Studies On Bond Behavior Between Reinforcement Bar And Semi-lightweight Concrete On Meso-level

The Semi-lightweight Concrete has been widely used in super-high building structure、Long-Span Bridge Structure、offshore platform structures and others due to its advantage of lightweight and high strength、thermal insulation、fire resistance、antifreeze and etc.In order to grasping the relative performance of Semi-lightweight Concrete better and Developing its practicality and economy,This paper implement a research project about the Bond Behavior between Reinforcement Bar and Semi-lightweight Concrete basing on the studying the bond theory of reinforced concrete and ordinary concrete.The Bond Behavior between Reinforcement Bar and Semi-lightweight Concrete is complex and changeable,and according to existing research,Concrete has been regarded as a single and homogeneous material,this method of processing has been proven to be effective over time.But There is a necessary that starting with the nature of the polyphase and compound material in order to understanding the mechanism of bond failure of bar and concrete for further study.In this paper,numerical analysis model about Reinforcement Bars to Semi-lightweight Concrete under direct pullout was built by using the method of meso-mechanical simulation from the perspective of micro-level.The main research contents and conclusions are as follows:(1)The mesoscopic numerical model was built and pullout specimen of Reinforcement Bar and Semi-lightweight Concrete was to be thought as a kind of polyphase and compound material made up by reinforcement bar,mortar,ordinary aggregate,lightweight aggregate and interface adhesive material between bar and mortar.Firstly,the aggregate quantity is calculated through the aggregate gradation theory,and then ordinary aggregate and light aggregate were put in randomly through the Monte Carlo method,at the same time,there is an algorithm established to avoid interference and overlap between materials.The parameter definition and mesh generation were done by using a finite element preprocessor module of ANSYS.The model was built basing on APDL,and it forms an effective parameterized program in ordering to facilitate the analysis of different conditions.(2)It has done the meso-mechanical simulation of bond behavior between reinforcement bar and semi-lightweight concrete to studing the overall process of bond failure between reinforcement bar and semi-lightweight concrete from the cell damage,progress of fracture,stress distribution.And it provided the factual basis for the research of the failure mechanism and the cohesion failure in macroscopic.The simulation results are compared with the experiment,and the feasibility of the model is verified.(3)This paper modeled bond failure process of different water cement ratio and light aggregate replacement rate by using the method of variable control,and it studied the effect of the ratio of water cement ratio,light aggregate ratio and anchorage length of steel bar to bonding strength and adhesive property,and the paper analyzed the regularities of distribution about bond stress along the length of reinforcement.Finally,formulas about relative bond strength and relative anchorage length were summarized.