Abstract
Abstract In Brazil, reinforced concrete structures designed based on NBR 6118 [1] must be assessed in fire conditions through NBR 15200 [2], which proposes multiple test methods. Concerning beams, this standard offers the tabular and simplified methods as possible choices. This study aimed to compare these two methods by applying their principles to isostatic and hyperstatic beams with section of 20x50 cm, designed at room temperature according to NBR 6118 [1]. The temperature distribution along sections was obtained by means of a software program. The results from this study indicated that the simplified method yielded higher fire-resistance ratings (FRR) in 75% of cases, although not surpassing the tabular method by 30 minutes. The simplified method allowed an optimization of the results, despite the longer design time.
Highlights
Mechanical and physical properties of structural elements of reinforced concrete vary according to temperature
The criteria for structural analysis at high temperatures were applied to an isostatic beam and a hyperstatic beam measuring 20 cm x 50 cm, dimensioned at room temperature for durability design classes I to IV of
Based on designs at room temperature and assuming that analyses at high temperatures regard a verification, the aforementioned beams were assessed for safety in fire conditions through the methods of NBR 15200 [2]. n The fire-resistance time (TRF) of the 20x50cm beams were higher for exposure classes III and IV of NBR 6118 [1] for both methods due to the higher thickness of the C1 coefficient, as expected; n The staticity of the beam turned out to be influent as it tended to increase tempos de resistência ao fogo (TRF) by 30 minutes
Summary
Mechanical and physical properties of structural elements of reinforced concrete vary according to temperature. The higher heating of the beam’s bottom half, directly exposed to the burning environment, in conjunction with the lower heating of the other half, thermally protected along the intersection with the slab, makes the mechanical properties of the less heated part undergo transformations milder than the others [8]. Such fact promotes an uneven redistribution of stresses in the section of the beam, which starts to present different tensile strengths in the multiple layers that compose it
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
