Building structure report

Building Structures [ARC 2523]

PROJECT 1: FETTUCCINE TRUSS BRIDGE

A4 Documentation

Name (Student ID): Eunice Chan Yu Ming 0315729Foo Wei Min 0321577Koh Kar Yi 0320567Teo Chen Yi 0320618

Lecturer: Pn. Norita Johar

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Table of Content

1.0 Introduction1.1 Objectives1.2 Project requirement1.3 Report overview 1.4 Timeline

2.0 Methodology 2.1 Precedent study 2.2 Materials testing and Equipment preparation2.3 Model making and design development 2.4 Structural analysis 2.5 Bridge efficiency calculation

3.0 Precedent Study 3.1 Background history 3.2 Joints and connections3.3 Structure

4.0 Material and Equipment4.1 Material 4.2 Equipment

5.0 Structural Analysis and Design Solution5.1 Compression and tension5.2 Member profile and orientation5.3 Joint

6.0 Final bridge 6.1 Amendments and final bridge design6.2 Final model making 6.3 Final bridge testing 6.6 Calculation and diagram

7.0 Conclusion

8.0 Appendix

9.0 Reference

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1.0 Introduction

1.1 Objectives

The objectives of project 1 are as following:

To develop understanding of tension and compressive strength of construction materials.

To develop understanding of force distribution in a truss To design a perfect truss bridge which fulfils the following two main criteria which

are efficiency and minimal usage of material.

In the end of the project, we will be able to evaluate, explore and improve attributes of construction materials. By applying understanding of load distribution in a truss, we will evaluate and identify tension and compression members in a truss structure. Different arrangement of members in a truss structure will be explored according to understanding and analysis of load distribution.

1.2 Project Requirements

Project 1 is divided into 2 parts – individual and group.

Individual: Each member is required to solve a case of a truss system and determine the most effective and efficient truss arrangement for the load system.

Group: In a group of 4-5, we are required to design and construct a fettuccine bridge of 350mm clear span and maximum weight of 70g.

1.3 Report Overview

This project requires a group of 4 to build a perfect truss bridge made of fettuccine in 7 weeks. The beginning of this project started with exploration of different truss design through precedent studies. Analysis on strength, profile and joints, as well as the reasons of failure are recorded in every test. A series of testing are carried out and modification on design is discussed to achieve higher efficiency. Lastly, we are to solve the calculation assigned for individual case studies and all data are to be recorded in this project.

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1.4 Timeline

Date Event

2/4 Testing of compressive strength of different brands of fettuccine Prego, San Remo original and San Remo spinach.

9/4 Testing of tensile strength of different brands fettuccine Testing of different profile and orientation for chosen brand Design and testing of first truss bridge (Warren).

17/4 Research of different bridge design Design and testing of second truss bridge (Pratt).

20/4 Compare and analyse Warren and Pratt truss bridge. Identify and analyse breaking points. Decision on truss design and profile.

30/4 Design and testing of third bridge (Warren). Decision of type of fettuccine.

1/5 Design and testing of forth bridge (A).

6/5 Design and testing of fifth bridge (A).

7/5 Design and testing of sixth bridge (A).

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2.0 Methodology

2.1 Precedent studies

Exploration on various design of perfect truss through precedent studies allow us to pick up the strengths and limitation of existing bridges. Modifications are made to increase the efficiency.

2.2 Material Testing and Equipment Preparation

Equipment such as weighing scale, water bottle, pail, and s hook are prepared and set up for testing to be carried out. A series of testing are done to figure out the following:

Best fettuccine brand to be used based on the material strength Strongest profile and orientation to resist compression force Strongest profile and orientation to resist tension force Suitable joints and connection to resist different force The best adhesive in connecting the members

2.3 Model Making and Design Development

After the analysis on single members is done, we progress further on making the whole bridge. Different perfect truss are tested to determine the strongest structure. Strengths and weakness of different trusses are taken into consideration for best bridge design.

2.4 Structural Analysis

Structure model is analysed through calculation to show understanding of truss and load transfer. The factors causing failure of bridge structure is analysed and discussed for improvement.

