EVALUATION OF STEEL REBARS MANUFACTURED IN PAKISTAN AND THEIR PERFORMANCE IN RC MEMBER

ABSTRACT

The manufacturing of steel bars in Pakistan includes raw materials from various sources. Steel rebars produced from ship scrap materials are unlikely to exhibit sufficient deformation capability or ductility. As a result, mechanical properties of these bars can vary from one batch to the next. other. It is generally recognized that steel re-bars to be used in reinforced concrete application should exhibit adequate strength and ductility and should meet other requirements for adequate durability. There are several regulations concerning re-bar testing in Pakistan. These include BS standards, ISO standards, ASTM standards and PSQCA (PS) standards.

The aim of this project was to evaluate the behavior of Reinforced Concrete (RC) beams reinforced with steel rebars manufactured in Pakistan.   The scope of this project is limited to the results of the statistical analysis performed on the test data provided by Material Testing Laboratory, Civil Engineering Department, NED-UET.  The objectives were:

  • To conduct statistical analysis of tests of limited number of steel rebars manufactured in Pakistan.
  • To study the behavior of RC beams by using different stress train curves of rebars and evaluate the effects of increasing yield strength and decreasing ultimate elongation (material ductility) on flexure behaviour of RC beam.

The results showed that:

  • Most of the steel bars tested at NED testing lab have adequate tensile yield strengths and ultimate strengths which is greater than required by ATM 615 and ASTM 706
  • Most of the steel bars satisfy the criteria of the ratio (ultimate strength/yield strength) to be less than 1.20 which is prescribed in ASTM 706.
  • Most of the steel rebars, fail to meet the ultimate elongation criteria of ASTM.

The results of the Analytical Model (RESPONSE 2000) show that:

  • The curvature ductility of RC beam decreases with the decrease in the ultimate elongation of steel rebar.
  • The curvature ductility of RC beam decreases with the increase in yield strength (fy) of steel rebar.
  • The curvature ductility of RC beam decreases with increase in the reinforcement ratio.

From one case study (Gulbahar Rizvia Society Building), it is concluded that by using the stress-strain curves of the steel rebars used in the construction, the computed yielding moment (My) and ultimate moment (Mu) are smaller than those computed for a Typical Grade 60 steel bar.