History, basic concept, production and erection of prefabricated structures

1. 3. Prefabrication & Prefabricated
Structures
MSc Program in Construction Technology and
Management
College of Engineering & Technology
Department of Construction Technology & Management,
Wachemo University
Behailu Z. (Ph.D. Candidate)
2023/24

2. 3. Prefabrication and
Prefabricated Structures
Behailu Z. (Ph.D. Cand.)

3.  21st century design technologies present us with endless
possibilities to ‘rethink’ how we design and manufacture
and:
 create a shift from mass-production to mass-
customization;
 embrace parametric modelling for site specific,
value driven responses;
 maximize the interface of these technologies
with manufacturing.
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

4.  Social, economic and environmental factors suggest an
urgent need to consider new ways to build. These factors
include:
 shortages of skilled trade labour in many communities;
 need for increased construction quality and lower costs;
 need to improve construction productivity;
 need for more sustainable, cradle to cradle solutions;
 increased acceptance of quality prefabrication.
Behailu Z. (Ph.D. Cand.)
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

5. Behailu Z. (Ph.D. Cand.)
5
Prefabricated homes were produced during the Gold Rush in the United States, when
kits were produced to enable Californian prospectors to quickly construct accommodation
Prefabricated housing was popular during World War II due to the need for mass
accommodation for military personnel.
The world's first prefabricated, pre-cast panelled apartment blocks were pioneered in
Liverpool
Many buildings were designed with a five-ten year life span, but have far exceeded this,
with a number surviving today.
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

6. What is prefabrication?
Prefabrication is the practice of assembling components of a structure in
a factory or other manufacturing site, and transporting complete assemblies or
sub-assemblies to the construction site where the structure is to be located.
 It is combination of good design with modern high performance components and
quality controlled manufacturing procedures.
This work is carried out in two stages, manufacturing of components in a place
other than final location and their erection in position.
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Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

7. Prefabricated sections are produced in large quantities in a factory and then shipped to
various construction sites.
This procedure may allow work to continue despite poor weather conditions and should
reduce any waste in time and material at the site.
Precast concrete units are cast and hardened before being used for construction
Sometimes builders cast components at the building site and hoist them into place after
they harden.
This technique permits the speedy erection of structures.
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Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

8.  The Prefabrication as defined will be done in two stages Manufacturing
at factory condition and erection of components at the required location.
 This requires certain stages of preparation. They are
a) Casting.
b) Curing.
c) Transportation and erection.
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Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

9. a) Casting
Precast components are casted with
controlled cement concrete in moulds
of required shape and sizes.
The vibrator is used to vibrate
concrete and this removes any
honeycombing inside the components.
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Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

10. b) Curing
After 24 hours of casting, the
casted components are released
from the mould and transported to
curing tanks. Certain special
components like railway sleepers
where high strength is required are
steam cured.
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Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

11. c) Transportation and erection
After complete curing is done the
components are transported to the
site with heavy trucks and erection
will be done using cranes with
skilled labour force.
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Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

12. PARTIAL - PRE FABRICATION
In India, partial prefabrication
has been well suited.
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Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

13. Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures
Conceptual and Historical Overview

14. Some of the prefabricated components are as explained below
a) Columns
 A column is a vertical member carrying the beam and floor loadings to the
foundation.
 It is a compression member and therefore the column connection is
required to be proper.
 The main principle involved in making column connections is to ensure
continuity and this can be achieved by a variety of methods.
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PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

15. 15
Column to Column
Connection
PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

16. b) Beams
Beams can vary in their complexity of design and reinforcement
from the very simple beam formed over an isolated opening to the
more common encountered in frames where the beams transfer
their loadings to the column.
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PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

17. b) Beams
Methods of connecting beams and columns are
A precasting concrete haunch is cast on to the column with a locating dowel or
stud bolt to fix the beam.
A projecting metal corbel is fixed to the column and the beam is bolted to the
corbel.
Column and beam reinforcement, generally in the form of hooks, are left exposed.
The two members are hooked together and covered with insitu concrete to
complete the joint.
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PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

18. 18
Beam to
Column
Connection
PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

19. 19
Beam to Beam
Connection
PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

20. c) Waffle unit for flooring / roofing
These are suitable for roofs / floors spanning in two directions.
They are laid in a grid pattern.
 These units are cast in moulds.
The saving achieved is not much. Also Shuttering are complicated and
costly.
Time consumption for construction is less
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PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

21. 21
PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

22. 22
Slab to Beam
Connection
PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

23. 23
Glance at building
process
PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

24. 24
Glance at building
process
PREFAB BUILDING COMPONENTS
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

25. Advantages:
Saving in cost, material, time & manpower.
Shuttering and scaffolding is not necessary.
Installation of building services and finishes can be done immediately.
Independent of weather condition.
Components produced at close supervision .so quality is good
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ADVANTAGES AND DISADVANTAGES
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

26. Advantages:
Clean and dry work at site.
 Possibility of alterations and reuse
Correct shape and dimensions and sharp edges are maintained.
Very thin sections can be entirely precast with precision.
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ADVANTAGES AND DISADVANTAGES
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

27. Disadvantages:
 Handling and transportation may cause breakages of members during
the transit and extra provision is to be made.
Difficulty in connecting precast units so as to produce same effect as
monolithic. This leads to non-monolithic construction.
They are to be exactly placed in position, otherwise the loads coming on
them are likely to get changed and the member may be affected.
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ADVANTAGES AND DISADVANTAGES
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

28. Disadvantages:
High transport cost
Need of erection equipment
Skilled labour and supervision is required.
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ADVANTAGES AND DISADVANTAGES
Behailu Z. (Ph.D. Cand.)
Prefabrication and Prefabricated Structures

29. THANK YOU!
Behailu Z. (Ph.D. Cand.) 29
Behailu Z. (Ph.D. Cand.)

30. Individual Assignment
Behailu Z. (Ph.D. Cand.)
30
1. Discuss the key stakeholders and their drives in
prefabrication.
2. Write short note on the challenges and possible solutions of
the Ethiopian Industrial Construction Technologies.