SD700 reinforcing steel was added to KS D 3504 revised in 2016, but current design code does not allow the specified yield strength of reinforcing steel to exceed 600MPa because of lack of experimental verification. The purpose of this study is to suggest design equation, which should be able to predict the development length for high strength steel with yield strength of 700MPa in tension with high accuracy and should not differ significantly from current equation for normal strength steel. To evaluate anchorage performance of high strength steel with yield strength of 700MPa in tension, 38 splice specimens with SD700 D19 or D25 reinforcing bar were constructed and tested. The variables of the specimens were splice length, compressive strength of concrete, cover thickness, and amount of transverse reinforcement. Using 24 this test results occurred bond failure before steel yielding and 388 other test results, the ratio of calculated development length by current code to splice length of specimen was compared.
The findings indicated that the development length calculated by KCI Model Code 2017 is unsafe as the yield strength increased when is less than 2.5 for reinforcing bar with specified yield strength exceeding 550MPa. Based on the results, it was concluded that the design equation needs to be modified to apply SD700 reinforcing steel. Therefore, a modified factor for the development length was suggested for the next revision of KCI Model Code 2017.
The development length calculated by KBDC(LSD, 2015) was found to be safe even if the yield strength increased when transverse reinforcement was placed along developed reinforcing bars with specified yield strength exceeding 550MPa. Therefore, it was concluded that the development length of KBDC(LSD, 2015) does not require modification for the application of SD700 reinforcing steel.