CEN/TC 250/SC 2/WG 2 - Design of fastenings for use in concrete

1.1   General
This Technical Report provides design rules for fasteners used to connect statically indeterminate non-structural light weight systems (e.g. suspended ceilings, pipe work, ducting) to concrete members such as walls or floors (see Figure 1)).
The proposed design model may be applied to post-installed mechanical and bonded anchors covered by EN 1992-4:2017, 1.2. Their suitability will be confirmed in a European Technical Product Specification.
The design rules assume the following:
-   under extreme conditions (e.g. large crack width) excessive slip or failure of a fastener might occur;
-   elements or systems are attached with at least three fixing points with one or more fasteners at each fixing point;
-   where more than one fastener is used at a fixing point (MF, see Figure 1), only fasteners of the same type, size and length are used;
-   the attached system is sufficiently stiff to transfer the load at any fixing point to adjacent fixing points without significantly impairing the performance characteristics of the system both at serviceability and ultimate limit states.
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This Technical Report applies to non-structural applications in structures covered by EN 1992-1-1. In applications where special considerations apply, e.g. nuclear power plants or civil defence structures, modifications may be necessary.
This document does not cover the design of the fixture. The design of the fixture will be carried out to comply with the appropriate Standards.
1.2   Type of fasteners
Post-installed fasteners according to EN 1992-4.
1.3   Fastener dimensions and materials
EN 1992-4:2017, 1.3 applies with the following addition: In precast pre-stressed hollow core elements the minimum embedment depth may be reduced to a value to ensure proper functioning if placed in a flange (wall) of minimum thickness of 17 mm. In this case the minimum embedment depth and the admissible position of the fastener in the hollow core slab given in the relevant European Technical Product Specification will be observed (Figure 2).
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1.4   Fastener loading
Loading on the fastenings will only be quasi static. Fatigue, impact and seismic loads are not covered.
Any axial compression on the fixture will be transmitted to the concrete either without acting on the fastener or via fasteners suitable for resisting compression.
1.5   Concrete strength
EN 1992-4 applies.
1.6   Concrete member loading
EN 1992-4 applies. However, fatigue, impact and seismic loads are not covered.
1.7   Concrete member dimensions
The minimum thickness of members in which fasteners are installed is at least 80 mm unless otherwise specified in the European Technical Product Specification. For precast pre-stressed hollow core elements, the minimum wall thickness is 17 mm.

EN 1992-4:2018 covers anchor channels located in cracked or uncracked concrete subjected to tensile loads and/or shear loads transverse to the longitudinal channel axis as well as combinations of these loads. Shear loads acting in direction of the longitudinal axis of the channel and combinations of shear loads acting transverse and in direction of the longitudinal axis of the channel, combinations of tensile loads and shear loads acting in direction of the longitudinal axis of the channel and combinations of loads in all three directions are excluded.
This Technical Report provides design rules for anchor channels under static and quasi-static shear loads acting in direction of the longitudinal channel axis and all possible combinations of shear and tension loads acting on the channel as well as design rules for anchor channels with supplementary reinforcement to take up shear loads, additional and alternative to the provisions of EN 1992- 4:2018. All relevant failure modes are considered and will be verified. Fatigue, impact and seismic loads are not covered.
The design rules in this document are only valid for anchor channels with a European Technical Product Specification. The design provisions for shear loads acting in direction of the longitudinal axis of the channel cover the following anchor channels and applications:
-   Anchor channels with 2 or 3 anchors.
-   Anchor channels where the shear load in the longitudinal axis of the channel is transferred to the channel by corresponding locking channel bolts creating mechanical interlock by means of a notch in the channel lips or serrated channel bolts which interlock with serrated lips of the channel (Figure 1).
-   Anchor channels produced from steel with at least two metal anchors rigidly connected to the back of the channel (e.g. by welding, forging or screwing). The anchor channels are placed flush with the concrete surface. A fixture is connected to the anchor channel by channel bolts with nut and washer.
-   Anchor channels close to the edge placed either parallel or transverse to the edge of the concrete member. The design provisions for concrete edge failure do not cover channel orientations inclined to the concrete edge.
The design method for anchor channels loaded in shear in direction of the longitudinal axis of the channel follows closely the existing design model for headed fasteners. For reasons of simplicity modifications specific for anchor channels are used where necessary.
The design provisions for the supplementary reinforcement to take up shear loads in case of anchor channels situated parallel to the edge and loaded in shear transverse to the longitudinal axis apply to anchor channels with unlimited number of anchors.
Examples of anchor channels and channel bolts ensuring mechanical interlock are given in Figure 1.

