Study On Mechanics Performance Of Adherence Of New And OLD Concrete After High Temperature

This thesis is a part of subject "Research on mechanism of adherence and measure method of young on old concrete", which is sub-subject of country's momentous foundational research subject (Climbing Project B) <> .New and old concrete adherence has exited in reinforcement, repair and new built project of concrete structures widely and has been the key problem for water conservancy and civil engineering. In order to disclosure new and old concrete bonding mechanics performance and mechanism under high temperature, the paper studies the influence of high temperature on new and old concrete bonding mechanics behavior with two types adherences: bonding first to heating second and heating first to bonding second. The main contents of the thesis are as follow:1. The splitting tensile test and shear test results of 168 new and old concrete bonding specimens of bonding first to heating second type are presented. The influences of several important factors on bond mechanics property are discussed, such as temperature, cooling way, interface roughness, interface adhesive agent. Based on tests, new and old concrete bonding mechanism after high temperature is analyzed.2. The splitting tensile test and shear test results of 114 new and old concrete bonding specimens of heating first to bonding second type are presented. Several important factors are mainly researched, which are temperature, cooling way, interface roughness, interface adhesive agent and new concrete strength. In additional, the main adhesive mechanism is discussed. Furthermore, the rational suggestions are put forward for bonding repair and reinforcement of concrete structures after fire.3. On the basis of related datum, Z shape specimen is designed for shear test and shear stress ~ slip curves and corresponding fitting formula of new and old concrete bonding interface are measured. As to bonding first to heating second type, the multi-factor unified formulas for bonding splitting tensile strength and shear strength are reduced. With regard to heating first to bonding second type, the fitting formulas of adhesive shear strength and shear stress ~ slip curves are presented.4. Based on analyzing abroad and domestic roughness treating method and evaluating ways for new and old concrete bonding interface, a simple surface roughness measure device is designed and corresponding surface fitting method is put forward to deal with measure data. At the same time, this method makes comparison with traditional data average method and pouring-sand method and is suggested to use in fact engineering.5. The shear test results of 60 new and old concrete bonding Z shape specimens arepresented and the roles of roughness, interface agent and new concrete strength on bonding shear strength are obtained. According to the test data, the impact of different water cement ratio on interface agent's effect is clarified and three factors are analyzed by means of square-residual method.6. Concerning that new and old concrete bonding mechanics behavior is not obvious subjected to many affecting factors for heating first to bonding second type, the multi-factor prediction model is established for forecasting new and old concrete bonding splitting tensile strength and shear strength by means of artificial neural network (ANN). Furthermore, the extended predictions are offered for some factors such as roughness, interface agent, cooling way and so forth.7. Based on summarizing present concrete structure's damage evaluation and reinforcement status after fire, the temperature field of structural member in the course of fire is calculated with nonlinear limited element program. After that, the bearing capacity formulas of norm section for compressive member after fire are deduced in the second load strengthening stage.8. The atrium reinforcement calculation of compressive member of certain fire structure is presented. By means of the reduced fo...