| The bond between reinforcing steel bars and concrete plays a crucial role in estimating the deformation and ultimate conditions of reinforced concrete structures. During the service life of structures, they may be suffered from severe earthquakes or dynamic loading with high loading rates. Moreover, in simply supported structures or beam-column joints, the lateral pressure around the anchorage region exerts great influence on the bond behavior. To accurately evaluate and rehabilitate the concrete structures under dynamic loading, the knowledge of the bond behavior between concrete and reinforcing bars with lateral pressure and different loading rate or reversed loading are important. However, such knowledge is now extremely lacking. Therefore, the objective of this thesis is to study the bond performance of plain round and deformed reinforcing bars on pull-out specimens subjected to lateral pressure and monotonic dynamic loading. The bond behavior of deformed bar under different lateral pressure and reversed loading are also considered. The main research contents and findings are summarized as follows:(1) The experimental study on the effect of loading rate on the bond behavior of plain round bars in concrete under different lateral pressure shows that, when no lateral pressure is applied, the effect of the loading rate on the bond behavior of plain bars is negligibly small. When lateral pressures are applied, the bond strength is dominated by the friction between the plain bar and concrete and the loading rates have a great influence on the bond performance. For a given lateral compressive stress, the bond strength is basically a linear function of the loading rate ratio, the larger the lateral pressure is, the more pronounced the loading rate effect is. The ratio of ultimate and residual bond strengths basically keeps constant. Through analyzing the test results, the ultimate bond strength, the corresponding slip and the residual strength are fitted with respected to the lateral pressure and loading rate.(2) The bond behavior of deformed bars under different uniaxial lateral pressure and loading rates was studied. The test results show that, when the lateral pressure is applied perpendicular to the transverse rib, a higher loading rate leads to a smaller crack width, but the percentage decrease is almost independent of lateral pressure. The ultimate bond strength is proportional approximately to the logarithm of loading rate ratio. The percentage increase of the bond strength decreases with the increase of the strength of concrete or the bar diameter.(3) The bond behavior of deformed bars under different biaxial lateral pressure and loading rates was studied. The test results indicate that, the bond resistance of deformed bars is dependent mainly on the strength of concrete between the ribs. With the increase of loading rate, the increasing extent of bond strength is decreased with higher lateral pressure. According to the test results, expressions for bond parameters and bond stress-slip relationship were proposed.(4) The experimental study on the bond behavior of deformed bars in concrete subjected to lateral pressure and reversed loading indicates that, for a given controlling slip, the percentage decrease of the bond strength greatly influenced by the presence of lateral pressure with larger diameter steel bars. Based on the test results, a regression analysis is conducted for the bond parameters with respected to the lateral pressure and reversed loading. When bar diameter, strength of concrete, lateral pressure and controlling slip are given, the models proposed in this study can be determined to predict the bond stress-slip relationship of deformed bars under different lateral pressure and reversed loading, and the results show an agreement with the experimental results. |
