Analyzing the Effect of Hoops

The hoop can be used to measure the compressive strength of concrete cube specimens, and different specimen sizes can also be selected based on the maximum particle size of coarse aggregate. However, different sizes and shapes of specimens can affect the results of compressive strength measurement.

Because when the concrete specimen is compressed on the press, it undergoes longitudinal deformation along the loading direction and also undergoes lateral expansion according to the Poisson's ratio effect. The lateral expansion of steel pressure plates is smaller than that of concrete, thus forming frictional forces on the compression surface between the pressure plate and the concrete specimen, which plays a restraining role in the lateral expansion of the specimen. This restraining effect is called" Hoop effect".

After being reinforced with prestressed hoops, a reinforced concrete chimney generates a uniformly distributed radial pressure along the circumference at the contact between the outer surface of the chimney wall and the hoops. The calculation formula for circumferential pressure, circumferential compressive stress, and pressure influence height generated by radial pressure in the cylinder wall was derived using the theory of cylindrical shells. The circumferential compressive stress shows a curved distribution. The calculation results of several examples show that the maximum circumferential compressive stress value at the position of the hoop is about -1.0MPa and increases with the increase of the hoop position.