PROJECT 1: UNDERSTANDING FORCES IN SKELETAL STRUCTUREARC 2513: BUILDING CONSTRUCTION 2

SOE WOEI HAO – 0309924 l SEAN HIU – 0309874 l WILLIAM YAP – 0314127 l TREVOR HOAREAU – 0308914 l YEE HERN – 0314674 l CHU SZI WEI - 0314160

OBJECTIVE

In this assignment, we are required to design and test a tower of popsicle sticks which allows us to gain experience in terms of learning how to the alignment of skeletal structures function and in what way do they transfer the load efficiently. `

Additionally, this assignment also focuses on the joints used for the structure to hold it in place to show how joints plays a role in securing a structure and also the design of the skeletal structure itself.

The Efficiency is calculated using the following formula which is:

Efficiency = (Height of tower x total Mass of weights)

Mass of Model

There are a few requirement when designing our popsicle model in order for it to be eligible for marking such as:

A maximum of 100 popsicle sticks should be usedA minimum of 30cm in height must be reached

With the given criteria, our objective is to obtain the highest amount of load possible because we believe the higher the load the better the efficiency. Hence, we tried to reduce the number of popsicle sticks used to make our tower lighter and also reinforce the columns as much as possible.

BASE

We began our explorations with two types of bases ; triangular and square as mock ups. unfortunately, our triangular bases failed us before being able to record them. the disadvantage we had with triangular base and modules is the connection part, and designing a suitable brace.

So with our square base, we experimented with different arrangement methods for example double layering, double stacking, as well as different brace arrangements.

FACADE

We finally came up with 3 layers of the same module, with the middle module having its inner columns placed slightly further inside. we thought this would help in the weight distribution. we connected the three layers by groove and thread method.

JOINT METHOD

SLOTTING

We cut grooves at specific measurements on our popsicle sticks, from columns and beams, they are then interconnected with each other.

TOOTHPICK DOWEL

We decided to use toothpick as dowels for connecting our braces. we found that this helped in terms of controlling the rigidity of the structure.

THREADING

When all layers and joints had been assembled, to further strengthen the model, we applied threaded ties to some joints and connections.

DESIGN STRATEGY

STRENGTHThe model has a stable bracing that allows the columns to maintain Vertical. This allows the columns to reach maximum efficiency.

WEAKNESSColumns are too weak to support the weights, Causing the columns to fail

IMPROVEMENTImprove the strength of the column by increasing The number of sticks

STRENGTHThe model is strong and able to take high amount of loadAs well as able to stack efficiency

WEAKNESSThe model has exceeded the amount of sticks allowed and the efficiency is low due to the amount of stick present

IMPROVEMENTDecrease amount of sticks as well as create columns to help increase efficeincy.

MOCK UP MODELS

STRENGTHThe model has strong columns that are able to withstand high amount of load because of the high amount of popsicle sticks on each column. Toothpicks were use to attach the brace to the columns to ensure the brace does not fail.

WEAKNESSOne of the major flaws of the model is that the joints of the model that used thread to tie was inconsistent as the number of loops as well as the amount of thread used was not standardize. The weight placement played a major factor in the failure of the this model.

IMPROVEMENTThe workmanship of the model needs to be improved as the slits and thread was not consistent which decrease the efficiency of the columns as well as the bracing. The placement of the weights had to be more precise and even.

MOCK UP MODELS

Sticks = 76Height = 33cm

After many trial and failure, we came up with a design to strengthen both or beam/base and also the columns. The way we did this is by attaching a two layered column with groove cut in the middle of them and slot it at all ends of our base/beam.

The outcome was decently strong model but we needed to strengthen it even further so we used a hand drill to punch a hole between each column. We then cut toothpicks into smaller pieces to use as the joint to hold the bracing and the columns together as shown in the picture.

The final model that came up is the picture you see to the left. We continued using the same strategy of applying bracing into the double layered columns to increase the load it may be able to hold. The bracings are places in way to ensure the load distribution is separated equally.

Top View

First Tower

Beam

Beams placed together

Elevation Perspective

FINAL DESIGN MODEL

Weight of Model = 91grams

Load Applied until Break = 50kg

On the day of the testing, we were short on weights as no one was able to bring extra besides the one the lecturer provided for us. The weights provided only reached up until about 42kg. However, we were given permission to use the Taylor’s University gym as they provided more weights to test the model. We took turns entering the gym and started right away when it was our turn. We placed the weight one by one starting from 10kg. We had a bit of a panic attack and took the weights out and replaced it again due to the model suddenly twisting to the side. However, even replacing the weights did not help as the twist in the model caused us to only obtain a 50kg load before it broke.

LOAD TESTING

10kg 30kg20kg20kg 40kg35kg

50kg45kg

ANALYSIS : STRENGTH

MINIMIZE MATERIALWe used as little material as possible because as the weight of the skeletal structure increases, the efficiency decreases.

SLITSThe slits we each cut on the columns are even and neatly done. The slits play a major role on this skeletal structure because it makes the skeletal structure firm on all edges and makes the load rests evenly on it.

COLUMNSThe columns are strong because we realized that the load are spread towards the columns. Hence, we overcame this problem by lapping two popsicle sticks for one column.

There are a few weaknesses in our model that causes structural failure.

1. Inconsistent popsicle stick - The popsicle sticks that come in packs are not the same. A lot of variations in terms of size, shapes, weight and quality. There might also be some deformations in the sticks that we cannot see. A lot of choosing has to be made for the best sticks.

2. Braces are not enough – The braces did contribute to a stiffer model, but in the end the model still twists under pressure. Maybe added bracings that form an X shape will further strengthen the model as a solid whole.

3. Tying – While generally the ties that we made are strong, the ties are not consistent in workmanship and methods. They are tied differently and some are thicker than the others. As result, some can withstand stronger forces and some can’t, making the force distribution unequal.

4. Workmanship – Even though the final model is built with the best workmanship and measurements we can manage, the model is still slightly tilted at the end. This is probably due to small differences in each components that add up to become very obvious.

ANALYSIS : WEAKNESS

In the end, the model withstood a total load of 50kg. After the testing, we calculated the efficiency(E) as below:

E = (Load/Mass of tower)(Height) = (50/91)(33) = 18.13

As conclusion, our model has an efficiency of 18.13. The efficiency might increase if we made each component of the model with better consistency and add more bracings to make the model stiffer, mode solid block. The mass of the model will increase, but the increase in load will definitely overcome the disadvantage of added weight, and achieve the model’s fullest potential.

EFFICIENCY

CONCLUSION