2.4 Bridge efficiency Calculation

The efficiency of the bridge is calculated using this formula:

Efficiency, E = Maximum Load

Weight of Bridge

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3.0 Precedent Study

3.1 Background history

The “Waddell A” Truss Bridge, currently located in English Landing Park, Parkville, designed by engineer John Alexander Low Waddell in 1898. It was previously built as a railroad bridge in Linn Branch Creek, and now crosses Rush Creek carrying a pedestrian path between a day-use recreational and two isolated ball fields. In 1980, the bridge was disassembled and was kept by the U.S Army Corps of Engineer for 7 years. Nevertheless, the bridge retains its integrity of design as drawn by John Low Waddell; it was then reassembled with the same standards as originally specified by the designer.

This bridge is approximately 40 feet high and 100 feet long. It rests on two concrete abutments and is composed of pin-connected riveted units. Waddell's "A" truss was developed to meet the need for a consistent, easily erected, short-span railroad bridge and is regarded as a transitional phase in bridge design.

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Figure 1: Photograph showing Waddell A truss bridge in Parkville, Missouri.

3.2 Joint and Connections

Figure 2: Photograph showing members in Waddell A Truss Bridge.

Figure 3: Diagram showing joints between each member.

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Figure 4: Photographs showing pinned (left) and gusset plate (right) connections.

Figure 5: Diagram (left) and photograph (right) showing cross

bracing of Waddell A truss bridge.

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Figure 6: Photographs showing cross bracing under the bridge (left) and bottom chord lateral cross bracing (right).

Figure 7: Photograph showing gusset joint found at the top chord.

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Figure 8: Photograph (left) and diagram (right) showing pinned joint.

Figure 9: Diagram showing detailed drawing of pinned joint connection.

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3.3 Structure

The Waddell “A” Truss Bridge is a triangular shaped steel through-truss bridge; it is single span and length around 100ft with the deck width of 16ft and 40 meters high. Each truss has four panels, the distance between are around 5.2 meters.

Figure 10: Diagram showing force distribution of bridge under load pressure.

The A shaped top post that are connected by top bracing are usually in compression. Therefore, X bracing that sandwiches between the two trusses were to provide sideway stability.

The compression members are shop riveted built up sections, made out of angles, plates and channels, conversely, tension members are made of pairs of eye-bars. The bottom chord is divided into four sections, 25ft by 17ft, sway-braced by angle braces and supporting a pair of girder stringers, angle braced.

Figure 11: Photograph showing dataplate of the bridge.

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4.0 Material and Equipment

4.1 Materials

4.1.1 Fettuccine

Three types of fettuccine are measured/tested for the following characteristics:

Weight of one 25cm of fettuccine, W (g)10 strips of 25cm fettuccine are weighed to calculate the average weight for a single fettuccine.

Cross-sectional area in ascendant order, A (small to large) Strength ranking. *Data tabulated in 5.1.1 Compression (Page 15)

Type of Fettuccine W (g) A Strength ranking

Prego

1.3 1 3

San Remo original

1.5 2 2

San Remo spinach

1.73 1

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4.1.2 Adhesive

Three types of adhesive are compared to achieve the most effective result:

Types of Adhesive Advantages Disadvantages

UHU Glue

Easy to use

Slow solidify time Joints flexible after

dry

V Tech 502 Super Glue

Easy to use Strong and firm

connection High efficiency Fast solidify time

Makes fettuccine brittle

Expand and bending might occur

Hot Glue

Strong adhesion

Long solidify time Creates bulky

finishing Hard to control Carries contain

weight

Conclusion:

Based on the comparison made, V Tech 502 super glue performs the best on the Fettuccine Bridge as firm and strong connections are required to withstand load. Also, it does not affect much on the weight of the bridge compared to the other two. Therefore, V Tech 502 super glue is selected.

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4.2 Equipment

Different equipment are used throughout the project

Types of Equipment Function

Weighing scale

Measure the weight of Fettuccine bridge and the load.

Craft knife

To cut the fettuccine precisely.

Sand paper

To sand the edges of fettuccine to ease connections.

Pail

Act as load together with the water added in.

