ISO 22111:2019— Safe Structural Design

Whether it is an office tower swaying imperceptibly in the wind, a bridge carrying thousands of vehicles every hour, or a stadium roof spanning hundreds of feet above cheering crowds, a structure must safely withstand forces throughout its service life. Each structure is constantly responding to changing loads, shifting temperatures, strong winds, and the gradual effects of time. By specifying the procedures for the structural design of buildings and civil engineering works, ISO 22111:2019—Bases for design of structures – General requirements enables safe performance.

Designing Safe Structures for a Growing Urban Population

Today, 55% of the world’s population lives in urban areas—a proportion that is expected to increase to 68% by 2050. Assuring that today’s structures remain safe and resilient require more than strong materials; it requires a consistent, reliability-based approach to structural design. ISO 22111:2019 provides that foundation by establishing standardized methods that help engineers account for uncertainty while achieving consistent levels of structural reliability.

What Is ISO 22111:2019?

ISO 22111:2019 establishes the general requirements for structural design using a semi-probabilistic limit approach to help engineers achieve consistent levels of structural reliability. Building on the principles of ISO 2394:2015, the international standard provides a framework for developing design values and verifying structural performance for conventional structures where established engineering knowledge and construction practices exist.

ISO 22111:2019 also emphasizes the importance of accounting for uncertainties in materials, loads, and analytical models to assure structures can reliably withstand the demands placed upon them throughout their service life.

Understanding the Semi-Probabilistic Approach

One of the key concepts within ISO 22111:2019 is the use of a semi-probabilistic design method (often referred to as Load and Resistance Factor Design [LRFD] or the partial safety factor method). Instead of attempting to predict every uncertainty exactly, engineers apply partial safety factors that provide appropriate margins of safety while maintaining economical designs. By considering a range of loads—including dead, live, wind, snow, and seismic forces—LRFD helps engineers achieve consistent, reliability-based designs while maintaining an acceptably low probability of structural failure.

Semi-probabilistic design has become the basis for many modern engineering codes and standards worldwide as it provides a consistent, reliability-based approach to structural design.

Building Confidence Through Proven Design Principles

When designing commercial buildings, industrial facilities, transportation infrastructure, or public venues, engineers must make decisions that balance safety, performance, and efficiency. ISO 22111:2019 provides a practical framework for achieving this balance through standardized reliability-based design methods. By accounting for uncertainty, applying semi-probabilistic limit state principles, and supporting consistent engineering practices, the international standard helps designers create structures capable of performing safely throughout their intended service lives.