B UILDING STRU CTU RE TREVOR N JC HOREAU 0308914 / TEH KAH KHEN 0314502 / LEE MAY WEN, ANDREA 0314320 CHEN ROU ANN 1001G76463 / WONG KWOK KENN 0300146 / NUR ADILA ZAAS 0310417
TABLE OF CONTENT
I N T R OD U C T I ON P R E C E D E N T S T U DY M AT E R I A L A N D T R U S S ANALYSIS M OD E L T E S T I N G C ON C L U S I ON APPENDIX REFERENCES
1.0 INTRODUCT ION “Introduction of our understanding and briefs”
COMPRESSION
TENSION IMAGE 1
Image 1 Analysis of compression (LEFT) and tension (RIGHT)
1.1 OBJECTIVE
The aim of this project is to develop a deeper understanding towards
the tensile and compressive strength of construction materials. Students are required to design a perfect truss bridge with a high level of aesthetic value and minimal construction materials. The bridge has to be of a 750mm clear span, not exceeding the maximum weight of 200g. This report is a compilation of our undertanding and analysis based on precedent studies conducted, construction materials and the deisgn of our truss bridge.
1.2 INTRODUCTION OF TENSION
Tension describes the pulling force exerted by each end of any one-
dimensional continuous object, be it a string, rope, cable or wire. The tensile force is focused along the length of an object and pulls uniformly on opposite ends of it.
1.3 INTRODUCTION OF COMPRESSION
Compressive force (or “compression strength�) refers to the capacity of
a material in resistingpushing forces that are focussed axially. Compressive force can also be defined as the capacity of a structure to withstand loads tending to reduce its size.
2.0 PRECEDENT ST UDY
“ K n o w l edg e an d u n ders t an d ing to aid us in d esigning our fettuccini br idge ”
IMAGE 2
Image 2 Forth Road Bridge on the east coast of Scotland
2.1 FORTH ROAD BRIDGE
Officially opened in 1890, the Forth Road Bridge occupies a beautiful
location in the Firth of Forth on the East coast of Scotland, connecting Fife and the North of Scotland with capital city Edinburgh and the South. The bridge is composed of two railway lines cross the Forth Bridge, supported 47.8 meters above high water, linking much of Northern Scotland with Edinburgh and England to the South. The lines of track sit on a ‘bridge within a bridge,’ an internal viaduct supported within the enormous cantilever towers and arms which is often overlooked.Construction techniques as well as design improvements can be administered due to ongoing advances in design and construction, the development of materials and reduction of cost in what is considered a necessity in a modern day bridge.
2.2 ELEMENTS OF THE BRIDGE Image 3 Two men represent main cantilever tower
The bridge spans up to a total of 2460 meters. It is composed of two
approach viaducts, six cantilever arms supported by three towers, with two central connecting spans. Abutments (supports the lateral pressure of an arch or span) are found at the end of each of the two outer-most cantilevers. Two railway lines sit on an internal viaduct supported within the cantilevered towers; these carried 47.8 meters above high water.
The centre of the bridge consists of three main piers, with two cantilever
arms built out from each pier. Two viaducts consisting of a pair of lattice girders each spanning over fifty-one meters lead up to the centre, which is ultimately supported over forty meters above high-water level on masonry piers.
Four of the six cantilever arms are fixed. These are held strongly in
position by the two granite abutments at the ends of each approach viaduct. Two ‘suspended spans’, over one hundred and five meters long link the two outer cantilever towers with the central one. In a nutshell, the superstructure for this bridge functions as a standard truss – with specific members carrying out either tension or compressive forces.
IN C O M PA R I S O N Image 4 Elevation drawing of Forth Road Bridge
The two men sat on chairs with outstretched arms represent the main
cantilever towers, in between them is a central span connecting the two. Anchorage for the cantilevers is provided by the bricks at either side. As load is applied to the central span (in this case by a third man) the outside men’s arms come into tension, and the sticks they’re holding and the men’s bodies experience compressive forces. In reality the bridge has three cantilever towers, but the principle can be applied equally to this third tower. All compression members (struts) in this bridge are tubular sections made up of many small steel plates riveted together, while tension is carried in lattice truss members. Wind bracing is provided by further lattice trusses spanning between the main superstructure members.
