Study On The Dynamic Property Of The Concrete Material And Structure Considering The Ambient Humidity

ABSTRACT:For concrete structures under water immersion, such as cross-sea bridges, high-arch dams, offshore platforms, etc., the internal moisture of them must be influenced by the ambient humidity, which leads to the change in the dynamic behavior of the concrete material and structure. Therefore, the dynamic property of the concrete material and structure under water immersion need to be studied necessarily.With the combination between the theory and experiment, this paper analyzed the elasticity modulus and energy dissipation of the concrete material with different moisture contents and connected the energy dissipation performance of the material and the structure; based on the above, the dynamic characteristics and response of the concrete structure with different moisture contents was investigated. The detailed methods and conclusions are as follows:(1) According to the experiment on moisture-influenced elasticity modulus of concrete, this paper studied the relationship between the elasticity modulus and moisture content; besides, the mechanism of the moisture influence was investigated; the moisture-related natural frequency of the cantilever beam was studied according to the dynamical experiment. With the moisture content growing, the elasticity modulus of the concrete and natural frequency of the cantilever beam increase.(2) The paper presented the relationship between the material loss factor and moisture content on the basis of the experiment of the effect of the ambient humidity on material damping dissipation; the energy dissipation of the concrete material grows as the moisture contents increasing. The micro-mechanical of the moisture-related material damping dissipation was studied from some aspects like the composition, ITZ and water itself.(3) The viscosity coefficient of the concrete was calculated based on the constitutive model of the viscoelasticity material; it decreases with the moisture content increasing. The moisture-related damping dissipation coefficient was studied according to the complex damping theory; the loss factor and damping ratio of the flexural member with any section types under any load patterns is related to the damping dissipation characteristics of the material itself, section type, load pattern, constrained type and amplitude of the stress; the moisture-related damping ratio of the cantilever beam was studied. (4) Based on the above studies, taking the concrete pier as an example, the finite element calculation method of the moisture-related damping was proposed. With the same moisture content, the damping ratio of the concrete pier increases as the seismic intensity increasing, but the increase trend gradually levels off; under the low seismic intensity, damping ratio meets an increase trend with the moisture content increasing, however, under the high seismic intensity, the damping ratio decreased when the concrete pier is nearly saturated; the damping ratio is larger than the constant damping ratio under the concrete being nearly saturated or saturated.