bstructure report final

Table of Content

Introduction 1

Methodology 2

Precedent study 4

Analysis 6

i) strength of materials

ii) truss analysis

- Mock up 1 8

- Mock up 2 13

Final model testing 15

Conclusion 20

References 21

Appendix – exercise

1.1 Study Objective

The objective of this particular study is to explore and thus evaluate and improve on

knowledge of skeletal construction. In the event of constructing a truss bridge with

fettuccine, exploration on truss members in different arrangement was carried out while

applying the understanding of load distribution in truss systems. Besides that,

understanding and the application of the knowledge on calculating the reaction force and

internal force within the truss design. Lastly, gaining the ability to identify the tension and

compression members in a truss structure to fully utilize the potential of the material -

Fettuccine.

1.2 Project Overview

In a group of 6, a truss bridge was produced by using fettuccine as the construction

material. Before starting with the model making, students were required to carry out

precedent study of a truss bridge.

With a clear span of 750 mm and a maximum weight of 200 g, the truss bridge is then

subjected to a point load which determines the efficiency of the structure. The efficiency

of the bridge is calculated with the formula:

𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦, 𝐸 =(𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝐿𝑜𝑎𝑑)2

𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐵𝑟𝑖𝑑𝑔𝑒

For this project, only glue is allowed for the connection of the bridge members.

1.3 Report Overview

This report includes the precedent study of the bridge our group referred to while

designing the truss systems of the fettuccine bridge. Besides that, the report also

includes the development process of the fettuccine truss bridge including the analysis

and calculation of the particular design.

Introduction

1

Methodology

Working Schedule:

DESCRIPTION

Precedent Study A study on different types of bridge

trusses will be conducted. We will study

the connections and arrangements of

members. This will be then applied to

our model bridge.

Material Testing The strength of different types of

fettuccine and glue will be tested out.

Model Making Based on the AutoCAD drawings done,

the sides of the bridge will be

constructed before joining them together

using members.

Structural Analysis The analysis of both mockup and final

model will be carried out after each

testing.

DATE TASKS

21 September 2014 Material strength testing of different

fettuccine.

24 September 2014 1st Mockup model making and testing.

28 September 2014 2nd Mockup model making and testing.

30 September 2014 Final model making.

1 October 2014 Final model submission and testing.

3 October 2014 Final report submission.

2

MATERIALS DESCRIPTION

Butter Paper Design of chosen truss bridge is drawn

on the butter paper as a reference for

placement of each member.

Fettuccine Fettuccine is used to construct the entire

truss bridge.

Masking Tape Masking tape is used to keep the

alignment of each member in place

before gluing.

Super Glue This glue instantly holds the fettuccine

together due to the strong bonding.

Plastic Bag Tied around center point of bottom chord

of the bridge for testing purposes.

Water Bottle Used to measure the amount of water

as weight during testing process.

Camera Recording of all work progress.

Electronic weighing scale To obtain accurate weight measurement

of the Fettuccine bridge.

For the final bridge model, we weighed

the members before assembling it

together to ensure it’s within 200g.

3

Precedent Study -Railway Bridge Tulle

Railway Bridge Tulle is a railway bridge which built at 104 years ago. The

railway bridge across the Danube at Tulle has been completely reconstructed. The

new bridge is based on warren truss construction. The construction period only took

15 months. The total length of the bridge is approximately 440m, each span width

around 13m.

Image 1 : Railway Bridge Tulle

Joint connection

Image 2 & 3 : Rigid Joints. Gusset Plate and Bolts Joint Connection

In order to have a stable and strong truss bridge, the concept of force

equilibrium should be apply. Assuming the point load is at the centre of the bridge,

and both side of truss bridge are fixed points.

Load

4

Arrangement of Members

The base of Tulle Bridge is connected by horizontal members.

Image 4 : Bottom view of Tulle Bridge

Image 5 : Tulle Bridge side view

Point of Horizontal Member Connect to

Truss

Top view of Tulle Bridge

Points of Horizontal Members at lower

chord connected to the truss

For the upper chords, horizontal members are welded to the intersection point of

the truss to hold both sides of the truss members in shape and ensure the distance is the

same along the bridge. The bracings hold the horizontal in position to prevent deformation

of the bridge when load is applied.

As the report mentioned previously, the top chord of warren truss are greatly

affected by compression while the bottom chord of warren truss is experiencing tension

force. The bracings as shown on diagram above act as a member to distribute the

compression force and hold the members in position. The bottom chord of Tullen Bridge

does not required as much bracings as the members (steel beams) are great in tension

force.

