Ethical issues in engineering design - 3TU.Centre for Ethics and ...

Ethical issues in engineering design
the amount of material required to build the bridge. The preliminary design was
calculated using NEN 6723 and NEN 6788, because the calculations were
preliminary and only general, no details were known at the time, it was not
necessary to continue to use the NEN 6723 and 6788 codes in further design
phases. The Rijkswaterstaat Civil Engineering Division, which was asked by the
IBA to check its calculations, had a strong preference for the European code. The
IBA engineers were undecided as to which code they wanted to use. They knew
the NEN 6723 and 6788 very well and had a lot of experience in using them.
Using the European code would require them getting to know that code and
might cost more calculation time. The engineers did not decide which code to
use in the definite design phase; the customer, the OGA, had to decide this.
Because the engineers did not know what the consequences of using the
European code were they made a quick analysis, which was incorporated in the
preliminary design report. The customer could choose based on this analysis. In
the analysis the following arguments were given for and against using the green
version of the European code [Aalstein, 2004].
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‘-The prediction of the fatigue loads are more accurate in the European
code.
-Using the European code the non-permanent loads are higher. 5 The
total loads, the combination of non-permanent and permanent loads,
however, is lower due to lower safety factors
-Using the European code the dynamic fatigue loads are higher and
can be decisive for minimal thicknesses. The stresses calculated in the
preliminary design phase are low enough to assume that the
preliminary design will also suffice according to the European code.
-The financial consequences of using the European code will be
limited. In total the use of the European code can even lead to the use
of less material.’ [Aalstein, 2004]
Considering all these arguments the IBA advised OGA to choose the European
code.
Besides having to choose between NEN codes or the European code, a choice
needed to be made between different types of codes for some parts of the bridge.
For example, the design involved making a wall on either side of the canal to act
as a support for the bridge and keep soil from sliding into the canal. What is the
primary function of such a wall? If the primary function is to support the road
then the calculations should be made using construction codes. If the primary
function of the wall is to keep the soil from sliding into the canal then
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5 Non-permanent loads are loads caused by traffic on the bridge, loads caused by snow or
temperature differences and other non-permanent conditions. Permanent loads are loads
caused by such things as the weight of the bridge, creep and uneven settlement.