Due To Prestress
The term “circular prestressing” refers to the prestressing of circular constructions like pipes and tanks using prestressing wires that are twisted in circles. Contrary to popular belief, “linear prestressing” refers to any sort of prestressing in which the cables are straight or curved but not looped in circles around a circular structure. Prestress is applied circumferentially and longitudinally in most prestressed circular structures, with the circumferential prestress being circular and the longitudinal prestress being linear.
The circumferential prestressing resists the internal pressure-induced hoop tension. Wires or tendons are spiralled or put over sectors of the member’s circumference to prestress it. Outside the concrete core, the wires or tendons are located. As a result, the prestressing steel’s (CGS) centre is located outside the core concrete portion.
The prestressing is called circular prestressing when the prestressed components are curved in the direction of prestressing. Circular prestressing, for example, can be seen in pipes, tanks, silos, containment structures, and other similar structures. Prestressing in the longitudinal direction (parallel to the axis) is also possible in these constructions. In domes and shells, circular prestressing is also used.
The circumferential prestressing resists the internal pressure-induced hoop tension. Wires or tendons are spiralled or put over sectors of the member’s circumference to prestress it. Outside the concrete core, the wires or tendons are located.
As a result, the prestressing steel’s (CGS) centre is located outside the core concrete portion. A thin shell’s hoop compression is thought to be uniform across its thickness. As a result, the pressure line (or Cline) runs through the core concrete section (CGC). The internal forces are depicted in the following diagram under service conditions. The analysis is carried out for a unit-length slice in the longitudinal direction (parallel to axis).
Circular prestressing is ideal for liquid-retaining structures including circular pipes, tanks, and pressure vessels. Prestressing counterbalances the hoop tension created due to internal fluid pressure by causing circumferential hoop compression in concrete. A high quantity of reinforcement is required in a reinforced concrete pressure pipe to ensure low tensile stresses and a crack-free structure. Circular prestressing, on the other hand, eliminates cracks while also maximising material efficiency. In addition, prestressing protects liquid holding structures from shrinkage fractures.
Due To Prestress
Due To Internal Pressure
Prestressing can be done over sectors of the circumference to prevent prestress loss due to friction. The anchorage of the tendons is provided by buttresses. The buttresses along the circumference are seen in the diagram below.