Chemical and Mechanical Properties of Steel Rebars Manufactured in Pakistan and Their Design Implications

Abstract

The use of steel to reinforce concrete has been a long tradition, which is made possible by its strength and compatibility with concrete. Steel is also considered an ideal material for carrying out seismic-resistant construction due to its ductility and high-energy-absorption capacity. Raw materials from different sources are used in the manufacturing of steel bars in Pakistan. As a result, chemical composition, crystalline structure, and mechanical properties of these bars can vary from each other. This paper presents the results of chemical and mechanical tests on the cold-twisted ribbed and hot-rolled deformed steel reinforcing bars. Both types of bars are used in the construction industry in Pakistan. Although chemical composition of the bars met the requirements of the respective standards, a significant number of bars were unable to meet the specified strength and elongation requirements. The bar-failure percentage to meet the specified minimum yield strength was as high as 60%. A large variation in the data of rebar strength was noted. Design implications of using these bars were studied and it was found that the failure mode of flexural members may change from ductile to brittle. Therefore, suggestions are made for safe structural design. A reliability analysis is also carried out and modified values of strength-reduction factors in flexure and shear are suggested.