Thank you for the response OSUCivlEng. Yes this platforms will be permanent mounted on the bridge and need to be mobile to perform inspections and maintenance works for the entire span as per contractors request.
They don't want a mobile truck inspection for this.
I'm interested in design standards and specifications if any are available for this. The contractor just said want this on every bridge and span on a project I'm working on and I have no idea were to begin. If any of you know something about designing this type of platforms I would appreciate...