Abstract
Traffic volume increase and higher proportion of heavier trucks have raised the potential risk of fatigue failure of short-span reinforced concrete beams. To investigate the fatigue behavior of short-span reinforced concrete beams with and without the overload effect, nine 5 m reinforced concrete T-beams were cast and tested. Two beams were tested under static loading to determine the ultimate strength; the remaining seven beams were subjected to cyclic loading with constant-amplitude load ranges. In addition, two of the seven beams were subjected to instant overloading. It was observed that the typical failure mode under cyclic loading was the fatigue fracture of tensile reinforcing bars. The introduction of instant overloading resulted in a remarkable reduction of fatigue life. Among all the parameters, the stress range of the reinforcing bars showed the highest effect on the fatigue life. In the end, the fatigue safety provisions in the current reinforced concrete beam design codes were evaluated based on the fatigue limits and S-N curves.
Highlights
Reinforced concrete (RC) beam bridges have been widely used
Based on two large-scale fatigue tests and the S-N curve established from 120 small-scale reinforced concrete beams, the current fatigue provision in the AASHTO LRFD Bridge Design Specifications (2012) was proven to be applicable to high-strength reinforcing bars as well
It has been concluded that instant overloading leads to a significant reduction of the fatigue lives of reinforced concrete beams due to the remarkable stress range increases in reinforcing bars
Summary
Reinforced concrete (RC) beam bridges have been widely used. According to the US National Bridge Inventory and Chinese official statistical reports, nearly 70% and 90% bridges were classified as concrete bridges in the United States and China, respectively. Two full-scale reinforced concrete beam bridges were subjected to real truck load for two and a half years. More experimental investigations of fatigue behavior of RC beams were conducted later on with low stress ranges to simulate real service conditions. Under such low stress ranges, the fatigue fracture of tensile reinforcing bars was the typical failure mode (Helagson & Hanson, 1974; Menzies, 1971; Roper & Hetherington, 1982). Based on two large-scale fatigue tests and the S-N curve established from 120 small-scale reinforced concrete beams, the current fatigue provision in the AASHTO LRFD Bridge Design Specifications (2012) was proven to be applicable to high-strength ( fy < 690 MPa) reinforcing bars as well. This research strengthens the findings of the preliminary study on this issue
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