The
general philosophy governing the design of bridges is that, subject to a
set of loading rules and constraints, the worst effects due to load
application should be established and designed against. The process of
load application can be complex as governing rules can impose
interdependant parameters such as loaded length on a lane, lane factors
and load intensity. To obtain the maximum design effects, Engineers have
to try many loading situations on a trial and error basis. This leads
to the generation of many live load application instances and a large
volume of output data that has to be combined with dead load effects as
well. In view of the above, a computer program has been developed to
minimise the load application process while complying with national code
requirements. Users can avoid the trial and error approach and
eliminate any possible errors arising from inaccuracies associated with
it. The program is based on the use of influence surfaces, which are
generated by STAAD.Pro as part of the loading process. An influence
surface for a given effect on a bridge deck relates its value to
movement of a unit load over the area of interest. The influence surface
is a three dimensional form of an influence line for a single member.
STAAD.Pro will automatically generate influence surfaces for effects
such as bending moments for elements, deflection in all the degrees of
freedom of nodes and support reactions. The engineer will then instruct
the program to utilise the relevant influence surfaces and, with due
regards to code requirements, optimise load positions to obtain the
maximum desired effects. Once the influence surfaces have been
generated, they are saved and can be used for any further investigation
that may be required. This will remain valid as long as the user has not
altered the structural model. Changes to the structural model can alter
the pattern of the influence surfaces and the user must ensure that a
further run takes place before any further processing. The Engineers
knowledge and judgement is critical in deciding which effects are
required and at what position to obtain them. This is where users can
save a lot of processing time and also, can ensure critical positions
are not missed.
Download
Code
Bridge Engineering Automated Vehicle Application
http://communities.bentley.com/cfs-filesystemfile.ashx/__key/CommunityServer-Components-PostAttachments/00-00-07-99-18/STAAD.Beava-Doc-1.3.pdf
