DAfStb guideline - Strengthening of Concrete Structures with Adhesively Bonded Reinforcement - page 5

construction products whose usability as components in a strengthening system must be
verified within the scope of a national technical approval for the strengthening system.
The main elements of such a strengthening system are:
- the strengthening elements made from carbon fibre materials (CFRP strips or CF

sheets) or steel flats/angles,

- the adhesive,

- a primer based on epoxy resin as a component for protecting steel parts against

corrosion, and

- a repair mortar based on epoxy resin which includes a bonding agent.

2.4.4 Execution
The third part of the DAfStb guideline deals with the work on site. It contains advice and
provisions for carrying out the strengthening measures. For example, it provides
information on the pretreatment of members and the associated inspections to be
carried out. In addition, it speci es the requirements to be met by contractors who carry
out strengthening measures.

2.4.5 Planning
The fourth part of the DAfStb guideline contains supplementary regulations for
planning strengthening measures. It includes definitions of the requirements to be
satisfied by the member being strengthened. There are also recommendations regarding
the scope of the planning and the measures required to determine the actual condition of
the member to be strengthened. In addition, all design and construction work must take
into account the DAfStb

' s guideline on the maintenance of reinforced concrete [23].

2.5 Safety concept
As with DIN EN 1992-1-1 [20] and its associated National Annex [21], the DAfStb
guideline is based on the safety concept of DIN EN 1990 [24] together with its National
Annex [25].
The guideline speci es partial safety factors for externally bonded reinforcement,
which are given in Table 2.1. A distinction is made between the partial safety factors
for the strength of the bonded reinforcement and those for the bond of the bonded
reinforcement.
The partial safety factors for the strength of externally bonded reinforcement were
chosen according to the b recommendations [26]. The partial safety factor proposed
in [26] for CFRP strips has also been evaluated statistically by Blaschko [27] and used in
the design rules of earlier approvals [28, 29].
The partial safety factors for the bond of reinforcement attached with adhesive depend
on the mode of failure. In the case of near-surface-mounted reinforcement and when
bonding steel to steel or CFRP to CFRP, it is generally the adhesive that governs a bond
failure, and the safety factor for the adhesive according to [27] is used, as it was already
the case in the earlier approvals (see [29], for example).