Structural fire engineering for innovative solutions

 

SFE insights

• Structural fire engineering (SFE) offers a cost-effective and practical approach to optimizing fire protection by analyzing the thermal and structural responses of buildings, enhancing safety and reducing reliance on traditional fire protection measures.
• Incorporating SFE from the early design stages of construction projects can lead to innovative, sustainable and aesthetically pleasing buildings, while ensuring compliance with fire safety standards and potentially reducing construction and maintenance costs.

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Imagine a scenario where buildings not only endure fire but do so with reduced dependence on conventional fire protection measures. This notion might seem groundbreaking, yet it is the reality that structural fire engineering (SFE) can offer when properly implemented with precision.

Load-bearing structures must be designed to achieve an adequate level of fire resistance specified by relevant standards and building codes. SFE is a practical and cost-effective way to help manufacturers, architects and designers determine the potential impact of a fire on the construction’s structural elements and systems while also addressing various fire safety challenges related to new building products and designs.

Through a comprehensive analysis of thermal and structural responses to various fire conditions, structural fire engineers can assess structural fire safety and optimize fire protection for a range of building types, from large, multiuse buildings to offices, industrial units, airports, hospitals and shopping centers.

Incorporating fire safety measures into the design of a building right from the beginning can aid in reducing construction and maintenance expenses in the long run while also achieving an innovative, functional, sustainable and aesthetically pleasing building design.

SFE as a performance-based approach

Designers are increasingly searching for alternatives to conventional structural fire protection approaches due to the emergence of new and rapidly changing building trends. Prescriptive building codes and standards, however, are often unable to account for all possible cases and solutions for structural fire protection.

Holistic, performance-based approaches to structural fire design specifically prove valuable when nonstandard, innovative approaches are required or when a project’s characteristics create challenges for cost-effective design.

SFE may be the only way for some buildings to demonstrate that a sufficient level of safety can be attained, such as when the prescriptive code does not recognize the proposed building or structural types. SFE analyzes the behavior of the structure in more detail than just using the traditional prescriptive methods. When executed carefully, SFE can enhance structural fire safety while reducing reliance on costly passive defenses.

This approach not only helps in optimizing passive fire protection and other resources, it also contributes to finding the best possible structural solutions by highlighting the critical points of the structure. Fortunately, building codes and standards, such as Eurocodes and the International Building Code, recognize alternative methods like SFE as a potential route to verify the compliance of a structure. Eurocodes specifically provide useful information and design methods related to SFE.

Applying SFE to construction projects

Assessing new structure types and systems: Fire tests for all new structural systems are crucial for ensuring the safety of buildings and structures. Because it is not feasible to test all possible variations, SFE allows stakeholders to find best practices for new structure types and structural systems that have not been fire-tested. By conducting rigorous testing or SFE analysis and adhering to established standards, fire performance can be confidently assessed and informed decisions can be made regarding their incorporation into construction projects.

Steel-timber hybrid structures, for example, are becoming increasingly popular due to their many advantages, including lightweight, sustainable and fast installation (see Figure 1). A 2023 study in “Fire Technology” showed that SFE methods can enhance fire protection strategies for these structures. Fire experts used furnace tests and numerical simulations to investigate their fire performance, analyzing thermal profiles, temperature development and charring behavior, as well as the effects of steel profiles and intumescent paint on the charring of timber slabs.

Although researchers confirmed that the extent of the timber charring was similar for both unprotected steel profiles and scenarios without steel, applying intumescent paint ultimately reduced the charring (see Figures 2 and 3). Overall, this study illustrates that SFE methods can help predict fire performance in novel or unconventional structural designs and aid in the identification of fire-safe solutions.

Analysis of steel and composite structures: For many industrial and sports arena projects, incorporating massive steel structures is common practice, necessitating substantial fire protection measures as per prescriptive requirements. A notable opportunity for SFE arises when the fire load is inherently low or the steel structure is situated considerably far from potential fire sources.

Composite floors built with steel beams and steel/concrete composite slabs often perform better as a system during a fire than their individual components. This can enable reduced fire protection thicknesses, especially in the secondary steel beams. The challenge is how to analyze the structural behavior during a fire in a safe and realistic way. To address this, a thorough analysis using comprehensive SFE methods is needed. This meticulous examination often reveals opportunities to reduce or even eliminate prescriptive fire protection measures.

Thermal analysis, used frequently in SFE, has proved to be a valuable tool for offering a cost-effective and efficient means of exploring optimal solutions for various challenges (see Figure 4). This includes scenarios where full protection of steel structures is unattainable or where steel studs within load-bearing walls require careful consideration. This approach aids in developing informed decisions to ensure a balance between safety, efficiency and cost-effectiveness to meet the client’s needs.

Considerations for SFE

Getting it right from the start is critical to successfully integrating SFE into a project. Anticipating any potential issues and addressing all inquiries at the beginning of the project can help maintain progress and avoid unexpected setbacks.

Early involvement of a structural fire engineer can certainly add value to the project, as there is more room to optimize the structural system together with structural engineers. Structural fire engineers can help:

• Develop SFE solutions for steel, timber, concrete and composite structures.

• Determine the most effective practices for new types of structures and structural systems (e.g., choosing where to rely more on inherent fire resistance and where to apply more passive fire protection).

• Examine the thermal behavior of structures exposed to fire and the structural response of building elements exposed to fire using analysis techniques.

• Ensure compliance by providing recommendations for structural fire testing and assessments and suggesting actions to correct any issues

Involving relevant stakeholders from the beginning can be extremely helpful as well, especially on large-scale projects. Conversations with authorities having jurisdiction, designers and contractors will help effectively identify the best strategy for structural fire protection and ensure that all the relevant concerns are addressed during the design process.

Also, before carrying out the final analysis, it is usually beneficial to conduct a preliminary analysis or feasibility study to get a better understanding of the potential solution, savings and critical items in the structure.

For example, a preliminary analysis can be done for the smaller part of the structure rather than a final analysis or by using more simplified methods. Sometimes, it may be beneficial to present preliminary analysis results to the authorities, especially if they are unfamiliar with SFE methods.

Innovative fire protection solutions

SFE ultimately helps to ensure that structural members and systems within buildings, whether steel, timber or concrete, are able to maintain structural integrity during a fire. The benefits of SFE extend beyond mere cost savings, encompassing streamlined project timelines, enhanced aesthetics and improved sustainability.

By leveraging advanced analytical tools, these projects can strike a harmonious balance between safety compliance and resource efficiency, ushering in a new era of innovation in construction practices.

[bio] Mikko Salminen, Ph.D., is the Structural Fire Engineering Lead, Europe, with Jensen Hughes. Salminen has more than 15 years of experience in performance-based structural fire safety analysis of steel, timber and concrete structures for major commercial, industrial and residential projects in Finland and the United States.

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