Download Model Making Workshop — Structure of Tall Buildings and Towers

Science Teaching Kit for Senior Secondary Curriculum
Force and Motion
Model Making
Workshop —
Structure of Tall
Buildings and Towers
[Teacher notes]
Organizer
Sponsor
Research Team
Preamble
Teaching plan
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Lesson 1 : Model Making Workshop - Structure of Tall Buildings and Towers
1.1 Introduction to Tall Buildings
1.2 Loads and Forces on Buildings
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1.2.1 Vertical Forces
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1.2.2 Horizontal Forces
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1.2.3 Internal Forces
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Exercise: Forces on the Structure
1.3 Typical Structural Systems in Tall Buildings
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Project Brief on Tower-Making Workshop
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Summary, Key words and Further reading
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Disclaimer
Create Hong Kong of the Government of the Hong Kong Special Administrative Region provides funding support to the project only, and does not otherwise take part
in the project. Any opinions, findings, conclusions or recommendations expressed in these materials/events (or by members of the project team) do not reflect the
views of the Government of the Hong Kong Special Administrative Region.
© 2012 Hong Kong Institute of Architects
Science | Model Making Workshop — Structure of Tall Buildings and Towers
Contents
Topic 03
Model Making Workshop —
Structure of Tall Buildings and Towers
Major teaching areas
Interdisciplinary teaching areas
Physics: Chapter II Force and Motion
Design and Applied Technology
• Strand 1 Design and Innovation
•
Force and motion
Strand 2 Technological Principles
Related teaching areas
Physics: Chapter X Investigative Study in Physics
Learning objectives
•
To understand the forces acting on a stable structure
•
To learn the major structural systems for buildings
•
To apply new knowledge in a hands-on exercise
Teaching plan
Lesson
Lesson 1
Contents
•
1.1
Introduction to tall buildings
Model Making Workshop
— Structure of Tall
Buildings and Towers
•
1.2
Explanation of the forces that act on buildings
•
Exercise Understanding of internal and shear forces, structural elements,
and the relationship between action and reaction
•
1.3
Examples of typical structural systems for high-rise buildings
•
Project
Brief and assessment methods for tower-making workshop
Science | Model Making Workshop — Structure of Tall Buildings and Towers
•
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Science | Model Making Workshop — Structure of Tall Buildings and Towers
Lesson 1
Model Making Workshop —
Structure of Tall Buildings and
Towers
01
Lesson 1
Model Making Workshop —
Structure of Tall Buildings and Towers
1.1 Introduction to Tall Buildings
Tall buildings are symbolic elements within any city, carrying significant political, social, cultural and
even religious meanings. Today cities compete to produce the tallest building in the world as a way of
showcasing financial and economic power. Understanding the structures of these buildings, and how
they support themselves as well as the loads imposed on them by the environment, is a fascinating
way to see the real-life applications of physics.
Science | Model Making Workshop — Structure of Tall Buildings and Towers
q The Eiffel Tower is a 320-m-high steel
structure that was completed in 1889 as the
entrance arch for that year’s World’s Fair.
p The Leaning Tower of Pisa (55.86 m)
was built in 1372, using marble stone in
a Romanesque style. Its current leaning
appearance is due to sub-soil settlement.
02
In the early 20th century, cities became bigger
and denser. Urban populations were growing
but land supply was limited. High-rise buildings
became an essential solution to the problem.
New technologies and building materials, such
as industrial reinforced concrete, steel and
elevators, made high-rise structures feasible and
drove innovation.
Science | Model Making Workshop — Structure of Tall Buildings and Towers
t The 90-m-high Royal Liver Building in
Liverpool was one of the first concrete
buildings in the world. It was completed in
1911 after a Neoclassical design by Walter A.
Thomas. © Chowells - Wikipedia User
p The modernist Wainwright Building p Equitable Life Assurance Building in New York was completed in 1890. It was
in St. Louis was completed in 1891
the first building equipped with elevators. It was destroyed by the fire in
by architects Dankmar Adler &
1912.
Louis Sullivan. Its 10 storeys are
supported by an early steel framing
The 36-storey Equitable Building in New York was completed in 1915. Its
system.
architect, Ernest R. Graham, used a Neoclassical style despite the building’s
modernity. It triggered the implementation of height limits and setbacks for
tall buildings to allow sunlight to reach street level.
