No abstract

We researched aging of the LRB (Lead Rubber Bearing) installed in a base-isolated building which was constructed 15 years ago. The hardness of the cover rubber and the height were measured for 35 LRBs which were installed in the building. The compression test and combined compression shear test with monitor samples and actually installed LRB were performed to search changes in their hysteresis characteristics. The monitor samples were composed of 4 LRBs and 1 RB. Main results obtained were as follows: 1) The LRBs installed in the TC building crept approximately 1 (mm) during 15 years and did not changed during last 5 years. 2) The hardness of the cover rubber did not change against that of 15 years ago. 3) From the testing of the monitor samples, the compression stiffness increased approximately 17% and the shear stiffness increased approximately 5%, however the yield force changed quite a little during 15 years on average. As a result, the suitability of the design specifications of the LRB was confirmed.

In this paper, a new vibration control device called pendulum-type tuned mass damper (P.T.M.D.) is proposed to reduce an ordinal house vibration. In recent years, three or four stories houses are built increasingly in the urban areas to obtain wide living space. These houses are subjected to a problem caused by the traffic vibration, because a dominant frequency of the traffic vibration is coincident with the natural frequency of these houses. Although tuned mass dampers (T.M.D.) are considered to solve the problem, it needs to prepare a large mass on the top floor of these houses in order to obtain effective vibration reduction. On the contrary, P.T.M.D. can be placed between the first and second floor and it acts effectively on the principle of lever mechanism, since an action of the mass is expanded. A semi-optimal design approach for the P.T.M.D. is described, while it has an adjustable mechanism to adapt to various specifications of these houses. Effectiveness of the P.T.M.D. is demonstrated theoretically and experimentally by controlled results using frequency, time and seismic responses. Also this paper shows that the P.T.M.D. is effective against random vibration like earthquakes.

In Japan, there are many houses built on limited space and also besides side of causeways and railroads, due to population concentration in the cities in recent years. Houses with 3-stories or slender structure houses are susceptible to traffic vibration induced by external forces. This affect frequency creates an uncomfortable environment for habitation. Because houses often have a complex geometry, it is difficult to establish the vibration characteristics of a structure. Furthermore, the response characteristics of a house will change with environmental condition. To address some of these issues, an Active Mass Damper (AMD) has developed in order to supply for users with a reasonable price. This AMD has a mass of 176kg in weight supported by guide springs, and driven by an AC servomotor and a wire rope. The AMD is controlled by two methods, LQ Control and Direct Displacement Feedback (DDFB) Control. In this report, a control effect is examined through simulation when the AMD is installed in the RF level of a 3-story house model. The simulation results are demonstrated that the AMD could improve the uncomfortable environment in houses. A matter of particular note was reduction of about 4 dB in the overall vibration level. Concerning an experimental study about this equipment, refer to the following report, “Fundamental experiment of Active Mass Damper for houses against traffic vibration”.