Strategies for Enhancing Fire Resistance and Resiliency of Modern of Concrete Structures
V.K.R. Kodur – University Distinguished Professor, Dept. of Civil and Environmental Eng., Michigan State University
In recent years, the construction industry has shown significant interest in the use of high performance concretes (HPC) in building applications due to the improvements in structural performance, such as high strength and durability, that HPC provide as compared to conventional normal-strength concrete (NSC). These high performance concretes, which include concrete types such high strength concrete (HSC), fiber reinforced concrete (FRC), self-consolidated concrete (SCC), and ultra HPC, are typically characterized by higher strength, lower permeability and thus enhanced durability properties. The use of HPC, together with innovative cross-sectional configurations (such as hollow-core slabs, double T beams and deck slabs), and advanced analysis techniques, often lead to slender structural members in modern buildings.
Structural members in buildings have to satisfy appropriate fire resistance requirements as specified in building codes. This is because fire represents one of the most severe environmental conditions to which structures may be subjected; therefore, provision of appropriate fire safety measures to structural members is an important aspect of building design.
Conventional concretes possess good fire resistance properties and hence concrete structural members made of NSC exhibit good fire resistance and resiliency properties. However, number of studies have clearly shown that HPC exhibit poor fire resistance properties, as compared to NSC. Specifically, certain HPC types undergo rapid degradation of strength at elevated temperatures and are also susceptible to explosive spalling under severe fire conditions. These poor fire resistance properties of HPC, together with reduced cross sectional sizes of structural members, can lead to lower fire resistance and lower resiliency in HPC structural systems.
In the last two decades, a series of fire resistance experiments and numerical studies have been carried out by a number of organizations world-wide to evaluate fire performance of HPC at material and structural level. Results from these studies clearly show that fire performance of HPC, in general, and spalling in particular, is complex phenomenon and is affected by a number of factors. Based on these fire tests and numerical studies, a set of innovative solutions have been developed for enhancing fire performance of HPC structural members.
In the presentation, severe conditions such as fire intensity, structural configuration, and material characteristics that can be present in modern buildings, with respect to fire performance will be highlighted. The performance problems associated with high performance concretes under fire conditions will be discussed. Examples of innovative strategies for enhancing fire performance of HPC structural systems will be presented. Specific guidelines to enhance fire resistance of HPC members, such as use of bent ties in columns and addition of fibres to HPC to mitigate fire induced spalling, will be discussed. Through case studies it will be demonstrated that by adopting proper strategies, both at material and structural levels, fire resistance and resiliency of HPC structures can be enhanced.
Dr. Venkatesh Kodur is a University Distinguished Professor in the Department of Civil and Environmental Engineering at Michigan State University. He also serves as Director of the Centre on Structural Fire Engineering and Diagnostics at Michigan State University. His research interests include: Evaluation of fire resistance of structural systems through large scale fire experiments and numerical modeling and Characterization of materials under high temperature. His research contributions has lead to the development of fundamental understanding on the fire behavior of material and structural systems and also resulted in numerous design approaches and innovative and cost-effective solutions for enhancing fire-resistance of structural systems. He has published over 425 peer-reviewed papers in journals and conferences, and has given numerous invited key-note presentations. He is one of the highly cited authors in Civil Engineering and as per Google Scholar, he has more than 10,500+ citations with an “h” index of 56. The methodologies, techniques and design guidelines, resulting from his research, have been incorporated in to various codes and standards, as well practical applications, in the US and around the world and are instrumental in minimizing the destructive impact of fire in the built infrastructure.
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