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Fire Tests of Reactive Fire Protection Systems Applied to Steel Tension Members with Solid Circular Section



In civil engineering, steel tension members are normally used for bracings, suspensions and underbracing systems. Typically, slim circular solid sections (CSS) are used for such tension members. However, sufficient knowledge about the performance of reactive fire protection systems (RFPS) applied to solid steel tension members has so far been missing. The application of RFPS on such members was not covered by national German approvals (abZ) as well as European technical assessments (ETA) and therefore only possible by approvals in individual case by the building authority. This paper describes the world’s first scientifically investigated fire tests of RFPS applied to steel tension members with CSS. The influence of various parameters such as profile geometry, dry film thickness of the RFPS, level of the load utilization as well as member orientation was tested. In addition, the foaming and cracking behaviour and thermal protection of the RFPS used are investigated and failure mechanisms are identified. To measure the steel temperature of the tension member without weakening the cross-section a special method for the application of thermocouples was developed. The fire tests show that an application of RFPS on steel tension members with solid section is generally possible. However, due to the slim cross-sections and the missing possibility of load distribution within the tension member, high requirements are placed particularly on the effectiveness and reliability of the RFPS. In particular, the testing of mechanically loaded tension members is essential, since the necessary three-dimensional foaming results in the highest stress level for the RFPS. The findings obtained from the performed fire tests are of general nature. Recommendations for the testing and assessment of RFPS applied to steel tension members with solid section are briefly described in this paper and explained in detail in [1] and [2]. Based on this research, the German building authority (DIBt) has defined national approval guidelines for the testing and the assessment of RFPS applied to tension members with solid section. Since November 2015, a general building approval for a RFPS is available in Germany [3].

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