Evaluation of the Adequacy of Development Length Requirements for 500 MPa Reinforcing Bars

Abstract

This paper compares the development length requirements of several international codes for 500 MPa steel reinforcing bars with test results obtained from eighteen reinforced concrete beams. These beams were designed specifically to allow the pull out of bars in the tension zone before bar yielding in order to determine the anchorage capacity and hence the development length necessary to obtain yield. After introducing the background to development length requirements and summarizing eight different international code provisions, this paper reports the results of the eighteen beam tests and compares these results with the code provisions. Following the development length comparison among the international standards, several conclusions are drawn. Of all the approaches examined in this paper, AS3600-2001 is always the most conservative one and has the worst correlation with the test data in most conditions, while AASHO has the lowest factors of safety for the smaller bars. These factors are considered reasonable and appropriate. ACI318-05 and ACI Committee 408 are more conservative and provide worse agreement for the larger bars. CEB-FIP Mode Code 1990 and Eurocode 2 always follow a similar trend and have lower, appropriate factors of safety, and also provide a better agreement with the test data in most conditions. GB50010-2002 has the similar factors of safety to CEB-FIP Mode Code 1990 and Eurocode 2. However, it doesn't provide good agreement with the test data for larger diameter bars. Of all the approaches examined here, AS3600-2009, which brings the Australian Standard into line with FIP Mode Code 1990 and Eurocode 2, provides better consistent agreement with the test data and is a significant improvement on the method provided in AS3600-2001. All current codes appear to be over conservative for small diameter bars.