Meriam, Kraige & Bolton — Equilibrium of Rigid Bodies: Problem 4_49

⚡ Mecademy AIENG정역학 · ch4  Problem Statement A design model for a transmission-line tower is shown in the figure. Members and are insulated cables; all other members are steel bars. For the loading shown, compute the forces in members and Use a combination of methods if desired. Problem 4/49 (a) Analysis of symmetry and general equilibrium ● Calculation Process 1. Equilibrium of the entire structure: The tower and the loading are perfectly symmetric about the central vertical axis passing through peak . Total downward load: . Vertical reactions at supports and : By symmetry, (upward). Horizontal reactions: Since there are no external horizontal loads, the total horizontal reaction is zero. For a symmetric structure, . 2. Global Section Analysis: For any horizontal cut through a symmetric truss under symmetric vertical loading, the total internal shear force across the section must be zero. For a symmetric arrangement of members, this implies that the horizontal components of tension/compression in symmetric pairs of diagonal members must cancel each other out. In many statically determinate symmetric trusses, when the global shear is zero and there is no global moment unbalance in the section, the internal forces in the diagonal "cross" members are zero. ● Final Conclusion: Due to the perfect symmetry of both the structure and the loading, we can identify several zero-force members by inspection or simplified section analysis. (b) Force in member GH,FG,OP,NO FI,FJ,EJ,EK,ER.