250 mm
250 mm
Perfil HEM140
250 mm
60 mm
150 mm
300 mm
500 mm
65 mm
100 mm
500 mm
30 mm
Localização do
antigo soalho
300 mm
Localização das novas vigas
secundárias em castanho
Investigation of the Use of Iron in Construction
from Antiquity to the Technical Revolution
Anastasios Drougas
Universitat Politècnica de Catalunya
Department of Construction Engineering
Barcelona, Spain
a_drougas@yahoo.gr
University of Minho
University of Padova
Czech Technical University in Prague
Technical University of Catalonia
ARCCHIP- ITAM
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Contents
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10.
Introduction
History of the Use of Iron in Construction and Restoration
Iron in Ancient Greek Architecture
Material Properties
Material Identification
Deterioration
Inspection
Repair and Maintenance
Case Study – The Parthenon
Conclusions
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
History of the Use of Iron
in Construction and Restoration
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Alloy Types
Historical Production Techniques
Application Typologies in Construction
Extent of Use and Examples
Iron as a Restoration Material
Further Aspects of Iron Production and Use
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Wrought Iron
• Transition from meteoric to terrestrial iron
 Iron Age c. 2000BC
• First iron type to be manufactured
• Largely replaces copper
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Wrought Iron – Production
Techniques
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Smelting in bloomeries
Introduction of coke
Osmond process
Finery Process
Puddling + Rolling
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Wrought Iron – Structural Uses
• Clamps and dowels in masonry
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Wrought Iron – Structural Uses
• Connections in timber
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Wrought Iron – Structural Uses
• Gothic architecture
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Wrought Iron – Structural Uses
• Reinforcement of masonry assemblies
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Wrought Iron – Structural Uses
• Riveted wrought iron members
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Cast Iron
• First produced in China 6th century BC
• Introduced in Europe 13th century AD
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Cast Iron – Production Techniques
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Smelting in presence of phosphorus
Chinese puddling
Water powered bellows
Blast furnace
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Cast Iron – Structural Uses
• Arched bridges and aqueducts
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Cast Iron – Structural Uses
• Columns, piers and beams
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Cast Iron – Structural Uses
• Skeletal structures
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Steel
• Produced as early as wrought iron
• Much more expensive and time
consuming to produce
• Wrought iron was preferred as a structural
material
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Steel – Production Techniques
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Smelting in bloomeries
Melting of wrought with cast iron
Cementation process
Bessemer process
Open-hearth process
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Steel – Structural Uses
• Mixed systems with wrought or cast iron
• Replacement of wrought iron in all
applications
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Iron as a Restoration Material Historical Applications
• Tension ties in arches – Replacement of timber
ties
• Crack bridging in masonry with clamps
• Bracing and repair of timber members and
trusses
• Mechanical pinning
• Fire proofing of textile mills
• Strengthening of cast iron bridges with wrought
iron or steel girders
• Historically, opinions of experts clash
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Iron as a Restoration Material Modern Applications
• Its use encouraged in steel frames and R.C.
rebars by the Athens Charter (1931)
• Criticized by the Venice Charter (1964)
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Iron as a Restoration Material Modern Applications
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Confining straps in adobe
Tension ties in brick and stone masonry
Steel connection plates in timber trusses
Bracing trusses in damaged R.C. structures
Temporary bracing
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Further Aspects of Iron Production and Use
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Production rates
Production cost
New structural needs
Grasp of material properties
Design and analysis methods
Building methods and construction management
Development of structural systems
Attained spans and heights
Rapid development in all fields
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Historical Application Example
Ancient Greek Architecture
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Introduction of iron to Greek territory
Production techniques
Application typologies
Development of applications
Structural role
Iron as a restoration material
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Introduction of Iron to Greek Territory
• Forceful import from the East (Caucasus) after
the 11th century
• Rapid development after 7th century; possible
influence from central Europe
• Indications of knowledge of rudimentary heat
welding and iron alloy casting
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Iron Production Tecniques
• Advanced form of smelting for items of high
quality
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Iron in Ancient Greek Architecture
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•
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Horizontal connections
Vertical connection
Structural reinforcement
Various minor uses
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Horizontal Connection
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Vertical Connection
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Structural Reinforcement
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Structural Reinforcement
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Structural Reinforcement
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Structural Reinforcement
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Structural Reinforcement
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Structural Role of Iron in Ancient Greek Architecture
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•
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Relieves stresses from stone blocks
Prevents overall structural movement
Allows greater spans
Reduces self weight of superstructure
Prevents relative movement of stone blocks
during construction and in the final setup
• Stressed near its elastic limit
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Experimental and Numerical Investigation
• Mainly associated with restoration projects
• Verification of design approaches for structural
intervention
• Restoration of tensile connecting elements often
reduces risk of collapse
• Dowel influence in joint strength is often very
small
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Iron in Historic Restoration of Ancient Greek Architecture
• Ancient practices only partially followed in
restoration of connecting elements
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Iron in Historic Restoration of Ancient Greek Architecture
• Use of iron frames and rebars in R.C.
