CLT Design Software for AS1720.1 | Engineering Platform

Universal Supplier & Code Integration

Effective floor design begins with the CLT supplier. Our platform allows you to toggle seamlessly between local and international data:

• Australian Standards: Automatically apply AS1720.1 modification factors such as k1, k4, and k6 for local products like XLam and NeXTimber.

• Eurocode Compliance: For European suppliers like KLH or Binderholz, the platform applies Eurocode 5 factors including kmod and γm, ensuring the right approach for imported CLT.

Analytical Methods for CLT Stiffness

• The Gamma Method: Best for standard, uniform CLT panels with 3, 5, or 7 layers. It accounts for the rolling shear deformation in the cross-layers by using a simplified efficiency factor.

• The Extended Gamma Method: Our recommended method for thick panels (7-ply and above) or non-uniform layups. It provides a more refined calculation of effective stiffness by accounting for the rolling shear stiffness of every individual cross-layer, preventing overly conservative designs.

• The Shear Analogy Method: The most rigorous analytical approach, suitable for highly complex or asymmetric layups. It treats the panel as a composite beam with distinct bending and shear stiffness components, providing the highest level of accuracy for all layup configurations.

High-Performance Vibration Design

Vibration is often the governing serviceability limit state for CLT floors. We have included the latest Eurocode drafts to provide a superior design outcome:

• Support Conditions: Model realistic scenarios including stiff or flexible supports to accurately predict floor behavior.

• Performance Levels: Specify target performance levels to meet specific building requirements, moving beyond simple frequency checks to holistic occupant comfort.

This calculator goes beyond simple static deflection. The tool analyzes the Fundamental Frequency (f1) and Impulsive Velocity Response, allowing you to tune the floor mass and stiffness to meet strict vibration criteria (e.g., 8Hz for offices), ensuring the “feel” of the floor matches the quality of the building.

Advanced CLT Fire Engineering

Structural fire design for mass timber is a critical component of any NCC 2025 Performance Solution.

SPEC Toolbox simplifies this complexity by offering multiple verification pathways aiding engineering judgement, ranging from the widely adopted ÖNORM B EN 1995-1-2:2011 (Austrian National Annex) to the cutting-edge prEN1995-1-2:2023 (2nd Generation Eurocode). Whether you are utilizing a standard fire curve or a physically based fire model, the platform calculates precise charring depths and residual load-bearing capacities, helping your CLT panels meet stringent safety and integrity requirements.

Precision Charring & Bond-Line Integrity

Our engine accounts for the sophisticated physics of timber charring, moving beyond simple uniform rates. You can define the basic charring rate based on timber density and moisture content, and the platform automatically applies relevant ki factors to determine notional rates. Crucially, our 2nd Generation Eurocode module explicitly models bond-line integrity and gap effects, preventing the catastrophic loss of protection often ignored in simplified calculations.

Automated Factor Analysis for Performance Solutions

To provide total engineering transparency, SPEC Toolbox enables granular control over charring variables. The platform automates the calculation of Char Factors, including the GAP coefficient and specific k2, k3, and kg values required for layered protection systems. This “No Black Box” approach allows engineers to either use code-specific defaults or bypass them with manual inputs from manufacturer fire tests, creating a verified path from first principles to project certification.

1. Moving Beyond AS1720.1 Limitations

While AS1720.1 is the current Australian standard, it is widely recognized as having limitations regarding modern mass timber connections.

• Advanced Yield Modeling: SPEC Toolbox utilizes the latest Eurocode methodologies, including the Johansen Yield Models, to provide more accurate and appropriate design outcomes than simplified local methods.

• ETA Integration: We integrate supplier-specific European Technical Assessments (ETAs), ensuring your designs utilize ultimate performance data unique to specific product families.

2. Simplified Screw & Joint Design

Our platform transforms complex connection math into a streamlined, high-speed workflow:

• Preconfigured Joint Types: Rapidly design and verify Half Laps, Splines, and Butt Joints with automated geometry checks.

• Steel-to-CLT: Specialized modules for timber-to-steel connections, handling the complex stress distributions at the interface.

3. The “Global-Local” Connection Library

SPEC Toolbox is the only platform that allows you to pair your choice of CLT Supplier with the world’s leading Connection Manufacturers:

• Universal Fastener Selection: Choose from top-tier brands including Rothoblaas, Spax, Eurotec, Sihga, Klimas, Simpson Strong-Tie, or Anzor.

• Verified Compatibility: Seamlessly verify these fasteners against local and European panels like XLam, NeXTimber, or Red Stag.

In-plane CLT Design

ProHolz vol 1 Clause 5.8

ProHolz identifies three failure mechanisms for CLT shear walls:

• Mechanism 1: Shearing of failure of the boards along a joint
• Mechanism 2: Shearing failure of the glued surface at the intersection of joints.
• Mechanism 3: Shearing failure of the entire plate.

FP innovation Clause 3.8

By considering the shear stresses in the lamellas and the crossing areas, three different failure modes exist in CLT beams subjected to shear stresses such as

• Failure Mode I: Shear failure parallel to the grain in the gross cross-section
• Failure Mode II: Shear failure perpendicular to the grain in the net cross-section
• Failure Mode III: Shear failure in crossing area of orthogonal lamination

Wall Connection Models

In summary of the methods that are used to determine the capacity of the CLT shear wall at the connection points include:

Methods	Summary
Method I, Casagrande et al. 2016	Analyzes shear walls using rigid body rotation and static equilibrium, with the rotation point at the panel edge, focusing on internal force balance.
Method II, Wallner-Novak et al. 2014	Uses a simplified rectangular stress block and accounts for frictional resistance, providing a more detailed approach to sliding resistance.
Method III, Tomasi, 2014	Similar to Wallner-Novak but with different compression zone length and assumes an extremely stiff foundation with a refined neutral axis calculation.
Method IV, Pei et al. 2012	Treats the CLT panel as a rigid body rotating around a corner with connectors modeled as elastic springs, relying on back-calibrated connection resistance and excluding sliding resistance from the analysis.
Method V, Reynolds et al. 2017	Enhances the triangular tensile distribution method by including a compression zone and factoring in friction to improve sliding resistance evaluation.

If you’re looking to design CLT on your next project, then SPEC Toolbox has you covered!