Numerical Study of Pre-tensioned concrete joints under fire conditions

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Numerical Study of Pre-tensioned concrete joints under fire conditions

ارائه دهنده: Provider: Niousha Sayad Sedgh Herfeh

اساتید راهنما: Supervisors: Freydoon Rezaie (Ph. D) Javad Taheri Nezhad (Ph. D)

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: دکتر محمد شوشتری- دکتر امیر رضایی صامتی

زمان و تاریخ ارائه: Time and date of presentation: March 16, 2021 at 18:00

مکان ارائه: Place of presentation:

چکیده: Abstract: Beam and block roof as one of the most common construction slabs in Iran has weaknesses such as weakness during fire, which is due to cracking under the roofs and the penetration of heat from the fire to the rebars. Therefore, by removing these cracks, the fire resistance of building roofs can be significantly increased. Prestressing a concrete member means pulling high-strength steel wires by the jack and then releasing it and creating a compressive force in the concrete to compress the concrete section and create a negative rise in them from the compressive capacity of the concrete, which is much higher than its tensile capacity. Is, optimized use. This method eliminates tensile cracks, which makes them more resistant to fire than conventional beam and block roofs. In this study, the effects of fire on prestressed prestressed beams, manufactured by Iran prestressed beam factory, were investigated by ABAQUS finite element software. In this regard, first, in order to ensure the accuracy of the modeling method, two samples of pre-stretched adhesive pre-stretched slabs tested by Bailey and opacity were modeled and a good agreement between the results of this modeling and the results of his research experiments was observed. The modeled slab has an opening consisting of two prestressed beams with a slab 50 mm thick and one meter wide. The beams have an inverted T-section and are located half a meter apart. The beams are prestressed by 3 wires with a diameter of 5 mm. Slab loading as dead load plus 21% live load was applied widely on the slab surface, then the slab was exposed to 0.1 of its bending capacity as a 4-point load. Slab contraction joints should intersect at the openings for columns and should intersect at the openings for columns. Then the changes of 4 parameters on the behavior of this roof in 9 samples were examined, which included the effect of beam length, concrete cover, prestressing force and compressive strength of concrete. The effect of prestressing stress for 3 values of zero, 600 and 1120 MPa, the effect of beam length for 3 values of 4.5, 6 and 7.5 meters, the effect of compressive strength of concrete for 3 values of 30, 45 and 60 MPa and concrete cover for 3 values of 10, 20 and 30 mm were evaluated. The results showed that the effect of various parameters, especially beam prestressing, has a significant effect on the fire resistance of the studied slab. The other parameters studied also showed their effect, but the effect of the prestressing parameter was the most. Also, according to the transverse cracks observed in the middle of the beam, in all samples, the same fracture mode occurred in the middle of the beam in a bending manner. The results showed that the effect of various parameters, especially beam prestressing, has a significant effect on the fire resistance of the studied slab. The other parameters studied also showed their effect, but the effect of the prestressing parameter was the most. Also, according to the transverse cracks observed in the middle of the beam, in all samples, the same fracture mode occurred in the middle of the beam in a bending manner.

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