Effects of environmental changes on the dynamic characteristic of reinforced concrete beams

In this paper, the effects of environmental changes on the dynamic characteristics of reinforced concrete beams are studied. The study comprised manufacturing and testing 10 reinforced concrete beams. Concrete strength, reinforcement ratio and temperature varied in different specimens. The specimens were lifted up and suspended by elastic cables and tested using a modal test setup. Frequency changes and damping ratios of beams were measured at different ages of specimens. Test results show that the frequencies of all specimens decreased with the age of specimens. The frequencies of the specimen kept outdoors in dry and hot conditions decreased significantly. The average values of the frequencies of specimens with 40 MPa concrete strength were approximately 18 percent larger than those of the specimens with 21 MPa concrete strength. The frequencies of the specimens with the larger tensile reinforcement ratio were larger than those of the specimens with the smaller one. No meaningful trend is seen in the relationship between the damping values and the age of the specimens. The damping values of the specimen kept outdoors in hot and dry conditions are larger than those of other specimens.