Comments for Section 3 Flowchart   
Steps 6 to 7 (of 15)              


Step 6



1. Concrete – Concrete Society Report TR55
2. Metallic – CIRIA Report CP595


Design Calculation

Step 6 defines the inputs and outputs of the design calculation. It requires inputs from Steps 1 to 5. The output of the design calculation is cross-sectional area of reinforcement, i.e. thickness times width of reinforcement.

The details of the composite reinforcement required include dimensions, taper details or profile, fibre orientation, and stacking sequence.

The Qualification Scheme is concerned with inputs and outputs from the detailed design calculations. It is not the intent of the qualification scheme to provide specific guidance on design methods. This design guidance can be obtained from, CIRIA C595 (2004) (steel substrate), TR 55 (2004) (concrete substrate) or other relevant standards or guidelines.



Step 7



1. Appropriate level of strengthening achieved
2. Specified plate can be obtained
3. Dimensions of reinforcement are appropriate for structure
4. Resin Tg temperature
5. Reinforcement strength/strain allowable criteria met
6. Adhesive strength criterion
7. Substrate strength criterion

Design conformance check

Step 7 defines the checks on the design calculation to ensure conformance to the original specification.

The checks on the design calculation include:


1. Appropriate level of strengthening achieved
2. Reinforcement can be made by chosen procedure
3. Dimensions of reinforcement can fit within structure
4. Resin Tg satisfies temperature criterion
5. Composite reinforcement strength (or strain) criterion – maximum stress (or strain) criterion is used.
6. Adhesive strength criterion – use stress based criterion as defined by Frost et al (2004)
7. Substrate strength criterion – maximum stress (or strain) criterion is used from relevant design standard.

The first 3 checks relate to the reinforcement: is the area sufficient, can it be made by the chosen method, and are the dimensions within bounds set in the original specification?

The next check concerns the suitability of the adhesive and resin of the composite reinforcement. This check is expressed in terms of the quoted Material Supplier value of the glass transition temperature of both the resin (of the composite reinforcement) and adhesive compared with the design temperature and is given by:

The final 3 checks involve assessment of the stress (or strain) magnitudes within the reinforcement, adhesive and substrate. For the reinforcement and substrate a maximum stress (or strain) criterion is used, whereas for the adhesive an assessment of the principal stress compared to back-calculated peak stresses from lap shear tests is used (Frost et al (2003)). Note, however, that it is not possible to assess if the composite reinforcement delaminates (i.e. debonds) from the substrate.

If any of the checks are not passed, then the design must be repeated. On repeat of Steps 2 to 6 it may be the conclusion that strengthening of the structure is not possible or a reduced but acceptable factor of safety must be introduced for the strengthening to be possible or remedial works may be required (only if it has been demonstrated that the re-design is acceptable).

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