how to obtain a balanced span arrangement for a bridge

huangyhg

how to obtain a balanced span arrangement for a bridge.
can anyone explain to me how to go about obtaining a balanced span arrangement for a continuous span bridge.
thanks in advance,
pat
pat,
for continuous steel beam bridges, the ratio of the length of the end spans to the intermediate spans usually should be 0.7 to 0.8. the latter ratio is preferred because it nearly equalizes the maximum positive moment of all
spans.  i assume this is what you meant by a balanced span arrangement.
mike
mike80, thanks for your response. will this rule deal with uplift issues at the end supports? if not, how do you arrange your spans so that uplift is not an issue?
check uplift conditions at the end supports for dl + ll +i & other applicible conditions.  uplift is usually not a problem except for short end spans.  
further to tincan's comments, the live load should be placed to give worst case, i.e load second and 4 span only.
stephena