Composite rehabilitation systems materials

Composite rehabilitation systems (CRS), i.e., structural hybrid systems involving advanced polymer composite (APC) materials (generally referred to as fibre-reinforced polymer, FRP), structural adhesives (SA) and conventional construction materials (CCM) (e.g., timber, concrete, masomy, steel, iron), constitute one such technology. 

The materials, systems/applications and design/regulations presented in the following sub-sections are concerned primarily with the rehabilitation of timber and concrete structures. In spite of this, a brief section is also added to very succinctly discuss the use of composite rehabilitation systems in metallic and masonry structures. 

Some novel analytical methods that can be used to effectively design composite materials for internal repair were presented. Finally, available experimental studies conducted on internal FRP repair rehabilitation systems for steel pipe were discussed, demonstrating the high potential of composite materials for restoring the pressure capability of damaged pipelines. 

Abstract This chapter continues the discussions of the development of advanced polymer composite material applications associated with bridge engineering. It focuses on the rehabilitation of metallic bridge structures, all-FRP composite bridges and bridges built with hybrid systems. Chapter 16 covered the materials used in FRP composites, in-service properties and applications of FRP composites in bridge enclosures, the rehabilitation of reinforced and prestressed concrete bridge beams and columns. 

It should be noted that the ultra-high-modulus carbon fibre composite has a low strain to failure of the order of 0.4% strain, and a modulus of elasticity value of the composite of about 28 GPa, so the system will fail with a small inelastic characteristic. The high-modulus CFRP composites have an equivalent value of ultimate strain of the order of 1.6% for a value of modulus of elasticity of 220 GPa. This implies that the material is ductile and is unlikely to fail in a rehabilitation situation by ultimate strain but by some other criteria (Photiou, 2005). 

Photiou, N. K. (2005), Rehabilitation of steel members utilising hybrid FRP composite material systems , PhD Thesis, University of Surrey, Guildford, Surrey, UK, March 2005. 

Structural rehabilitation of timber and concrete structures with composite systems can be generally accomplished in one of two ways (Karbhari and Seible, 2000) using wet lay-up or cured in-situ systems, by application of composite overlays, fabrics, sheets or fibre tows (Fig. 22.4) and using systems involving the bond of prefabricated APC materials, such as straight pultruded strips, and factory-made curved or shaped elements (Fig. 22.5). 

In addition, composite systems can be manufactured with smart materials to identify damage and lead to self-healing or even self-cleaning mechanisms [8]. Composite applicahons are not limited to new structures, as they can be utilized to rehabilitate or upgrade existing structures for safety or to increase load-carrying capacity. A few of these aspects are briefly described in the sections given later. 

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