Design and analysis of recycled content sign blanks

Abstract

This report documents a study of the feasibility of using sign blanks constructed of reclaimed materials instead of conventional high-grade plywood and aluminum. This study presents the engineering techniques necessary for judicious use of recycled materials in roadside sign applications. Various types of recycled materials were solicited from commercial manufacturers and subjected to an array of laboratory tests and numerical simulations. Materials that were received were manufactured from a variety of materials including high density polyethylene (HDPE), polycarbonate, polyvinyl chloride, and calcium carbonate. This study encompasses analysis, performance, and properties of tested materials. A total of seven recycled materials were tested in flexure, uni-axial tension, creep, free vibration, and exposure to ultraviolet radiation. Corollaries of this study are development of performance-based specifications and a new design procedure for sign blanks. A preliminary design procedure is developed for two-pole supported and tee-pole supported sign substrates. The procedure is based on simple mechanics of materials bending formulae for a variety of deflection criteria. Design environmental loads are determined using ASCE 7-95 Minimum Design Loadsfor Buildings and Other Structures. A design example for a two-pole sign is performed for one of the recycled materials collected during the study. Adequacy of the preliminary design is checked using a finite element model of the structure in conjunction with a set of performance-based specifications. In addition, a combined laboratory and numerical procedure for duplicating wind induced vibrations is developed using a frequency domain-based method. Numerical simulation of a wind loading is carried out using two dynamic wind events. The response of several locations on the sign are recorded and converted to the frequency domain using fast Fourier transform. Simultaneously, a full-scale laboratory model is constructed and an electromechanical actuator is connected to the supporting structure. The laboratory structure is struck at the actuator connection with the same impact hammer used to analyze the field model. From a complex frequency response function an actuator time history is produced that elicits a structural response at a particular node that closely approximates the response obtained by finite element analysis. This procedure is capable of modeling dynamic response in the substrate to nearly any dynamic wind event, including impulse events caused by large highway vehicles. A brief listing of estimated cost for some of the recycled materials that were tested in the laboratory is included for quantities varying by order of magnitude from 1,000 to 1,000,000 sheets.