The number of aged bridges is increasing so that bridges over 30 years old account for about 11% of all bridges. Consequently, the development of a seismic performance evaluation method that considers the effects of ageing is essential for a seismic retrofitting process for improvement of the seismic safety of existing old bridges. Assessment of the damage situation of bridges after the recent earthquakes in Korea has been limited to the bearings, anchor, and concrete mortar on piers. The purpose of this study is to evaluate the seismic responses of PSC box girder bridges by considering the ageing effect of rubber bearings (RBs) and lead-rubber bearings (LRBs). The modification factor proposed by AASHTO is used to take into account the ageing effect in the bearings. PSC box girder bridges with RBs and LRBs were 3D modeled and analyzed with the OpenSEES program. In order to evaluate the ageing effect of RBs and LRBs, 40 near fault and 40 far field records were used as the input earthquakes. When considering the effect of ageing, the displacement responses and shear forces of bridge bearings (RBs and LRBs) were found to increase mostly under the analytical conditions. It was shown that the effect of ageing is greater in the case of RBs than in the case of LRBs.

It is very important to assure the seismic performance of equipment as well as building structures in seismic design of nuclear power plant(NPP). Seismically isolated structures may be reviewed mainly on the horizontal seismic responses. Considering the equipment installed in the NPP, the vertical earthquake responses of the structure also should be reviewed. This study has investigated the vertical seismic demand of seismically isolated structure by lead rubber bearings(LRBs). For the numerical evaluation of seismic demand of the base isolated NPP, the Korean standard nuclear power plant (APR1400) is modeled as 4 different models, which are supported by LRBs to have 4 different horizontal target periods. Two real earthquake records and artificially generated input motions have been used as inputs for earthquake analyses. For the study, the vertical floor response spectra(FRS) were generated at the major points of the structure. As a results, the vertical seismic responses of horizontally isolated structure have largely increased due to flexibility of elastomeric isolator. The vertical stiffness of the bearings are more carefully considered in the seismic design of the base-isolated NPPs which have the various equipment inside.

In order to increase the seismic safety of nuclear power plant (NPP) structures in high seismicity regions, seismic isolation techniques can be adapted to NPP structures. In this paper, the applicability of multi-step analysis of seismically isolated NPP containment structures with lead-rubber bearings (LRB) is evaluated. The floor response spectrum of NPP containment structures with equivalent linear LRB and nonlinear LRB are compared. In addition, the force-displacement relationships for equivalent linear LRB and nonlinear LRB are compared.

본 논문에서는 납삽입 적층 고무베어링의 비선형 모델링에 대해 신경망 이론을 적용한 수학적 모델링 기법을 제안하였다. 신경망 모델의 수치검증을 위해 납삽입 적층 고무베어링이 설치된 프레임 축소모델의 진동대 실험 자료가 사용되었는데, 제안된 신경망의 학습 및 예측을 위한 하중 자료로써 백색잡음과 세 종류의 지진파를 선택하였다. 지진파의 경우 PGA의 세기를 달리하여 신경망 모델의 계산정도를 고찰하였다. 그 결과, 납삽입 적층 고무베어링의 전단변위가 신경망의 학습 영역을 벗어나지 않는 경우 실험결과의 복잡한 이력곡선을 잘 추종하였고 신경망 이론에 의한 비선형 모델링 기법이 유용하게 활용될 수 있다는 가능성을 확인할 수 있었다.