Neutron radiation-induced volumetric expansion (RIVE) of concrete aggregate is recognized as a major degradation mechanism causing extensive damage to concrete constituents (Hilsdorf et al. 1978; Seeberger and Hilsdorf 1982; Field et al. 2015). Nearly 400 RIVE data obtained in test-reactors on varied rock-forming minerals were collected by Denisov et al. (2012). These data were input into the Oak Ridge National Laboratory (ORNL) irradiated minerals, aggregates and concrete (IMAC) database and were reanalyzed in order to develop a general empirical model for minerals RIVE and interpret the susceptibility of silicates toward expansion. The empirical models best regression coefficient (r2 ≈ 0.95) is obtained by combining two different modeling techniques: (1) an interpolation-like model based on the relative distance to existing data points, and, (2) a nonlinear regression model assuming varied mathematical forms to describe RIVE as a function of the neutron fluence3 and the average irradiation temperature. The susceptibility to develop irradiation-induced expansion greatly varies with the nature of minerals. Silicates, i.e., [SiO4]4– bearing minerals show a wide range of maximum RIVEs, from a few percents to what appears as a bounding value of 17.8% for quartz. The maximum RIVE of varied silicates appears to be governed, macroscopically, by three parameters: (1) Primarily, the dimensionality of silicate polymerization (DOSP), (2) the relative number of Si–O bond per unit cell, and, (3) the relative bonding energy (RBE) of the unit cell.
The aim of this study is to experimentally investigate the effect of drying on a shear wall, and to clarify the mechanism of the changes in the structural performance due to drying. Two sufficiently hydrated wall specimens are prepared. Then, one is loaded without drying, while the other is tested after sufficient drying until the shrinkage of concrete reaches an equi-librium state. The results show a reduction in the initial stiffness and little change in the ultimate shear strength in the dry specimen, in spite of an increase in the compressive strength. Reproduction numerical analysis using Rigid Body Spring-network Model (RBSM) coupled with a truss network model for moisture transport is conducted, and an ac-ceptable agreement is confirmed in the ultimate strength and the crack patterns. From the numerical results, it is revealed that two factors are balanced in the ultimate shear strength after drying in this experiment: 1) an increase in the com-pressive strength due to aging (material scale), and 2) a strength reduction due to lateral strain, which is evaluated using the formula suggested by Vecchio and Collins (1986) (member scale). This indicates that the wall reinforcement ratio and concrete shrinkage have the influence on the ultimate strength through increasing/decreasing the number of cracks and the crack width.
The mechanical characteristics of CRTS III (China Railway Track System III) slab ballastless track structure under high-speed train load were analyzed by both the full-size fatigue test and numerical simulation in commercial FEM (finite element method) software Ansys. Considering the damage characteristics of concrete, a concrete fatigue damage constitutive model with the concept of mode-II microcracks for concrete was selected and applied in the FEM model. Based on this model, the fatigue FEM model of CRTS III slab ballastless track system was established and relative numerical simulations were conducted. Also, the simulation results were verified by full sized fatigue test on full sized CRTS III slab ballastless track structure. In addition, through the FEM analysis of CRTS III slab ballastless track structure under fatigue loading, the damage evolution law of CRTS III slab ballastless track structure under high-speed train load was also explored and concluded. It was illustrated that the numerical simulation results by FEM model es-tablished in this work was in well agreement with the fatigue test results. Therefore, the relative findings and conclusions from the tests and FEM analysis in this work were able to provide significant references for relevant researchers.