ASTM D6555-23 PDF

Overview

ASTM D6555-23: Standard Guide for Evaluating System Effects in Repetitive-Member Wood Assemblies provides guidance for assessing the performance of repetitive-member wood assemblies utilized in parallel framing systems. This standard identifies key variables, defines essential terminology, and discusses approaches for quantifying assembly adjustment, focusing on system effects such as load sharing, composite action, and residual capacity. While not a test method or modeling guideline, it assists engineers, designers, and standards developers in understanding the factors that influence the strength and stiffness of wood assemblies beyond those of individual members. The guide forms part of ASTM’s suite of standards aimed at the evaluation and use of structural wood products.

Key Topics

System Effects in Repetitive-Member Assemblies

• Load Sharing: Distribution of applied loads among adjacent, parallel members, often resulting in increased apparent strength and stiffness.
• Composite Action: Increased effectiveness when two or more wood members are connected, raising the performance above individual member capabilities.
• Residual Capacity: Additional strength provided by the assembly after the first member failure, often due to system redundancy and interconnections.

Variables Affecting Performance

• Loading conditions and load magnitude
• Member span, spacing, end and support conditions
• Stiffness and connection type of members and load-distributing elements (e.g., sheathing, decking)
• Sheathing gaps and their position
• Number of assembly members and level of bracing
• Material property variability and correlation (e.g., stiffness and strength)
• System configuration and structural redundancy

Evaluation Approaches

• Quantification Methods: Based on mechanical analysis and statistical evaluation. Do not detail specific testing or modeling techniques, but emphasize the importance of both analytical and confirmation test data.
• Limitations: Excludes creep effects and does not establish safety levels, instead highlighting the need for higher safety margins in assemblies compared to individual members.
• Default System Factors: Provides system strength factors, but recommends rigorous analysis and testing as the primary basis for design adjustments.

Applications

ASTM D6555-23 is widely used across the wood construction industry to:

• Guide design stress adjustments for assemblies such as joists, studs, rafters, trusses, and decking in residential and commercial buildings.
• Inform engineering evaluations and code compliance for parallel framing wood systems.
• Support standards and product specification development for engineered and traditional wood construction.
• Establish a consistent terminology and evaluation framework for system effects in repetitive-member assemblies, enhancing interoperability between engineering design practices and regulatory standards.

By understanding and applying the principles outlined in this guide, structural engineers and designers can account for factors that enhance the performance of wood assemblies, leading to safer, more efficient, and cost-effective construction. This guide is especially relevant when justifying design adjustments based on system effects, and when specifying assemblies in compliance with national and international building codes.

Related Standards

To ensure comprehensive evaluation and use of repetitive-member wood assemblies, ASTM D6555-23 is commonly used in conjunction with:

• ASTM D245: Practice for Establishing Structural Grades and Related Allowable Properties for Visually Graded Lumber
• ASTM D1990: Practice for Establishing Allowable Properties for Visually-Graded Dimension Lumber from In-Grade Tests of Full-Size Specimens
• ASTM D2915: Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based Products
• ASTM D5055: Specification for Establishing and Monitoring Structural Capacities of Prefabricated Wood I-Joists
• ANSI/AWC NDS: National Design Specification for Wood Construction
• ANSI/TPI 1: National Design Standard for Metal Plate Connected Wood Truss Construction
• ASCE/SEI 7: Minimum Design Loads and Associated Criteria for Buildings and Other Structures

These standards together facilitate robust assessment, design, and documentation of repetitive-member wood assemblies, ensuring structural wood systems meet performance, safety, and durability criteria required in today’s construction industry.

Keywords: repetitive members, wood assemblies, system effects, load sharing, composite action, residual capacity, wood construction standards, ASTM D6555-23.