Method of section utilizes equilibrium and provides quick solution to selected members. In this video, we will look back to the truss which we solved using method of joint. We are now attempting to solve it using method of section.
Given the reaction forces, we cut through members and utilize three equilibrium equations. For each cut we avoid cutting more than three unknown members to make sure our method remains useful. After solving the left halve, we will mirror again and get the forces in remaining members.
The following shows the procedure to solve our truss problem using method of section. Watch the video above for full details.
Support reactions are required prior to analysis
Section BC-CF-FG
Section BC-CF-FG
Equilibrium in y to solve for CF.
Section BC-CF-FG
Equilibrium in moment about A to solve for FG.
Section BC-CF-FG
Equilibrium in x to solve for BC.
Section AB-BF
Section AB-BF
Equilibrium in y to solve for AF.
Section AB-BF
Directly solve for AB.
Section AF-BF-CF-CG-GH
Section AF-BF-CF-CG-GH
Equilibrium in moment about F to solve for CG.
Section AF-BF-CF-CG-GH
Equilibrium in x to solve for GH.
Section AF-BF-CF-CG-GH
Equilibrium in y to solve for BF.
Determined member forces after we cut three sections.
Forces in all members are determined by utilizing the nature of symmetrical structure.
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