How to apply consider braking load for bridge super structure since one has a lot of live load combinations .
Do one has to consider notional load concept as mentioned by Sye Chakroborthy with the moving load and take the envelope of it
Yes as of now the option using notional load, as outlined in the wiki below, is the only option.
http://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/25708.how-to-apply-horizontal-moving-loads
There are plans to include the horizontal components for moving loads in the software this year.