Study On Durability And Impact Resistance Of RC Beams Under Combined Action Of Load And Chloride Dry-wet Cycles

With the implementation of"the Belt and Road"policy in China,a large number of construction technology is exported,and the construction quantity of coastal construction,marine construction and port engineering has greatly increased.Chloride pollution in the marine environment is liable to steel corrosion,which is a main serious threat to the durability of marine engineering structures.At the same time,the structures of offshore engineering are vulnerable to the impact of sea transportation,ships for example,large containers in harbours and even tsunami disasters.In this paper,the durability of reinforced concrete beams under the combination of loads and dry-wet cycles is studied and the impact resistance of these beams are investigated.It provides an important theoretical basis for the future design,reinforcement and maintenance of a large number of marine engineering structures.The main work of the study is as follows:(1)The corrosion tests of 10 reinforced concrete beams under the combination of loads and dry-wet cycles were carried out.Rules of chloride corrosion are investigated through three perspectives,which include the influence of different parameters on chloride concentration distributing in concrete,the influence of bending load on velocity of chloride transporting,and fitting data between chlorine ion diffusion coefficient and chloride ion concentration on concrete surface.The corrosion rules of steel bar are studied by the characteristics of steel corrosion and their weight loss.(2)An analytical method is promoted to comprehensively consider the effects of structural damage and chloride corrosion under dry-wet cycles.The influence function F_d of concrete damage under load is introduced to consider the effect of load and mechanical damage on chloride diffusion in this method.The model of chloride diffusion coefficient model under the influence of multiple factors is summarized and expounded.The significance and value range of each parameter in the model are analyzed.Concrete damage function is introduced modify the model,and chlorine ion transport model in unsaturated condition is comprehensively expounded.The model is adopted in the COMSOL multiphysics software to simulate the experiment.Numerical results are compared with test results and the influence of chloride corrosion rules is studied by parameter analysis.(3)Exploratory experimental study on impact resistance of 4 reinforced concrete beams and 2 corroded ones was carried out.The energy is defined as invariant to investigate the deformation process,strain time and failure characteristics of normal beams with different drop-weight height.Dynamic responses and failure patterns of corroded beams with different dry-wet cycles are studied while the drop-height and the weight of hammers are controlled.Dry-wet cycles of 2 corroded reinforced concrete beams are 182 days and 364 days respectively.Based on the comparison and analysis of the test results and the static load test,the research results of the drop hammer impact test were collected and summarized,and the relevant reference coefficients of the load bearing capacity of the calculated components were obtained.The results of impact tests are collected and compared with that of static load tests to obtain the reference coefficients for determining bearing capacity.