Ikuo Shimoda

Survey of Aging for LRB of a Base-Isolated Building Completed 15 Years Ago

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.Copyright

A STUDY OF SPECIAL SPACER WITH DAMPING DEVICE FOR SUPPRESSING WAKE GALLOPING IN TANDEM CABLES OF CABLE-STAYED BRIDGES AND ITS APPLICATION TO FULL SCALE BRIDGE

本文では, 長さがl=200mおよびl=100mなる並列ケーブルモデルを対象として複素固有値解析を実施し, 減衰機能付きスペーサ方式 (並列ケーブルのほぼ中間に治具を介して粘弾性体を設置するタイプ) によって付加される減衰特性はケーブルのねじれ剛性の大きさに著しく依存すること, ケーブル中心間隔やケーブル径の差異によっても変化することなどを明らかにした. また, アスファルト系の粘弾性体を減衰材とばね材として使用した減衰機能付きスペーサを製作して実橋ケーブルに適用し, 本方式の実橋ケーブルにおける減衰付加特性を定量的に把握した. さらに, 実橋ケーブル試験結果と複素固有値解析結果との対比から, 実橋ケーブルのねじれ剛性を評価するなど, ウェイクギャロッピングの制振に関する実務上きわめて有用な技術資料を提供した.

New Damping Device Developed for Suppressing Wind-induced Cable Vibrations of Cable-stayed Bridges.

This paper deals with a new damping device for suppression of wind-induced cable vibrations. For the purpose of developing the new damping device using viscous-shear resisting force, model tests are carried out to examine the relationship between viscous-shear resisting force and parameters such as amplitude, velocity, and temperature. Cable vibration tests on a full-scale bridge are also performed. As a result, the effectiveness of the proposed damper is verified.