Section
10 External glass balustrades
10.1 General
10.1.2 The requirements of this Section apply solely to external glass balustrades. External
glass balustrades are barriers constructed with glass that are used on exposed
decks.
10.1.3 Free-standing glass balustrades are not to be situated in areas deemed
essential for the operation of the craft. Such areas include mooring decks, lifeboat
decks, external muster stations and in the vicinity of davits. Infill glass
balustrades may be situated in these areas subject to the agreement of the Flag
Administration. Where external glass balustrades are not to be used, more
traditional bulwarks or guard rails are to be fitted in accordance with Pt 3, Ch 4, 8 Bulwarks, guard rails and other means for the protection of crew.
10.1.4 In general, glass balustrades are not to be situated in the forward quarter of the
freeboard deck.
10.1.5 Glass is to be manufactured in accordance with the requirements given in ISO 11336-1
Large yachts Strength, weathertightness and watertightness of glazed
openings Part 1: Design criteria, materials, framing and testing of
independent glazed openings or an equivalent recognised National or
International Standard.
10.2 Design considerations
10.2.1 External glass balustrades are to be designed to resist the most unfavourable
anticipated loads within service, including weather loads or personnel loads,
without unacceptable deflection. Detailed plans and calculations are to be submitted
clearly indicating the position, arrangement and the anticipated loads for all
external glass balustrades.
10.2.2 Laminated toughened glass is to be used for the glazing of all external glass
balustrades.
10.2.3 The minimum characteristic breaking strength of the glass corresponding to a 90 per
cent confidence level is to be as required by Table 2.10.1 Characteristic breaking
strength of glass.
Table 2.10.1 Characteristic breaking
strength of glass
Glass type
|
Characteristic breaking strength N/mm2
|
Thermally strengthened glass
|
120
|
Chemically strengthened glass
|
160
|
10.2.4 External glass balustrades are to be not less than 1,0 m in height.
10.2.6 In general, openings (e.g. the gaps between panels or the gap between the deck and
the bottom of a panel) should not be greater than 76 mm unless required for water
freeing. Openings for water freeing are not to be greater than 230 mm.
10.2.7 Consideration is to be given to minimising the possibility of surface deterioration
of the balustrade glass panels in service by means of suitable edge protection or
finishes.
10.3 Types of glass balustrade
10.3.1 The following types of glass balustrade are acceptable:
- free-standing glass balustrade;
- free-standing glass balustrade with top rail;
- barrier with infill panel.
10.3.2 A free-standing glass balustrade is clamped at the bottom of the glass
panel, see
Pt 4, Ch 2, 10.8 Connections, and free to rotate at the
top.
10.3.3 A free-standing glass balustrade with a handrail is clamped at the bottom
of the glass panel, see
Pt 4, Ch 2, 10.8 Connections, and free to rotate at the
top. The handrail is to be designed such that it spans between panels of glass
within the balustrade so that in the event of the failure of one panel, the handrail
will remain attached.
10.3.4 A barrier with an infill panel is a steel or aluminium framed structure
with a glass infill panel which is supported either with a continuous edge or by
isolated bolt fixings or clamps, see
Pt 4, Ch 2, 10.8 Connections.
10.4 Loads
10.4.1 The weather load, Pgb, in kN/m2, for glass balustrades
is to be as required for secondary stiffeners by Pt 5, Ch 3, 3.1 Hull structures 3.1.1 for deckhouses, bulwarks and superstructure and is not to be
taken as less than 2,5 kN/m2 for the location under consideration and
orientation of the balustrade.
10.4.2 The horizontal pressure (applied perpendicular to the balustrade) due to personnel
loads is to be taken as 1,5 kN/m for unpopulated areas (e.g. Owners sun deck) and
2,25 kN/m for populated areas (e.g. areas where people could congregate). The load
is to be applied to the top of the balustrade.
10.4.3 A safety factor of 4,0 is to be applied to the personnel load.
10.4.4 A safety factor of 2,0 is to be applied to the weather load.
10.4.5 When calculating the applied bending moment, Mg, free-standing
glass balustrades are to be considered as cantilever beams of unit width and infill
panels are to be considered as simply supported beams of unit width.
10.4.6 The loads are to be considered as separate load cases.
10.5 Glass thickness
10.5.1 The required thickness of monolithic glass, treq, is
given by:
where
Zreq |
= |
is the required section modulus of the glass panel, in mm3 |
10.5.2 The effective thickness of laminated glass, td, in mm, for
deflection is given by:
t1, t2, tn |
= |
thickness of each ply, in mm |
d1, d2, dn |
= |
distance between the middle of each plyand the middle of the laminated glass
pane, in mm |
10.5.3 The effective thickness of laminated glass, ts, in mm, for bending
is given by:
10.5.4 The shear transfer coefficient is dependent on the interlayer, where a shear transfer
coefficient of 1 indicates that all the load is transferred between the plies.
