Civil Engineering Reference
In-Depth Information
(a)
(b)
1200 mm long straps with 100
s w
ith 100
mm return down wall -
wn wall
-
fixed
fix
ed
1200 mm long st
ng
st
wi
ps
wi
th 100
th
turn down wall - fixe
- fi
xe
d
ra
st
ra
ps
ra
ps
mm re
mm
re
mm
to so
to
so
lid wood noggins - typically at 1200 to 2
to
2
to
000 nn centre
nn cent
re
to solid wood noggins -
od
typi
ty
pi
lly
at 2000 nn centres
tr
es
s
ca
pi
ca
Figure 20.4
Restraint straps (a) Timber joists parallel; (b) Timber joists perpendicular
S1, S2 Active soluble salt content category (BS EN771-1)
gives guidance on limits on total percentage of soluble
salts by mass. When S1 units are specifi ed for condi-
tions MX2.2, MX3.2, MX4 and MX5 sulphate resist-
ing mortars should be used.
P, M, S Passive (P), Moderate (M) or Severe (S) exposure con-
dition for mortar designation (refer to BS EN998-2). If
passive exposure conditions are used mortars need to
be protected against freeze/thaw during construction.
Ancillary products are typically stainless steel, galvanised or
plastic. BS EN1996-2 Tables C.1, C.2 and C.3 give guidance
on the material specifi cation for ties, straps, lintels and bed-
joint reinforcement in relation to categories MX1 to MX5.
Austenitic stainless steel components (ties, straps and lin-
tels) have unrestricted use for categories MX1 to MX4, with
a requirement to consult the manufacturers for category MX5.
Bed-joint reinforcement can be used unrestricted for categories
MX1 to MX3.
Galvanised components generally have unrestricted use for
category MX1. However, certain elements can be used in more
severe categories (MX2 and MX3) depending on the g/sqm of
coating and the type of component.
Figure 20.5
Masonry cladding on support angles
Masonry units, mortar and ancillary products should be spe-
cifi ed based on the assumed exposure conditions.
Table 20.4
and
Figure 20.6
relate exposure conditions to masonry unit
type and mortar which should be specifi ed.
Table 20.4
has
been modifi ed to account for the guidance in BS 5628-3 as
the National Annex (NA) to BS EN1996 precludes the use of
annexes B and C of BS EN1996-2.
20.3 Preliminary sizing
20.3.1 Overall stability
Structural stability of masonry buildings can be provided in
a number of ways depending on the form of building. In all
forms the stability system should resist loads in two orthog-
onal directions, as well as any twisting forces due to asym-
metry of applied loading or building geometry.
F0, F1, F2
Freeze/thaw resistivity of masonry unit spe-
cifi cation. Defi ned as Passive (F0), Moderate
(F1) or severe (F2) (refer to BS EN771-1). If
passive exposure conditions are used mortars
need to be protected against freeze/thaw during
construction.
