Researches in Devision of Fire Safety

Research Area

Fires and their consequences can cause serious damages to property, people or the environment. The division of fire safety specializes in the investigation on fire and smoke propagation as well as fire phenomena. Heat and gases released from combustible materials are key variables that are analyzed and evaluated in this division. The fire ranges from small-scale samples to large-scale superstructures, can be investigated in the new (ZeBra) Center of Fire Safety Research building.

One of the main expertise of the fire safety division is in the design of innovative structural components and construction methods in the case of fire. The research and optimization of high-strength structural materials under high-temperature stress play an important role, as do building products made of renewable building materials and facade systems. From the individual building material to the entire load-bearing structure, a large number of experimental and numerical tests can be carried out thanks to the extensive testing equipment.

The Fire Safety Division is the leader in the assessment and control of fire risks at the national and international levels. Risk and reliability analyses are used to precisely identify and quantify fire hazards. By investigating the flow of people and developing effective evacuation concepts, it is possible to design optimal structural and technical preventive fire protection measures as well as organizational and defensive fire protection measures. Beside the improvement of common fire protection measures, a major research area includes intelligent assistance systems, which can detect and prevent the fire already in the development phase.

Current Projects

This research project is defined among different innovative ideas and beyond the conventional columns with the highest market share. Since normal strength steels regulated by Eurocode are used less and less, composite steel columns with high strength steel made of S960 are of special interest for high rise and normal structures. Not only do they provide significant savings in cross-sectional area and weight in construction, but they also behave very well at high temperatures or in the event of fire. These composite columns also demonstrate higher load bearing capacity and longer fire resistance than conventional columns.

The cross-section of the columns studied in this project consists of a core of ultrahigh-strength S960 steel centered in the middle of the column. The section covers by a round hollow section. In order to delay the temperature transfer to the steel core, a concrete filling is considered between the steel core and the cladding tube.

The lack of information on material properties of the high-strength steel S960 and this type of composite columns, complicates their usage in construction industry. In order to obtain approval for their application, the following steps should be processed.

The aim of this research project is to investigate the load-bearing behavior and performance characteristics of universal, non-welded composite steel columns made of S960. To achieve the research objectives, a comprehensive work program consisting of experimental tests, numerical simulations, theoretical investigations and practical construction considerations has been developed. They consist of small scale tests and structural element tests in real dimensions. In the experimental tests, the composite columns are investigated under various loading situations such as bending, tensile and fire loads (without adding a fire-resistant cladding) in order to find out the material properties of S960This research project was carried out in a cooperation between RWTH Aachen, Institute of Steel Construction, RWTH Aachen, Institute of Solid Construction and IBMB, Institute of Building Materials, Concrete Construction and Fire Safety. The fire tests are carried out with equipment of the Fire Safety division at IBMB.

Project sponsors: German Federation of Industrial Research Associations (AIF), FOSTA - Research Association for Steel Applications and industrial partners

Funding period/term: 2020 – 2022

Contact person: Asieh Jalaeeyan, M.Sc.

Lamellenpaket 3D Ansicht — 3D Modell eine Blechlammellenpaketes, bestehend aus dem Hüllrohr (türkis), dem Füllmörtel (grau) und dem Lamellenpaket (blau).

High-strength steels (HSS) are opening their market in the construction industry due to their mechanical advantages, and using the composite systems can improve their behavior in the fire events. In the last decades, researcher tried to improve structural performance of conventional concrete-filled hollow sections (CFHS) by adding solid high-strength steel cores in their section. However, in steel solid sections the yield strength and residual stress distribution depend on the diameter, which has a negative effect on the buckling behavior of these composite columns.

This project proposes a new type of column named “Blechlamellenstützen” in order to reduce the mentioned weak points and improve the structural performance of these types of composite columns, which is replacing solid steel core with high strength steel sheets. Utilizing high-strength steel sheets means higher load-bearing capacity with more slender columns along with high filling ratios. Besides, steel sheets have smaller dimensions than solid steel elements, therefore, thickness-dependent yield strength reduction can be largely avoided, so that the high yield strengths can be fully utilized. Finally, the cladding tube and the concrete cover beside their contribution to the load-bearing capacity of the column at room temperature, have a significant role in protecting the steel core in fire events.

Lamellenpaket Querschnitt Ansicht — Innenansicht eines unverfüllten Lamellenpaketes.