This Technical Report gives provisions for design of ultimate limit states in addition to EN 1992 4 for headed and post-installed fasteners excluding concrete screws, which only transmit static actions to the concrete, when the loads on individual fasteners are determined according to plastic analysis of the joint where only equilibrium conditions but no compatibility conditions are considered. Fatigue, impact and seismic loads are not covered.

This document relies on characteristic resistances and distances which are stated in a European Technical Specification. In minimum the following characteristics should be given in a European Technical Specification as base for the design methods of this CEN/TS:
-   NRk,p, NRk,s, VRk,s
-   
-   ccr,N, scr,N
-   ccr,sp, scr,sp
-   cmin, smin, hmin
-   limitations on concrete strength classes of base material
-   kcr, kucr, k2, k4, k6, k7
-   dh, dnom, hef, lf
-   yMi  partial factors for material see also CEN/TS 1992-4-1:2009, clause 4.

1.1   General
1.1.6   This document relies on characteristic resistances and distances which are stated in a European Technical Specification. In general the design concept is valid in the product dimensions 6 inferior, or equal, to hef/dnom inferior, or equal, to 20. The actual range for a particular fastener may be taken from the relevant European Technical Specification. In minimum the following characteristics should be given in the relevant European Technical Specification as base for the design method of this CEN/TS.
-   NRk,s, VRk,s
-    (...)
-    (...)
-   ccr,N, scr,N
-   ccr,sp, scr,sp
-   cmin, smin
-   hmin
-   limitations on concrete strength classes of base material
-   kcr, kucr, kT, k2, k3, k4, k8
-   dnom, hef, lf ,   limitations on hef/dnom
-   yMi, recommended partial factors see CEN/TS 1992-4-1:2009, clause 4

1.1   General
1.1.6   This document relies on characteristic resistances and distances which are stated in a European Technical Specification. In minimum the following characteristics should be given in a European Technical Specification as base for the design methods of this CEN/TS.
-    (...)
-   NRk,p
-    (...)
-   ccr,N, scr,N
-   ccr,sp, scr,sp
-   cmin, smin, hmin
-   limitations on concrete strength classes of base material
-   k5
-   Ah, bch, d, hef, hch, Iy
-   yMi  partial factors for material see also CEN/TS 1992-4-1:2009, clause 4
1.4   Anchor channel loading
1.4.3   Actions not covered
The following actions are not covered by this CEN/TC:
-   shear in the direction of the longitudinal axis of the channel;
-   fatigue loading;
-   seismic loading.

This document relies on characteristic resistances and distances which are stated in a European Technical Specification. The characteristic values shown in Table 1 should be obtained from the relevant European Technical Specification as base for the design methods of this CEN/TS.

1.1   General
1.1.1   This CEN/TS provides a design method for fasteners for structural purposes, which are used to transmit actions to the concrete.
Inserts embedded in precast concrete elements during production, under FPC conditions and with the due reinforcement, intended for use only during transient situations for lifting and handling, are covered by the CEN/TR “Design and Use of Inserts for Lifting and Handling Precast Concrete Elements”, by CEN TC 229.
1.1.2   This CEN/TS is intended for applications in which the failure of fastenings will:
1)   result in collapse or partial collapse of the structure, or
2)   cause risk to human life, or
3)   lead to significant economic loss.
1.1.3   The support of the fixture may be either statically determinate or statically indeterminate, defined as multiple anchor use in some European Technical Approvals (ETAs). Each support may consist of one fastener or a group of fasteners.
1.1.4   This CEN/TS is valid for applications which fall within the scope of the series EN 1992. In applications where special considerations apply, e.g. nuclear power plants or civil defence structures, modifications may be necessary.
1.1.5   This CEN/TS does not cover the design of the fixture. The design of the fixture shall be carried out to comply with the appropriate Standards. Requirements for stiffness and ductility of the fixture are given in clauses 5 and 8.
1.2   Type of fasteners and fastening groups
1.2.1   This CEN/TS applies to:
a)   cast-in fasteners such as headed fasteners, anchor channels with rigid connection between fastener and channel;
b)   post-installed anchors such as expansion anchors, undercut anchors, concrete screws, bonded anchors, bonded expansion anchors and bonded undercut anchors.
For other types of fasteners modifications of the design provisions may be necessary.
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