From the results of extensive tests, which DEMU has conducted on its inserts in the course of the years, it has been established that exact figures cannot be determined to give exact load-capacity for each insert. Aspects such as the composition, homogeneity, strength and age of the concrete are factors which influence the load-capacity considerably.

 

The starting point for determining the admissible static tensile-loads as given on this site is all information from the various test reports combined, with mean values established and the elimination of the extremes.

 

The admissible static loads for the inserts apply for a purely normal (pull out) or shear load and give 4- to 5-times certainty compared to the breaking strain if the concrete is normative and 3- to 4-times certainty if the strength of the insert is the determining factor.

With the “admissible load” indication the admissible load is intended for static fixing applications. The inserts must always be fully cast in the concrete.

 

The cross-pin of the inserts types 995-A, 1074-A, 1036-A and 1168-A causes no increase in the admissible load, but gives extra certainty with the presence of voids or airpockets in the concrete.

 

The maximum load of inserts 995-G, 1074-G, 1036-G and 1168-G can be increased by the application of a U-shaped anchor of sufficient length in the cross-hole.

 

The VEMO inserts without cross-pin are not applicable in the stress-area of the concrete, except types 1130 and 1140.

 

The load must meet following requirements:

N_sd/N_rd <= 1

V_sd / V_rd <= 1

N_sd/N_rd + V_sd/V_rd <= 1.2

N_sd = appearing pull out load

V_sd = appearing shear load

N_rd = admissible pull out load

V_rd = admissible shear load

 

Because of the minimum required sizes and the absence of a clear "anchoring length", the inserts can not be calculated according the CUR25 calculation method (see bolt anchors group).

 

 

The maximum admissible load on these anchors can be retained providing that with tension the edge distance is 1.5 x L, with transverse force the edge distance is 2.5 x L, with tension the centre-to-centre distance is 3.0 x L and with transverse force the centre-to-centre distance amounts to 5.0 x L (L = the length of the anchor).

 

Minimum edge distance: 3 x d with a minimum of 50 mm!

 

Reduction factors with reduced distances from the edge:

With a reduced edge and/or centre-to-centre distance the admissible load must be reduced. The reduction percentages must both be applied with tension (ND) and with transverse force (Vd) (see table 1).

 

For shear load towards the edge the use of reinforcement can increase the value again. This increased value may never, however, exceed the specified admissible load. The following reinforcement and the associated factors (Y) for increasing transverse force are applicable:

 

straight edge reinforcement: Y = 1.2 (see table 1)

mesh reinforcement/edge reinforcement and brackets: Y = 1.4 (see table 1)

 

If the occurring transverse force is above the reduced admissible load, one must use sufficient reinforcement in the form of U-shaped bars to be able to fully accommodate this force. With a transverse force towards the edge the U-shaped bars must be fitted above the anchor. With transverse force from the edge the U-shaped bars must be fitted below the anchor.

 

Table 1

 

Edge distance	Nrd	Edge distance	Vrd	Y=1,2	Y=1,4
2.5 x L	100%	2.5 X L	100%	100%	100%
2.0 X L	100%	2.0 X L	85%	100%	100%
1.5 X L	100%	1.5 X L	65%	78%	91%
1.0 X L	75%	1.0 X L	40%	48%	56%
0.5 X L	50%	0.5 X L	15%	18%	21%

The admissible load for the inserts are applicable for both cracked and uncracked concrete and determines the concrete strength class C20/25.

For pull out the following factors may be used for other concrete qualities:

 

Concrete strength class        C20/25    C28/35    C35/45   C45/55   C55/65

Factor                                         1.00          1.18         1.34         1.48          1.61

 

If the centre-to-centre distance between two fasteners is less than 3 x L one can proceed as follows: divide the applied centre-to-centre distance by two and use the reduction values as applying for the distances from the edge.

 

When the inserts are in recessed position, for example by using the re-usable plastic nailing plate type 2280, an adequate filling is necessary in order to load the insert properly without loading the conrete.