Image 5 Axono Angle of Franciss Scott Bridge
2.3 FRANCIS SCOTT BRIDGE The Francis Scott Bridge, also known as Outer Harbour Bridge or Key Bridge is a continuous truss bridge spanning over the Patapsco River in Baltimore, Maryland, The United States of America. This is the longest bridge (17540 metres) in Baltimore and the third longest span (366 metres) of any continuous truss in the world. Upon completion, the bridge was officially opened in March 1977 and estimated to carry 11.5 m`illion vehicles annually. The technique used in the construction of this bridge can be identified as the Baltimore truss.
The Baltimore truss is a subclass of the Pratt truss. It is designed to
prevent buckling in the compression members and also control deflection by having additional bracing in the lower section of the truss. Due to the rigid and strong design of this truss, it is mainly used for train bridges.
Image 6 Front Photo of Scott Bridge (Top)
Image 7 Elevation of Pratt Truss (Left Bottom)
of the suspended cables in the arch section.
Elevation of Baltimore Truss (Right Bottom)
The construction of this bridge is complicated in which the order of this
bridge is meticulously calculated. It is achieved by having consistent spacing of the trusses in the middle section of the bridge together with equal spacing
Due to the long span of the arch section of the bridge, a suspended,
continuous truss design is used for this span. The suspended cables linking between the truss and the deck will prevent the deck from any construction failures due to tensile and compressive forces when there is presence of load acting on this section. The trusses on top of the deck are in the form of an arch because of its stronger structural property than the beam and column form. In addition, the arch adds for aesthetic value to the design. Apart from that, the arches will transfer loads back into the bearings on the piers then into the foundation. Steel sections incorporated between front truss and the back trusses are to provide stability and torsion resistant to the structure.
Image 8 Cables linking the truss and deck together.
The bridge’s superstructure involved few construction phases. The first
phase involved building all the span of the bridge across the top of the piers built in the substructure. A total of eleven piers are constructed in reinforced concrete prior to provide support to the bridge in which the decks are placed. Later on, they are further supported and strengthen by the continuous truss.
Image 9 Construction of the truss in multiple parts.
The main steel trusses are prefabricated in four major parts, which
the arch truss would be constructed in two parts, and the regular trusses on the either side of the arch truss. These separated components made up of I-beams are then transported to the site by heavy lift floating whereby they are connected together through welding and girder plates with the aid of crags on ships to hoist the parts 56.4 metres above the decks (highest point of the span to the deck under) of the bridge.
3.0 MATERIAL ANALYSIS
“B efo re ex perimen t star ted , analysing m ater ials are the m ain c on c e r n ”
Image 10 San Remo Fettuccine (left) Image 11 Agnesi Fettuccine (middle) Image 12 Barilla (right)
3.1 TYPE OF FETUCCINE ANALYSIS
As stated in the brief, fettuccine is the only material used for the model.
With this, the tensile and compressive strength of different brands of fettuccine were studied and tested. The most suitable one to be used for our model was determine.
Methods: i.
Strips of fettuccine were laid on a flat surface
ii.
Load was placed to test the rate of buckling
iii.
Time taken until failure was measured in order to determine the strength & flexibility of the fettuccine
iv.
Steps were repeated with a different brand
Results: i. San Remo (chosen fettuccine)
- carried most weight - medium flexibility - medium rough surface
ii. Agnesi
-carried medium weight -flexible -lightweight and thin fetuccini
iii. Barilla
- carried less weight -very flexible -lightest and thinnest fetuccini
3.2 ADHESIVE MATERIAL ANALYSIS
Different kinds of glue were tested to determine which was more
efficient in terms of holding the fettucine together. The results obtained from our analysis is stated below: -
Image 13 3 Seconds Glue (left) Image 14 Elephant Glue (middle) Image 15 Hot Glue Gun (right)
RANKING
ADHESIVE MATERIALS
REASON
1
3 Seconds Glue
2
Elephant Glue
i. Moderate Efficiency ii. Time consumingin terms of workmanship iii. Longer solidify time
3
Hot Glue Gun
i. Low Efficiency ii. Long solidify time iv. Bulky Finishing v. Drastic increase in weight when dried
i.Highest efficiency ii. Dries the fastest iii.Will flow into smallest corners and joints
3.3 SUPPORT MATERIALS ANALYSIS Materials that helped us throughout fetuccini bridge’s assignment
i. Weighing Machine
ii. Bucket
A measuring instrument in determining
A vertical cylinder with an open top
the weight or mass of an object. This
and a flat bottom, used to carry both
was used to measure the weight of
liquids and solids, aiding in the load
fettuccine pieces to ensure the final
distribution process.
weight of our bridge did not exceed the maximum limit.
