Study on Damage and Strengthening Effects of Building Structures based on Vibration Tests using Impactor Machine

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In earthquake engineering, it is important to investigate the change of dynamic property of building structure resulting from damage during earthquake and strengthening by seismic reinforcement work. The change of natural period and vibration modes of soil-structure interaction system based on vibration tests make it possible to identify the damage and strengthening effects of each structural parts. In this project, first, damage and strengthening effects were investigated based on the forced vibration tests at an existing building before and after reinforcement work. Second, the shaking table testing technique of soil-structure interaction system based on the substructure method was developed and system identification of the model structure was performed.Up to the fiscal year 2001, the vibration tests using impactor machine and unbalanced-mass type excitor are performed at the actual 9 story RC building of Tohoku University. The vibration tests were performed before the reinforcement … More work and after the work. Based on the before-test, the damage detection technique was first discussed by comparing the vibration characteristics using the structural model which explain well those after the building's completion. The stiffness reduction factors were detected for each portion of the structural elements. Then, the seismic strengthening effect was discussed using the test results after the reinforcement. The same technique as the damage detection for the before-test was used to identify the stiffness increase for each portion of the structural elementsIn fiscal year 2002, the shaking table testing technique based on the substructure method was developed using a controlable electro-magnetic type shaking table. The testing method makes it possible to perform the vibration test of structure on assumed arbitrary soil conditions. First, the numerical simulation of the test was performed and verified the validity of the testing technique through the system identification of the used soil spring using the acceleration observation record. Then, the model tests of the different soil-structure system are performed using the testing device and the efficiency of the testing technique was confirmed through the system identification of the interaction system. The damage/reinforcement effects of the testing model can be evaluated based on the developed testing method. Less