SUMMARYThe paper under discussion presents a detailed study on the reduction of pounding force on buildings due to expansion joints being filled with rubber. From shake table experiments and numerical simulations, the authors of the paper concluded that the rubber can reduce the maximum pounding force and hence the pounding damage to buildings. However, the writers of this short communication observed some significant issues in the experimental results as well as the numerical simulations. These observations are presented and raise questions about the validity of the results and the subsequent conclusions.

The detailed seismic responses of pile-soil systems are usually evaluated by a three-dimensional finite-element model which requires a lot of computational resources. In the actual structural design for these models, a computationally efficient method with a reasonable accuracy is preferred from the viewpoint of cost and time. As for the seismic response of a pile-soil system, a kinematic effect due to the forced displacement of the surface ground is considered to be important, especially in soft ground, together with the inertial effect due to the inertial forces from superstructures. In this paper, a new response spectrum method in terms of complex modal quantities is developed for the evaluation of the maximum kinematic seismic response of the pile-soil model to the ground motion defined at the engineering bedrock surface as an acceleration response spectrum. The ratio of the pile-head moment due to the kinematic effect to that due to the inertial effect will be discussed in detail.

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The energy input to a soil-structure interaction (SSI) system during an earthquake is an important measure of seismic demand. It is formulated here in the frequency domain. Exact higher-order sensitivities of the input energy to the SSI system are derived with respect to uncertain soil stiffness and damping parameters. It is shown that the input energy can be derived in a compact form through the frequency integration of the product between the ground-motion input component and the structural model component. By taking full advantage of this compact form, it is demonstrated that the formulation of earthquake input energy in the frequency domain is essentially appropriate for deriving the exact higher-order sensitivities of the input energy to the SSI system with respect to the uncertain parameters. The exact higher-order sensitivities facilitate to express the input energy variation due to uncertainty of ground stiffness and damping, and to find the most unfavorable combination of the uncertain parameters leading to the maximum energy input.