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Iron in Historic Restoration of Ancient Greek Architecture
• Resulted in further damage, loss of architectural
fabric and structural authenticity
• Main problems caused by corrosion and
mechanical strain
• Iron use influenced by contemporary
construction practices in building engineering
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Iron in Modern Restoration of Ancient Greek Architecture
• Largely replaced by other materials, such as
titanium, FRP and stainless steel
• Restoration projects focus on removal of
corroded iron
• Minor applications include temporary bracing
with steel frames and confinement
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Properties of Iron
• General properties of each alloy
• Effect of properties in every alloy’s adoption for
specific historical structural uses
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Wrought Iron
• Orthotropic behaviour, high strength  Replaces
timber in several applications
• Properties depend on raw material and shaping
process
• Strength is more consistent than ductility
• May have superior corrosion resistance than
that of steel
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Cast Iron
• Strong in compression, weak in tension 
Replaces masonry in several applications
• High fire resistance  Used for fireproofing of
industrial buildings
• High corrosion resistance
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Steel
• Isotropic behaviour, high strength and elastic
modulus, production methods produce different
batches of highly consistent properties  Has
replaced all other iron alloys in construction
• May corrode easily
• Properties require careful chemical control
during production, carbon content is the chief
parameter
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Material Identification
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•
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Visual inspection and historical knowledge
Member typologies
Spark test
Breaking test
• Microstructure investigation
• Chemical testing
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Historical Iron Deterioration
• % of affected material 
Electrochemical>Chemical>Mechanical
• Development Speed 
Mechanical>Chemical>Electrochemical
• Frequency 
Electrochemical>Mechanical>Chemical
• Biological deterioration usually aggravates
corrosion
• Iron deterioration greatly affects neighbouring
historical materials
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Historical Iron Inspection
• Historical data often available
• Historical testing techniques  Percussion,
spark test, liquid penetrant method, hardness
test, tension test, impact test
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Historical Iron Deterioration
• Historical data often available
• Historical testing techniques  Percussion,
spark test, liquid penetrant method, hardness
test, tension test, impact test
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Historical Iron Repair & Maintenance
• Historical Methods
 Replacement & complementing
 Cold repair of members, mixing of alloys
 Protective coatings: painting, electroplating, BowerBarff method
 Cathodic protection
• Modern methods
 Compatibility established by chemical methods
 Mild steel
 Welding
 Passivation layer
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Case Study – The Parthenon
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Structural layout and brief historical overview
Description of connecting element types
Pathology of connecting elements
Restoration of connecting elements
Restorations incorporating iron
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Structural layout and brief historical overview
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Description of connecting element types
• Clamps and dowels
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Description of connecting element types
• Clamps and dowels
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Description of connecting element types
• Placement along the length of the stone assemblies
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Description of connecting element types
• Sufficient tension anchoring area
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Description of connecting element types
• Investigation to determine mechanical properties
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Description of connecting element types
• Structural function
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
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Invisible substitute for mortar
Prevent small movement during placement
Clamps also work in shear and dowels also work in tension
Dynamic loads on assemblies cause such deformations that
clamps primarily function in shear and not in tension
 Relative displacements are larger in horizontal joints; dowels are
more stressed than clamps
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Pathology of Connecting Elements
• Corrosion
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Pathology of Connecting Elements
• Forced removal and loss
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Pathology of Connecting Elements
• Mechanical failure
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Stone Pathology due to Iron
• Stone fails first in shear
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Restoration of Iron Elements
• Historical efforts
 Iron/lead ratio larger than in original structure
 Longer tension elements used
 Joints not securely closed
 Mechanical pinning
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Restoration of Iron Elements
• Modern efforts
 Iron replaced by titanium
 Designed according to Ultimate State philosophy
 Elements fail after anchoring area
 Material ductility  Elements function when deformed
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Iron in Restoration of the Monument
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Joining of fragmented stones with iron clamps
Mechanical pinning
Rebars in R.C. anchored in original marble
Stainless steel rejected in modern efforts
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Conclusions
• Chemical compatibility is satisfactory, new material is appropriate
• Mechanical properties of material for intended function are
appropriate
• Marginal understanding of structural function when restoration was
compiled, only on a local level and not on the structure as a whole
• ULS without safety level assessment
• Experimental and numerical approaches have not completely
verified design approach
• Restoration of iron elements may perpetuate the deterioration
mechanisms it aims to remedy
• Elements do not contribute to preservation of architectural or
structural authenticity
• Contribution of elements to safety against earthquake action is null
for some assemblies, such as walls
• A rethinking of the design and execution approach for connecting
elements is necessary