Nature of change of logarithmic decreement as a result of cracking in the beams with loop joints

Paying attention to the quite wide spreading of precast and cast-in-situ reinforced concrete in Ukraine, it was necessary to expand the scope of application of various butt joints. In particular, the use of loop rebar joints is itself one of the main design decisions that determines the industrial implementation of construction, primarily hydraulic structures. Loop rebar joints connect elements for assembling precast-monolithic reinforced concrete elements without the use of welding. A large territory of south-western and southern parts of Ukraine is classified as seismically dangerous. The use of modern probabilistic technologies at the design and operation stages of construction projects improves the accuracy of hazardous seismic load estimates and allows to optimize the probable losses from the negative impact of earthquakes. The proper assessment of the level of seismic impact depends on knowledge of the pattern in the logarithmic decrement changes as a result of building structures and buildings damage. Available information does not give a clear understanding of this pattern. A comparative analysis of the change in the logarithmic damping decrement of vibrations because of cracking in beams with a loop joint was carried out. The loop joint was located in the clean bending zone of beam, with keyed and keyless execution of the ends of the joined elements. The data for analysis were obtained from the experiment. We use the power method to achieve the objectives − the instant load removal method. As a result the nature of the change in the logarithmic damping decrement of the beam in case of violation of the integrity of the loop joint zone was established. The values of the logarithmic decrement in the beams with key joints were comparable with the similar values obtained for beams without joints. At the same time, the absolute values of the decrement in beams with keyless loop joints were maximum in these studies.