.

Pin Joints

5

Types of glue Time taken to dry

out

Strength Weakness

UHU glue Takes relative long

time to dry.

• Large surface

contact area with

material

• Flexible when

force is applied

Superglue

(Dolphin)

Solidifies fast. Could bear relative

heavy load.

• Becomes

fragile after it

dried off a few

days later.

• Low surface

contact area

with materials

Hot glue gun Solidifies very fast. • Large surface

contact area with

material

• The glue peels

off easily.

• Messy and bulky

in size.

Rubber glue

(Dunlop)

Takes relative long

time to dry.

• Large surface

contact area with

material

• Stronger than

UHU

• Needs 24 hours

to gain maximum

strength

• Flexible when

force is applied

Analysis

Materials analysis

The diagram above shows different orientations of fettuccine and the load being applied

from the top.

When the fettuccine is placed horizontally, the thickness of the fettuccine is thinner,

therefore the load it can withstand is small. The area of breaking point of the fettuccine

also increases with the horizontal placement.

The vertical fettuccine is stronger in this case as it has a smaller breaking point surface.

But when the fettuccine is 4 members thick, the length of the fettuccine for both sides

are the same (5mm).

Load Analysis of Fettuccine

6

Types of design

Number of members 3 6 6

Load withstand (kg) 2.5 6.1 5.4

Types of Fettuccine Shape Strength

Standard San Remo Flat

(Easier to glue)

Weak

San Remo Spinach Slightly rounded

(smaller surface area

in contact with the glue)

Stronger than standard San

Remo Fettuccine

Standard Divella Relative rounded

and larger in size

Strongest

Standard San Remo San Remo Spinach Standard Divella

Types of designs for middle support of the bridge

We decided to use the 2nd design instead of triangles after the test due to the realization

that we could not create a perfect triangle to efficiently transfer the load.

1 2 3

7

Truss AnalysisTruss analysis

Pratt truss has been chosen as the mock up bridge to test the load bearing of the

truss. The load will be hang at the center of the bridge to act as point load. There

are several factor to be considered to ensure that it can withstand 50N.

Factors affecting strength of bridge:

1. Types of bracing used

2. Span to depth ratio

3. Joint connection and displacement of fettuccine

4. Design of middle member supporting load

5. Number of fettuccine used in one member

Side Elevation of Mock up Fettuccine Bridge

Mock Up Fettuccine Bridge 1

Top elevation of Fettuccine Bridge

Total weight :236g

Height : 10cm

Length : 90cm

Load : 4.1kg

Pratt truss has high efficiency due to the vertical member and horizontal member. The

diagonal member act as tension member and vertical member act as compression

member. The purpose of this orientation of the members is to achieve force of

equilibrium. Imagine it as a simple triangle, 3 forces acting at a point can be represented

in size or direction by the sides of a closed triangle, then the forces are in equilibrium,

provided their directions can form a closed triangle.

8

As to prove the assumption is correct, calculations has been done to determine the

efficiency of fettuccine bridge.

+ ↑ 𝐹𝑦 = 0

𝐴𝑦 + 𝐵𝑦 − 50 = 0

𝐴𝑦 + 𝐵𝑦 = 50

𝑆𝑢𝑏𝑠𝑡𝑖𝑡𝑢𝑡𝑒 𝐵𝑦𝐴𝑦 + 25 = 50

∴ 𝐴𝑦 = 25N

Clockwise = positive

𝑀𝐴 = 0

50 9 × 5 − 𝐵𝑦 90 = 0

2250 - 90𝐵𝑦 = 0

2250 = 90𝐵𝑦∴ 𝐵𝑦 = 25𝑁 → 1

25N 25N

Section equation is used to interpret the internal tension force or compression force.

𝐹𝑎𝑏

𝐹𝑎𝑐

𝐹𝑑𝑐

25Ntan 𝜃 =

10

5

cos 𝜃 =5

125

sin 𝜃 =10

125

10

5

𝜃 𝐴𝐵

𝐶 𝐷

9

𝑀𝑏 = 0

− 𝐹𝑎𝑏(10) − (𝐹𝑎𝑐cos 𝜃)(10) − (𝐹𝑎𝑐 sin 𝜃)(40) = 0

− 10 𝐹𝑎𝑏 −5

12510 −

10

12540 = 0

𝐹𝑎𝑏 =4.472 − 35.777

−10∴ 𝐹𝑎𝑏 = 3.13𝑁 → 1

+ ↑ 𝐹𝑦 = 0

− 𝐹𝑎𝑐 sin 𝜃 + 25 = 0𝐹𝑎𝑐 sin 𝜃 = 25

𝐹𝑎𝑐 =25

sin 𝜃

𝐹𝑎𝑐 =25

(10

125)

