Capstone Competition

1.0 Introduction

Capstone project is part of Integrated Design Project (IDP) assessment where student required to complete certain task and will be evaluate by panels. For our group EC2208AM, we are entitling with a project of bridge design and modeling. Bridge model are analyze and design using computer software and experimental setup is done to compare the result of theory (computerize) and real value (experimental). This bridge must meet the requirement set by the panel and will compete in a competition held by Faculty of Civil Engineering

1.1 Model Specification

The model should comply with the following specification:

Material - The bridge model shall be made from non-metallic materials such as balsa wood, bamboo, paper, thread, straws, glue, masking tape or similar materials. Composite materials such as carbon fibers or plastic materials are not allowed.

Element Dimensions - The cross section of each element must not be greater than 5 x 5 mm for square section and 6 mm diameter for circular cross section or equivalent area for rectangular section.

Clear Span – Clear span between supports should be 1000 mm.

Length – recommended overall length should be 1200 ± 25 mm.

Support – Simply supported with a base area at both ends must not be greater than 100 x 100 mm

Bridge Deck – Horizontal and part of the model structure with a maximum width 100 mm and can accommodate dual carriageway of at least 30 mm wide each.

Height – maximum 300 mm

Connection – glue or tie (thread)

Element – each element must exceed 150 mm each

Load – model must be able to carry a 5 kg loading block for at least 30 seconds.

1.2 Computer software

Computer software used for analyze our bridge model is LUSAS Finite Element Analysis. LUSAS is one of the world’s leading structural analysis systems. With a support up to 500 nodes, meshing and custom material properties, we was able to analyze our model efficiently and able to compare the result.

2.0 Mock-Up Test

Mock-up test is done to test the materials (balsa wood, glue and string) to get the parameter required as input in computer software. The size of mock-up test should be smaller than the real model and compared with computer software. For our mock-up test, we decide to make a bridge with a simple truss system. A simple truss system is sketch and the dimension of each element is then label for ease of model making.

Figure 2.1 Design of Mock-Up Model

Figure 2.2 Simple Truss System

2.1 Computer Software for Mock-up test

The model is created in LUSAS by entering the coordinate of each node available according to our design. Those nodes will then be connected with line. Bracing is provided to joint these two plane truss to form a simple bridge model. Attributes of our model is then being input. Those attributes are:

• Mesh for line (cross section)
• Geometric for line (truss)
• Material – Isotropic (balsa wood)
• Support – Roller and pin (simply supported)
• Loading

For loading, the value of 50 N is applied. This value will then be divided by 4 as the load is distributed to 4 no of nodes. The requirement of this test is that the load is applied to the joint, not on the member as member will then to fail due to load whereas joint able to distribute the load to other members.

For material, an assumption is being made. This is the attribute that needs to be manipulated in order to obtain the same result as experimental. The result that will be compared is the deflection. The parameter that will be manipulated is Young’s Modulus.

2.2 Mock-up Model Testing

Mock-up model was tested in Lightweight Structure Laboratory. The model is put on a testing frame with a clear span of approximately 200 mm. For mock-up test, the clear span is different for each group and the platform on the testing frame can be adjusted. A dial gauge is place on the lower chord of the truss while 2 strings with a hook is place on 4 joint of the bridge to cater the load. A load of 10 N is added until 50 N to get 5 reading of deflection. The value of deflection is recorded and will be compared with compute deflection. An assumption parameter of material is used as a starting value.

2.3 Result of Mock-up Test

From the laboratory testing, we obtain that the mockup model deflect 1.99 mm when loaded with 50 N loads.

From the LUSAS Modeller, we obtain that the deflection on the bottom chord is 0.701392 x10-9 m when the loading is 50 N.

Figure 2.3 LUSAS Mock-Up Deflection

To match our computer calculation and experimental value, we do a try and error method of determining the value of Young’s Modulus. Based on our method, we obtain the following value:

Figure 2.4 Young's Modulus Value

3.0 Bridge Model

Bridge model is made when the mock-up test is completed. A sketch is done to know the layout of the bridge model. A few concepts have been made and the final concept is finalized when all of us agree with the bridge configuration.