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1.2 Loads and Forces on Buildings
The statics of a building deal with its structural stability. When an
object is in equilibrium, the sum of all forces equals zero. Various
forces from the environment, the weight of the building elements,
furniture and equipment installations, users and other sources act
on the building structure. There are three types of loads generally:
Dead Load
Dead loads are the loads of the structure and fixed components.
It is a permanent force that is relatively constant for a extended
period of time. The force is gravitational.
Live Load
Live load is a changing force generated by mobile objects inside
the building, such as people within the building or stock in a
warehouse. The force is gravitational.
Environmental Loads
e.g. Wind
Live loads
e.g. Weight of
people at the
building
1.2.1 Vertical Forces
Dead loads and live loads contribute to the vertical forces on the
structure of buildings. Vertical loads are transferred from the floors
to the columns and walls, and eventually to the soil or bedrock. At
times, environmental loads also act vertically.
p Live loads, dead loads and environmental
loads are the three major types of forces
on the Bank of China Tower. The loads are
transferred to the ground via columns and
pilings.
1.2.2 Horizontal Forces
Environmental loads contribute most of the horizontal forces
acting on the structure of a building, with loads from wind being
the most common. Architects refer to these horizontal forces
as shear force. Adding cross bracing or shear walls can improve
structural resistance to shear forces.
Compressive force
1.2.3 Internal Forces
The internal strength of the entire structure must be equal to or
larger than the total forces applied on the building in order to stay
in equilibrium. The ability to withstand all forces depends on the
structural component’s dimensions and the solidity and elasticity
of the material. Internal forces include compressive force, tensile
force and torque.
Science | Model Making Workshop — Structure of Tall Buildings and Towers
Environmental Load
Environmental loads are forces acting on the building from its
environment and may include wind, rain, earthquakes and
temperature changes. The forces created can be either horizontal
or vertical, positive or negative.
Dead loads
e.g. Weight of the
building
Tensile force
Compressive and Tensile Forces
According to Newton’s Third Law, forces act in pairs. In structural
terms, tensile force pulls a structural element apart while
compressive force compresses it.
Torque
If opposing forces are applied at different points, a structural
element may become twisted. This is called torque in the building
industry.
Torque
p Internal forces in a structural element
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[Exercise]
Forces on the Structure
1
Illustrate the action and reaction pairs, and distinguish dead loads and live loads acting on the following structure. Assume the weight of the mass is FA and the weight of each building block is FB , and the structure is in equilibrium.
Possible perspectives
The weight of mass ( FA ) is the live load and the total weight of
the structural blocks ( 3FB ) is the dead load.
1. Action by the mass on the block = FA
Reaction by the block on the mass = FA
2
3. Action by each vertical block on the ground
= 0.5 (FA + FB) + FB
Reaction by the ground on each vertical block
= 0.5 (FA + FB) + FB
Can you identify the internal forces acting on each piece of the structure? What paths do they take?
Compression
Tension
Loads
Stress points
3
Possible perspectives
The horizontal structural block is supported at two points. When a
force is applied on the member between the two points, the upper
surface of the member is in compression where the lower surface is
in tension.
On the other hand, vertical structural blocks are in compression
mainly. The loads are then transferred to the earth.
This shows the difference between the load-supporting behaviours
of vertical members (e.g. columns and wall) and horizontal members
(e.g. floor and ceiling). When the internal strength of a structural
member cannot withstand the loads imposed on it, it will buckle or
even break at the most stressed point.
Science | Model Making Workshop — Structure of Tall Buildings and Towers
2. Action by the horizontal block on each vertical block
= 0.5 (FA + FB)
Reaction by each vertical block on the horizontal block
= 0.5 (FA + FB)
How would you modify the below structure to resist shear force?
Possible perspectives
Cross bracing can be added at the joints of the horizontal and
vertical block.
Cross bracing is usually constructed of diagonal supports between
structural members. It can resist both compression and tension
forces, depending on the direction of the shear forces acting on the
building.
Shear Force
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1.3 Typical Structural Systems in Tall Buildings
Outrigger
Core
Columns
Core and Outrigger structure
The International Commerce Centre is built using a ‘Core
and Outrigger’ concept. The core at the centre of the
building bears most of the vertical load, while columns
at the perimeter carry less weight and are thus smaller
in dimension. Loads are transferred to the core through
steel outriggers that balance the lateral forces on the
whole building.
p Outrigger connecting the core and the columns
s
Columns at the perimeter
carry less weight.
