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Forensic Investigation of Fire-affected Concrete Buildings

Awoyera, P. O. (2014) Forensic Investigation of Fire-affected Concrete Buildings. Lap Lambert Academic Publishing, Germany. ISBN 978-3-659-57278-4

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The post-fire residual strengths of in situ concrete and laboratory steel samples were evaluated in this research using non-destructive and destructive test methods. Non-destructive tests entailing visual inspection, Rebound hammer and Ultrasonic pulse velocity tests were performed on three fire-affected buildings. The averages of the hammer numbers and pulse velocities taken from the fire-affected structural members were fitted into an already established model to determine the corresponding compressive strengths. Furthermore, sixty samples of 320 mm x 150 mm x 100 mm reinforced concrete beams were cast in the laboratory in four batches. Each batch contains fifteen samples with concrete cover for reinforcement varied at 10 mm, 15 mm, 20 mm and 25 mm respectively. After 28 days of curing, the beam samples were subjected to simulated fire in the laboratory furnace at temperatures ranging from 50 oC – 700 oC in steps of 50 oC. Thereafter, the samples were allowed to cool to room temperature and later subjected to rebound hammer and ultrasonic pulse velocity tests. Subsequently, samples of reinforcement were removed from the beam samples and tested with the universal material testing machine. From the results, visual examination of the fire-affected buildings revealed changes in colour of the concrete, delamination of plaster of slab and exposure of reinforcement at various locations on the concrete members. In addition, there was notable reduction in the in situ strengths of the fire-affected structural members in comparison with the unaffected members. For the laboratory samples, it was observed that rebound hammer number initially increased with increasing temperature to about 250 oC and later decreased as the temperature increased towards 700 oC. However, pulse velocity decreased with increasing temperatures. Results of tensile tests on reinforcements showed that ultimate tensile strength of steel decreased with increasing temperatures. The greatest loss in strengths of steel reinforcements was recorded for beams with 10 mm concrete cover, which reduced from a value of 592.0 N/mm2 at room temperature to 224.50 N/mm2 at a temperature of 700oC.

Item Type: Book
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Divisions: Faculty of Engineering, Science and Mathematics > School of Civil Engineering and the Environment
Depositing User: Engr. Paul Awoyera
Date Deposited: 08 Jan 2016 08:50
Last Modified: 08 Jan 2016 08:50

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