1) The document discusses the design and testing of a popsicle stick tower model. Different designs for the tower are considered, including shape, layering, joint type, and bracing configurations. 2) The completed tower model used a double layer vertical column design with slot-in joints. Additional horizontal sticks and alternating horizontal beam gaps were used to better transfer load. 3) During testing, the tower failed due to structural instability from inaccurate measurements, lack of internal bracing, and weak joints from pinning. The failure occurred from torsion forces rather than downward compression as the bracing design intended.

1. LAU EE TIAN
0309596
CH’NG XING YUE
0310425
Project 1: Understanding Forces in Skeletal Structure
FAM LI KIAN
0310639
WESLEY HEW XIN HAN
0307585
GOH CHIN ZHI
03145623
ELAINE BONG POH HUI
0310432
• • • • •

2. There are several type of forces has been applied into a popsicle sticks tower. The internal forces included tension force, torsion force, shear
strength, bending force and compression force.
Triangular Square
• Lessen the amount of sticks used by an estimation of 25% but
reduces the stability of the tower as the base surface area is lower.
• Remain in shape well when force is applied.
• Higher stability and more vertical columns to support the tower but
will increase the mass of tower.
• Easily deformed when force is exerted to the shape.

3. Double Layer Single Layer
Strength • Able to withstand higher pressure by increasing
the contact surface area of the popsicle sticks.
• Able to tolerate stronger compression force.
• Lighten the weight of the tower and the amount of
popsicle sticks used to increase the efficiency of the
tower.
• Time span on construction is shorten.
Weakness • Increase the weight of the tower and amount of
popsicle sticks used reducing the efficiency of the
tower
• Work labor is increased
• Increases the stress received as the force does not
distribute to other popsicle sticks.
• Hard to combine the sticks together without using
slot in
• The horizontal sticks acting as the beam for the tower are
placed upwards to reduce the possibility of the bending of the
sticks as easily as horizontally positioned stick due to the
rigidness and inflexibility of popsicle sticks.
• Upward placed stick will receive more pressure than horizontally
positioned stick due to its smaller surface area, so double layer
pinned together strengthen the joint making it acting as a three layer
unit channeling the force from the top to bottom.

4. Slot-in with groove
• Will reduce the structural strength of the sticks as it will break more easily when force is
exerted
• It might cause the sticks to split into half when force is applied
• It is easier to combine the sticks together using slot in compared to other methods
• Transfer of load is more efficient and direct
• The use of pin might causes the stick to split according to the direction of wood rays
• Able to fix all sticks together firmly
Slot-in with double layer
• Requires more sticks and very strong bond joining all three sticks to ensure the load force
transfer down all three sticks as one unit
• Might break easily at the joint if the load doesn’t transfer vertically down as the slot-ins are at
the end of the sticks

5. Square Lashing Diagonal Lashing
Strength - More aesthetic and neat
- Use lesser string
- Lesser contact area with the vertical
popsicle stick, hence lesser pressure
applying to the popsicle stick and causes
it to break
- Distribute more force among threads
- Able to hold the popsicle stick in position more
firmly
Weakness - Higher tension force in thread compared to
diagonal lashing
- Requires more effort and more time consuming in
comparison to square lashing

6. Strength • Able to withstand greater pressure and weight due to the spreading of force.
Weakness • The center point between two bracing become the weak point due to the
intersection of force hence easier to break.
Strength • To avoid the popsicle sticks intersection with the popsicle sticks of other floors
Weakness • Increases the height of the tower hence the center of gravity is higher, weaker
the stability of tower
Strength • Avoid unnecessary extra weight to increase the efficiency of tower
Weakness • Increases the chance of breaking due to less spreading of force at vertical
columns
Strength
Weakness Joint is extended beyond boundaries causing tower to be unstable on smaller points.
Small area of force creates higher pressure even with low force being applied.

7. Strength Ensuring force from shorter brace can be transferred to horizontal bracing.
Weakness Exertion of force is not efficient. Joints might break when pressure is applied.
Strength Reduces force applied on horizontal bracing by transferring it to the vertical and
diagonal brace.
Weakness Single diagonal bracing may cause tower to twist in a spiral motion .
Strength Larger surface reduces amount for pressure and force being transferred to the
ground.
Weakness Spiral direction of force abruptly ends as diagonal bracing isn’t directly in contact with
ground surface.

8. Strength • Withstand the greatest pressure among all bracings due to it’s triangular design
Weakness • Horizontal sticks become the weak point due to uneven distribution of forces/
sudden pressure.
• Might break at the top part when large force is exerted due to weak bonding
strength of slot in bracing
Strength Ensuring force from shorter brace can be transferred to horizontal bracing.
Weakness Extension has fewer proper connection that may result in rigid stance.
Strength Larger surface reduces amount for pressure and force being transferred to the
ground.
Weakness Horizontal brace absorbs less pressure as force from 3 directions are transferred to
end points instead.

9. Mass of tower: 137g
Total of sticks used: 96 sticks
Time span: 2 minutes 10 seconds
Efficiency of tower =
=
= 9.27
Load Held (g)
Mass of Tower (g) X Height of Tower (cm)
40000g
137g X 31.5cm
Bracing used: Bracing 2
Double layer vertical columns
Joint used:

11. Tower before model testing
• The force of the tower supposedly
to move in torsion and downwards
vertically.
• The vertical supports were
strengthen with double layer
• Additional horizontal sticks were
added at the extension gap to allow
the load from the top to transfer to the
horizontal beams below and not just
rely solely on the vertical supports.
• Alternating gaps of horizontal
beams were used(without
changing the degree or length of
the slanted bracing).
• This reduces the length of the
columns in between the
horizontal beams and increases
the load capacity.
gap
Added horizontal
sticks

12. Precision of the tower is very important as inaccurate measurements lead to uneven distribution of forces and contribute to the racking of the
structure. Tower built using double layer slot -ins requires higher level of accuracy due to its more complicated structure than single layer tower with
slot-ins that have grooves. This makes single layer tower easier to construct and have lighter mass but double layer structure could withstand more
load if it is built well.
Besides, internal bracings could be added to the tower to prevent the deformation of the vertical and horizontal structures.
• The tower was not
structurally straight in the
first place. Hence torsion in
opposite direction of the
bracing happened once
weight are applied. This was
the main reason of the
structure failure since the
bracings and columns could
not perform their function
well as supposed to transfer
the load.
• Since the force was wrongly
transferred, it falls on one
side at the end and causes
the horizontal element at
one of the corners breaks.
• Lack of internal bracing
allowed the deformation of
the tower to happen.
• Besides, joining the popsicle
sticks by using pin made
them crack. It might weaken
the ability of the sticks to
transfer load as it will split
with strong shear force.
• The bottom part of the tower
is still in good condition
proves that the force are not
going downwards efficiently.
Tower after model testing