Common shear transfer coefficients are given in Table 2.10.2 Shear transfer
coefficient; where
an alternative interlayer is specified, the shear transfer coefficient can be
obtained by means of a four-point bending test in accordance with EN-ISO 1288-3 or
an equivalent recognised National or International Standard.
Table 2.10.2 Shear transfer
coefficient
Load type
|
Family 1 (e.g. PVB)
|
Family 2 (e.g. Ionoplast)
|
Weather
|
0,3
|
0,7
|
Personnel - normal
|
0,1
|
0,5
|
Personnel - crowding
|
0
|
0,3
|
Note Refer to EN 16613 Glass in building Laminated glass
and laminated safety glass Determination of interlayer
viscoelastic properties.
|
10.6 Assessment
10.6.1 The effective thickness of a laminated glass panel, see
Pt 4, Ch 2, 10.5 Glass thickness 10.5.2 and Pt 4, Ch 2, 10.5 Glass thickness 10.5.2, is to
be greater than or equal to the required thickness of a monolithic glass panel,
see
Pt 4, Ch 2, 10.5 Glass thickness 10.5.1. Alternatively, the strength of
the glass balustrade can be assessed using Finite Element Analysis where the loads
and safety factor are to be as required by Pt 4, Ch 2, 10.4 Loads in association with the glass strength given in Pt 4, Ch 2, 10.2 Design considerations 10.2.3 and the shear transfer
coefficient given in Pt 4, Ch 2, 10.5 Glass thickness 10.5.4.
10.7 Balustrade stanchions and top rail
10.7.1 Where fitted, balustrade stanchions are to have adequate strength to
resist the anticipated loads specified in Pt 4, Ch 2, 10.4 Loads.
10.7.2 Where fitted, the top rail is to be sufficiently stiff so as not to
deflect more than Lb/96 when subject to the personnel loads
specified in Pt 4, Ch 2, 10.4 Loads, where Lb is the span of the top rail between
stanchions.
10.7.3 The top rail minimum section modulus is to be greater than:
where
qk |
= |
line load on top rail, in kN/m, determined based on the
personnel loads and associated safety factor given in Pt 4, Ch 2, 10.4 Loads |
Lb |
= |
the span of the top rail between stanchions, in m |
fσ |
= |
bending stress coefficient, not to be taken less than 0,6 |
σo |
= |
specified minimum yield stress, in N/mm2 |
10.8 Connections
10.8.2 Where sealant is used in association with a clamping system, the minimum depth of the
clamp is to be 100 mm for free-standing glass balustrades and 50 mm for infill
panels (i.e. 50 mm for each clamp top and bottom).
10.8.3 The strength of connection designs is to be verified using a prototype
strength test, see
Pt 4, Ch 2, 10.9 Testing 10.9.4. Where a designer proposes
to change a design including, but not limited to, a change in clamp size, bolt size,
sealant type, overlaps, clearance and manufacturer, the prototype test is to be
repeated. Where testing is impractical or where the proposed connection design is
unusual, Finite Element Analysis is to be used to confirm the strength of the
connection.
Table 2.10.3 Typical glass balustrade
connections
Figure 2.10.1 Bolt fixing
Figure 2.10.2 Clamp fixing
Figure 2.10.3 Continuous fixing
clamp
Figure 2.10.4 Alternative clamping
system
10.9 Testing
10.9.1 External glass balustrades are to be subjected to a prototype pendulum test in
accordance with EN 12600 Glass in building Pendulum test Impact test method
and classification for flat glass or an equivalent recognised National or
International Standard utilising a drop height of not less than 1,2 metres. The
glass is not to fracture, no cracks are to form and the glass is to be retained in
its frame/retaining arrangement. Note that the actual arrangement of glass and
connections is to be tested.
10.9.2 Free-standing glass balustrades are to be assessed for post-failure strength where
failure is to be induced in one glass ply and the impact test is to be repeated. The
remaining glass ply or plies are not to fracture, no cracks are to form and the
glass is to be retained in its frame/retaining arrangement.
10.9.3 Where it is proposed to use thermally strengthened glass, the failure mode of the
glass balustrade is to be assessed where failure is to be induced in one of the
plies. The glass is to fail in such a way that the glass fragments do not detach
from the balustrade.
10.9.4 External glass balustrades (including both glass and retaining
arrangement) are subject to a prototype strength test where the test pressure is
taken as the design pressure multiplied by the safety factor, see
Pt 4, Ch 2, 10.4 Loads. The glass plies are not to fracture, no cracks are to form and
the glass is to be retained in its frame/retaining arrangement and the
frame/retaining arrangement is not to detach from the deck.
|