[EN1992-1-1] This guide explains how to calculate the critical slenderness limit, which determines whether second-order effects can be neglected in the structural analysis of a member. If the slenderness of a member is below this critical limit, second-order effects, such as buckling and geometric non-linearity, can be ignored, simplifying the design process. The calculation is based on an empirical formula provided in Eurocode, which accounts for factors like member shape, boundary conditions, and axial force. In this guide, default values are used for the mechanical reinforcement ratio or the effective creep ratio when these ratios are unknown, simplifying the calculation process.

This table outlines different design situations, categorized into persistent, transient, and accidental conditions. Each category represents a specific scenario that may affect the design and safety considerations of a structure.

Design situations

Compressive strength classes categorize concrete based on its compressive strength, typically indicated by a standard notation such as C30/37, where the first number represents the cylinder strength and the second the cube strength. For more detailed information, refer toEN 206-1 (Table 7).

Compressive strength classes

The concrete cross-sectional area represents the total area of the concrete member's cross-section, typically measured in square millimeters. It is used in various structural calculations, including determining the notional size of the member for creep and shrinkage analysis.

Concrete cross-sectional area

This represents the first-order moment acting at the bottom end of the structural member. The user is expected to input the value of the moment applied to the bottom of the member, which will be used to determine the smaller and larger moments in subsequent calculations.

Moment acting at bottom

This represents the first-order moment acting at the top end of the structural member. The user is expected to input the value of the moment applied to the top of the member, which will be used to determine the smaller and larger moments in subsequent calculations.

Moment acting at top

The design axial load represents the design value of the axial force acting along the axis of a structural member. It accounts for all relevant loads, such as dead and live loads, and is used to ensure the member can safely resist compression or tension forces.

Design value of the applied axial force

This option allows you to choose how to input the A, B, and C coefficients needed to calculate the critical slenderness limit. You can either calculate the coefficients using formulas or use suggested values if certain required ratios are unknown.