Distributive relationship of anchorage force relative to reinforcement and headed bars: Fid-Bau Portal

Distributive relationship of anchorage force relative to reinforcement and headed bars

Miao, Tianming / Zheng, Wenzhong

Highlights • 120 specimens with different parameters were tested. • Experimental phenomena were explained and verifying the accuracy of the programs by test data. • The concept of stable development length was proposed and the fitting equation was given. • The distributive relationship between F b/F y and l ah/l as was found at reinforcement yield moment.

Abstract When using headed bars, the distributive relationship of anchorage force between reinforcement and headed bars is crucial. This study conducted pull-out tests on 120 specimens, categorized into 24 groups, with a cross-sectional area of 150 × 150 mm, and the parameters considered were diameter (d), yield strength of reinforcement (f y), embedment length (l ah), and strength grades of concrete (f cg). The corresponding programs were proposed and verified based on test results. The concept of a stable development length (l as) was proposed as the critical length to determined whether the headed bars entered a working state. An analysis indicated that the ratio of l as to d increased linearly with the ratio of f y to the tensile strength of concrete (f t,m), and decreased nonlinearly with the ratio of the protective thickness (c) to d. A formula was established for l as using two independent variables. l as and the critical development length (l ac) were determined to be 1.28 times and 0.66 times the general development length (l a), respectively. A further analysis demonstrated that the ratio of the pressure of headed bars (F p) to f y and the ratio of l ah to l as were only related to the ratio of c to d. Thus, the distributive relationship of the anchorage force between the reinforcement and the headed bars was obtained.