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Prestressed concrete

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 Prestressing concrete is done by subjecting concrete to a permanent stress to improve the reinforced concrete member characteristics such as strength and durability. In prestressed concrete, the concrete is subjected to a compressive force. The compressive force will improve concrete flexural, shear strength and reduce the tensile stresses on concrete which reduces the possibility of cracks formation and this will result in extending structure service life.

The applying of compression force will be done by tensioning of high tensile strands then release them in a controlled manner to provide the required compressive stress. Applying the prestressing force can be done by two methods. Pretensioning method, in this method the strands tensioned first then the concrete is casted. When the concrete attained the desired strength, strand will be cut and released to compress the concrete to produce the required compressive stresses.

Figure 1


Post-tesnsioning method is the second method, in this method the concrete is casted first, then the strands is inserted into the pre-placed ducts and tensioned when the concrete reached the desired strength, the strands will be tensioned to the required force and released to produce the required compressive stresses. The post-tensioning system will consist from anchor plate, wedges, wedge plate, ducts and others. For post-tensioning system tendons (group of strands) is grouted to prevent it from corrosion.

The profile of the tendons will play a significant role in increase the structure strength and the compressive stresses produce by the tendons. For example if the tendon placed at the center of the structure then the produced compressive stress will be P/A, P is the prestressed force and A is the cross-sectional area of the structure but if the tendon placed at an eccentricity of “e” from the center line the produced stress will be P/A ±(P*e)*y/I in which y is the distance from the center of the structure to extreme fiber under consideration and I is the moment of inertia for the structure. Therefore, in continuous structure, the tendons at the center of span will be placed at the bottom part because this part is subjected to tensile stresses. while, above the span it will be placed in the upper part because it is the tension fiber.

The use of prestressed concrete enable us to construct a structure with smaller dimensions and longer spans, this very important because the number of column will be reduced and a significant space will be saved and it is very important for structure such as parking floors and bridge structures. Also, it will increase structure durability.

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  1. gokulJuly 28, 2023 at 5:50 AM

    This blog is amazing
    Peb Building Contractors focus on delivering durable, cost-effective, and aesthetically pleasing PEB structures. They cater to various sectors, including industrial, commercial, and institutional projects. Their portfolio may include warehouses, manufacturing facilities, storage buildings, retail spaces, showrooms, sports facilities, and more. Throughout the construction journey, Peb Building Contractors prioritise communication and collaboration with clients, keeping them

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