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 • • • • •

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.

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.

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

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

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.

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.

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.

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:

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

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