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    Assessment of constructions structures problems in high temperature in Niger
    (İstanbul Gedik Üniversitesi, Lisansüstü Eğitim Enstitüsü, 2025) Yasser, Hamissou Oumarou; Ghasemlounia, Redvan
    In high temperaturre, concrete begins to crack due to thermal expansion, which varies based on the type and quantity of sand, the type of gravel, and the proportions of cement and water in the mix. Additionally, the age of the concrete after the fire can influence its expansion. Within the first half hour, surface concrete tends to fall off, and thin surface layers fissure, especially under high temperatures. This phenomenon, known as fission precipitation, occurs when the concrete contains moisture. Another type of damage, called peeling, involves the gradual separation of surface layers, particularly in columns and bridges, where parallel cracks may cause these layers to detach. After a fire, a condition assessment of the affected concrete structure is conducted to determine whether it needs repair or demolition. This assessment includes mapping visual damage and using measurement methods to detect the extent of the damage, which is crucial for safety and economic reasons. The assessment report has two parts: a literature review of common test methods and an experimental section comparing traditional methods (such as rebound hammer tests, ultrasound measurements, and microscopy) with a new methodology involving optical deformation measurement under pressure testing on drilled cylinders. This new method allows for continuous evaluation of damage across the fire-affected concrete cross-section. Based on the study, two investigation levels are recommended. If the first level does not provide sufficient information, more complex methods are suggested. Visual examinations of the fire site, including the affected structure and other objects, as well as the fire's intensity, duration, and spread, are estimated. Damage such as splitting, deformations, and delaminations are documented. Delaminations and weak zones can be identified using a hammer and chisel. For complex scenarios, a classification system and tools like the rebound hammer and ultrasound measurements help quantify the damage but do not indicate its depth. When necessary, cores are drilled and evaluated using laboratory methods to determine the damage depth accurately. Ultrasound measurements across different core depths provide a direct understanding of the damage's extent. In the laboratory, cracks and color changes are examined under a microscope to infer the maximum temperature the reinforcement experienced during the fire. Cracking patterns reveal information about the structure's durability, as high cracking intensity implies higher permeability and increased risk of reinforcement corrosion. To measure the fire's impact on the concrete's mechanical properties, cores are subjected to pressure tests while deformation is measured using a non-contact system, offering a comprehensive view of damage across the cross-section and leading to a more reliable assessment.