........ published in NEWSLETTER # 46
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........ published in NEWSLETTER # 46
RELIABILITY-BASED DESIGN OF ENGINEERED WOOD STRUCTURES
by Professor J. Bodig, Engineering Data Management, Inc., Fort Collins/CO (U.S.A.)
This volume (NATO ASI SERIES E215) contains the proceedings of the NATO Advanced Research Workshop, held in Florence, Italy in June 1991, on Reliability-Based Design (RBD). The volume includes invited and contributed papers as well as the deliberations of four working groups.
Timber represents an important renewable construction material and efficient use of timber products in engineered construction requires the harmonization of design codes used in various countries. The workshop focused on the fundamental methods of reliability and on comparisons of major national and multi-national design codes. The technical issues were divided into four topics:
- Fundamentals of Reliability Assessment
- Reliability Assessment of Multi-Member Structures
- Material Resistance Considerations
- Formulation of Internationally Harmonized Codes
Four working groups, covering the above topics, deliberated on the research and development needs to move toward internationally harmonized RBD codes. In addition to a keynote presentation, for each of the above topics the state-of-the-art was summarized by a speaker. Two supplementary presentations enhanced the range of topics covered. The papers covering all the presentations are part of the proceedings.
It was concluded by the workshop participants that sufficient fundamental knowledge and analytical tools exist to conduct reliability assessments. However, because of the unique mechanical properties of wood, modifications in methodologies are needed to allow for assessment of the true reliability of timber structures.
The participants concluded that special focus needs to be given to the long- term reliability of timber structures, especially as their reliabilities are affected by time-dependent behavior, cyclic environment, and biological degradation. Both strength limit states and serviceability limit states should be considered.
Unified definitions of structural subsystems are needed so that proper mathematical model representations can be assigned to them. In a typical engineered timber structure, components are interacting at several organizational levels. This multi-level interaction makes it difficult to utilize simple reliability assessment methods and, hence, accurate reliability assessments of entire timber structures are not available today.
Material characterization is a critical component of reliability assessment and reliability-based design. A unified approach to the characterization of strength and elastic parameters of wood products is critical for code harmonization. The harmonization must begin with the coordination of various mechanical test methods.
The overall logistics of international code harmonization depends on the acceptance of common nomenclature, glossary, and data collection format. These issues need immediate attention as most countries are in the process of developing or modifying RBD codes.
It was unanimously agreed by the participants that the Workshop represented a very important first step toward the long and extensive effort needed to harmonize RBD codes. The participants suggested follow-up workshops, seminars, and short courses to begin addressing a number of key issues.
Reference books: A210, E5, E70, E215