Civil Engineering Reference
In-Depth Information
Environmental factor
Response in structural beam form
The need to bring in maximum daylight
Taper down the beam at the ends near the windows
■
The need to put the material in the right
place and conserve resources
Design the 'perfect beam': deeper and narrower in the centre, wider and shallower at its ends
■
The need for thermal mass to balance out
day and night cooling loads
Provide a beam system with at least 75 mm of concrete ceiling that can be 'seen' by the interior of the
■
space
The need to take advantage of the free
cooling offered by lower air temperature
at night
Use a beam with ventilated hollow core linked to both office interior and the outside air
■
Make it even more efficient by increasing the internal surface which comes in contact with the air (the
■
reverse radiator)
The need not to collapse in a fire
Use a beam with minimised heated perimeter over area
■
Apply fire resistant covering such as intumescent paint or fire-resistant board
■
Choose a beam made from concrete or use a vaulted masonry structure
■
For small projects, use timber beams and oversize to allow controlled charring
■
The need to avoid a 'hard' acoustic
Adopt a beam with a soffit profile that doesn't provide either acoustic focusing or flat panel reflections■■
■
Provide a beam/floor system with soffit coffers to accommodate acoustic absorption panels
■
The need not to block up our roads
Limit maximum beam size to about 18 m by 3.5 m to avoid the need for police escorts and oversize trucks
■
The need to reduce embodied energy
Choose beam material, sourcing, labour and fabrication complexity; transport methodology: maintenance
■
materials and resources; re-use at end of working life; quantify and act on all of this at the time of
deciding on structural system
The need to cut down on the use of zinc
as a protection system
Do proper risk assessment of corrosion in marginal zones
■
Reduce total area of beam surface in at-risk areas to cut down protection
■
The need to reflect light around the space
Provide directed, sloping and curved soffit■■
■
The need to eliminate geometrical waste
in all of the non-structural building
components
Choose a rhythm which avoids cutting of materials by mapping to the minimum waste available modules
■
of secondary components such as floor tiles, ceiling panels, façade glass, furniture
The need to use every part of the structure
to help its neighbour
Look at load-sharing from beam to beam (needs width to provide torsional stiffness)
■
Look at using moment continuity over supports and into walls and columns
■
The need not to add material to prevent
sagging
Get the rules changed: In floors, challenge the received wisdom about the limit for floor deflections (ask
■
what does it really matter?)
To avoid over-designing edge beams, ask whether or not the façade really needs joints only 10 mm thick
■
Design a live-load sharing system between floors■■
■
The need for beauty
In the eye of the beholder, but has a fighting chance if natural rules and some of the relationships
■
described here are allowed to express themselves
Table 2.5 The many complex factors which go into the design of a 'simple' beam
or a planet. All of them need to be designed somehow. But I
know that at least if I can think my way through a beam design
I might have some chance at doing something more compli-
cated one day. I cannot run before I can walk. If cannot even
design a beam, with all its contextual richness, what right do I
have to be trusted with anything more?
I hope the thought process is clear. The need for a structure
to resist the forces of gravity to hold up in the air a group of
people sitting around work-desks begets an integrated concep-
tual response called 'beam' which only then can be tested using
a combination of theory hard-won from engineering science
coupled to equally important subjective value judgements. It
is important to realise, as many do not, that you cannot just do
the scientific tests, as tests have no purpose in practical real-
world engineering without a conceptual proposition. A beam
designed without context is as likely to fail as to succeed. This
is why many wonder why they struggle to be 'conceptual'
when they sit down in front of a powerful scientific testing
tool like a computer. You cannot only test your way to a good
answer no matter how big your hard drive is.
2.10 Enough is enough: A little challenge to use
resources more wisely
Case studies into the material efficiency of typical buildings
show results which highlight a bewildering iceberg of waste-
fulness in the construction industry. To take one revealing
example: in a typical four-storey concrete frame building, less
than 40% of the concrete in the columns is actually working.
The received wisdom behind this is that it is 'cheaper to make
all the columns the same size'. But the old timber shuttering
