報告書番号

N10025

タイトル（和文）

振動特性評価に基づく鉄骨造建物の損傷検知技術（その1）－実大振動台実験により梁破断した高層建物の振動特性評価－

タイトル（英文）

Vibration test-based damage detection for steel moment frame building (Part. I)- Changes in modal properties on a high-rise building with steel girder ruptures caused by the full-scale shaking table test-

概要 （図表や脚注は「報告書全文」に掲載しております）

被災建築物に対する構造ヘルスモニタリングを実用化するためには、実大構造物の実地震損傷の評価データに基づき，損傷と振動特性変化の関係に関する定量的評価を確立する必要がある。本研究では、E-ディフェンスにおいて実施された長周期地震動を受ける高層建物の震動台実験の機会を利用して、地震経験に伴う鉄骨建物の剛性や固有振動数の変化を定量的に把握することを試みた。その結果、以下の知見を得た。（１）加振実験観測から算出した層剛性に基づき地震経験との関係を分析した結果，弱い加振による初期の地震経験と鉄骨梁破断の重大損傷による層剛性の低下が顕著であった。（２）縮約により4つの層を一括した剛性として評価しても，これらのふたつの地震経験による損傷は検知できる。（３）常時微動から評価した層剛性や振動数によっても地震経験に伴う剛性変化を検知できる。（４）鉄骨梁破断による層剛性の変化は有限要素解析で定量的に予測できる。

概要 （英文）

Changes in modal properties of a full-scale high-rise steel building specimen during shaking table test are evaluated from early stage just after the completion to the final collapse, which are expected to be employed as damage index for structural health monitoring. The shaking table test is conducted to investigate structural performance of an ordinary high-rise building subjected to strong earthquakes with long duration and large velocity amplitude. The building specimen consists of the lower four stories of the real-size building and the upper portion a multiple-layer mass-spring system is installed to adjust and elongate the fundamental period of the specimen, which models a 21-story building. The changes in the modal properties are evaluated from continuous ambient vibration test and the shaking table test, and the effectiveness of damage detections using ambient vibration and earthquake observation for the real building was tested. As a result, the frequency shifts dues to severe damage can be clearly detected after the lower flanges and webs were completely cut along the welded joint of girder-to-column connection; the specimen was in a final state of near completely collapse. Shifts in story stiffness is also observed clearly, which are identified both from the shaking table record in small earthquake motions and from ambient vibration record in very tiny tremors. Condensed stiffness in the lower four story of the building changes with seismic experience similarly to story stiffness, which can treated as one parameter of multiple story stiffness. These severe damage-induced shifts in natural frequency and story stiffness can be well-estimated by a numerical analysis of a three-dimensional finite element model, therefore, a priori damage criterion can be established for evaluating damage index in structural health monitoring. However, another shift in natural frequency and story stiffness was observed in early stage of the shaking table test, when the building was in non-damaged state. The shift in non-damage state is as large as one in severe damage, which cannot be negligible in damage detection. Thus a discrimination scheme of the shift between non-severe damage state and severe damage state must be needed in the future problem.

報告者

キーワード