Task:
- Group work
- Construct an arch by Using Plasticine
- To enhance understanding of the arch's structural superiority
What is an arch
An arch is a curved structure that spans a space and may or may not support weight
above it.
Types of arches
circular, pointed, and parabolic
Characteristics of an arch
- Able to span a large area by resolving forces into compressive stresses and, in turn eliminating tensile stresses.
- Can resist compression.
- The greater the degree of curvature (the larger the semicircle of the arch), the greater the effects of tension on the underside of the bridge.
- The more weight that was put onto the bridge, the stronger its structure became.
- A keystone in the middle of the bridge bear the weight of the rest of the bridge.( To solve spanning problem)
Ideas to Make a better Arch/ How to build an arch
- Build a frame ( centring) which exactly follows the form of the underside of the arch to support the arch until the arch is complete and self-supporting.
- Strong foundation to ensure it won't sink
- Strong and heavy material which is good at compression
- Cut plasticine (Stone) properly (Equal Size on both sides)
- Make sure arch is in semi-circle shape to allow weight to transfer effectively
Ideas of Arch that we want to construct
Process
We are given time to construct our very own arch and then we tested it with different loads ( Seismic loads, Dead loads and hailstorm)
Step 1: First, we make the foundation and pillars of the arch. To make it stronger, we also added wooden stick inside the pillars.
Step2: Then, we make the temporary support and cut out plasticine into several pieces
Step 3: We stacked up the pieces of plasticine to make the arch.
Step 4: Lastly, we added some deisgn for the arch to make it more attractive.
We build an arch with the theme of "the connection between human) which involve male and female on both sides
Female
Male
Final Result
After we construct our arch, several tests were started:
- Dead Loads (include smartphones, keys & coins)
- Seismic Load
- Hailstorm
Test was started!!
Dead load test
Seismic Experiment Video..XD
Testing Outcomes
Test
|
Time
|
Result
|
Reason
|
Test 1(Dead load)
|
10sec
|
PASSED
|
Fairly anticipated result, because plasticine(Stone) is good at compression.
|
|
50sec
|
FAILED
|
Height from both sides of arch is not equal.
|
Test 2(Seismic load)
|
|
FAILED
|
Almost every model cannot survive because interfere the mechanism of arch, which is worked by utilizing the gravitational force.
|
Test 3(Hailstorm)
|
|
FAILED
|
Without the support of internal structure to hold the plasticine together, plasticine structure cannot withstand because of low tensile strength.
|
Reasons of failures
*Our arch did not have a huge pillar that can withstand loads that well.
*Unlike most of the team, our arch did not have internal support like wooden stick to make it stronger
*Plasticine on both sides did not precisely cut out and not perfectly balanced
Learning Outcomes:
*We should be more cautious when measuring the size and the shape of the plasticine (Stone) to achieve balance on both sides
*The bigger the foundation the more steady the arch.
*Arch with small span is more steady.
*Arch shape need to be measured before build so that weight can transfer more effectively.
*Keystone need to be in the centre so that the force of the weight load is channeled out and down.
