Nuclear power plants are required to act as barriers to gases, liquids, and to hold negative pressure during the earthquakes. The maximum crack width is frequently used as the damage indicator of these properties, but the authors think it is inadequate to evaluate the shielding performance of nuclear power plants by means of the maximum crack width. The nonlinear finite element (FE) analysis is widely used for simulating the seismic behavior and crack patterns of reinforced concrete (RC) structures. However, it is difficult to predict crack width and crack spacing through conventional nonlinear FE analysis with smeared crack concept.
Therefore, a series of cyclic loading test on RC shear wall specimens were conducted to obtain validation data on the crack width, length, and spacing. Five specimens, with each having a wall of 1280 mm × 800 mm area and 85 or 100 mm thickness, were constructed. Two columns, a base stub, and a loading stub were attached to the wall of each specimen. The variables of the specimens were as follows: the shear reinforcing bar ratio (1.0% or 0.5%), reinforcing bar arrangement type (double or single), and diameter of reinforcement bar (D6 or D10). The compressive strength of concrete was approximately 30 N/mm2. The specimens were subjected to horizontal cyclic load under constant axial force. When the drift angle reached peak points (±0.1%, ±0.15%, ±0.2%, ±0.25%, ±0.3%) and each unloading points in the cyclic load, the crack width and length of the wall were comprehensively measured using a crack scale. The experimental results show that the maximum crack width and crack spacing depend on reinforcement bar arrangements, such as the reinforcement bar ratio, rebar diameter, rebar spacing, and arrangement type. However, crack area, which is defined as the product of the crack width and crack length, is unaffected by these factors but correlated to the drift angle of the wall.
Furthermore, nonlinear FE analyses were conducted using widely-used smeared crack model to simulate the test results. The horizontal load and drift angle relationships of the FE analysis agree well with the experimental ones. In order to estimate the crack area from the FE analysis results, the increase in the wall area was calculated using two methods. One is based on the nodal displacement, whereas the other is based on the normal strain of the element. The increase in the wall area evaluated using these two methods correspond to the actual crack areas of the specimens. However, the method based on the normal strain of the element is supposed to be more rational because it is able to exclude the thermal expansion and shrinkage.
It is concluded that the quantitative tendency of the relationship between the wall drift angle and crack area can be evaluated through nonlinear FE analysis, but the accuracy of the evaluation method needs to be improved further.
