Carbon tension member installed in the furnace at BAM
Source: BAM FB 7.3
The application of carbon tension members is motivated by the exceptionally good fatigue and high tensile strength of the material. Consequently, the cross-section can also be significantly reduced compared to steel tension bars. Carbon tension members will be a good alternative to be used in network arch bridges and building construction. The load-bearing behaviour of carbon tension members exposed to fire has not yet been investigated. Although, fire is generally not considered for the design of bridges, a general statement about the behaviour of carbon tension members and a comparison with steel tension members is intended. In the research project "NeZuCa", BAM investigated the failure mechanisms of special carbon tension members in fire tests and assessed their equivalence to steel tension members. This publication describes the procedure and results of the carbon tension members tested in real-scale under mechanical load and fire exposure.
The test programme consists of four carbon tension members with a circular cross-section in two different diameters, 36 mm and 51 mm. In addition, unloaded steel bars with circular solid section and diameters of 36 mm and 50 mm were fire-tested simultaneously to measure the heating. For reasons of reproducibility and applicability of the results to building construction, the standard fire curve prescribed in building construction was chosen. In the fire tests, the failure of the carbon tension members occurred after 13 to 26 minutes of fire exposure. The rupture took place near the connection area and transition area of the specimens. Despite, the addition of thermal insulation material to the connection and transition area, a rupture in the normal area of the carbon tension member did not appear. In the fire tests the specimen and furnace temperatures as well as the longitudinal deformation of the carbon tension members were recorded. The investigations provided valuable information on the load-bearing behaviour and failure mechanisms of the carbon tension members exposed to fire.
Brandversuche an mechanisch belasteten Carbonzuggliedern (Fire testing of loaded carbon tension members)
Jan Kremberg, Dustin Häßler, Ludwig Stelzner, Sascha Hothan
published in Stahlbau 92 (2023), Issue 7, Pages 427-436
BAM Department Safety of Structures
BAM Division Fire Engineering