14 Pages

New materials

ABSTRACT: For decades, metallic and reinforced concrete poles have been used to support lighting fixtures and traffic signs as well as power and communications lines. Nevertheless, corrosion has been a major problem to the structural integrity and architectural appearance for both metallic and concrete poles. Moreover, the collapse of poles due to corrosion jeopardizes the safety of people, traveling vehicles and nearby properties. Therefore, poles made of Fiber Reinforced Polymers (FRP) are becoming favorable candidates to replace the conventional ones because of their non-corrosive nature, high strength and light weight. Not only are the structural and durability characteristics of FRP poles unique but also their architectural and decorative features. They can be produced in different shapes, colors and textures. Special profiles are also feasible through the molding process of the product. However, regardless the construction material for light poles, related research programs are rarely dedicated to other than fatigue and crash analysis. Furthermore, most of the conducted research work adopts a fixed base approach for both static and dynamic analysis of light poles. While wind and impact loads applied on a free-standing cantilever may represent a light pole anchored directly to a footing buried in the ground on the side of a highway, the scenario can be quite different for light poles anchored to a structure subject to seismic loads. The study presented herein investigates the dynamic behavior of different types of light poles (steel, concrete and FRP) anchored to a bridge deck at different locations as well as anchored to footings. The bridge is located in one of the highest seismic zones of South America and its deck is supported by, specially designed, nonlinear friction/spring type of seismic isolation bearings. A three dimensional Finite Element Model (3D-FEM) has been developed for both bridge and poles including the details of the pole base connection and anchorage assembly. Modal analysis as well as non-linear time history analysis have been performed. Based on the conducted analysis, the minimum anchorage forces due to seismic loads are associated with the FRP poles where their light weight constitutes a dominant parameter in their dynamic behavior. Also, under seismic loads there is a significant difference in the anchorage straining actions between the poles anchored to footings and those anchored to the bridge deck. In addition, the magnitude and direction of such straining actions for the poles anchored to the bridge deck depend on the pole location on the deck as well as the direction of the seismic excitation.