Abstract
Sitecure is a technology developed by the author to enable advanced FRP materials (Prepreg) to be applied to infrastructure on-site in raw form, whilst maintaining the same mechanical and environmental benefits realised in the aerospace industry.
Site-Cure uses vacuum consolidation to wrap and consolidate raw Prepreg material to infrastructure, and applies steam to the surface of the sealed vacuum bag in a controlled fashion, heat curing and bonding the FRP laminate in a repeatable way that no other on-site FRP application can match for mechanical performance and durability. It takes the advantages of both systems currently used for infrastructure rehabilitation (fibre wrap and prefabricated strips), whilst eliminating the disadvantages.
This thesis examines the important aspects concerning the Sitecure application of FRP to concrete, steel, and timber, with a specific structural focus on bridges and fatigue focus on steel. The work recorded here is a combination of both in-laboratory detailed testing, and full-scale, on-site applications.
Chapter 2 is a literature review concerning the role of FRP’s in infrastructure repair and details the important properties and environmental resistance needed for a successful repair. It details the current commercial techniques used, Fibre Wrap and Prefab, discussing the advantages and disadvantages with each system, then introduces the Sitecure process in detail.
Chapter 3 examines the effects of the Sitecure process on the development of the mechanical properties of the FRP. The resin system provides the bond mechanism with which load is transferred from the structure to the fibre and between individual fibres. Several resin properties together determine how efficiently this is achieved and how durable it will be under extreme environmental conditions. Resin system properties appear sensitive to cure schedule (temperature ramp rates, final dwell temperatures and dwell Mmes) and it is important to maximise the properties that are important to infrastructure repair. An experimental program investigated:
1. Inter-laminar shear strength and modulus: (load transfer mechanism and bond strength to concrete)
2. Fracture toughness: (durability, resistance to peel failure)
3. Compressive strength: (resistance to fibre buckling, a peel failure mechanism)4. Void levels: (dictates fatigue life, moisture uptake and associated property degradation)
5. Glass transition temperature: Tg (temperature at which load carrying capacity is lost)
A discussion follows on the relative importance of each property and how different applications may call for performance in different properties. A minimum performance level in each property is established, and from this, a range of acceptable cure schedules are determined. Prepreg systems from several different suppliers are examined and a testing procedure is developed(prequalification) to help determine whether various FRP systems meet the minimum mechanical properties and durability required for infrastructure repair.
Chapter 4 looks at the effects of the Site-Cure process on concrete. Elevated temperature exposure has been shown to have effects on the concrete microstructure, as well as various concrete properties including fracture toughness, compressive and tensile strength and modulus. An extensive literature review shows that most studies are in relation to fire and nuclear radiation exposure and do not cover the lower temperature and duration exposures of the Site-Cure process. Compressive cylinder tests were conducted to assess the effects of a broad range of Site-Cure steam exposures.
Finally, Chapter 5 looks at specific problems related to Western Australian infrastructure that now have FRP solutions incorporating Sitecure. These are, concrete flexural strengthening, fatigue strengthening of steel structures, rehabilitation of corroded steel structures, and rehabilitation of degraded wooden structures. The fundamental behaviour of composite materials is discussed along with the elementary guidelines required by structural engineers when considering the use of composite materials in infrastructure repair. It will be shown, through testing, how these materials can be used to gain significant strength, stiffness and fatigue performance improvements, without sacrificing toughness and ductility.
This thesis makes original contributions to the field of composite infrastructure repair in the following ways:
1. Through development of a process that enables FRP’s on infrastructure to be cured in a repeatable, controlled fashion.
2. development and investigation of a process that enables aerospace materials to deviate from the suppliers intended use,
3. Investigation of the effects and sensitivity on suppliers’ composite materials when cure schedules deviate from those specified.
4. Effects of the varied cure schedules on the shear bond strength of FRP to steel substrates.
5. Investigation into the effects of dwell temperature (up to 100°C) and rate of temperature rise on the physical properties of concrete.
