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 loadapplication 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 loadpositions 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.
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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
