Study On Dynamic Characteristics Detection And Damage Identification Of The Chloride Corroded Reinforced Concrete Beams

In coastal areas, steel corrosion may happen easily because of chloride-induced for engineering structures, resulting in damage or collapse, moreover causing huge economic losses. That’s the reason for reinforced concrete structure in marine environment, damage identification should be carried out prior to the failure state, so that we can be warned in time and adopt appropriate measures to repair and reinforcement. Only there’s little dynamic characteristics damage identification research for steel corrosion currently, more studies tendency to the damage exists, damage location and extent of damage in a single level of damage identification, less identify studies mentione multi-level damage identification. Therefore, in order to carry out multi-level damage identification in actual engineering structures, carrying out dynamic feature detection and damage identification to chloride corroded reinforced concrete beams has important application value.This paper carried out three parts research basing on reinforced concrete beams: in order to determine the appropriate dosage to ensure the reinforced corrosion rate during the power on and the relative smaller effect of mechanical properties of concrete,we studied the impact of different chloride content on reinforcement corrosion and performance of concrete; according to both cases of different positions of steel, uniform corrosion and different localized corrosion positions, we designed and produced mixed chloride testing beams, through the whole process dynamic testing, we studied the variation of modal shape and frequency with the change of steel corrosion rate; basing on the parameters of dynamic characteristics,we proposed the multi-level damage identification method, after exploring the feasibility of the method by the theoretical model, we verified the method by the damage identification of testing beam. The main results are as follows:(1) Through the study of compressive strength, electric flux, corrosion potential and polarization potentials for seven different dosage specimens chloride, we learned that when the NaCl content was1.90%, the reinforced corrosion rate during the power on and the relative smaller effect of mechanical properties of concrete could be ensured;(2) In the power-accelerated corrosion during1d～30d,we found that with the increase of steel corrosion rate, the first three frequencies of testing beams are corresponding happen, decreased up to15.00%, and the three modal shapes also changed significantly at the corroded position;(3) Based on the frequency and modal shape, we proposed multi-level damage identification method, then used it in damage detection of local corrosion testing beam, we identified the presence of damage, damage location was the same location as the preset position, the extent of damage was reduced59.90%agreeing with experimental results, so the multi-level damage identification methods can be used in actual project..