Site-Cure uses vacuum consolidation to wrap and consolidate raw Prepreg material to infrastructure, and applies steam to the surface of the sealed vacuum bag in a controlled fashion, heat curing and bonding the FRP laminate in a repeatable way that no other on-site FRP application can match for mechanical performance and durability. It takes the advantages of both systems currently used for infrastructure rehabilitation (fibre wrap and prefabricated strips), whilst eliminating the disadvantages.
This thesis examines the important aspects concerning the Sitecure application of FRP to concrete, steel, and timber, with a specific structural focus on bridges and fatigue focus on steel. The work recorded here is a combination of both in-laboratory detailed testing, and full-scale, on-site applications.
Chapter 2 is a literature review concerning the role of FRP’s in infrastructure repair and details the important properties and environmental resistance needed for a successful repair. It details the current commercial techniques used, Fibre Wrap and Prefab, discussing the advantages and disadvantages with each system, then introduces the Sitecure process in detail.
Chapter 3 examines the effects of the Sitecure process on the development of the mechanical properties of the FRP. The resin system provides the bond mechanism with which load is transferred from the structure to the fibre and between individual fibres. Several resin properties together determine how efficiently this is achieved and how durable it will be under extreme environmental conditions. Resin system properties appear sensitive to cure schedule (temperature ramp rates, final dwell temperatures and dwell Mmes) and it is important to maximise the properties that are important to infrastructure repair. An experimental program investigated:
1. Inter-laminar shear strength and modulus: (load transfer mechanism and bond strength to concrete)
2. Fracture toughness: (durability, resistance to peel failure)
3. Compressive strength: (resistance to fibre buckling, a peel failure mechanism)4. Void levels: (dictates fatigue life, moisture uptake and associated property degradation)
5. Glass transition temperature: Tg (temperature at which load carrying capacity is lost)
A discussion follows on the relative importance of each property and how different applications may call for performance in different properties. A minimum performance level in each property is established, and from this, a range of acceptable cure schedules are determined. Prepreg systems from several different suppliers are examined and a testing procedure is developed(prequalification) to help determine whether various FRP systems meet the minimum mechanical properties and durability required for infrastructure repair.
Chapter 4 looks at the effects of the Site-Cure process on concrete. Elevated temperature exposure has been shown to have effects on the concrete microstructure, as well as various concrete properties including fracture toughness, compressive and tensile strength and modulus. An extensive literature review shows that most studies are in relation to fire and nuclear radiation exposure and do not cover the lower temperature and duration exposures of the Site-Cure process. Compressive cylinder tests were conducted to assess the effects of a broad range of Site-Cure steam exposures.
Finally, Chapter 5 looks at specific problems related to Western Australian infrastructure that now have FRP solutions incorporating Sitecure. These are, concrete flexural strengthening, fatigue strengthening of steel structures, rehabilitation of corroded steel structures, and rehabilitation of degraded wooden structures. The fundamental behaviour of composite materials is discussed along with the elementary guidelines required by structural engineers when considering the use of composite materials in infrastructure repair. It will be shown, through testing, how these materials can be used to gain significant strength, stiffness and fatigue performance improvements, without sacrificing toughness and ductility.
This thesis makes original contributions to the field of composite infrastructure repair in the following ways:
1. Through development of a process that enables FRP’s on infrastructure to be cured in a repeatable, controlled fashion.
2. development and investigation of a process that enables aerospace materials to deviate from the suppliers intended use,
3. Investigation of the effects and sensitivity on suppliers’ composite materials when cure schedules deviate from those specified.
4. Effects of the varied cure schedules on the shear bond strength of FRP to steel substrates.
5. Investigation into the effects of dwell temperature (up to 100°C) and rate of temperature rise on the physical properties of concrete.
| Original language | English |
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| Qualification | Doctor of Philosophy |
| Supervisors/Advisors |
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| Publication status | Unpublished - 2016 |