∴ 𝐹𝑎𝑐 = 27.95 (𝑇𝑒𝑛𝑠𝑖𝑜𝑛) → 2

10

𝐹𝑥 = 0

− 𝐹𝑎𝑏 − 𝐹𝑑𝑐 − 𝐹𝑎𝑐 cos 𝜃 = 0𝑆𝑢𝑏𝑠𝑡𝑖𝑡𝑢𝑡𝑒 𝐹𝑎𝑏 𝑎𝑛𝑑 𝐹𝑎𝑐

− −4.025 − 𝐹𝑑𝑐 − (27.95)(5

125) = 0

𝐹𝑑𝑐 = 4.025 – 12.4996𝐹𝑑𝑐 = − 8.475N

Joint Connection

A gusset plate like fettuccine is used to improve the load distribution. It acts as a

connection to increase the contact surface area between horizontal member and

the diagonal member.

At the other side, the horizontal member and diagonal member does not

connected by gusset plate. These arrangements are to test the difference of

having gusset plate, hence to reduce the unnecessary weight.

Joint with gusset plate Joint without gusset plate

Number of fettuccine for one member

Position Number of fettuccine

Top horizontal 4

Top diagonal 1

Top vertical 2

The number of fettuccines for each members has been done according to our

truss analysis. The compression members should use the most fettuccine to

reduce the compression force. As fettuccine is good in tension force, the tension

member required 2 fettuccine to stack together to support the fettuccine bridge.

The diagonal member act as a member to distribute the force and to avoid

torsion force act on the bridge, hence it requires 1 fettuccine only.

11


Bottom horizontal 4

Bottom diagonal 1

Bottom vertical 2

Bottom vertical

(triangular column)

3

The number of fettuccine stacking for one member is similar to top of the

fettuccine. There are only one changes as to allow the member withstand the

point load. A triangular column-liked fettuccine is used for the bridge. The

strength of triangular column has been tested and shown in fettuccine-testing

(methodology).


Side Vertical 2

Side Diagonal 2

As the weight of top structure is heavier than the bottom structures, we worried

that the side structures cannot withstand the weight itself, causes bending and

reduce the strength of fettuccine bridge. Hence, we decided to stack 2 fettuccine

for each member to reduce possibility of bending.

After testing

The bridge breaks when the total point load weight 4.1kg. The triangular column

itself does not broke, but the horizontal members. We concludes that it is

possibility of 3 second glue affects the strength of fettuccine bridge as the

horizontal has been done before 2 days we test the bridge. The placement of

broken member should be changed to improve efficiency of fettuccine bridge.

The whole structures are still rigid after testing. Hence, we decided to change the

number of fettuccine stacks for each members to reduce the total weight.

12

Diagram : the attachment of members on bridge. Diagram : Bracings are attach to the bridge only by glue.


Total weight :191.68g

Height : 10cm

Length : 90cm

Load : 3.5 kg

Similar to the first mock up model, the bridge was also constructed using the pratt

truss. In order to reduce weight, certain members of the initial design was

removed. The members removed are mainly:

bracing along the top and the bottom of the bridge.

internal bracing at the vertical elements.

Besides that, some minor changes had also been made to the connection of the

members of the bridge, which are,

slotting in the vertical elements

rotating the main beam 90 degrees from its original placement.

13

14

Member of Bridge Number of layers

Main truss 4

Top & Bottom Horizontal 2

Vertical 2

Bracing 2

Failure:

The bridge had failed due to the lack of bracing on the top and bottom of the

bridge, leading to the twisting of the bridge. Decision hence had been made to

replace the next bracing on the next model but reduce the layers of the bracing to

reduce the bridge’s weight. Besides that, observation have been made that the

surface area for gluing is insufficient if the fettuccine is slotted in between the

horizontal chords due to uneven surfaces.

Conclusion

Bracing is crucial element on the truss bridge to maintain its form and prevent it for

twisting.

Final Model Testing

1st bottle

4th bottle

7th bottle

11th bottle

15

▲ Side Elevation of Mock up Fettuccine Bridge


Total weight :196g

Height : 100mm

Length : 850mm

Load : 5.744kg

A Pratt truss similar to the previous test models was used due to the high efficiency

of the vertical and horizontal member. The diagonal member act as tension

member and vertical member act as compression member. The purpose of

orientation of the members is to achieve force of equilibrium. Although the spinach

fettuccine has smaller contact surface, but it is stronger than the normal fettuccine.