S hook

To hook the load to the fettuccine bridge.

strings

To tie the pail to the fettuccine bridge.

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5.0 Structural Analysis and Design Solution

5.1.0 Compression and tension

5.1.1 Compression

A test is carried out to find the relationship between the length of fettuccine and its compressive strength. The compressive strength is represented by the maximum weight a single fettuccine can withstand before it buckles.

Manipulated variable: Length of a single fettuccine, L (cm)

Responding variable: Maximum weight withstand before buckling, W (g)

Controlled variable: Type of Fettuccine (San Remo Spinach and San Remo Original)

Result:

L (cm) W (g)

Prego S.R Original S.R Spinach

5 448 601 947

7 280 301 394

9 154 177 222

11 126 133 182

13 85 92 127

15 69 73 76

17 63 64 75

19 51 48 56

21 34 41 35

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Figure 12: Photograph showing compression test fettuccine.

23 24 35 34

25 23 30 34

Conclusion:

The longer the fettuccine is, the more weight it can withstand before buckling.

There are two effects of compression on a structural member - crushing and buckling. Members below a certain length will experience crushing while the members exceeding the length will experience buckling. However, force required to cause crushing is much larger in comparison with buckling. Therefore, there is a limitation that compressive test showing crushing effect cannot be tested using this method.

The compressive strength of the types of fettuccine in descendent order: San Remo Spinach, San Remo Original, Prego.

Factors of compressive strength:

It is found that compressive strength of a structural member can be affected by others factors besides its length. Below shows all factors that affect compressive strength:

Length Type of material used Width and thickness of cross-section Profile of cross-section.

5.1.2 Tension

Unlike compression, the length and profile of cross-section of a structural member are not factors of tensile strength. Below shows the factors of tensile strength:

Type of material used Width and thickness of cross-section

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5.1.3 Conclusion

The factors affecting compressive and tensile strength can be summarized as below:

Affecting Factors Compression Tension

Length of material ✓ ✘

Type of material used ✓ ✓

Width and thickness of cross-section ✓ ✓

Profile of cross-section ✓ ✘

As tensile strength is not affected by length while compressive strength is, there is no way to decide the length of fettuccine used for testing to compare its compressive and tensile strength. Therefore, it is not possible to test if fettuccine is stronger in compression or tension by the amount of force it can withstand.

However, unlike compressive strength, tensile strength is only affected by two factors. This makes fettuccine more efficient in withstanding tension than compression.

5.2 Member profile and orientation

A bending test is carried out to find the relationship between member profile/orientation and its strength. The strength of fettuccine is represented by the maximum weight it can carry before rupture.

Manipulated variable: Fettuccine profile

Responding variable: Maximum weight withstand before rupture, W (g)

Controlled variable: Type of fettuccine (S.R Spinach),

Clear span (175mm)

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Figure 13: Photograph showing bending test for different profile and orientation of member.

Result:

Fettuccine profile (cross section) W (g)

185

264

469

476

684

1085

1276

1365

1523

637

1770

1267

2624

1795

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Conclusion:

As weight is a factor to be considered in this project, strength of each profile is compared by the number of layers used in the profile. It is assumed that the number of layers is directly proportional to the weight of the member, with the amount of glue used for connection as a neglected factor.

Below shows the strength of profile made of different numbers of layer in descendent order:

Number of layers Strength in descendent order

1,

2 ,

3, , ,

4 ,

5 ,

7,

Therefore, for compression, it is more efficient to use vertical and I profiles instead of horizontal and H profiles.

For tension, as it is not affected by cross sectional profile, 3 layer laminated profile maybe more efficient than I as the surface in contact for connection between layers is larger.

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5.3 Joints

Joint A

The end posts are pushing against each other under compression. Figure 1.1 shows the first attempt, with its connection beten the top chords and the middle chord relatively weaker. Use of gusset could give more rigidity. However, total weight would increase. Figure 1.2a and 1.2b show improvements made to allow stronger adhesion of top chord with middle chord made of ‘I beam’ profile.

