(32b) Risk-Based Approach to Building Designs and Decision Making

Accidental releases of flammable and toxic materials from hazard sources of different sizes ranging from small leaks to full-bore pipe ruptures can represent a wide range of impacts to buildings.  Facility siting for petrochemical and chemical plants is required to cover credible accident scenarios.  Results of such studies often include catastrophic consequences that may be impractical to eliminate through structural designs.  Rather than designing buildings for a high level of protection against the most severe credible events, a risk-based approach provides a practical and a cost effective approach to maximize safety.

Two fundamental principles are required to be met for a design to qualify as “Risk-Based”.  One principle is that each occupant of the building is safe.  This principle is achieved by designing the building in such a way that each occupant’s individual risk is within defined tolerance criteria.  The other principle is that the building is designed in a way such that it reduces risk to a level that is as low as practical.  This principle is achieved by comparing costs of enhanced designs against the safety benefit they afford and implementing as much mitigation as is practical.  Employing these fundamental principles ensures that safety is optimized, allowing risk mitigation resources to be optimized.

This paper outlines a methodology to perform a risk-based building design, accounting for predicted impacts of a wide range of credible accidents, associated frequencies, and building occupancy.  The necessary input data for this type of design is calculated in a Quantitative Risk Assessment.  The proposed methodology will help designers establish practical structural requirements to minimize risk while achieving cost effective designs.