question#1

This is a page regarding Rating Analysis (redundant much?)
Assumptions and Criteria for the Westfield bridge out in Western Mass.

In this page, we note the type of loads used due to the method of design, either ASD/LRFD or LRFR.
Mostly guided by the Manual of Bridge Evaluation, also referred by its initials MBE, both parts B or A, respectively.

The main difference starts on the types of live loads that are applied on structures.
For Method A, LRFR, where instead of an HS20 truck, we have the so called HL-93 truck, and the evaluation with the Truck Lane applied as well.

For Method B, instead of those two values, the typical four trucks are the ones that soon will be referred here.

Live Loads (LL) Distribution Factors (DF) are used according to the Standard Specifications for Highway Bridges, under Part C, Distribution of Loads. As usual, there are more than one method to determine that, in general the concept of tributary areas added to structural analysis can produce quick and effective answers to most questions an engineer would pose.

Since this /bridge /rating /bridges is about two Westfield bridges, here we have a note regarding a description of such structure, which is two continuous through trusses with floor beams and stringers supporting a concrete deck, assumed with the support conditions as described on the page.

Back when this analysis was first done, the current software AASHTOWare was called Virtis and had several versions released, ever since, I dont know when or who.
Hand calculations are often necessary to complement the work that is done and can be done by these software. All along with other mathematical tools and discipline specific softwares such as RAM, AutoCAD, Staad.Pro, SAP 2000, Excel and Mathcad.

Gusset Plates are now ran by AASHTOWare, however, Excel calculations are still common. They are done according with the AASHTO Manual for Bridge Evaluation and the time of evaluation interims.
These plates are however, only evaluated according to the ASD/LFD method.

Sidewalk along with other accessories and appurtenances a bridge has, can be calculated separately for validation on the results that can be provided by the current software.