Seismically isolated nuclear power plants (NPPs) can provide substantial benefits towards reducing the failure probability of NPPs, especially for beyond design basis earthquake shaking. One risk posed by seismic isolation is the potential for pounding to a stop or moat wall, with currently little guidance provided by design standards on how to address this concern. In this paper, a structural model of an isolated NPP based on the Advanced Power Reactor 1400 MW is enveloped with moat walls and advanced bearing models. The bearing models account for large strain behavior through failure based on full-scale experiments with lead rubber bearings (LRBs). Using these analytical models and a measured ultimate property diagram from LRB failure tests, the range of clearance to the stop considering the performance criteria for the NPP is investigated. Although the analysis results are dependent on the particular models, ground motions, and criteria employed, this research provides an overview of the seismic response and performance criteria of an isolated NPP considering the clearance to the stop.

An anchorage system is necessary in most reinforced concrete structures for connecting attachments. It is very important to predict the strength of the anchor to safely maintain the attachments to the structures. However, according to experimental results, the existing design codes are not appropriate for large anchors because they offer prediction equations only for small size anchors with diameters under 50 mm. In this paper, a new prediction model for breakout shear strength is suggested from experimental results considering the characteristics of large anchors, such as the prying effect and size effect. The proposed equations by regression analysis of the derived model equations based on the prying effect and size effect can reasonably be used to predict the breakout shear strength of not only ordinary small size anchors but also large size anchors.

This study investigates a prediction method for the compressive strength of concrete considering the pore relative humidity. Water within concrete not only facilitates the bonding of cementitious materials and aggregates but also influences the pore structure, thus affecting the compressive strength of concrete. While the relationship between the water–cement ratio and mechanical properties has been extensively explored, the quantitative effects of curing and moisture history on compressive strength remain insufficiently demonstrated. This research aims to fill this gap by proposing predictive models that consider the history of pore humidity. Experimental data from previous studies were utilized to develop and verify these models. Pore humidity was assessed through self-desiccation and diffusion processes. A self-desiccation model was formulated based on existing experimental results, and the finite element method was employed for diffusion analysis. The prediction model for compressive strength was derived from the rate constant model, incorporating apparent activation energy and adjusting for various curing conditions. The proposed models provide a robust framework for predicting the compressive strength of concrete under diverse curing scenarios. This research contributes to the development of practical tools for ensuring the safety and durability of concrete structures in the construction industry.

In nuclear power plants, anchors connect large safety-related equipment to concrete structures, with relatively deep embedment. In these plants, structural members contain orthogonal surface reinforcement to resist flexural actions and control cracking. Therefore, in practice, anchors are installed in reinforced concrete members with reinforcement located near the concrete surface. However, current design codes do not account for the influence of surface reinforcement on concrete breakout strength, and the literature has not focused on substantially deeper embedment. This study investigates the effects of surface and supplementary reinforcement on the tensile behavior of anchors embedded in concrete. Experimental results, supported by internal strain measurements, showed that surface reinforcement has negligible effect on tensile capacity, with measured strains remaining below 6% of the yield strain at peak load. By contrast, supplementary reinforcement using D19 and D22 bars increased both the tensile strength and post-peak ductility of the anchor system. However, the degree of improvement depended on the absolute distance between the anchor and supplementary reinforcement. In specimens with larger absolute distances, the supplementary reinforcement reached its maximum resistance only after the overall system had already attained its peak load. Consequently, the synergistic contribution of the concrete and supplementary reinforcement was lower than that predicted by existing analytical models, including the INFASO model. The results revealed that sufficient embedment length is essential to develop the yield capacity of supplementary reinforcement and achieve ductile failure. These findings suggest that the absolute geometric arrangement of supplementary reinforcement should be considered when evaluating anchor performance and reliability.