Experimental Study on the Relationship between the Natural Frequency and the Corrosion in Reinforced Concrete Beams

Abstract

Due to many nondamage factors such as temperature, humidity, carbonation, and corrosion effects on natural frequency, the key problem of the application frequency-based method to detect damage is to reveal the rules of these factors affect natural frequency and further to eliminate their effects. The long-term characteristics of reinforced concrete structures require a lot of attention, especially in corrosive environment. In this paper, an experimental investigation was conducted to study the deflection and natural frequency of reinforced concrete beam in a marine environmental chamber for six corrosion stages (accelerated corrosion for 0, 20, 40, 70, 100, and 140 days). The experimental results demonstrated that deflection increases with corrosion time, while natural frequency decreases with corrosion time. Based on the accelerate corrosion test data of reinforced concrete beams, the general expression of the relationship between corrosion depth and natural frequency has been established through the fitting curve method. The polynomial model has been selected for establishing the relationship between steel corrosion depth (including the main reinforcement and stirrup) and natural frequency. The reason for selecting the polynomial model is that the sum of squares due to error (SSE) is closer to 0 and the coefficient of multiple determination (R-square) is closer to 1. This investigations help to discriminate the cause of reinforced concrete beams natural frequency change, to eliminate nondamage factors affects, and to apply many structural damage identification methods effectively.

Challenges in assessing corrosion damage in reinforced concrete beams by vibration-based monitoring: literature analysis and experimental study

“…Furthermore, the results show a clear decreasing trend since all values are derived from a single beam which was tested at different CLs. Finally, Zhang et al 49 reported a relatively large decrease in f 1 with respect to the low CL. However, Figure 3 only shows the CL of the main reinforcement while the stirrups of the beams tested by Zhang et al 49 reached more than double the CLs of the main reinforcement.…”

“…Finally, Zhang et al 49 reported a relatively large decrease in f 1 with respect to the low CL. However, Figure 3 only shows the CL of the main reinforcement while the stirrups of the beams tested by Zhang et al 49 reached more than double the CLs of the main reinforcement. Furthermore, it should be noted that the change in f 1 for the experiments of Zhang et al 49 is calculated relative to the natural frequency after 20 days of corrosion since no initial reference value was obtained from a non-corroded beam.…”

“…Furthermore, it should be noted that the change in f 1 for the experiments of Zhang et al 49 is calculated relative to the natural frequency after 20 days of corrosion since no initial reference value was obtained from a non-corroded beam. Figure 3 shows the results for four different specimens tested by Zhang et al, 49 while Table 1 contains an average value since the CLs of all four beams are very similar.…”

“…Spalling reduced the natural frequencies up to 75% more than moderate cracking. Additionally, Zhang et al 49 observed relatively large changes in f 1 , which were likely related to corrosion of the stirrups, causing transverse cracking of the concrete. However, more research is needed on beams with various crack patterns to further investigate this topic.…”

“…Overview of experimental results regarding monitoring of the natural frequencies of corroded beams reported in the literature. (The results by Zhang et al49 …”