SUMMARYThis paper describes the results of shaking table tests to ascertain the ultimate behavior of slender baseisolated buildings and proposes a time history response analysis method, which can predict the ultimate behavior of base-isolated buildings caused by buckling fracture in laminated rubber bearings. In the tests, a base-isolated structure model weighing 192 kN supported by four lead rubber bearings is used. The experimental parameters are the aspect ratio of height-to-distance between the bearings and the shape of and the axial stress on the bearings. The test results indicate that the motion types of the superstructure at large input levels can be classified into three types: the sinking type; the uplift type; and the mixed type. These behaviors depend on the relationship between the static ultimate lateral uplifting force on the superstructure and the lateral restoring characteristics of the base-isolated story. In the analysis method, bearing characteristics are represented by a macroscopic mechanical model that is expanded by adding an axial spring to an existing model. Nonlinear spring characteristics are used for its rotational, shear, and axial spring. The central difference method is applied to solve the equation of motion. To verify the validity of the method, simulation analysis of the shaking table tests are carried out. The results of the analysis agree well with the test results. The proposed model can express the buckling behavior of bearings in the large deformation range.

In this study, we made examinations by means of experimental and analytical methods for the purpose of grasping the shear characteristics of RC walls with corroded reinforcement and verified the validity of analytical models and constitutive laws by making comparisons between the analysis results and the test results. First of all, we conducted two kinds of element tests on the bond strength of reinforcement greatly affected by corroded reinforcement and tension stiffening of concrete around the reinforcement. Regardless of the diameter of the reinforcement, we found that the bond strength could be assessed using past equations and, for tension stiffening, proposed an equation in consideration of the effect of corrosion weight loss by obtaining data of constitutive laws for FEM analyses. Then, we conducted in-plane shearing tests on the RC walls with corroded reinforcement and found that the effect of the corrosion weight loss of reinforcement on the shear strength of the walls was low. Finally, we found that the analyses almost follow the test results through FEM analyses of the RC shear walls with corroded reinforcement using the constitutive laws obtained through element tests and past constitutive laws.

Lateral loading tests using reduced reinforced concrete (RC) walls affected by alkali-silica reactions (ASR) and their simulation analyses were performed in order to evaluate the influence of ASR on the structural performance of shear walls that act as seismic resistant members in nuclear power facilities. The state of RC walls was also measured by several techniques to assess applicable monitoring methods during ASR expansion. The transition of the elastic wave velocity of the walls by the ultrasonic method has a good co-relationship with the transition of the static elastic modulus of the cylindrical specimens, indicating that non-destructive testing could capture the degradation trend of concrete due to ASR expansion. The initial stiffness of the ASR specimens became slightly smaller than that without ASR, but the maximum strength remained at the same level with or without ASR. Based on the results of experiments and analyses, a practically appropriate structural performance evaluation method and a monitoring method of ASR affected RC members were proposed.

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