Joint B

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To achieve clear span of 350mm, we have made the bottom chord 40cm long, thus impossible to avoid using end joint. 2cm gussets are added in exposed side to get the benefits of a lap joint, making the joint as strong as possible.

Joint C

Lap joint is applied in the core where the point load is applied. This joint helps members in compression to resist bending and maximises the surface area in contact between bottom chord and middle core.

Joint D

The struts used in connecting the top chords are to resist moment. By applying to real life examples, the end posts are connected this way. Only three struts were used initially and were added to six struts (three on each half of the chord) to allow a more efficient load distribution of compressive force.

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6.0 Final Bridge

6.1.0 Amendments and final bridge design

6.1.1 Amendments

Bridge 1: Pratt Truss Bridge

Weight of the bridge: 60g

Maximum load withstand: 2570g

Failure: Joint

Structure analysis and design solution:

1. Joint connectionsFettuccine is not cut properly. Uneven surface at the tip reduces the surface area in contact with adhesive hence lowering the strength of the joint. Sand paper can be used.

2. Bottom chordsBending is observed at the bottom chord of bridge. Bottom chord member profile (3 layer laminated) is not strong enough to withstand the load.

3. Height and angleHeight of the bridge not only increases the amount of fettuccine used (hence increasing its weight), it affects the angle of diagonal member to be more than the optimum angle of 45°.

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Bridge 2: Warren Truss Bridge



Failure: Top chord


1. Top chordBending is observed at the top chord. Top chord member profile (3 layer laminated) is not strong enough to withstand the load.

2. AngleAngle of the diagonal member is not kept at 45° optimum angle.

3. HeightBridge is made too high increasing its weight.

4. Diagonal memberOrientation can be changed to increase its strength.

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Bridge 3: Warren Truss Bridge



Failure: Top chord


1. Deflection Major deflection is observed. It is believed to be the misalignment of two truss by struts. The two trusses are not perfectly parallel to each other.

2. Top chordBridge fails at the top chord although 2 layers I-beam is used. Straight top chord will be replaced by stronger ‘A’ end post.

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Bridge 4: “A” Truss Bridge (Spinach)



Failure: Strut Insufficient of strut that pushes against each other when it is being compressed


1. StrutInsufficient strut fails when excessive compressive force pushes trusses against each other.

2. Diagonal memberOnly 2 out of 6 diagonal members are of 45° optimum angle. Another 2 diagonal members will be changed to 45° optimum angle by changing its orientation.

3. Middle chord3 layers laminated middle chord will be changed to single layer I-beam.

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Bridge 5: “A” Truss Bridge



Failure: Bottom chord


1. Bottom chordBottom chord fails at splice when two fettuccines are connected. An additional piece of fettuccine will act as gusset plate to strengthen the joint.

2. ConnectionI-beam middle chord and I-beam end post are not securely joined together.

3. Truss membersTruss members will be reduced to reduce weight.

4. End postEnd post will be made taller for better load distribution.

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Bridge 6: “A” Truss Bridge



Failure: Bottom chord


1. Bottom chordBottom chord fails near to the contact point with the support (table). Piece of fettuccine will be added at the side of the I-beam bottom chord near the support.

2. StrutMore strut will be added to hold the truss together more securely.

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6.1.2 Final bridge design

1. End post Increased angle for stronger structure. Single I-beam

2. Diagonal member- 45° optimum angle- Single layer

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3. Bottom chord- 1-2-2 layers I-beam is used for bottom chord to resist bending moment.- Additional pieces of fettuccine are added at splice and near to support where are prone to snapping.

4. Middle chord Single layer I-beam.

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5. Vertical member- Single layer

6. Middle core where point load is applied.

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7. Strut- More struts are added.- 8 double layer struts are used.

8. Final Bridge

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6.2 Final model making

1. First, an accurate measured bridge drawing is drawn out to use as a template for bridge making. Each truss is cut and trims with the exact length according to the template.

Figure 14: Hand-drawn template for bridge design.

2. All of the components are cut out exactly to the length desired. Extension of 40cm I-beam is added at the bottom chord. The composition of the I-beam stack is 1-2-2.

