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Thin layers of textile reinforced concrete (TRC) can be used as strengthening for reinforced concrete (RC) slabs or beams to increase their foad-bearing capacity. The concrete matrix consists of a fine-grained concrete with a thickness of 8 to 15 mm. Information on the behaviour of strengthened structures subjected to fire is of particular inlerest for practical applications of this innovative construction method. A total of 7 RC slabs with Steel reinforcement were produced: 2 slabs were used as reference and 5 slabs were strengthened with three layers of textile reinforcement. Ultimate capacity of reference slabs and particular TRC strengthened slabs was determined from statie load results fom 4-point-bending tests.
Fire tests on these slabs were carried out with utilization fectors using a Standard temperature curve (ISO-834-1) for fire testing. Test loads varied between 0 % and 65 % ofuMmate load.
To detect temperatures during fire exposure thermocouples were arranged throughout the cross-section of the slabs. Depending on the utilization the slabs were exposed to fire for 30 minutes or for 60 minutes. In some cases bending fäilure occurred, in other cases the slabs survived. None of the specimens exhibited any visual damage or concrete spalling during fire exposure. Results of deformation measurements and residual strength measurements are presented. Even though mechanisms are not fifily understood, it is important to discuss the presumable reasons for the surprisingiy positive test results. It is presumed tbat the key mechanisms contributing to the outstanding fire resistance capability presented are: superior crack control of the TRC and load redistribution between textile and Steel reinforcement as well as the primary load transfer directly into the slabs.
Intumescent coatings are commonly used in civil engineering to improve the fire resistance of steel constructions. Especially in the case of tension bars, where mostly circular or rectangular solid sections are used, intumescent coatings offer an efficient measure to improve the fire resistance taking advantage of profile-following application and low coating thickness requirements. Thus, the architectural appearance of slender profiles can be preserved. The paper describes real-scale mechanically loaded and unloaded fire tests of circular and rectangular solid steel tension bars with intumescent coating. The aim of these tests is to investigate the influence of the different profile types as well as different bar orientations on the performance of intumescent coatings. The results are used to specify a normative test and assessment procedure to be implemented in a new European standard for determining the contribution of intumescent coatings to the fire resistance of circular or rectangular bars used as tension members.
Intumescent coatings are used in civil engineering to improve the fire resistance of steel constructions. Due to the thin coating thickness and the profile-following application, the architectural appearance of the steel structure can be preserved. EN 13381-8 provides regulations to determine the contribution to the fire resistance of intumescent coatings applied to steel beams and columns. The scope of this standard excludes tension members and steel members with solid sections. For products that have already been successfully tested and assessed on beams and columns, EN 13381-10 offers the possibility based on unloaded fire tests to extend the scope of application of intumescent coatings to tension bars with solid sections. This approach contradicts the national safety level in Germany, where mechanically loaded testing is mandatory. Therefore, a new part of the test standard series EN 13381 is currently developed to enable the application of intumescent coatings on steel tension bars with solid section based on mechanically loaded fire tests. BAM has already carried out numerous fire tests on loaded steel tension members with intumescent coatings. Currently, in the BAM research project FIRESTEMIC, the influence of the steel bar orientation and the profile type on the thermal performance of intumescent coatings are investigated. Both questions concerning the thermal protection ability of intumescent coatings were analysed based on three different test sets, which were carried out in the tension furnace (Fig. 1a). The fire exposure corresponds to the standard temperature-time curve according to EN 1363-1.
This paper summarises the main findings from the fire tests conducted in the FIRESTEMIC project. The results serve as an experimental background for the proposal of the new standard. Regarding the bar orientation, a new test setup was developed and proposed for the new standard. The two tested commercial water-based intumescent coatings with applied dry film thickness from 1.5 mm to 2.5 mm showed only a slight dependence on the bar orientation. In terms of the steel profile type, circular and rectangular solid sections with identical section factor and applied dry film thickness were tested. It was observed that the circular solid bars with diameter 30 mm heat up faster compared to the solid rectangular bars with dimension 30×30 mm (Fig. 1b). Also at larger steel bars, i.e. diameter 40 mm and dimension 40×40 mm, the same trend occurred. Thus, it is recommended for the new test standard to allow a transfer of the test results from circular to rectangular solid sections. In addition, the paper will describe and explain the test and assessment procedure proposed for the newly developed standard.
Die hier vorgestellten Untersuchungen dienen der Erweiterung des Anwendungsbereiches für reaktive Brandschutzsysteme auf Stahlbauteilen im nationalen Zulassungsverfahren.
Für die Wirksamkeit reaktiver Brandschutzsysteme ist die Haftfähigkeit der reaktiven Brandschutzbeschichtung auf dem Untergrund (Stahl) von entscheidender Bedeutung. Die Haftfähigkeit der Beschichtung ist neben der Oberflächenbeschaffenheit und den Eigenschaften des reaktiven Systems selbst im Wesentlichen von der Form des Bauteils und den sich im Brandfall einstellenden erformungen (Krümmungen und Dehnungen) abhängig.
Reaktive Brandschutzsysteme
(2022)