Why does ENGR Mechanics: Statics cover *hinged* trusses?

[swampwiz]

Something that has always been off for me is the canonical pedagogical treatment of analysis of trusses in the course typically called "Engineering Mechanics: Statics". Certainly, every cantilever bridge I see has completely attached joints, although lately I have seen some airy, open structures like airports have what looks like it could be a ball joint on major beams (I presume this is intentionally done to allow for wind loading).

The only explanation I can come up with is that students need to start somewhere, and hinged trusses offer the ability to do fancy analysis of statically determinant structures - while completely fixed trusses require an understanding of deformation that is typically covered in a subsequent course in "Solid Mechanics", and the proper analysis of fixed trusses gets it proper treatment in more advanced courses that cover the stiffness method. An understanding of statically determinant structures must precede learning about deformation, so it's basically a pedagogical chicken & egg problem.

 

[Stephen Tashi]

According to some video lectures I viewed (The Great Courses: Understanding the World's Greatest Structures), historically, hinged trusses were the first that could be mathematically analyzed, so structures were actually built with hinged trusses just for that reason. Of course that doesn't imply that pedagogy should mimic the historic development of a subject.

 

[PhanthomJay]

To get an exact solution of a truss with fixed joints and supports would be a tedious task using hand calcs, and the last thing you want to do , while learning about these things , is to shove it into a computer for the results. But even if joints and supports are fixed, there is very little error when assuming pinnned joints and supports; member forces are primarily still axial. This has been confirmed by testing.