Composite rehabilitation systems

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. 

The main applications of composite rehabilitation systems in the rehabilitation of timber structures are described in Table 22.1 and Fig. 22.6, and of concrete structures in Table 22.2 and Fig. 22.7. 

As already evidenced in the above text, currently and at a European level, no well-established design and detailing calculation methods embracing all techniques have been developed for the on-site use of composite rehabilitation systems in timber and concrete structures. Nevertheless, the development of suitable design guidance standards is far more advanced in the case of the rehabilitation of concrete structures than of timber stmctnres. Therefore, for most applications the designers of timber structures composite rehabilitation... 

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

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. 

Applications of advanced fibre-reinforced polymer (FRP) composites in bridge engineering rehabilitation of metallic bridge structures, all-FRP composite bridges, and bridges built with hybrid systems... 

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. 

As discussed in the previous chapter, advanced FRP composites have a key role to play in the repair and construction of bridge stmctures. They have been used in the rehabilitation of both ageing concrete and metallic bridge structures. The unique in-service and mechanical properties, viz. durability, high specific stiffness and strength, etc., of advanced FRP composites for the civil infrastructure suggest their suitability for integration in hybrid structural systems as well as the development of all advanced FRP composite structures. 

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). 

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). 

As part of the rehabilitation intervention, which included strengthening, structural consolidation and repair of the roof of the main building of Quinta do Calvel, a composite system was used to repair deteriorated structural timber members. These repair works were carried out by STAP- Repara9ao, Consolida9ao e Modifica9ao de Estruturas, S. A. in the scope of the European Project LICONS - Low Intrusion CONservation Systems for Timber Structures (STAP, 2005 Raquel and Cruz, 2006 LICONS, 1999). 

A composite system was used to rehabilitate a concrete bridge deck. The reinforcement works were carried out in the scope of a pioneer research project in Portugal in this area, promoted by the Portuguese Innovation Agency, named Strengthening of bridges with advanced composite -... 

The wider implementation of bonded composite systems for on-site rehabilitation of structures has been hindered by the lack of well-established guidance on the design and construction with these systems, of systematic quality assurance procedures and of harmonized European standards concerning the bonding products, and by concerns about the performance of CRS against... 

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. 

Use of composites to rehabilitate existing infrastructure is not dealt with in this chapter due to space limitations. However, readers must note that great strides are being made in applying polymer composite wraps and laminates to reinforce the infrastructure systems in a cost-effective manner so that hundreds of millions of dollars can be saved through the rehabilitation techniques with a simultaneous reduction of user inconveniences. 

Depending upon the level of degradation or distress within the host pipe at the time of repair, the CFRP liner is designed to resist the design loads through either composite action with a part of the pipe wall or as a stand-alone system. Levels of degradation of host pipe for CFRP rehabilitation and strengthening of PCCP are as follows ... 

---