Image 16 Weighing Machine (Top Left) Image 17 Blue Bucket (Top Right)
iii. Hook
iv. Water Bottle
Serves as a connection between the
Loads used in tests conducted.
fettuccine bridge and the bucket. Image 18 Steel Hook (Bottom Left) Image 19 Water Bottle (Bottom Right)
3.3 STRENGTH OF MATERIAL ANALYSIS
As fettuccini is the only material used for the model, its quality and
strength is required to be studied and thoroughly tested before making the model. We aim to: i)
Achieve a high level of aesthetic value
ii)
Use minimal construction material to achieve high efficiency.
2.
The table (Table 1) below shows the strength of each fettuccine analysed
by applying point pressure on the middle. Different numbers, orientation and arrangements of fettuccine were used to form the members. Clear Span (cm)
Length Of Fettuccine (cm)
Perpendicular Distance
Weight Sustained (Horizontal Facing)
Weight Sustained (Horizontal Facing)
20
26
1
2
2.7
20
26
2
3
3.7
20
26
3
4
4.8
20
26
4
5
5.8
20
26
5
6.8
6
TABLE 1 Strength of each fettuccine analysed by applying point pressure on the middle
IMAGE 20 The loads (and reactions) bend the fettuccine and try to shear through it.
3.
The strength of one fettucine appears to be lower when faced horizontally than
when it is faced vertically from 1 stick to 4 sticks. However, after 5 sticks, results turned out to be the opposite. In conclusion, the greater the area exposed relative to its volume, the weaker the fettuccine member is in resisting strains and stresses (The easier it is for the member to break apart)
DIRECTION OF FORCES
DIRECTION OF FORCES
IMAGE 21 When the fettuccine is loaded by forces, stress and strains are created throughout the interior of the beam.
4.
From the result, we decided to use fettuccine members of 1 to 4 sticks with vertical
facing on the truss member that required less strength.
TESTING ON SINGLE MEMBER Strength: Very strong This design is most preferable in terms of efficiency and workmanship IMAGE 22 I-Beam
Strength: Not so strong This is an effective design with minimal human error
IMAGE 23 Layerrings
4.0 BRIDGE ANALYSIS
“St u dyin g different kind of b r id ges giving answer to the co n c lu sion ”
BRIDGE TESTING ONE Details of the Bridge: Height and width = 750mm (width) Length (top chord) = 600mm Length (bottom chord) = 750mm Weight of this bridge = 125g Maximum load = 2350g Efficiency = ANALYSIS The bridge did not bend or twist as weight is gradually added. Nevertheless, only the hook support broke when load reached at 2350g. The bridge holds it form and position.
CONSIDERATION: -
Image 24 First Part Image 25 Second Part Image 26 Third Part Image 27 Fourth Part Image 28 Fifth Part
IMAGE 24
IMAGE 25
IMAGE 26
IMAGE 27
BRIDGE TEST ONE IMAGE 28
BRIDGE TESTING TWO Details of the Bridge: Height and width = 750mm (width) Length (top chord) = 600mm Length (bottom chord) = 750mm Weight of this bridge = 125g Maximum load = 2430 g Efficiency = ANALYSIS After the failure of the previous hook support, we improvised and came up with a different hook support design. A cross-bracing support was added. This support is able to withstand up to 2.4kg until the hook support broke. The failure of this bridge is only at the hook support. Meanwhile, the bridge retained its form and did not collapse.
CONSIDERATION: -
Image 29 First Part Image 30 Second Part Image 31 Third Part Image 32 Fourth Part
IMAGE 29
IMAGE 30
IMAGE 31
IMAGE 32
BRIDGE TEST TWO
BRIDGE TESTING THREE Details of the Bridge: Height and width = 750mm (width) Length (top chord) = 600mm Length (bottom chord) = 750mm Weight of this bridge = 130g Maximum load = 8100g Efficiency = ANALYSIS The hook support was rectified and an I-beam replaces the horizontal support. The bridge remains stable has load is gradually added. The hook support did not break this time but however, the bottom chord snapped causing the whole bridge to collapse.
