NCC 2016 Volume One
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Section D Access and Egress (Verification Methods)

Section D Access and Egress (Verification Methods)

VERIFICATION METHODS

DV1 Wire barriers

Compliance with DP3(f) and (g) for wire barriers is verified when the wire barrier passes the test described below:

(a)

Application

The test must be carried out on either—

(i)

a prototype of a wire barrier that is identical to that proposed to be installed on-site; or

(ii)

a wire barrier installed on-site.

(b)

Test equipment

The test equipment must consist of the following:

(i)

A horizontally suspended 125 mm diameter, 405 mm long cylinder of 1 mm thick steel having a highly polished 105 mm long cone at one end with a 20 mm diameter flat leading edge to which an eye bolt is fixed.

(ii)

A sufficiently flexible horizontal cable with mechanisms capable of applying and measuring a tension of 150 N (or a 15.3 kg weight suspended over a low friction pulley) is to be attached to the eye bolt (see Figure DV1).

(iii)

A mechanism capable of measuring the tension force applied to each wire.

Figure DV1

APPARATUS FOR TESTING WIRE BARRIERS

v1_dv1_2015.svg
(c)

Test procedure

The test procedure must be as follows:

(i)

Tension the wires, within their safe load, to the same tension in all wires and measure the tensions with a strain indicator.

(ii)

For—

(A)

horizontal or near horizontal wires, position the cone against a pair of wires at the mid-span between supports, then apply the 150 N tension force to the cone; and

(B)

vertical wires, position the cone against a pair of wires at the mid-span between supporting rails, then apply the 150 N tension force to the cone; and

(C)

near-vertical wires, position the cone against a pair of wires at the widest opening between the wires, then apply the 150 N tension force to the cone.

(iii)

Attempt to pull the cone through the gap between the wires under the 150 N load, and—

(A)

increase the tension in the wires and repeat (ii) until such time as the cone will not pull through; or

(B)

if it does not pull through, reduce the tension in the wires and repeat step (ii); and

(iv)

When the cone is just prevented from pulling through the gap, the wires are at the correct tension in which case the cone is withdrawn and the tension recorded.

(v)

Reduce the tension in the wires and repeat steps (ii) to (iv) twice more, recording the tension in each case after the cone has been removed and then calculate the average of the three tensions as the required tension for each wire.

(vi)

For prototype tests of horizontal or near horizontal wires, record the deflection of each wire at the average tension calculated in accordance with (v) when a 2 kg mass is hung at mid-span between supports.

(d)

Test report

The test report must include the following information:

(i)

The name and address of the person supervising the test.

(ii)

The test report number.

(iii)

The date of the test.

(iv)

The wire manufacturer's name and address, and specifications of the wires used in the test including the safe load limit of the wires.

(v)

The construction details of the test specimen, including a description and drawings and details of the components including supports, post or railing spacings and wire spacings.

(vi)

For a prototype test, the required tension calculated in accordance with (c)(v).

(vii)

For prototype tests of horizontal or near horizontal wires, the deflection measured in accordance with (c)(vi).

is a means to verify whether or not a proposed wire barrier achieves the requirements of and , in other words whether the wire barrier is—

  • constructed to prevent people from falling through the barrier; and
  • capable of restricting the passage of children.

cannot be used to verify compliance with the other provisions of DP3.

It is not compulsory for a designer to use . The designer has the choice of using—

  • to verify that the proposal achieves and ; or
  • the Deemed-to-Satisfy Provisions in .

As set out in , the Verification Method may be carried out on—

  • a prototype that is identical to that proposed to be installed; or
  • a wire barrier installed on site.

The meaning of the phrase "prototype that is identical to that proposed to be installed" is similar to that for the testing of prototypes for fire resistance. That is, it must be identical with respect to the type of wire, the wire diameter, the number of lays, the wire tension, the post spacing and size, etc.

The test procedure is slightly different for barriers with horizontal or near horizontal wires and vertical wires or near vertical wires (see the test procedures set out in ).

If is to be used for horizontal or near horizontal wire barriers, , whereby the deflection of the tensioned wires is measured as part of the prototype test, allows a simple method of checking that the barrier wires installed on site have been installed at the required tension if a tension gauge is not available.