Civil Engineering Reference
In-Depth Information
18.7.5 Interfaces with architectural and M&E
requirements
Interpretation of the architectural characteristics requires ite-
ration between detail construction of the building fabric and
likely thicknesses of finishes and fixings that drive the sizes
and location for the structure. This most critical stage in the
designer's interpretation of the building and the appropriate
structure requires peer review and coordination with the team.
increasing impact on the UK. Hybrids exploit the most favour-
able structural characteristics in the materials.
In buildings that incorporate different structural materials,
there are key architectural and structural details that drive the
structural design.
A mix of architectural and building service parameters
will tend to dictate structural positions and shapes. The struc-
tural 'joining' details will generally incorporate high strength
material to facilitate factory manufacture, delivery and erection.
There is a large body of research and knowledge in the design
and detailing of conventional steelwork and, for example, in the
UK the steelwork industry remains at the forefront in the off-site
production and site assembly of structures.
Challenges of interface management and by implication de-
sign of details will become crucial for designers and contractors.
Expertise in hybrid construction will be important for designers.
18.7.6 Element studies on floor and wall thickness
Simple member designs determine the order of magnitude
of structure integrated with the output from the review of the
architectural and M&E requirements.
18.7.7 Preliminary beam and column sizing
Figures 18.43
and
18.44
summarise the options for a simple
two-storey 18 m wide building. This work would allow the
client and design team to agree the frame topology that is sub-
sequently modelled in detail, probably in 3D software.
18.8.2 Reuse/recycle
Sustainable design with particular regard to future dismant-
ling and reuse of structural materials will introduce additional
design considerations in all structure types.
The realities of the market for second-hand construction mate-
rials suggest it is challenging to successfully dismantle and sell on
any complete frame except the most straightforward single-storey
buildings often finding a second use in agriculture.
In the case of multi-storey office-type buildings steel fram-
ing with precast floors is simpler to dismantle and reuse. In an
assessment of a building framed in composite decking, compos-
ite steel secondary beams and non-composite primary beams
buyers could be found for only 107 tonnes of the 670 tonnes of
steel in two buildings. A price of £260 ($400, €300) per tonne
(2004 prices) for the 107 tonnes was offered but extracting that
tonnage was not financially viable. A demolition contractor
advised at the time that since prices for scrap were high it was
not worth their while to painstakingly dismantle the frames, bolt
by bolt. Other issues emerged such as:
18.8 Challenges and opportunities
So how do we draw on the design and detailing skills of the
designer, and the contractor making the structure? The steel-
work industry has a tradition founded in craft-based workshop
skills. The rigour imposed by modern methods of factory pro-
duction has, by necessity, led to close integration of design and
construction techniques.
Integrated steel design and manufacture is comprehen-
sively reviewed in the 'Computer integrated manufacture of
steel' (CIMSTEEL) explained in the two publications
Design
for Manufacture
and
Design for Construction
(SCI, 1995 and
1997). This initiative has not had the publicity it deserves and
the reader should consult these references.
The concrete industry has made significant advances over
the last few years in terms of rationalising site construction,
design aids, pre-fabricated reinforcement assemblies and
advances in off-site production of components. There is a con-
vergence where the designer/consultant integrates the work
of specialists in concrete structures in the same way as has
been the case in steel structures for some time. Just like steel-
work, success will depend on concrete details developed that
satisfy the parameters of design and practical construction.
A frame with composite secondary and primary beams with
■
through-deck welded studs will not easily be separated from the
composite slab; use of a non-composite precast might be more
attractive though not necessarily on cost grounds.
Column reuse would be straightforward.
■
75 microns of paint were specified but there were 400 microns in
■
places. 400 microns would significantly impede reworking/weld-
ing of steel sections retrieved from the building for reuse.
Galvanised sections were a problem for any reworking/welding of
18.8.1 Hybrid construction
More complex buildings using mixed structural materials is
common as designers respond to the challenge of integrating
structure with building services and architectural challenges of
exposed structures and natural ventilation. Demands for rapid
construction on site and continued pressure on price and cost
of labour acts as a further impetus to use off-site manufactur-
ing methods.
Hybrid construction (see
Figure 18.45
) involves the com-
bination of site and off-site manufactured steel and/or concrete
members. This form of construction seems likely to make an
■
steel sections retrieved from the building for reuse.
Board cladding for fire protection, used in the past, might be a regres-
■
sive step but does not pose the same reusability problems of thin
cost effective intumescent coatings which are the current norm.
Demolition contractors were offering between £50 ($80, €60)
and £80 ($125, €95) per tonne for scrap making demolition a
cost-neutral exercise, as the cost to demolish would be around
the same as the price given for the steel.
