Multi-scale Review for Possible Mechanisms of Natural Frequency Change of Reinforced Concrete Structures under an Ordinary Drying Condition

Abstract

Based on a review from a view point of multi-scale perspective, it is concluded that possible mechanisms of natural frequency change of concrete structures under an ordinary drying condition are reduction of Young's modulus of concrete and stiffness reduction of reinforced concrete member due to shrinkage-induced cracking. Both two mechanisms can be provoked by drying, which is natural environmental condition for all the building structures. This natural frequency change is important for the integrity analysis of nuclear power plants because seismic response change and sympathetic vibration between structure and installed implementations are expected. In addition, to understand the mechanism this mechanism should contributed to post-earthquake integrity evaluation which is necessary to efficient and continuous operation of nuclear power plants. The lost parts of scientific knowledge and needs of experimental data for whole picture of this natural frequency change have been pointed out.

Development of Soundness Assessment Procedure for Concrete Members Affected by Neutron and Gamma-Ray Irradiation

“…Previous studies found that the shrinkage strain of matured cement paste was a function of the incremental statistical thickness of ad- sorbed water films (Badmann et al 1981), as shown in Fig. 120 (Maruyama 2016). Above 40% RH, the shrinkage associated with the first desorption process has a linear relationship with the incremental statistical thickness of adsorption.…”

“…Specimens exhibited slight shrinkage, as shown by the length changes in Fig. 40 (a); this was in the range of normal drying shrinkage (Maruyama 2016). pressive strength data.…”

“…Instead, we will discuss the changes in aggregate volume. Several studies have already found that the volumetric stability of aggregates against drying is a key factor causing the drying-induced shrinkage strain of concrete (Roper 1960;Fujiwara 2008;Maruyama 2016).…”

“…This, among other reasons, causes changes in the natural frequencies of buildings (Maruyama 2016). More data is necessary, however, to properly understand this problem.…”

Relationship Among the Permeation Rate of Water into Concrete, the Mix Design, Curing, and the Degree of Drying

“…Parrot (1992) and Dias (2004) indicated that the sorptivity corresponds to the amount of water lost by drying. C-S-H is known to shrink due to drying (Maruyama 2016) and Taylor et al (1999) mentioned that dried C-S-H swelled due to absorbed water. The absorption of water into concrete was reduced compared to that of n-decane and this difference was explained by the swelling of C-S-H.…”