ISO 3898:2013

Overview

ISO 3898:2013 - Bases for design of structures - defines standardized names, symbols and units for physical and generic quantities used in the design of structures. It provides a compact set of kernels (single-letter quantity symbols), systematic rules for composing compound symbols, and guidance on units following the SI conventions. The standard introduces the kernel‑index‑method (KIM) to create unique, readable symbols for quantities that are specific to a material, action, location, limit state or design method.

Key Topics

• Kernel‑Index‑Method (KIM): A formal method to form compound symbols by combining a one‑letter kernel (italic) with descriptive indices/subscripts (Roman). Enables clear naming of particular physical quantities in structural design.
• Symbol formatting rules: Kernels are single‑letter (Latin or Greek) in italic; indices are Roman (letters, digits or graphical symbols) and placed as subscripts/superscripts. Compound symbols are written without a final full stop.
• Index ordering and semantics: Multiple indices are ordered right-to-left into categories (probabilistic/partial factors; limit‑state type; descriptive aspects; basic variables/performance functionals; place/direction; material type). Examples in the standard include rep, nom, k, d (characteristic/design), u/ser (limit states), and material indices like c (concrete).
• Units and SI compliance: Unit names and symbols conform to the SI and ISO 80000 series. Unit symbols are upright Roman type, placed after numeric values with a space (e.g., F = 10.8 kN). Compound unit notation and use of prefix forms (e.g., MPa, mm) follow SI rules.
• Precautions and conventions: Guidance to avoid ambiguous symbols (e.g., use L or ℓ instead of l; avoid Latin O as main symbol; restrictions on certain Greek letters).

Applications

• Structural engineering documentation, calculation reports and design codes where unambiguous naming of loads, resistances, actions and responses is essential.
• Development of design standards, Eurocodes, technical specifications, and calibration of software for structural analysis, BIM and finite element models.
• Teaching, research and interdisciplinary communication where consistent units and symbol composition reduce errors and improve traceability.
• Useful for standards writers, structural engineers, academic authors, software developers and safety regulators who require standardized nomenclature in design-of-structures contexts.

Related Standards

• ISO 80000 series (Quantities and units - Parts 1, 2, 3, 4)
• ISO/IEC Guide 99 (VIM - International vocabulary of metrology / physical quantities)
• ISO 10241 (for term and definition formatting)

ISO 3898:2013 is therefore a practical reference for anyone needing consistent, unambiguous symbols, names and SI unit usage in structural design and allied documentation.