Structural Response in Facility Siting: Evaluating Building Resilience to Blast Loads and Overpressure
Industrial sites handling hazardous materials such as flammable, explosive, and toxic substances require Facility Siting Studies (FSS) to examine the placement of buildings relative to potential risks. One important aspect of FSS is Structural Response Analysis, which evaluates how buildings and personnel inside them would react to overpressure, thermal radiation, and toxic exposure resulting from accidental releases.
Industry standards like API 752 and API 753 outline methodologies to determine whether buildings, portable structures, and other critical infrastructure can withstand hazardous events. This blog focuses on structural response analysis, using techniques such as Pressure-Impulse (P&I) curves, Finite Element Analysis (FEA), and blast load studies. For a broader discussion on Facility Siting Studies, hazard modeling, and consequence-based studies, read our first blog: What is a Facility Siting Study? A Guide to Compliance with OSHA 29 CFR 1910.119
This post covers:
- Introduction to Structural Response in FSS
- Structural Response Methodologies
- Building Impact Assessment
- Risk-Based Facility Siting Study
- Structural Assessment of Facility Components
- Key Takeaways
Facility Siting Studies (FSS) evaluates exposure across an industrial site, but structural response analysis focuses on how buildings react to these hazards. This includes:
- Overpressure from explosions
- Thermal radiation from fires
- Toxic gas dispersion and exposure
API 752 and API 753 provide guidelines for assessing structural resilience in hazardous environments. The goal is to determine if buildings need reinforcement, shielding, or relocation based on exposure to these risks.
Structural Response Methodologies
1. Pressure-Impulse (P&I) Curves
- Used for preliminary building analysis.
- Helps determine whether structures are within acceptable damage thresholds.
- Categorizes buildings based on expected overpressure levels.
2. Finite Element Analysis (FEA)
- Provides detailed structural evaluations using computational models.
- Identifies areas of high stress when buildings are subjected to overpressure events.
- Used when further investigation is required after P&I curve analysis.
3. Blast Load Assessment
- Predicts the effects of explosion-induced pressure waves on structures.
- Helps recognize the need for additional reinforcements to withstand blast forces.
4. Thermal Radiation Exposure Analysis
- Determines whether fire-resistant materials or heat shields are required.
- Establishes safe distances for buildings from potential fire hazards.
Building Impact Assessment
Buildings within an industrial site experience varying levels of exposure to threats. A structured approach is required to understand how different types of structures react to these challenges. This includes:
Permanent Buildings
- Reviewed using P&I curves and FEA simulations.
- Structural modifications may be necessary depending on results related to overpressure and thermal load.
Portable Structures
- Comprehensive analysis using P&I curves and FEA simulations.
- Reviewed in accordance with API 753 guidelines for building classification based on proximity to hazardous operations.
- May need relocation or blast-resistant modifications if exposure levels exceed limits.
- May need relocation or blast-resistant modifications if exposure levels exceed limits.
Control Rooms and Occupied Buildings
- Inspection of overpressure resistance, thermal shielding, and protection from toxic gas exposure.
- Reinforcements or blast-resistant construction are often required for buildings housing personnel and critical operations.
Risk-Based Facility Siting Study
A risk-based FSS integrates probability analysis with consequence modeling to offer a more comprehensive analysis of potential impacts.
Key Steps in Risk-Based Structural Assessment:
- Scenario Definition: Identifies overpressure, fire, and toxic gas release situations.
- Consequence Modeling: Uses blast wave propagation models and thermal radiation simulations to predict possible outcomes.
- Frequency Calculation: Estimates the likelihood of damaging events using historical data.
- Structural Impact Evaluation: Analyzes whether buildings can withstand defined impact scenarios.
- Individual Risk and FN Curve Analysis: Graphs the probability of outcomes against potential fatalities to inform decisions.
- Exceedance Curve Development: Maps the likelihood of exceeding structural limits for key buildings.
Consequence-Based Facility Siting Study
A consequence-based FSS focuses on the potential severity and impact of identified hazardous scenarios, providing a detailed analysis of potential damage and risk outcomes.
Key Steps in Consequence-Based Structural Assessment:
- Impact Magnitude Evaluation: Quantifies the potential extent of damage from different hazardous events.
- Damage Propagation Analysis: Traces the potential spread of destructive effects across facility infrastructure.
- Vulnerability Mapping: Identifies critical assets and their potential exposure to various threat scenarios.
- Mitigation Potential Assessment: Evaluates potential protective measures and their effectiveness in reducing potential consequences.
- Worst-Case Scenario Modeling: Develops comprehensive models of maximum potential impact scenarios.
- Recovery and Resilience Planning: Analyzes facility recovery capabilities and potential downtime associated with different consequence levels.
Structural Assessment of Facility Components
Facility Siting Studies (FSS) can also examine non-building components that are critical to facility safety:
Pipe Racks and Equipment Structures
- Exposed to blast waves, heat radiation, and fireball effects
- Assessed for structural integrity and collapse potential
Storage Tanks and Pressure Vessels
- Reviewed based on thermal exposure, BLEVE (boiling liquid expanding vapor explosion) potential, and overpressure resistance
- May require additional protective barriers or insulation to withstand extreme conditions
Process Units and Loading Areas
- Analyzed for hazardous release scenarios and secondary ignition risks
- Mitigation strategies may include fireproofing, shielding, and adjusting placement distances
Important Takeaways
- Structural response analysis is an essential part of Facility Siting Studies (FSS), helping to understand how buildings and infrastructure react to hazards.
- API 752 and API 753 offer structured methodologies for evaluating structural integrity.
- P&I curves and Finite Element Analysis (FEA) are used to assess the potential damage to buildings and to identify the need for structural reinforcements.
- Risk-based studies incorporate probability calculations, improving mitigation strategies.
- Process units, pipe racks, and storage tanks must also be examined to reduce risks across the entire facility.
Structural response analysis provides crucial insights into how buildings react to overpressure, thermal radiation, and toxic gas exposure. By applying engineering techniques such as P&I curves, FEA, and exceedance curve modeling, facilities can determine whether buildings need modifications, shielding, or relocation.
Integrating risk-based studies into structural response analyses helps industries manage risks more effectively and implement enhanced hazard mitigation strategies. For further information on Facility Siting Studies and hazard modeling, read our first blog on What is a Facility Siting Study? A Guide to Compliance with OSHA 29 CFR 1910.119
