The design of pole-type structures for highway supports requires computation of second-order effects induced by the interaction of vertical gravitational and transverse wind loads. The 1994 Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals provides two methods to account for those second-order effects. The first method uses a simplified approach by introducing a factor, CA, into the combined stress ratio equation. The second method requires the computation of the exact bending stresses by means of a nonlinear analysis. Most structural design codes specify simplified methods for the evaluation of second-order effects to facilitate the design of structural members by using the forces obtained in a first-order static analysis. Therefore, simplified methods must be accurate to be considered an adequate alternative to a more sophisticated analysis. The purpose of this study was to determine the accuracy of the simplified method by using the CA factor to estimate the second-order effects for pole-type structures. An analytical study that included 241 pole configurations was conducted to evaluate the CA factor. Exact solutions were computed by using a computer program capable of performing second-order analysis. The study indicated that for typical pole-type structures, the results obtained with the CA factor were highly conservative. On the basis of the results, a modified expression for the CA factor is proposed. Results obtained by use of the modified expression for the CA factor were within 10 percent of those obtained by use of the “exact” nonlinear analysis.
Nonlinear Sum Operator Equations with a Parameter and Application to Second-Order Three-Point BVPs