Earthquake Engineering and Structural Dynamics
Sophisticated Innovative High Seismic Structures
In the past, the seismic design was to design a structure that shall be safe against earthquakes. However, since the 1995 Kobe earthquake, Japan's modern seismic design is to design a structure that shall localize limited damage and to prevent collapse against severe earthquake. In other words, the structure shall be designed to be failed as expected against severe earthquakes. Therefore, we are developing a new seismic structure based on new concepts such as robust structure, unbonded bar reinforced concrete structure (UBRC structure), and metabolic structure.
Bridge Bearings, especially Seismic Isolation Bearings
Since bridge bearings are the boundary condition of the bridge girder, it is necessary that bearings exhibit the performance as designed. However, since bridge bearings are installed at the connection between super- and sub-structures, many failures have been reported that the bearings were deteriorated due to regular service and cause damage to the superstructures.
Since the 1995 Kobe Earthquake, laminated rubber bearings have been standard bearings for new constructions and seismic retrofit of continuous bridges. However, in the 2011 Tohoku Earthquake and the 2016 Kumamoto Earthquake, fractures of laminated rubber bearings have been reported. In the current bridge earthquake engineering, the bearings are often the key to seismic performance, and we are conducting researches on seismic isolation bearings and structural control devices.
Development and verification of dynamic response of large-scale structural systems using hybrid simulation
The real-time hybrid simulation is an experimental verification technique to evaluate the dynamic response of large-scale structural systems, for which full-scale shake table testing is difficult. In this test method, the structural system is divided into a numerical substructure and an experimental substructure; response calculation of the numerical substructure with computers and dynamic loading test of structural elements using dynamic test equipments, including shake tables and dynamic actuators, are synchronously executed on a real-time basis by controlling the test procedure using the information of both processes, as a unified testing-computing dynamic simulation corresponding to the time evolution of actual dynamic phenomena. Implementation of experimental systems based on this advanced testing principle allows reliable performance validation in course of the development of advanced seismic response control devices and seismic isolation bearings.
Construction Materials of Infrastructures
Long-term Deterioration of Concrete Structures due to Air-born Salt
Evaluation and prediction on the environmental actions, material deteriorations and mechanical behaviors of concrete structures are being developed. Specifically, on clarifying the mechanism of chloride ingress into concrete under marine atmosphere, environmental action models and various time-dependent models of required behaviors are being constructed to simulate the long-term deterioration of concrete structures due to air-born salt.