PARAMETRIC STUDY OF HELICAL SPIRALS AGAINST COMPRESSIVE FORCE

Abstract

In compression member when we apply compressive force both axial and lateral stresses were produced in member. As axial stresses are compressive in nature, they are carried by concrete easily but lateral stresses are tensile in nature. As Concrete is weak in tension, it causes failure of concrete member by bursting or bulging. Here confinement reinforcement comes into picture by taking lateral tensile stresses produced in the member. Mostly in circular member circular ties were used as confinement reinforcement despite of knowing that helical spirals provide better confinement. Also helical spirals provides stiffness to the member unlike conventional ties. This paper presents parametric study of helical spirals related to confinement and stiffness provided. Parameters to be studied are pitch, loop diameter, and spiral diameter of reinforcement. This study were done theoretically, analytically and experimentally. Theoretically by stiffness and confinement formula using thin shell theory concept of confinement. Analytically by using Ansys Workbench and experimentally by casting concrete cylinders with helical spirals and testing it under UTM for compressive load at 28th day. Total 20 cylinders were casted for experimental study with 3 variation of pitch, 2 in loop diameter and 2 in spiral diameter. This paper shows an optimal pitch, spiral diameter and loop diameter and their effect on stiffness and confinement.