Power Transmission Tower Angli Iron Bar Critical Load Of Compressive Member

In this thesis, an introduction was made on the types and structural properties of power transmission steel towers. Specific loads acting on these structures were also discussed. Then the theory of stability and critical load calculation procedures were investigated. The actual ultimate compressive capacity of the angle irons in a transmission tower structure could be found through nonlinear structural analysis according to theory of compressive member stability. This problem can hardly be solved analytically. However, there are numerical methods to get the answer. In this thesis the critical loads for members with different structural considerations were calculated numerically with FEM software ANSYS. According to "Technical Specifications for Power Transmission Towers" (DL/T5154-2002), six types of load and boundary conditions were investigated, they were: perfectly centered compression at both ends, eccentricity at one end, eccentricity at both ends, rotation constrain at one end, both ends and none. Also included in the analysis was the consideration of initial imperfection of the members, such as initial deflection, residual stress, imperfect centered loading, manufacture imperfection and workmanship.It is concluded from the results that the geometrical imperfection of the cross section has most influence on the compression critical loads. However, this factor is not taken much into account in current Codes and Specifications.For members free of rotation at both ends, two most weakening factors of the members were combined and the values calculated. By applying the critical loads to Perry formula, coefficient a was found as a function of slenderness ratio X . Then could also be represented as a function of λ(w=w (λ) ).For the rotation constrained cases (constrained at one end or both ends), was obtained by the amendment of slenderness ratio as k λ .The comparison of the results revealed that the curve of value obtained from the study showed about -2% ~ 22% discrepancy from the curve in the "Code for Design of Steel Structures" and -19.1% - 4.8% from "Technical Specifications for Power Transmission Towers". The final results lay between those indicated by thetwo specifications.