Figure 3.1 Sketch of Concept Bridge Model

3.1 Concept of Bridge Model

The concept of our bridge model is star. From the elevation view, we can see the shape of star on our bridge. This is to show that our bridge have a strong and unique sense of aesthetic value. Other than that, it also shows that our bridge can cater heavy load of road users. The finalize concept is shown in figure below.

Figure 3.2 Elevation View of Bridge Model

3.2 Building the Bridge Model

Our group begin model making on Sunday 17th April 2011 until Tuesday 19th April 2011. With a good teamwork, we manage to complete the structure and landscape for our bridge on time. We make a good use of the material provided and try to reduce waste as efficiently as possible. We also able to color our bridge model so that it will look nice and shining as star.

Figure 3.3 Configuring the Star Shape

Figure 3.4 Support of Bridge Model

Figure 3.5 Configuring the Deck Bracing

3.3 Decorating the Landscape

The landscape that we agree to do is that the bridge will connect an urban area with a rural area. The bridge will cross a wide river and provide a mean of transportation for that area. Material use to complete our landscape is box, tissue, sand, ash, tree branch, water color and glue. With a creative mind, we able to come out with a beautiful landscape for our bridge.

Figure 3.6 Bridge Model with Landscape

4.0 Capstone Competition

To improve our motivation and teamwork in building this bridge model, Faculty of Civil Engineering held a Capstone Bridge Competition, where our bridge will be tested and a prize will be given to groups with a good strength (structural) and decoration (architectural). This competition is held at Engineering Complex on 20th April 2011. 36 companies take part on capstone bridge competition and 6 winners for structural and architectural is awarded respectively.

4.1 Preparation at Competition

We are provided a table based on vote and place our model on top to look elegant. With the bridge is place diagonally, it look good and will catch attention of architectural judge.

Figure 4.1 Bridge Model during Competition

4.2 Competition Procedure

The competition is divided into two categories which is architectural and structural. It began with architectural, where architect from industry is invited to be a judge. The architectural aspect that will be rated is concept, aesthetic value, model shape and decoration of landscape. After architectural category is done, we will proceed with structural category.

For structural category, first we will weigh the bridge. Before the bridge is place on the weight balance, the judge will inspect the bridge to check whether there is unwanted material is used or the bridge does not follow specification. Having the bridge weighted, we will proceed to the testing frame.

At the test frame, 3 aspects is being measure. First is the setting up time, where the time will start as soon as our bridge is placed on the platform. We will then need to place the dial gauge on the bottom of the deck to take the deflection reading, place 2 strings at our middle joint to cater the load and have our model ready for testing. Time will be stop when the dial gauge is set as zero, including the weight hook is place on the string.

Secondly, the deflection of our bridge is measured. This is done by putting a 5 kg (50 N) loads on the hook to made the bridge deflect. The value of deflection is taken after 30 second the load is applied.

Lastly, the dial gauge is removed and the bridge will be test with a maximum loading until failure. Load is added 10 N at a time and a few second of stability are given so that the bridge will not have a sudden failure. Having completed all this task, mark will be given by the judge and mark the end of our bridge competition procedure.

Figure 4.2 Bridge Failures after Testing

5.0 Result

Result for our bridge model is recorded during competition and also during computer analyze. Those results are tabulated and represent below.

5.1 Result from LUSAS

From LUSAS, we get the value of deflection is 0.0160287 m.

Figure 5.1 LUSAS Model Result

5.2 Result from Experimental (Competition)

Below is the result from the competition

Table 5.1 Architectural Category Mark

Table 5.2 Structural Category Mark

6.0 Achievements

Our hard work and time is blessed with an achievement during Capstone Bridge Model. We were awarded no 5th in architectural category and win a hamper. A souvenir and certificate also was given to us.

Figure 6.1 Fifth Prize

Figure 6.2 Souvenir

(copy paste from my report... too lazy.. take a few weeks to post this entry.. huhuhuhu)