In a joint research project between the iBMB and the Technical University of Munich, the structural behavior of Blechlamellenstützen is being studied experimentally and numerically at room temperature and under standard fire load. As part of the project, temperature-dependent material properties of high-strength steel with grade S890 and S960 which are used for cladding tubes and steel sheets of the columns and are not standardized yet, will be determined.

Project sponsors: German Federation of Industrial Research Associations (AIF), FOSTA - Research Association for Steel Applications and industrial partners

Funding period/term: 2020 – 2023

Contact person: Shaghayegh Ameri, M.Sc.

Hot-dip galvanizing can improve the fire resistance of steel, as shown by current research results. Based on these findings, the joint AiF research project ( Galvanizing Joint Committee - GAV; FOSTA; DASt) IGF 21536 N with the Chair of Metal Structures, TU Munich, and the Chair of Steel and Lightweight Metal Construction, RWTH Aachen University, analyzes how steel structures can achieve a fire resistance class of R30 without additional passive fire protection measures.

The aim of the research project is to develop and verify easy-to-use rules for determining the fire resistance of hot-dip galvanized composite beams made of high-strength structural steels in case of fire. The standard DIN EN 1994-1-2, which is valid for structural fire design, is currently being revised taking into account the positive effect of Hot Dip Galvanizing in case of fire. The combined application of composite construction using high-strength steels and hot-dip galvanizing has a significant positive effect on the fire resistance of composite structures.

For this purpose, the project clarifies important scientific questions in construction practice concerning the temperature distribution over the height of the steel profile of a hot-dip galvanized composite beam, the material behavior of high-strength steels at elevated temperatures, the heating behavior of connections of hot-dip galvanized components (also in combination with protected components), the subject of possible liquid metal brittleness of high-strength steels in case of fire, and the optimized formation of single-symmetrical hybrid composite beam cross sections.

Project sponsors:: German Federation of Industrial Research Associations (AIF) - Galvanizing, funded by BMWi

Funding period/term: 2020 – 2023

Contact person: Justus Frenz, M. Sc.

In Germany, the market share of steel and composite construction in multi-story buildings is limited. The reasons are complex and related to the lack of experience to prejudices regarding fire safety. In addition, the cost-effectiveness of the construction method always plays a major role.

High fire-resistant, high load-bearing capacity and at the same time slender and economical composite columns can be manufactured with the aid of a Bar-Bundle made of reinforcing steel with a yield strength of 670 N/mm2, which is placed in a steel tube and filled with pressed mortar. By bundling bars, it is also possible to achieve high degrees of filling of the cross sections, with the load-bearing capacities comparable with much larger cross-section dimensions. Compared with composite columns with solid cross sections, bar bundle columns also exhibit more favorable heating behavior, since the individual bars are only in direct contact with each other at specific points and heat conduction between the bars is therefore limited. If the interaction of the bars is ensured at both room temperature and in the event of fire, these columns can be expected to exhibit significantly better load-bearing behavior than conventional composite columns with solid steel cores.

In a joint research project between the iBMB and the Technical University of Munich, the design and manufacturing of the columns and their load-bearing behavior are investigated by means of large scale tests at room temperature and under standard fire load (ISO 834). In addition, the material properties of high-strength reinforcing steel and mortar are to be determined at high temperatures.

Project sponsors: German Federation of Industrial Research Associations (AIF), FOSTA - Research Association for Steel Applications and industrial partners

Funding period/term: 2019 - 2021

Contact person: Shaghayegh Ameri, M.Sc.

Sub-project 2: Assessment of the fire protection performance of structural components and systems

Within the TIMpuls joint project, a complete science-based system is provided to enable the use of load-bearing and space-forming timber structures in multi-story to the high-rise buildings. The project aims to demonstrate that the use of the structures described in the joint project provides equivalent solutions in terms of fire protection compared with the masonry, reinforced concrete or lightweight steel structures commonly used today.

Sub-project 2 (funding code: 22006917) provides essential information on the fire resistance and natural fire behavior of wooden structural elements by means of experimental and numerical analysis on structural components and material tests. These results, in combination with the provided information on technical and preventive fire protection in the joint project, are integrated into a holistic risk assessment for multi-story timber buildings.

The provision of a construction catalog together with the integration of technical building equipment as the final result of the joint project which provides the basis for revising the building regulations - in particular the Model Building Code (MBO) and the Model Guideline on Fire Protection Requirements for Highly Fire Retardant Building Components in Timber Construction (M-HFHHolzR). The aim is to provide a regulated and performance-optimized use of timber construction up to high-rise limits, which allows the construction of economical and visually appealing timber structures.

