Hiroshi Mikami

Elasto-plastic dynamic response analysis of prototype RC girder under falling-weight impact loading considering mesh size effect

This paper focuses on an applicability of the proposed numerical analysis method to the large scale RC girder under falling-weight impact loading using effective finite element mesh size distribution by comparing with experimental results. The results obtained from this study are: (1) displacement wave can be accurately estimated with seven-division of stirrup interval. (2) The maximum impact force and reaction force can be roughly estimated by using the mesh geometry with one-division for the each interval. (3) Damping constant should be used as 1.5%. (4) Drucker-Prager yield criterion should be applied. (5) The crack patterns can be roughly estimated with seven divisions between intervals of stirrup.

Numerical Simulation of Impact Response Behavior of Rectangular Reinforced Concrete Slabs under Falling-Weight Impact Loading

A numerical analysis method for rectangular reinforced concrete slabs under falling-weight impact loading is established. The proposed method using finite element analysis incor-porates a simple constitutive model for concrete elements. The applicability was investigatedcomparing the numerical results with the experimental data. Falling-weight impact tests wereconducted on reinforced concrete slabs with different supporting conditions. These were: a slabwith line supports on four sides; a slab with two line supports on two opposite sides (the othertwo sides were free); and a slab with one line and two corner-point supports. Following resultswere obtained from this study: (1) the time histories of dynamic responses are well predictedby using proposed numerical analysis method; (2) maximum reaction forces and the maximumdeflections in the slab center below the loading point, and characteristics of the damped freevibration after falling weight was rebounded, can be better predicted; and (3) major crackpatterns can be roughly predicted despite of support conditions.

CURVE JACKING OF PRE-STRESSED CONCRETE HALVED JACKING PIPES

分割型PC推進管は, 内径3000mmを超える推進工法に適用する新しい推進管である. 曲線推進を行う際には, 管径の拡大に応じて, 施工可能な曲線半径や推進管の長さ, 許容推進力等の検討が求められる. また, 推進管の円周方向に2箇所の継手を有する構造的特徴により, 施工時における円周方向継手の挙動や作用荷重の把握が, 継手に十分な安全性を確保するうえで重要となる.本研究では, これまでの規格を超える大口径推進管に対し, 日本下水道協会の指針に準じた曲線推進の適合性を検証した. また, 模型推進管を用いたS字曲線推進実験による既往研究結果と併せて, 曲線推進に対する包括的な評価を試みた結果, 実施工に対する有用な知見が得られた.

BASIC PERFORMANCE AND APPLICATION OF HALVED JACKING PIPE USING PRESTRESSED CONCRETE STRUCTURES

管渠推進工法では, 内径3000mmを超える大口径管による施工実績が極めて少ない. これは, 工場で製作した推進管を工事現場まで運搬する際, 道路交通法施行令に基づく積載高さの規制を受けるからである.一方, 推進工法は, 現行の積算基準によれば, 都市トンネル工法のなかでも経済性に優れている. このため, 運搬上の制約を技術的に克服し, 大口径に対する適用拡大を図れば, 建設コストの縮減に寄与できる.本研究では, 2等分割半円形の管体を工場製作して運搬し, 現地でプレストレストコンクリート構造により一体化した後, 通常の推進管として使用する工法を開発する. 今回, 基本性能確認試験を通じて, 日本下水道協会が規定する標準管と同等以上の性能が確認されるとともに, 適用に際しての知見が得られた.