Study On Uniaxial Tensile Performances And Durability Damage Of Hpc Under Cyclic Load

Nowadays, many concrete structures such as bridges, nuclear power station containments, offshore drilling platforms have withstood not only the static loads, but also dynamic loads like vehicle load, nuclear power,water force and so on. Therefore, the research on the properties of concrete structures under static and dynamic load is of vital importance to the proper design and analysis of the above structures.Compared with ordinary concrete, high-performance concrete(HPC) holds the advantages of high durability, high workability, high stability and so on, therefore, HPC has been widely applied in modern complex structures. However, the data of recent surveys suggest that damages of various degrees begin to appear when HPC has been used for several years. Once the HPC cracks, what closely follows is its fast invalidation, as a result, the protective layer of the steel bar will lose its protective effect and direct contact with medium, which accelerates the rusting of steel bars. This is more easily found under marine environment. The cracking of HPC is mainly affected by tensile strength of the material. Therefore, there has been a pressing need to study the axial tensile strength of static and dynamic load of the concrete, as well as simulate the durability change of the HPC in marine environment based on the axial tensile damage.This paper bases on Natural Science Foundation of Shandong Province"Study on the durability of marine concrete under mechanical damage",which is chaired by associate prof.Jiang Fu-xiang form Qindao Technological University.This thesis makes research on the relative properties of HPC mainly from the following aspects:(1) The changing data of physic-mechanical properties of concrete will be collected and the failure patterns of different specimens will be recorded in the loading procedure of tensile cyclic load and static tensile load. According to the analyzed result,features of mechanical properties and deformation properties of HPC during the procedure of axial loading will be pointed out. (2) Specimens, both loaded and unloaded by tensile cyclic load and static tensile load, would be used to carry out capillary water absorption experiment and total porosity test, then total porosity and volume of capillary water absorption would come out, which can reflect various damage degrees of the micro structure of concrete caused by axial load.(3) Specimens, both loaded and unloaded, would be used in an indoor experiment which is carried out in a laboratory with features of simulating marine tide zone and under water zone. After certain time, chloride concentration of different depths need to be tested to indicate the influence of different loading conditions to chloride permeability.(4) Proper predictation model of concrete's life-span need to be selected to determine model parameters, and the result of chloride erosion test need to be taken into consideration. Diffusion coefficient of chloride in HPC structure would be fitted after different axial damages. Then the durable life-span of concrete after different damages can be predicated.