SkyCiv Stress-Strain Calculator

In structural engineering, stress refers to the force applied to a material per unit area. Meanwhile, strain is the deformation or change in the shape of the material that results from the applied force. Stress and strain are directly proportional to the elastic limit of a material.

The SkyCiv Stress-Strain Calculator is a web-based app to provides stress-strain values for non-linear RC design parameters as per the theory proposed by John Mander et al. (1988). The theory is applicable based on a unified stress-strain approach for confined concrete applicable to both circular and rectangular-shaped transverse reinforcement. It consists of two parts, that is, a parabolic branch up to peak concrete stress and a linear falling tail up to a certain residual stress.

Mander’s (1988) model for the stress-strain relation of confined concrete proposed the stress-block parameters (α and β) for different levels of confinement. These equivalent rectangular stress-block parameters are extensively used in the analysis and design of concrete structural members and offer a convenient way to determine flexural capacity. These parameters are directly derived from the stress-strain relation of concrete. To determine the stress-block parameters (α and β), we equate the area and the first moment of area under the concrete’s stress-strain curve with the effective rectangular stress-block.

By testing materials with a universal testing machine (UTM), engineers apply a force (or pressure) with the help of hydraulic jacks to a specimen with a known cross-sectional area. From this, the stress is calculated. The deformation of the member under several instances of load (or pressure) is observed. Based on this actual deformation versus the original length of the specimen the strain is calculated.