BRidge table -Usage

I have a project table
activity table and Work order table.

One project has many Activities.Each activity is uniquely tagged to a project.
Similarly every project has workorders.Every work order is uniquely tagged to a project.
Every Workorder has may activities and is uniqely tagged to a Project .

I have designed a fact for WorkOrders ,Activities.

SHould i desgn a Bridge table for Linking WO's and Projects? and refer the key in Fact Activity?

What are uses of Bridge table and when to do we go for it?

No bridge. The work order and activity facts would simply have a foreign key to the project dimension.

Bridges are used to resolve M:M relationships between facts and dimensions. You do not have that situation.