Brandpåverkan på skyddskonstruktioner i funktionsskyddsrum : En undersökning av resthållfasthet i betongbalkar

Sammanfattning: In the beginning of the 21st century decisions were made regarding the decommission of the total defence in Sweden. Since then the security policy situation has changed, regarding both the risk of war and other types of treats such as terrorism. Due to this the total defence is now being re-established. The Swedish Fortifications Agency and Research Institutes of Sweden (RISE) has initiated the Centre of excellence for fortification (CFORT) to support the development of competence in fortification. In case of a crisis or war secured function shelters constitutes a significant part of the Swedish total defence by protecting important technology and activity.The purpose of this bachelor thesis is to investigate the remaining load bearing capacity in concrete constructions in secured function shelters after exposure to fire. This will provide a foundation for further research within the area of the effects of fire in secured function shelters. To achive this, experiments were conducted on nine concrete beams which were casted according to calculations based on the structural codes of the Swedish Fortifications Agency (FKR). Since fully scaled beams are difficult to manage and would not fit in the equipment being used, the beams were casted in a smaller size; 2000 x 150 x 210 mm. Samples of the concrete and the reinforcement were sent to the Swedish Cement and Concrete Research Institute (CBI) for tests which provided actual values of the compressive strength, yield point and modulus of elasticity. Six of the beams were in pairs exposed to fire in a specially built oven according to three different temperature curves. All the beams were later subjected to load until failure. Calculations regarding load bearing capacity were executed with both theoretical and actual values obtained from CBI. The results were compared to the results from the loading tests. During the last fire experiment the beams spalled, most likely due to the quickly rising temperature. The loading test showed that the strength of the beams which had not spalled were not significantly lower than the unaffected beams. Those beams showed a reduction of only 0 – 6 %. However, the beams which had spalled showed a reduce in strength of approximately 20 %.