1.0 INTRODUCTION 1.1 Background
Bridge is a structure built to span physical obstacle such as body of water, valley, or road. There are many different designs that all serves unique purposes and apply to different situations. Design of bridges varies depending on the function of the bridges, where the bridge is constructed, material used to make it and the funds available to build it. There are four major types of bridges that are arch, beam, suspension and truss bridges. Beam types of bridges are the simplest bridges and also the most common. Beam bridges are commonly built from concrete and steel or a mixture of steel and concrete. The supported for this type of bridges are pillar or column.
Figure 1.1.1: Beam bridges Second types of bridges are arch bridges. Arch as a main structural component and always located below the bridge never above. They are made with one or more hinges, depending on what kind of load and stress forces they must endure. In the arch bridges, weight is carried outward along two paths, curving toward the ground. Examples of arch bridges are “Old Bridge” in Mostar, Bosnia Herzegovina and The Hell Gate Bridges in New York.
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Figure 1.1.2: Arch bridges Suspension bridges are bridges that use ropes or cables from the vertical suspender to hold the weight of bridge deck and traffic. In a suspension bridge, cables which are suspended via towers which support them hold up the road deck. The weight is transferred by the cables to the towers, which then in turn transfer the weight to the ground. Example of suspension bridge is Golden Gate Bridge in San Francisco.
Figure 1.1.3: Suspension Bridges The last major type of bridges is truss bridges. Truss bridges are very popular bridge design that uses diagonal mesh of posts above the bridges. The two most common designs are the king post with two diagonal posts supported by single vertical post in the center. Second most common design is queen post with two diagonal posts, two vertical pots and horizontal post that connect two vertical posts at the top.
Figure 1.1.4: Truss bridges
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1.2 Objectives
i.
To build and test model bridges designed to carry a fixed load.
ii.
To apply mathematical, science and computer technology as problem solving tools.
iii.
To learn how real bridges are designed and built.
iv.
To develop student creativity in making bridge design.
v.
To build suitable concept of bridge that have higher withstand
1.3 Scope
Our research project will focus on designing bridges that can stand a load of 50N. This design aspect is including the concept design, concept selection, detail drawing, and Finite Element Analysis to get the best result. 1.4 Organization
This project focuses on how to design a bridge and the most suitable type of bridges that can stand 50N load. First, a short introduction on how the types of bridge affect withstand of bridges. After that, the problem has been on what the major problem that bridges can easily breakdown. Next, several concept of design has been choose before selecting the best concept to design the bridges. Finally, the findings are presented and conclusion is drawn. Four creative and hardworking students will be ideal for a team to this project. The team name is “Getok Corporation” where getok stand for bridge in Kelantan dialek.
Each group member member will look after the design and fabrication of
specific parts and coordination from the team leader is critical to the success of this project.
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2.0 FORMULATION 2.1 Problem Statement
Based on the outcome of the discussion and description of this bridge design identified a number of problems such as: i.
Durability is the major problem for most of the b ridges
ii.
Bridges component break down and soils becomes unstable.
iii.
Replacing bridge can be costly, time consuming and disruptive to traffic.
2.2 Product Design Specification
Preparing design specification was important to provide design guidelines for the engineers of the product. The PDS is a document that contains contains all of the facts related to the outcome of product development. Creating the PDS finalizes the process of establishing the customer needs and want, prioritizing them, and beginning to cast into a technical framework so that design concepts can be established. Pugh’s checklist (Pugh 1997) was used to determine relevant issues of the product. These issues were later transformed into a set of design requirement. The most relevant requirement in the design of bridges was the following:
Physical Description
External dimension i.
Length = 600mm
ii.
Height = 100mm
iii.
Height of support = 50mm
iv.
Deck width = 100mm
Material i. ii.
Balsa wood (10 x 5)mm Hot glue gun
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Performance
Can stand 50 N of load
Durability
Financial requirements
Time to complete project & key project deadlines = 1months
Warranty policy = none
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2.3 House of Quality (HOQ)
Engineering Characteristic (EC)
Improve direction Unit
Customer requirement (CR)
r o t c a f t h g i e w e c n a t r o p m I
d a o l m u m i x a M
s e g d i r b f o l a n o i s n e m i D
y t i v a r g f o r e t n e C
e g d i r b f o t h g i e W
l a i r e t a M
e g d i r b f o e r u t c u r t S
Cost
4
-
3
-
1
9
3
Durability
5
9
1
-
-
9
3
Can withstand heavy load
5
9
-
-
9
9
9
Stable
5
9
9
9
3
3
9
Long lasting
5
-
-
-
-
9
-
Design
4
-
9
-
-
3
3
Safety
5
3
-
-
-
1
9
98
45
64
203
174
Relative Weight % 20.4
13.4
6.1
8.7
27.7
23.7
Rank Order
4
6
5
1
2
Raw Score
Importance weight factor 1 through 5where 1 - Least important 5 - Most important
150
3
Relationship matrix (CR 9 - strong 3 - medium 1- weak
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EC)
House of quality (HOQ) constructed for bridge can be used as a references and guide for entire project. Among the most important factor in development of this bridge is material, structure of bridges, maximum load, dimensional of bridges, weight of bridges and center of gravity. The type of material use to design a bridge is an important factor in ranking of engineering characteristics. Engineering characteristics are variable for the design and can put unlimited number of variable. Relationship between engineering characteristic and customer requirement is from 9 for strong, 3 for medium, and 1 for weak. Type of material use is very important because it will affect the maximum load that bridge can stand. Next, the second important factor is structure of bridges. This is because there are many type structures of bridges such as truss, arch, beam and suspension. The third important factor is dimensional of bridges. Size of bridges must be stable with the load to make it stand in long time. The less important on function of the bridge according to engineering characteristics is center of gravity. Other observation from the need consumer in HOQ chart has shown that consumer are more focused on the requirements of can withstand in heavy load and stable. It can be conclude that consumers want that the bridge can be long lasting and stable with withstand heavy load.
