Civil Engineering Reference
In-Depth Information
cracked renderings following
carbonation of the render and loss of
galvanising to the mesh.
Although some rusting of rolled
steel angle columns and beams has
been observed by BRE in most steel
framed systems, in no case has any
dwelling needed to be taken out of
service because of structural
considerations. Pressed sheet steel
sections have less steel content, and
once the protective coating has
disappeared, there is therefore less
steel to survive. Trusteel dwellings,
particularly the Mark IIs, should be
particularly carefully examined. In
most cases this will mean exposing a
corner column. However, even nearly
complete rusting away of a column at
its base will not necessarily mean that
failure of the complete frame is
imminent. Normally there was some
redundancy in the frame, and loads
are shared with other parts of the
structure. Corroded structural steel
sections, other than lattice sections,
are not difficult to cut away and
replace, but it does mean opening up
the structure (Figure 3.13).
Dorloncos have concrete floors
and ceilings in which deterioration of
reinforcement has been noted
following carbonation of the
concrete. Some Dennis Wilds
external walls have bulged following
corrosion of wall ties.
Maintenance
Maintenance of a steel frame is
unlikely to be advantageous, unless
the cladding can be stripped to allow
corrosion protection to be restored.
As was implied earlier, spalling
concrete in the frames can be
repaired, provided the results can be
accepted visually, and there are a
number of techniques that can be
used. Generally, such repairs are best
left to specialist firms.
For brick masonry, see the same
section in Chapter 2.1.
Work on site
Inspection of a sample column of
steelwork can often conveniently be
made from the outside of the
dwelling. The most exposed position
should be chosen (Figure 3.14).
Figure 3.13
The internal leaf has been removed to
reveal a badly corroded steel column. In
this case there has been some load
sharing, and the brick outer leaf is now
supporting the column
Inspection
In addition to those listed in Chapter 2.2, the
problems to look for are:
Steel frames
◊
corrosion of steel frames
◊
corroded ties linking outer leaves with
frames
◊
thermal insulation in cavities acting as
wet poultices
Reinforced concrete frames
◊
spalling of concrete
◊
no soft joints at storey heights of panels
in concrete frames
Reinforced concrete frames
See the same section in Chapter 2.4
which deals in particular with
carbonation.
Figure 3.14
Cutting away rendered masonry at a
corner column. A vertical crack, signifying
corrosion product, shows above the cold
chisel
