Research on Short Term Flexural Stiffness of Concrete Beams with High Strength Steel Bars

Several batches of reinforced concrete (RC) and prestressed reinforced concrete (PRC) beams with 500MPa steel bars were tested in Tongji University, recently. The results indicated that the development of flexural stiffness after concrete cracking was influenced mainly by three parameters including initial elastic flexural stiffness, longitudinal reinforcement ratio and load level. Based on our 20 years' systematic research on crack and stiffness, a simpler unified formula is suggested after theoretical analyses for predicting short term flexural stiffness of concrete beams using high strength steel bars. Comparison with calculations from different codes at home and abroad exhibits that the suggested formula is precise and practical for both RC and PRC beams.