3. Next, 9cm middle chord that made up of 1 layer I-beam is glued on top of the centre bottom chord.

4. Further up with four 1 layer hip vertical standing columns. These vertical members serve as vertical pales for the fettuccine bridge to resist compression force exerted.

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5. Following with 2 sets of 1 layer 45º diagonal members connecting the top of the vertical member to the end of the horizon of bottom chord.

6. Next, two end post are added compelling the middle chord and bottom chord forming an “A” shaped framing. The span of bottom chord is 40cm while the end post is 35cm only to cut down unnecessary weight.

7. A few number of 3cm I-beam struts are glued in between both top chord and bottom chord to stabilized and connect two trusses together.

8. 2 vertical I-beam trusses with 1-2-2 stacking together with 1 horizontal 1-2-2 I-beam are placed literally on top of the bottom chord. It is constructed as a core to carry the S-hook for the pail to rest on.

9. Lastly, 2cm butt joint is added to every splice of bottom chord to strengthen the truss bridge.

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Formula of perfect truss bridge

2J = M + 3

2(12) = 21 + 3

24 = 24

Thus, it is a perfect truss bridge

Efficiency of bridge:



Efficiency:

Failure: End Post

Structure analysis:

1. DeflectionA major deflection can be observed. This is probably due to the two trusses at the sides that aren’t perfectly parallel to each other.

2. End postAfter reinforcing and having enough strength for the bottom chord, one of the end posts breaks first.

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102000g

66g= 154.66

8.0 ConclusionBy the end of this project, we had design and constructed a total of 7 fettuccine bridges

in order to achieve the highest efficiency of withstanding loads. With the help of the precedent study, Waddell “A” Truss Bridge, we get to understand as well as learn more about the construction of real truss bridge and to apply the essence into our own fettuccine bridge.

For the final model bridge testing, our bridge was unable to achieve the highest efficiency among the 7 other bridges that were previously constructed. Nevertheless, our 6th bridge has the highest efficiency, with the weight of 63 grams and total load withstand 10200 grams, an efficiency of 161.9E is achieved. Conversely, our final bridge was only able to achieve efficiency of 151.5E withstanding a total load of 10000 grams and its weight 66g. This project has made us understand more and allowing better comprehension on load distribution in a structure. We also learned to calculate and identify the tension or compression force applied on a structure member before constructing it in order to achieve highest efficient bridge design.

Furthermore, before constructing the final bridge, we had tried to play and experiment with several beam and truss design in order to select the finest one for bridge construction. Every trial and error while constructing the bridges has given us more in depth understanding upon structural forces acted on various trusses.

In a conclusion, although we could not achieve the highest efficiency for the final bridge, we were still very satisfied with our end product because each failure brings valuable lesson and we had definitely learned a great deal in proper structural design in hope that we will be creating a building that is safer with proper building structure.

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9.0 Appendix

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10.0Reference list

1. Ching. Francis D.K (2008) Building Construction Illustrated Fourth Edition. New Jersey: John Willey & Sons, Inc.

2. L. C. Tartaglione. (1991) Structural Analysis. New York: Mcgraw Hill Book Co. 3. W.T. Marshall, H. M. Nelson. (1990). Structures, 3rd Edition. (Revised By Bhatt,

P. & Nelson, H. M.). London: Longman.4. Chajes, A. (1990) Principles Of Structural Stability Theory: Second Edition.

Englewood Cliffs, New Jersey: Prentice-Hall, Inc.

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CASE STUDY

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Case Study Conclusion

Of all the case studies that have been done by our group, case study 1 is concluded as the best designed truss of all 4. Conversely, case study 2 is relatively weaker.

The load force of case study 1 has minimal interference acting in between; and is distributed evenly within the truss members, none of the member carries extremely high load, thus, lower down the chances of failure on a particular member. However, the load of case study 2 is not distributed decently as it has a lot of concentrated load within one member. Case study 1 also has high amount of tension force that providing more resistance force against pulling comprised within the bridge as compared to bridge 2.

Furthermore, case study 1 has the least ‘zero force’ truss members in it, prove that all of the truss members are functional and provide better load distribution throughout the whole truss.

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Education

Building structure report