CONSIDERATION: Add support on the top & bottom chord
Image 33 First Part Image 34 Second Part Image 35 Third Part Image 36 Fourth Part Image 37 Fifth Part
IMAGE 33
IMAGE 34
IMAGE 35
IMAGE 36
BRIDGE TEST THREE IMAGE 37
BRIDGE TESTING FOUR Details of the Bridge: Height and width = 750mm (width) Length (top chord) = 600mm Length (bottom chord) = 750mm Weight of this bridge = 130g Maximum load = 700 g Efficiency = ANALYSIS This bridge was an exact replicate of the previous bridge but blown up to a bigger scale to fit the requirements of a 750mm clear span. All members remain the same thickness and also the use of I beams as the hook support.The failure of this bridge was identified as workmanship effort. The bridge twisted as load is gradually added up to the point the sides broke causing the whole bridge to collapse. This is due to the bottom chord not being straight when constructing.
CONSIDERATION: - Improve workmanship - Ensure bottom chord is straight and sits balanced on the table.
Image 38 First Part Image 39 Second Part Image 40 Third Part Image 41 Fourth Part Image 42 Fifth Part
IMAGE 38
IMAGE 39
IMAGE 40
IMAGE 41
BRIDGE TEST FOUR IMAGE 42
BRIDGE TESTING FIVE Details of the Bridge: Height and width = 85mm (width) Length (top chord) = 843mm Length (bottom chord) = 850mm Weight of this bridge = 130g Maximum load = 2700g Efficiency = ANALYSIS All members remain the same thickness and use of I beams as the hook support. This bridge failed as the bottom chord snapped. However, the hook support did not break and retain its form.
CONSIDERATION: Strengthen the bottom chord
Image 43 First Part Image 44 Second Part Image 45 Third Part Image 46 Fourth Part Image 47 Fifth Part
IMAGE 43
IMAGE 44
IMAGE 45
IMAGE 46
BRIDGE TEST FIVE IMAGE 47
BRIDGE TESTING SIX Details of the Bridge: Height and width = 110mm from highest point to bottom (height) 775 (width) Length (top chord) = 881mm Length (bottom chord) = 850mm Weight of this bridge = 273g Maximum load = 2825 Efficiency = ANALYSIS After doing the precedent studies, we decided to try out another bridge with a different design. This bridge is steady and strong. However, the failure of this bridge happens on the hook support which is a cross-braced design. Upon adding load up to 2,8kg, the hook support snaps. However the members of bridge remained intact. The bridge remained its form.
CONSIDERATION: Straigthen its hook support.
Image 48 First Part Image 49 Second Part Image 50 Third Part Image 51 Fourth Part Image 52 Fifth Part
IMAGE 48
IMAGE 49
IMAGE 50
IMAGE 51
BRIDGE TEST SIX IMAGE 52
BRIDGE TESTING SEVEN Details of the Bridge: Height and width = 110mm from highest point to bottom (height) 775 (width) Length (top chord) = 881mm Length (bottom chord) = 850mm Weight of this bridge = 280g Maximum load = 5315g Efficiency = ANALYSIS The bridge has same design as the previous bridge. However, the only difference is the hook support, The conclusion was drawn based on the previous tests that a hook support made from multiple layers of fetuccini is not as strong as a hook support composed of I beams. In this test, the bridge withstand up to 5.3kg and “crack� sound can be heard. The failure of this bridge happens when one of the chord could not take the load causing the whole bridge to collapse. However, the hook support did not deform.
CONSIDERATION: Strengthen the supports on the side as it fails to hold up the bridge.
Image 53 First Part Image 54 Second Part Image 55 Third Part Image 56 Fourth Part Image 57 Fifth Part
IMAGE 53
IMAGE 54
IMAGE 55
IMAGE 56
BRIDGE TEST SEVEN IMAGE 57
5.0 FINAL MODEL TESTING
“The highlight of this assign m e n t”
FINAL DESIGN OF OUR FETTUCINI BRIDGE Details of the Bridge: Height and width = Length (top chord) = Length (bottom chord) = Weight of this bridge = Maximum load = ANALYSIS
FORCE DISTRIBUTION IN TRUSS
376.50
58° 91.19
58°
58°
35° 32°
32°
58°
58°
32°
32°
32°
32°
71.00 32° 55°
58°
32° 58°
81.23
32° 32°
32°
32° 58°
58°
58°
58°
58°
58°
58°
58°
43.88
753mm
71mm
breaking point
50mm
the chord is stressed to a snapping point, at the 2points shown. no other member was affected/broken.