Project sponsor: German Federal Ministry of Food and Agriculture (BMEL) on behalf of the Agency for Renewable Resources (FNR) Co-financing is coordinated by the Bavarian Carpenters' Guild Association (Landesinnungsverband des Bayerischen Zimmererhandwerks).

Website: https://www.bgu.tum.de/timpuls/startseite/

Contact person: Sven Brunkhorst, M.Sc., M.Sc.

Within the framework of the research project funded by the German Research Association (DFG) entitled "Theoretical and experimental investigations for extending the calculation basis of different types of concrete under natural fire exposure", extensive knowledge was gained on the material behavior of concretes in the cooling phase after exposure to high temperatures. In order to close remaining knowledge gaps, continued investigation is being funded by the DFG.

For fire protection design, the current generation of Eurocode standards allows the use of natural fire model beside the standard fire curve (ETK). Compared to the ETK, the temperatures of natural fires may exceed the ETK for a short time, but they drop again after the consumption of a large part of the fire loads, while the ETK increases gradually. In this regard, design with natural fire models can provide economic advantages.

By using the natural fire method, the load-bearing capacity of the structural components and structures must always be verified over the entire fire duration, including the cooling phase, since failure may occur due to delayed heating or excessive tensile forces in the concrete during the cooling phase. Due to the thermal properties of concrete, the outer cross-sectional areas cool down during the fire cooling phase, while the core continues to heat up.

The research project aims to perform experimental investigations on the thermal conductivity and stress-strain behavior of normal concrete (CC) and high-strength concrete (HPC) during the cooling phase and to translate them into constitutive material models for a general design approach.

Project sponsor: German Research Association (DFG)

Funding duration/term: 2021 - 2023

Contact person: Jan Lyzwa, M. Sc.

Fires in electrical cable systems represent a safety-relevant hazard potential for nuclear plants in operation and in the process of dismantling. Due to technical failures in the form of arcing or short circuits, electrical cable systems entail an increased risk of fire. In addition, due to the flammable insulating materials used in cables, there is a risk of fire spreading from the original source of the fire to adjacent, separated areas, since cables are passed through space-enclosing components.

In the research project " Numerical and experimental investigations of polymer fires in nuclear facilities to improve the predictive capability of fire simulations " (FKZ: 1501565), fire simulation models for the application case "cable fire" are validated on the basis of small- and medium-scale fire tests. Furthermore, based on existing research results, an existing sub-model will be further developed to consider pyrolysis processes and extended for safety-related fire scenarios, e.g. under-ventilated fires.

This research project complements the international joint project OECD/NEA PRISME 3, in which large-scale fire tests are planned at the Laboratoire d'expérimentation des feux of the Institut de Radioprotection et de Sûreté Nucléaire in Cadarache. This international cooperation offers the possibility to compare the methods currently available or used nationally with methods based on other approaches. This enables us to assess and limit the reliability of our own methods.

Project sponsor: German Federal Ministry for Economic Affairs and Energy (BMWi) represented by the Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH

Funding duration/term: 2018 – 2022

Contact person: Jens Spille, M.Sc.

The fire resistance required by the building authorities for load-bearing, space-enclosing wall constructions made of highly thermal insulating bricks in advance of the market launch of these products is determined by extensive and cost-intensive fire tests on full-height walls in accordance with European harmonized test standards. Based on these tests, the fire protection classification is then given in the certification. Eurocode 6 in case of fire protection allows lower-cost computational verification methods, which are not yet possible for masonry construction with highly thermal-insulating bricks due to the lack of material parameters in the high-temperature range and due to unproven computational methods.

The aim of the research project is to determine the relevant thermal and thermo-mechanical material properties at high temperatures and, on this basis, to develop a validated simplified calculation method for determining the fire resistance of masonry components. This calculation method provides the prerequisites for determining the fire resistance of full-height wall constructions instead of time-consuming and expensive fire tests in the future, or reducing the number of required fire tests.

The focus of the current investigations is on the development of a thermo-mechanical numerical model and linking the model to the experimentally determined material properties.

The AiF research project is being carried out as a joint project by the Institute for Building Materials, Solid Construction and Fire Protection (iBMB) of the Technical University of Braunschweig and the Institute for Brick Research Essen e.V. (IZF).

Project sponsor: German Federation of Industrial Research Associations (AIF) and industrial partners.

Funding duration/term: 2020 – 2023

Contact person: Lilia Maruhn, M.Sc.

Researches in Devision of Fire Safety

Research Area

Current Projects

Sub-project 2: Assessment of the fire protection performance of structural components and systems

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