Experiments and numerical modeling of a rockfall protective wire rope fence

To protect existing structures in mountainous areas against rockfall, various protection methods have been developed. A new type of rockfall protection fence is constructed of posts, wire ropes, and wire netting. To verify the performance of this rock fence, both experiments and numerical analysis based on finite element code were conducted. Collision tests were performed, in which a reinforced-concrete block rolled down a natural slope and struck the rock fence at the end of the slope. The performance of energy absorbers, which are effective in preventing wire ropes from breaking, was investigated. To measure the acceleration of a reinforced-concrete block rolling down a steep slope, a new system of measuring instruments was developed. © 2012 International Journal of GEOMATE

CFT補強筋によるRC複合橋脚の耐震性能の向上とその評価に関する研究

1.概要RC製橋脚の主筋の違いによる耐震性能すなわち変形性能を検討するために,断面の幅(200mm)×高さ(250mm)で,異形鉄筋(10-D13)を主筋とするB13-Type,コンクリート充填鋼管CFT(4-φ42.7x2.3)を主筋とするT43-Typeおよび径厚比の小さなCFT(6-φ27.3x2.3)を主筋とするT27-Typeの3種類のRC柱を製作した.荷重条件は一定の軸力比(N/N_Y-5%,10%)で横荷重を単調または交番載荷とした.断面の設計においてはN/N_Y-5%の一定軸力と曲げが作用するとき,材料の公称値を用いたそれぞれのタイプの終局強度が等しくなるように鋼材の量および配置を決めた.鋼管とコンクリートの付着はあまり期待できないため,鋼管の両端にアンカープレートを溶接した供試体を用いたが,T43-Typeではアンカープレートと鋼管表面へのグリットブラスト加工を併用した供試体(T43G)も製作した.2.結果1)単調載荷においては鉄筋タイプの変形能(=終局変位/降伏変位)がCFTタイプよりも優れているが,地震荷重のような交番載荷においてはGFTタイプが優れている.2)CFTの径厚比による変形能に対する効果は,用いた供試体(D/t=18.6,11.9)では認められなかった.3)曲げ耐荷力は軸力比10%の場合が軸力比5%の場合に比べて大きくなるが,逆に変形能は軸力比10%の場合が軸力比5%の場合に比べて小さくなる.軸力の付加モーメントよりも交番荷重によるコンクリートの劣化の影響が大きい.4)交番載荷を受けるRC橋脚におけるCFT補強筋の有効性を示した.また,グリットブラストにより鋼管とコンクリートの付着を強化することにより靭性率の改善が見られた.5)CFT複合柱の曲げ耐荷力は,断面分割法を用いて十分な精度で評価できることがわかった.The bridge piers of reinforced concrete lack the deformation capacity against an earthquake load. Namely, the compression rupture of reinforced concrete causes the buckling of a compression reinforcing-bar and consequently weakens the bending strength of RC structures sharply. Therefore, in order to improve the deformation capacity of RC structures it is effective to prevent reinforcing-bars from losing strength due to buckling. The concrete columns reinforced with CFTs or with reinforcing bars have been tested under an axially constant load and a transversely cyclic load. The reinforcement types, the diameter-thickness ratio of steel-tubes and the bond method of a tubular steel to concrete have been investigated in relation to the load carrying capacity and deformation capacity of the columns.The following have been found.(1)The cyclic load seriously reduces the deformation capacity, i.e. the ductility index, especially that of the concrete column with reinforcing bars.(2)Both yield load and maximum load are high in the concrete columns under the axial load ratio of N/f_c0=0.1 as compared with N/f_c=0.05, when the other conditions are same. Conversely, the ductility index, δ_U/δ_y, is high in the specimens under the axial load ratio of N/f_c=0.05.(3)The concrete column with CFT is excellent in load-carrying capacity, deformation capacity, and energy absorption capacity as compared with the concrete column with reinforcing bars.(4)The diameter-thickness ratio of tubular steel does not influence the load-carrying capacity, and deformation capacity. The surface treatment on a steel-tube has a good effect on those capacities. It is important for us to improve the bond method in order to employ CFT.研究課題/領域番号:14550476, 研究期間(年度):2002-200

