Lumber Span Length Determination via Mechanical Testing

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Solution Overview

Problem

Current methods for determining appropriate span lengths for lumber in construction are inefficient, as they often require premium lumber to meet design parameters, leading to unnecessary costs and material wastage, as not all locations in a floor system need premium lumber characteristics.

Innovation Solution

A method to determine and convey specific span lengths for individual pieces of lumber based on load type, amount, bending stiffness, and joist spacing, allowing for more efficient allocation and use of lumber by printing a span table directly on the lumber, which includes calculations for structural acceptability and deflection criteria.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If premium lumber is used to meet design parameters, then structural reliability is improved, but material cost increases

Engineering Contradiction:

Improvestructural reliabilityVSAvoidmaterial cost

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by determining span lengths for individual pieces of lumber based on their specific properties rather than treating all lumber uniformly. Each piece receives a customized span length recommendation based on its bending modulus, modulus of elasticity, and other properties, allowing premium characteristics to be applied only where necessary rather than across the entire structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent utilizes parameter changes by measuring specific physical properties of each lumber piece (bending modulus, modulus of elasticity, shear modulus) and using these parameters to calculate appropriate span lengths. This transforms the approach from using premium lumber universally to using precise parameter-based allocation, matching material properties to structural requirements.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If premium lumber is used to meet design parameters, then structural reliability is improved, but material wastage increases

Engineering Contradiction:

Improvestructural reliabilityVSAvoidmaterial wastage

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent determines that not all locations in a floor system require premium lumber characteristics. By calculating specific span lengths for individual pieces based on their properties, the system applies premium characteristics only where structurally necessary, reducing material wastage while maintaining reliability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent performs preliminary determination of span lengths during the lumber processing stage, before the lumber is installed. This allows for efficient allocation and sorting of lumber pieces to appropriate applications, preventing both overuse of premium material and installation errors that would lead to wastage.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If individual piece determination is implemented, then material allocation efficiency is improved, but measurement and calculation complexity increases

Engineering Contradiction:

Improvematerial allocation efficiencyVSAvoidmeasurement and calculation complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent replaces complex manual measurement and calculation processes with automated testing equipment that directly measures lumber properties and computes span lengths. The system uses mechanical and electronic devices to measure bending modulus, modulus of elasticity, and other properties, then automatically calculates appropriate span lengths, reducing the complexity of manual operations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent enables the lumber pieces to essentially determine their own appropriate applications through automated testing and calculation. Each piece is measured, evaluated, and assigned a span length recommendation based on its intrinsic properties, reducing the need for complex external assessment processes.

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables the efficient allocation and use of lumber by providing specific span length recommendations for each piece, ensuring structural adequacy while reducing material costs by identifying only necessary premium lumber requirements.

Implementation Method 1

measuring a bending modulus of the piece of lumber

Methodology Applied

Scientific EffectBending: Deformation

Implementation Method 2

measuring a modulus of elasticity of the piece of lumber

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 3

measuring a shear modulus of the piece of lumber

Methodology Applied

Scientific EffectShear stress: Shear Stress

Data Source

PatentUS7603912B2Method for determining span lengths based on properties of lumber

Publication Date: 2009.10.20 WEYERHAEUSER NR CO

AI summary

Methods for determining appropriate span lengths for a given piece of lumber for use as a joist and conveying that information to a user are provided. The appropriate span length may be a function of load type, amount of load, bending stiffness, joist spacing, or the like. The span lengths may be conveyed via, for example, printing of a table onto the lumber piece itself. A user may then review the table and determine into which applications the lumber may be implemented. Accordingly, the method of the present invention enables more efficient allocation of lumber towards building needs.