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University of Minho Czech Technical University in Prague
University of Padova Technical University of Catalonia ARCCHIP- ITAM
300 mm
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250 mm250 mm
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500 mm
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Perfil HEM140Localização do antigo soalho 250 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
Contents
1. Introduction2. History of the Use of Iron in Construction and Restoration3. Iron in Ancient Greek Architecture4. Material Properties5. Material Identification6. Deterioration7. Inspection8. Repair and Maintenance9. Case Study – The Parthenon10. 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
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
• 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
• Transition from meteoric to terrestrial iron Iron Age c. 2000BC
• First iron type to be manufactured
• Largely replaces copper
Wrought Iron
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Wrought Iron – Production Techniques
• Smelting in bloomeries
• Introduction of coke
• Osmond process
• Finery Process
• Puddling + Rolling
• 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
Wrought Iron – Structural Uses
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
• First produced in China 6th century BC
• Introduced in Europe 13th century AD
Cast Iron
• 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 – Production Techniques
• Arched bridges and aqueducts
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Cast Iron – Structural Uses
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
• 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
• 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• 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
Historical Application ExampleAncient Greek Architecture
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
• 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
• 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
• 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
• 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 MethodsReplacement & complementingCold repair of members, mixing of alloysProtective coatings: painting, electroplating, Bower-
Barff methodCathodic protection
• Modern methodsCompatibility established by chemical methodsMild steelWeldingPassivation layer
A. Drougas – Investigation of the Use of Iron in Construction from Antiquity to the Technical Revolution
Case Study – The Parthenon
• 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 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 structureLonger tension elements usedJoints not securely closedMechanical 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 titaniumDesigned according to Ultimate State philosophyElements fail after anchoring areaMaterial 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• 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