Timber I-Joist Web Embedding for Splitting Resistance

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Solution Overview

Problem

Timber structural members, such as I-joists, are prone to splitting or cracking under high loads due to imperfections in solid wood lumber and inadequate end grain connections in engineered wood composites, leading to potential catastrophic failure and design hindrances from metal braces that oxidize and collapse in fires.

Innovation Solution

A timber joist design featuring flanges connected by a web that extends at least 20% of the flange's diameter, providing enhanced structural integrity and resistance to splitting, with a dowel connection system that secures loads internally and protects against fire by encasing metal components within timber.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If solid wood lumber is used for flanges, then natural strength and load bearing capability are improved, but splitting and cracking occur under high loads due to imperfections and grain structures

Engineering Contradiction:

Improveload bearing capabilityVSAvoidresistance to splitting and cracking

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent uses composite construction by bonding a web member to flange members made from solid wood lumber. This composite structure combines the strength of solid wood with the stability of the bonded web, creating a unified I-joist that resists splitting and cracking while maintaining load bearing capability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The flange members are segmented into multiple layers or components that are bonded together with the web. This segmentation allows each component to perform its specific function while the bonded connections prevent splitting and cracking from propagating through the entire structure.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If engineered wood composites are used for flanges, then cost and lack of natural defects are improved, but end grain connection effectiveness deteriorates requiring metal braces that oxidize and collapse in fires

Engineering Contradiction:

Improvemanufacturing cost and material consistencyVSAvoidfire resistance and oxidation of metal braces

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent extracts and eliminates the need for metal braces by using a timber web member that extends into the flanges and is bonded securely. This web member provides the necessary connection and structural support without requiring additional metal components that would oxidize and collapse in fires.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces expensive and fire-vulnerable metal braces with a timber web member that is part of the integrated I-joist structure. The timber web member is less expensive, does not oxidize, and maintains structural integrity in fire conditions, effectively replacing the need for separate metal bracing components.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If web member is embedded deeply into flanges, then resistance to splitting and cracking is improved, but manufacturing complexity and processing difficulty increase

Engineering Contradiction:

Improveresistance to splitting and crackingVSAvoidmanufacturing complexity of web embedding

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The web member is pre-cut to the correct dimensions and shaped before being bonded to the flange members. This preliminary preparation simplifies the overall manufacturing process by ensuring the web member can be easily embedded and bonded without requiring complex on-site processing or adjustment.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9605431B2Timber structural member with embedded web

Publication Date: 2017.03.28 LOGGO IP PTY LTD IN ITS CAPACITY AS TRUSTEE FOR THORNTON IP TRUST

AI summary

A timber joist is provided, which includes first and second flanges connected together by a web, the web being structurally integral with the flanges. Both flanges comprise timber poles. The web inserts into the first and second flanges a sufficient distance so as to provide resistance to longitudinal splitting or cracking of the timber.