In staad if one member has multiple bracing members connected at different components of that member (e.g flange, web etc) how can I assign those connections? Is it a viable option to use offset? Also, in case of offset members it is also not possible to connect members from one offset to another one since we are not getting any additional nodes for the offsets. If we use plates to form a girder then we won't be getting the forces & moments of that element, we would only be able to check the plate stress? Can anyone attach any sample models?
Since beam elements are line elements, there is no way to connect braces to flanges or webs of beams. However, as you suggested, you can use offsets to ensure that braces are connecting at the right locations. At any location, both the braces are going to be offset with respect to a node which is at the center level of the beam. So the ends of the braces are going to be rigidly connected to that node and hence the these braces are effectively going to be rigidly connected to each other anyway and you do not need to define any additional member for that purpose. Modeling with plates will pose a different set of challenges and hence I would definitely go with modeling with beams.
Sample model attached
Bridge.std
Steel Bridge (SLD)1.std