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3.0 CONCEPT DESIGN 3.1 Morphological Chart
Component
Idea 1
Idea 2
Idea 3
Idea 4
Span
Support
Deck
Span = Idea 2 Support = idea 4 Deck = Idea 1 The idea for this comes from the bridge that already built in real life. It has three common things that important in making bridge that is span, support, and deck. Ideas 2 have been chose in making span of bridge because it can support heavy load and it has a lot of truss that carry on high force. Span is part above the bridge. Secondly is support and idea 4 have been chose because their structure and has 2 support beam at left and right of bridge. Lastly is deck that use as a road in bridge. Idea 1 is choose because it has suitable part for heavily load to use. For example at center of the bridge it has thick deck than other part.
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3.2 Concept Design st
1 concept
Figure 3.2.1: First concept This is the first concept as shown in Figure 3.2.1. The advantage for this concept is has more support. It also easy to build but their disadvantages is no support at the bottom part. nd
2 concept
Figure 3.2.2: Second concept The second concept is as shown in Figure 3.2.2. This design is inspired from ti tanic story. Their design is almost like a titanic ship. The different from other concept is their rods are at above of support.
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rd
3 concept
Figure 3.2.3: Third concept Based on the Figure 3.2.3 above it has been shown the third concept of bridge design. This concept is from the type of truss bridge. It has two supports to withstand the heavy load. th
4 concept
Figure 3.2.4: Fourth concept
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Based on the Figure 3.2.4 above it shows that the fourth concept of bridge. This concept is from the type of truss bridge. It also have two sting that use to tightly hold the bridge b ridge and use suspension concept of bridge.
3.3 Concept selection
Concept selection is a part to choose the best concept from among concept that has been listed. It considers the three import part of bridge that is span, desk and support. Other than that it also consider the customer requirement and engineering characteristic before choose the best concept. After consider all the important thing concept three have been choose because it concept relevant with the entire requirement. The final concept is as shown in Figure 3.3.1.
Figure 3.3.1: Final concept
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4.0 DESIGN ANALYSIS
Figure 4.1: Boundary condition Design analysis has been made for final concept that has been chosen. Figure 4.1 show the boundary condition of the bridge that need to analysis. Since the load are put at the center, so the clamp are use at the right and left side. The table 1 shows that the bridge properties during analysis. This includes the material used, young modulus, Poisson ratio, density, coefficient of thermal expansion and yield strength.
Table1: Bridge properties.
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Figure 4.2: The translational displacement The Figure 4.2 shows the translational displacement of the bridge analysis. The translational displacement also can be known as the beam deflection. The figure show the minimum translational displacement that shown by the blue (navy) area that is 0mm. The maximum displacement is 0.0161mm as shown in the red area in figure above.
Figure 4.3: The principal stress distribution
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The Figure 4.3 shows the stress principle tensor or the principle stress distribution. The value obtains at the end of o f bridge or at the bridge boundary b oundary condition. The maximum stress distribution is 2.24 MPa show at the red area while the minimum stress distribution is -4.37 MPa. The maximum value located at upper edge of the bridge and the minimum edge located at the lower edge of the bridge.
Figure 4.3: The Von Mises stress The Figure 4.3 shows the Von Mises stress of the beam. Von mises suggest that the yielding of the material begins when the second deviatoric stress invariant reaches a critical value. The Von Mises can be also formulated in terms of the equivalent tensile stress a scalar stress value that can be computed from the stress tensor. The Von Mises stress also used to predict yielding of materials under any loading condition from results of the simple uniaxial tensile tests. The Von Mises stress satisfies the property that stress states with equal distortion energy have equal Von Mises stress. In this case, the maximum Von Mises stress is 5.08 MPa while the minimum Von Mises stress is 5.17 MPa. The maximum Von Mises located at the edge of the bridge while the minimum Von Mises located at the blue (navy) area at the figure above.
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Figure 4.4: The estimated local area The Figure 4.4 shows the value of estimated local error .The maximum value is and the minimum value is J.
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J
5.0 CONCLUSION
As a conclusion, we found that our bridge can stand with the load of 5kg or 50N without any deflection. There are several problems in process of designing and developing this bridge. Among the problems that occur during the designing of bridge is in terms of expertise, time and cost. To produce a good and perfect bridge, developers must have strong spirit, creative, innovative, and not easily to give up and endure a possibility problem that will occur. Also throughout this project we have learned that the teamwork very important role to make this project successful.
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6.0 APPENDIXES
Figure 6.1: Prototype
Figure 6.2: Real Bridge
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Figure 6.3: Group member Getok coporation
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7.0 REFRENCES
I.
Tagarielli, V. L., Deshpande, V. S., Fleck, N. A., & Chen, C. (2005). A constitutive model for transversely
isotropic
foams,
and
its
application
to
the
indentation
of
balsa
wood. International journal of mechanical sciences, sciences , 47 (4), (4), 666-686.
II.
Comp, T. A., & Jackson, D. (1977). Technical Leaflet 95. Bridge truss types: a guide to dating and identifying. History news, news, 32 (5). (5).
III.
Ng, S. F., & Kulkarni, G. G. (1972). On the transverse free vibrations of beam-slab type highway bridges. Journal of Sound and Vibration, Vibration, 21 21(3), (3), 249-261.
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