This calculator allows the user to assess the structural integrity of timber columns to ensure compliance with the Australian Standard AS 1720.1:2010. The calculation will identify the design capacities of timber columns to meet flexural, shear and deflection design requirements to Ultimate Limit State (ULS) and Serviceability Limit State (SLS) methods.
❗This calculation has been written in accordance with AS 1720.
Seasoned or unseasoned
Type of timber material
Application of structural member
Characteristic strength in bending (f'b)
Compression strength parallel to grain (f'c)
Tension strength parallel to grain (f't)
Tension strength perpendicular to grain (f'tp)
Bearing strength parallel to grain (f'l)
Bearing strength perpendicular to grain (f'p)
Shear strength at joint details (f'sj)
Section and Member Geometry
Design density (kg/m3)
Gross cross-sectional area (Ag)
Section modulus (Z)
Moment of inertia, Ixx (mm4)
Modification Factor details
Australian Standards set out guidelines and minimum requirements for material properties, design parameters, design procedures and calculation methods. Here, we explain some pertinent timber properties that should be considered carefully when undertaking timber design calculations.
🎓 Stress Grade
Design Properties of Structural Timber Elements
Design capacities for all structural timbers are obtained by modifying characteristic capacities with factors appropriate to service conditions and material property type. This process applies to all types of timber.
Member Design Capacity
Characteristic values (f'o)
Capacity Factor (ϕ)
Geometric Properties (X)
Modification Factors (kmod)
Checking Limit States
AS1720.1 provides guidelines for Ultimate Limit State (ULS) design. The calculation methods for design forces and capacities of structural timber members, joints and fasteners are robust enough to account for different scenarios and environmental factors. According to AS1720 Clause 2.1.2 and 2.1.3, the design capacities of members and joints must satisfy the following (right).
Permissible allowable stress limits or design limit c
apacities of timber columns are then calculated for each check by multiplying the relevant characteristic properties, modification factors and geometric properties together:
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