CONCLUSION
APPENDIX
REFERENCES
IMAGE REFERENCES Image 1 : retrieved from http://santabarbarastrength.com/wp-content/uploads/2014/01/400pxcompression_tension_and_shear_forces-300x151.png Image 2 : retrieved from http://i2.wp.com/caledonianmercury.com/wp-content/uploads/2013/05/ForthBridge-2.jpg?resize=1502%2C738 Image 3 : retrieved from http://www.engineering-timelines.com/why/forthRailBridge/forthRailBridge_03.jpg Image 4 : retrieved from http://dita2indesign.sourceforge.net/dita_gutenberg_samples/dita_ encyclopaedia_britannica/html/entries/images/bridges_23.png Image 5 : retrieved from http://www.ce.jhu.edu/baltimorestructures/Buildings/Francis%20Scott%20 Key%20 Bridge/2.JPG Image 6 : retrieved from http://skyserver.sdss3.org/sdss2013/images/keybridge.jpg Image 7 : retrieved from https://www.cs.princeton.edu/courses/archive/fall09/cos323/assign/truss/ps2/truss2.png Image 8 : retrieved from http://static.panoramio.com/photos/large/8221330.jpg Image 9 : retrieved from http://betterarchitecture.files.wordpress.com/2014/01/sydney-harbour-bridge-under-construction.jpg Image 10 : retrieved from https://grocermart.com/image/cache/data/SanRemo1/fettuccine-1800x1800.jpg Image 11 : retrieved from http://en.creation.com.tw/userfiles/sm/sm350_images_E1/73/2012011963065545.jpg Image 12 : retrieved from http://ecx.images-amazon.com/images/I/81MRq%2BcQYdL._SL1500_.jpg Image 13 : retrieved from http://vitaltechnical.com/image/cache/data/product/super/VT-802-1qxt-500x500.jpg Image 14 : retrieved from http://www.buystationery.com.sg/upload/1262941565.jpg Image 15 : retrieved from http://letsmakerobots.com/files/field_primary_image/24076.jpg? Image 16 : retrieved from http://media1.in.88db.com/in/DB88UploadFiles/2012/11/21/17750650-294E-4435-AC428154EE2496E9.jpg Image 17 : retrieved from http://www.axis-cleaningsupplies.co.uk/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/u/h/uhbb1030l_10ltr_bucket_blue.png Image 18 : retrieved from http://www.preserveshop.co.uk/images/stainless-steel-hanging-hook.jpg Image 19 : retrieved from http://cdn5.triplepundit.com/wp-content/uploads/2009/11/bottled-water.jpg Image 20 : drawn by Chen Rou Anne Image 21: drawn by Chen Rou Anne Image 22 : drawn by Chen Rou Anne Image 23 : drawn by Chen Rou Anne Image 24 : photograph by Kenn Wong Image 25: photograph by Kenn Wong Image 26 : photograph by Kenn Wong
Image 27 : photograph by Kenn Wong Image 28 : photograph by Kenn Wong Image 29 : photograph by Andrea Lee Image 30 : photograph by Andrea Lee Image 31 : photograph by Andrea Lee Image 32 : photograph by Andrea Lee Image 33 : photograph by Andrea Lee Image 34 : photograph by Andrea Lee Image 35 : photograph by Andrea Lee Image 36 : photograph by Andrea Lee Image 37 : photograph by Adila Zaas Image 38 : photograph by Adila Zaas Image 39 : photograph by Adila Zaas Image 40 : photograph by Adila Zaas Image 41 : photograph by Adila Zaas Image 42 : photograph by Adila Zaas Image 43 : photograph by Kenny Teh Image 44 : photograph by Kenny Teh Image 45 : photograph by Kenny Teh Image 46 : photograph by Kenny Teh Image 47 : photograph by Adila Zaas Image 48 : photograph by Adila Zaas Image 49 : photograph by Adila Zaas Image 50 : photograph by Adila Zaas Image 51 : photograph by Adila Zaas Image 52 : photograph by Kenny Teh Image 53 : photograph by Kenny Teh Image 54 : photograph by Kenny Teh Image 55 : photograph by Kenny Teh Image 57 : photograph by Kenny Teh
Image 58 : photograph/image/diagram