Weight is centralised to
the core.
Outriggers help balancing
lateral forces.
p Plan of International Commerce Centre
Steel
Steel is a common construction material for tall buildings because it has good
performance in withstanding compressive and tensile forces, as opposed
to concrete’s low tensile strength in compression. Steel bars can be used
to reinforce concrete to add extra structural performance. However, steel is
relatively weak in fire-resistance. An extra layer of fire-resisting coating is often
put onto the steel surface.
Science | Model Making Workshop — Structure of Tall Buildings and Towers
p Installation of outriggers at the International Commerce
Centre © Raymond Wong
The Bank of China Tower is a steel trussed-tube structure. The whole building
acts as a single tubular truss, with the diagonals wrapping the building to
transfer loads.
Teaching Tips
Field trips to Central can be organized to
facilitate the learning of high-rise structure,
can refer to Science Topic 02: ‘VISIT: Central
- Structure of Skyscrapers ’.
Teaching Tips
More information on the construction
process, can refer to Design and Applied
Technology Topic 02: ‘Construction Process Victoria Park Swimming Pool Complex ’.
p Bank of China Tower
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result
External
force
External
force
result
External
force
Co
m
pr
es
sio
n
External
force
m
Co
Tension
Truss
Trusses are a very common structural
element in architecture. Steel
members are joined together into
triangular shapes, which are very
strong and able to resist external
forces. When joined together, these
triangles can form large truss systems
that can span long distances.
n
io
s
es
pr
Science | Model Making Workshop — Structure of Tall Buildings and Towers
q Common types of truss
© Structural Building Components Association
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Project
Model Making Workshop — Tower
Project
Model Making Workshop — Tower
Divide the class into groups of four to five students. Each group is required to build a tower that should be:
• structurally stable and aesthetically pleasing
• tall
• lightweight
• resistant to horizontal forces
• able to support a heavy load
Submit a laboratory group report after the workshop.
needed
Sketching papers and pencil
Scissors, cutters, tape, glue
Different weights (10 g/ 50 g/ 100 g/ 500 g/ 1 kg)
Weight scale
Measuring tape
Electric fans
Suggested materials
• Cardboard
• Bamboo sticks
• Recycled cans
• Recycled plastic bottles
• Fishing line
Assessment criterias:
Tests
Structural stability
Aesthetics
Height
Weight-height ratio
Resistance to wind
Load supporting
p Using rope to join the components
Descriptions
The tower should be free-standing without external supports.
Score
20
The teacher will judge the beauty of the tower and will give a score.
Measure the height of the tower from the ground to the highest point. The
tallest tower gets the highest score.
Weigh the tower and find out the weight-height ratio. The tower with the
smallest ratio will get the highest score.
0 - 10
10 - 20
R=
W
H
Blow the tower from the side with an electric fan. The tower that does
not fall will get the highest score.
10 - 20
Science | Model Making Workshop — Structure of Tall Buildings and Towers
Tools
• • • • • • 10
Test the maximum weight that the tower can support. The weight needs to
10 -20
be placed above the ground. Students should be able to explain how load is
transferred to the ground.
Total score 100
Teacher tips: To make the workshop more informative, teachers are recommended to summarize critical factors for a
light-weight and stable tower. Evaluations are useful to point out the reasons for structural failure.
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Summary
1.
2.
3.
4.
Although humans have long attempted to build tall structures, skyscrapers began to appear in our cities in the late 19th century as a result of technological breakthroughs in building materials and methods, including reinforced concrete, steel and elevators.
Buildings bear three types of loads: dead loads, live loads and environmental loads.
All loads are resolved into vertical and horizontal forces on the structure.
Typical structural systems used in tall buildings include core and outrigger structures, steel frames and trusses.
Key words
Further reading
1. Foster, Jack Stroud, Raymond Harington, and Roger Greeno. Structure and Fabric. 7th ed. Harlow: Pearson Prentice Hall, 2007.
2. Brotrueck, Tanja, Basic: Roof construction. Basel: Birhaeuser, 2007.
Organizer
Sponsor
Research Team
Science | Model Making Workshop — Structure of Tall Buildings and Towers
High-rise buildings
Skyscraper
Tower
Structure
Force
Equilibrium