Development of finite element method-based model equations for hollow tapered poles.

摘要

This study presents the development of three-parameter load-deflection models for steel and FPP poles commonly used to support closed circuit television cameras. An experimental investigation is carried out to obtain static load-deflection characteristics of tapered octagonal steel cross section and circular FRP cross section poles. Numerical results generated from three-dimensional isoparametric finite element model (FEM) considering coupled nonlinear algorithms for material, geometric, contact, and pretensioning effects are compared with those obtained experimentally. Eight-node elstoplastic solid element is employed to model the pole, end-plate, bolts, concrete base, and laboratory reaction floor. The laboratory reaction floor is modeled with a thick plate having infinite stiffness. The pre-tensioning effect is modeled by using a pre-tension element. A surface-to-surface contact algorithm is used to simulate the interaction between contact surfaces of bolt head, shank, and nut with end-plate and bolt holes. Newton-Raphson scheme is used in the nonlinear regime, and convergence is checked using Hilbert L-2 norm and energy-based convergence.; A parametric study is conducted to verify the validity of the FEM and the analysis algorithms by observing the effects of the geometric and force-related variables, one at the time, on the load-deflection characteristics of the poles. The three parameter power model is selected to mathematically model the load-deflection of the hollow poles. For this, two matrices of test cases are developed for steel and FRP poles by varying their geometric and force-related variables within their practical ranges. The load-deflection plots obtain from the FEM analysis of the aforementioned test case are fitted to the three-parameter power model and the three parameters of ultimate load, reference plastic deflection, and rigidity parameter are determined. Nonlinear regression analyses are conducted to obtain prediction equations for the parameters of the three-parameter power model in terms of the pole's geometric variables. To obtain a reasonable value for coefficient of multiple determination, R2, for the rigidity parameter, a "characteristic load" concept is proposed. The predicted load deflection plots are compared with these of experiments and FEM results. Error band and sensitivity analyses are conducted to check equations' accuracy and parameter sensitivity, respectively.