Hence, we have chosen the spinach fettuccine in building our final bridge model.

▲ Top Elevation of Mock up Fettuccine Bridge

The efficiency for the final bridge is:

E =(5.744𝑘𝑔)2

196𝑔

0.1683

16

Joint Connection


Top horizontal 4

Top diagonal 1

Top vertical 1

Through the first and second model testing, we realized that the top vertical

members could be reduce to just one layer since it is not in direct contact with

load applied. This is also one of the approaches taken in order to reduce the total

weight of the bridge. Besides, there are only one layer of diagonal members

because they act as bracing to prevent torsion force. Hence, one layer will be

sufficient to support the trusses.

At both sides, the vertical and diagonal members are laid on the outer surface of

the horizontal members by using super glue. After tested the first and second

bridge, we decided to use the first joint connection by removing the gussets. This

is to maximize the surface area in contact so that every members can hold still in

place and perform well in acting with the forces applied.

At the top and bottom part, the vertical members was stacked on the horizontal

member and following by the diagonal bracing on top of the vertical members.

While force is applied, the vertical members can transfer load down directly since

they are sitting on top of the horizontal member.

Number of fettuccine for one member

17


Bottom chord 4

Bottom diagonal bracing 1

Bottom bracing 1

Bottom bracing

(middle)

8 (divided into two, four on

each side)

The number of fettuccine supporting the horizontal chord for both top and bottom

have been reduced to one as it didn’t require to withstand much force but rather

to prevent torsion of the bridge. The middle bottom bracing which holds the load

applied are required to be stronger since it has direct contact with the load.

Hence 8 fettuccines are used to strengthen the member. The fettuccines are

divided into half, where four layers of fettuccine are stacked together to form a

member. The two members were placed side by side to provide a wider surface

area for the hook to hold the load and to prevent it from breaking easily.


Side Vertical 2

Side Diagonal 1

In order to withstand the force of the weight, the number of fettuccine in the side

bracings remain unchanged. The amount of fettuccine in the diagonal bracing

was reduced to one as it helps prevent sliding of the vertical and horizontal

members under pressure.

The middle bottom bracing

18

After testing

The final bridge managed to support a maximum of 5.744kg before breaking.

The middle bottom bracing remains unbroken as the bottom chord had snapped

first causing the entire bridge to cave in downwards. This is partly due to the

difference in height of tables used during the testing of the bridge, the improper

transfer of force causes the chord to split on both sides.

Middle beam didn’t break during testing The bottom chord after splitting

The bridge had broken on opposite ends at the moment of breakage. The torsion

caused all the horizontal bracings to twist and snap although several portions of

the side bracings remains in one piece a side from point breaks.

19

The final bridge has the highest efficiency out of all the model testing we did and was

considered a success to us. Throughout the whole project, different materials,

arrangement of members and joint connections are used to explore and improve the

bridges.

We came out with systematic ways to do the model in order to reduce the time taken for

the construction and to increase the precision of the Fettuccine bridge. We also realized

the importance of workmanship during the model making. Inaccurate or twisted

fettuccine will contribute to the deformation of the bridge and thus causing lower

efficiency.

We did identify the tension, compression members and weak points as to determine on

which parts to strengthen and which to reduce the layers of Fettuccine used. This

method allows us to reduce the weight of the bridge to meet the requirement of the brief.

Lastly, this project allows us to understand the importance of structure and construction

method in design and the load distribution in truss to enable us to create a better

structure for our designs in the future.

Conclusion

20

Reference List :

Analysis of Structures. (n.d.). Retrieved from

http://ocw.nthu.edu.tw/ocw/upload/43/733/static_ch6.pdf

Calvert, J. (2000, January 1). Truss Design. Retrieved from

https://mysite.du.edu/~jcalvert/tech/machines/bridges.htm

Trusses Introduction. (n.d.). Retrieved from

http://www.ce.memphis.edu/3121/notes/notes_03a.pdf

Image Reference :

Image 1 : Retrieved by http://structurae.net/photos/144783-tulln-danube-river-railroad-

bridge


bridge


bridge


bridge


bridge

Reference

21

bstructure report final

Education

fettuccine truss bridge

fettuccine bridge

model bridge

fettuccine fettuccine

bridge members

entire truss bridge

truss members

truss design