasticity. The strength is also determined by the amount of fettuccine used per part. The top and bottom chords of the bridge were using more layers than the posts and the braces. After testing the final model of the fettuccine bridge, we obtained calculations of forces and reaction forces acting upon the bridge. (Garrett, B., 2011) Aspect ratio or lower span to longer span ratio for truss frame is 1-1.5, 1.5-2.0 will affect effective load transfer in space frame member. In final design, ratio of 1.1 (5.5/5) is within the range. (Tian, T.Lan, 2005)
Figure 36 illustrates how Final Model is was bent during final testing.
Figure 37 shows labelling of Final Model in Structural Analysis (refer calculation in Appendix: Final Structural Analysis).
Conclusion After all it was a good experience to construct a truss bridge by using fettuccine because it is a totally new material for us to explore. We carried out tests to study the material’s tensile and compressive strength. By understanding the nature of the material, we can utilize it to its full potential in making a stronger bridge. Not to mention the type of adhesive, we also learn that workmanship plays an important role in increasing the bridge’s strength and efficiency. This reflects in reality, the stability and strength of a construction is massively affected by the adhesive too. Furthermore, we learned that the procedures in a construction need to be well-planned and organized. It is very important to have a well-thought construction sequence throughout the process. As a conclusion, I think that our group did a good job although the final testing is a failure compared to the previous one. We explored 4 prototypes by developing and improvising them based on two main designs from precedent studies. Analysis was done on the load distribution and at the same time, we successfully determined the critical members and enforced them by adding layers and pushing the weight of the bridge to 200gram which is the limit because our previous design weighed only 180gram. This is responding to the efficiency formula which has square for the maximum load, so by increasing the weight in order to strengthen it, the bridge can support heavier load, then the efficiency can be increased by higher rate. As a designer, it is not a big deal if once in a while our design does not work well or even fail, it is just that we have to absorb the lessons and learn from it so that in upcoming projects we can address it. This is because after all designing is a life-long process and we should always enjoy it by living it to the fullest.
7.0 Reference Godaddy software. (2010). Highestbridges. Retrieved 6 April, 2015, from http://www.highestbridges.com/wiki/index.php?title=Navajo_1995_Bridge Garrett, B. (2011). Garrett's Bridges. Retrieved 3 May, 2015, from http://www.garrettsbridges.com/design/pratt-truss/ Tian, T.Lan. (2005). Space Frame Structure. Retrieved 3 May, 2015, from http://www.gfsmaths.com/uploads/1/0/0/4/10044815/ch24spaceframestructure.pdf
8.0 Appendix (Attachment)
Final Structural Analysis