EF 202, Module 3, Lecture 1 Trusses - 2 EF Week 10

EF 202, Module 3, Lecture 1 2 Methods of Truss Analysis Method of joints (last week) Method of sections (today)

EF 202, Module 3, Lecture 1 3 Method of Sections Separate the structure into two parts (sections) by cutting through it. Draw an FBD of the section that is on one side or the other of the cut. Use method for noncurrent, coplanar systems. Three independent equations on the section. No more than three unknowns on a section.

EF 202, Module 3, Lecture 1 4 The method of sections involves analyzing nonconcurrent, coplanar force systems, and so uses moment summations. Yes-Yes

Example 1 Use method of sections to find forces in all members as functions of the applied load, F. x y +

x y +

Example 2 Use the method of sections to find the force in member BE. x y +

x y +

Example 3 Use the method of sections to find the force in member BF. x y +

x y +

Example 4 Use the method of sections to find the forces in members UV, MV, ME and DE.

EF 202, Module 3, Lecture 1 13 Hmmm A section that has four unknowns is statically indeterminate. On a statically indeterminate body, we cannot find all the unknowns. Even though we can’t find ALL of the unknowns, could we perhaps find SOME of the unknowns? How many do we need to find to make the previous FBD statically determinate?