Composites Growth Initiative

By John Busel

Growing Legs: Standards & Specifications
The newly published 2007 National Electric Safety Code (NESC) has elevated the use of composites for products in the electrical utility market such as insulators, poles, and crossarms. It all comes down to the design approach and how composites strength factors are used compared with other materials such as wood, steel, and concrete. New to the code will be that composites can be designed with the same strength factors as structures made from steel and pre-stressed concrete. This design factor recognizes the fact that composites are manufactured with much lower coefficients of variation in structural properties than wood, giving more confidence for in-field performance especially when subjected to sustained loads. This change in the code reflects a major milestone to the acceptance of composites in a market where FRP composite utility structures have been successfully used for over more than years. No longer will composites be compared with the lower strength factors used for wood products.

Electrical Utility Poles
Engineers and utilities want long-term solutions that are aesthetically pleasing for today’s environment. Now that composites have reached a new level in the code, there is a need to provide a consistent design methodology for FRP composites used in distribution and transmission pole and crossarm structures that the utility industry can use in the design and analysis of these structures. Design methodologies for steel and pre-stressed concrete structures already exist.

In 1997 the first steps were taken by American Society of Civil Engineers (ASCE) to develop a Manual of Practice as a reference for utilities wanting to use FRP utility structures, poles and crossarms. This document, ASCE 104, Recommended Practice for Fiber-Reinforced Composite Products for Overhead Utility Line Structures, First Edition, provided the utility industry with this basic guidance. Under the chairmanship of Dr. Habib Dagher from the University of Maine, ASCE Manual No. 111, Reliability-Based Design of Utility Pole Structures went a step further and introduced the concept of designing FRP utility structures using reliability-based LRFD concepts.

The American Society of Civil Engineers just recently approved the creation of a new committee under the Structural Division called “Task Committee on FRP Utility Structures” whose parent committee is the “Committee on Electrical Transmission Structures.” The objective of this Task Committee is to write a Manual of Engineering Practice entitled, Design of Fiber-Reinforced Composite Products for Overhead Utility Line Structures which will outline a methodology to analyze, design, and test FRP utility poles, Crossarms and other similar structures. The committee officers are: Chairman, Dr. James W. Davidson (formally with Shakespeare); V-Chair, Brian Lacoursiere, RS Technologies, and Secretary, Danny Lonergan, Creative Pultrusions.

It is expected to take three years to develop the proposed guide specification. Developing it will be difficult as there are different manufacturing methods (i.e. pultrusion, filament winding, molding) and materials that are used to make the poles, crossarms, and related assemblies. The diversity of how composites are made is in sharp contrast to other materials such as steel and prestressed concrete.

Composites and Concrete
The American Concrete Institute’s (ACI) 440 Committee on FRP reinforcement continues to be very active with producing reports and guide specifications on FRP composites for the concrete industry. Here is a summary of the committee’s activities:

• Durability: One of the design issues of concern is the consideration of overall durability of FRP materials, especially when subjected to the harsh environmental conditions of concrete structures. Since FRP composites are still relatively new to the practicing engineer, predicting the life of structures has been a testimonial of faith by the civil engineer with FRP materials. The committee is creating the first document of its kind related to durability and concrete. The report, “Durability of Fiber Reinforced Polymer (FRP) Composites Used With Concrete” is intended to provide guidance to structural engineers regarding durability of FRP composites used in concrete, including rebar, tendons, and external strengthening systems. This report compiles the worldwide state of knowledge in this area. This is a significant piece of work that many other markets would be able to reference.
• Repair: The committee is executing a major revision to the current ACI 440.2R-02 guide, including more updated information compiled by the task groups of this committee. A new design approach will be introduced that supports the current version of the building code, ACI 318-05.
• Internal Reinforcement – Rebar: A new task group has been created to develop two new documents: Material Specifications and Construction Specifications for FRP bars. These important specifications will complement the design guide ACI 440.1R-06 that provides a complete package of reference guides for the structural engineer, thereby increasing the acceptance and specification of FRP rebar.
• Material Characterization: The subcommittee is focusing its attention on refining laminate tension, lap shear, and bar creep test methods. The laminate test methods on simple tension and lap shear are being converted to ASTM language and will be balloted later in calendar year 2006. The bar creep rupture test method is being converted to ASTM language for balloting in 2006 as well. The ballots will be carried out as part of the ASTM D30 and D30.05 balloting system, and interested persons are encouraged to join D30 and D30.05 to participate in the process.

The work of Committee 440 continues to provide engineers and designers with tools to design and specify composites used in concrete. Each of these documents represents an extraordinary amount of volunteer work and help advances the state of the practice in emerging market applications. Without the motivation and the willingness to work together as a team between industry, academia, government agencies, regulatory, and the end-user, this committee could not be successful. Creating codes, standards, and specifications is a team effort and requires the expertise of many individuals. The composites industry has benefited from the work of this committee.

John P. Busel is director of the Composites Growth Initiative. He has over 24 years experience in the composites industry in design, tool engineering, manufacturing engineering, research and development and industry market development. He is Chairman of Committee 440 and participates in many standards committees representing the composites industry.