コンクリート充填鋼管の衝撃耐荷力およびエネルギー吸収能の向上とその評価法の開発

金沢大学工学部コンクリートを充填した鋼管はりは、静的な載荷において優れた塑性変形性能(エネルギー吸収能)を示す。本研究では、落錘式衝撃曲げ載荷実験を実施するとともに、耐衝撃性(エネルギー吸収能)を定量的に評価するための解析法を開発した。その概要は以下の通りである。1.落錘式衝撃曲げ載荷実験長さ2mの構造用鋼管STK400(φ165.2×4.5)の引張側に補強のためのアンボンド型PC鋼棒(φ13)を2本挿入した後、コンクリートを充填して試験体を製作した。衝撃曲げ載荷では重錘(1.2tf)を4mの自由落下により試験体に衝突させた。実験の結果、コンクリート充填鋼管はりのエネルギー吸収能の静的曲げ載荷あるいは衝撃曲げ載荷による差は顕著でないことが分かった。したがって、静的曲げ載荷の挙動を解析することにより、耐衝撃性を評価できる。2.エネルギー吸収能の評価エネルギー吸収能の評価は二つの方法を試みた。(1)一つは、汎用コード(FEM)を用いて、拘束圧を受けるコンクリートはりを静的および動的に解析する方法である。しかし、コンクリート充填鋼管のように塑性変形が大きくなる部材を解析するにはコンクリートの構成則の改良が必要であり、現在検討中である。(2)もう一つは、設計を意識した簡易解析による方法である。鋼管、アンボンドPC鋼棒あるいは拘束効果を考慮したコンクリートの一軸強度を限界強度とし、鋼管およびアンボンドPC鋼棒の伸び限界を終局限界ひずみとして用いた解析法(断面分割法と変位増分法の組み合わせ)により、エネルギー吸収能を評価できることが分かった。研究課題/領域番号:07650540, 研究期間(年度):1995出典：研究課題「コンクリート充填鋼管の衝撃耐荷力およびエネルギー吸収能の向上とその評価法の開発」課題番号07650540（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07650540/）を加工して作

RCおよびPC製構造部材のCFSTによるエネルギー吸収能の向上と評価方法の確率

金沢大学工学部RCおよびPC製構造物は、大地震や巨大落石あるいは土石流によって脆性的に破壊しやすい。このような生起確率は低いが巨大なエネルギーを有する荷重に対しては、構造物あるいは部材の塑性変形(靭性)によってエネルギーの吸収が図られるべきであることが提案されるようになってきた。そのためには、エネルギー吸収能の優れた部材の開発と評価方法の確立が不可欠である。本研究は,RCおよびPC製構造部材の鉄筋をコンクリート充填鋼管(CFST)で置き換えることにより新しい複合構造部材を開発し、高エネルギー吸収能を必要とする土木構造物へ適用することを目的としている.本研究成果報告書は,そのための基礎的研究結果を以下のような項目についてとりまとめたものである。1. コンクリートと充填鋼管(CFST)の付着強度に関する押し抜き強度試験(1) 有孔鋼管を用いてコンクリートダウエルを形成し,ダウエルのせん断強度を利用した。(2) 接着剤や鋼管表面のサンドブラスト処理による鋼管とコンクリート界面の付着力を増加させた。2. 鋼管コンクリート複合はりの静的曲げ試験および落錘衝撃載荷試験CFSTを圧縮補強鋼材とすることにより靭性(変形能)が著しく向上することを実験的に確 認した。3. 鋼管コンクリート複合柱の軸カ-曲げ載荷実験地震荷重のような交番曲げが作用する鋼管コンクリート複合柱では,有孔鋼管の孔が欠陥 となる。4. 鋼管コンクリート複合はりの実構造物への応用鋼管コンクリート複合はりの優れた変形能を落石覆工へ応用するための設計例を示し,1/2モデルはりの曲げ実験により,高靭性を必要とする落石覆工に有用であることを確認した。The RC and PC structures subjected to the impact-load such as earthquake and rock-fall are destroyed in brittleness. It is proposed that such a load having a low occurrence probability and huge energy should be absorbed by the plasticity deformation of structure. The development of structure members with excellent energy absorption and the establishment of its evaluation method are indispensable for that. This study has developed a new composite structure member by using concrete-filled steel pipe (CEST) instead of the compression steel-bars of RC and PC members and applied it to the structure which needs the high energy absorption. This report is arranged about the following items.1. Push-out tests concerning bond strength of concrete-filled steel pipe (CFST) and the concrete block(1)The concrete dowels, which are formed by using the bored steel-tube, are effective for the bond strength between the steel-tube and concrete block.(2)The adhesion of steel-tube and concrete has been increased by the sand blasting processing of the steel-tube surface and/or by spreading adhesive agent on it.2. Static bending test and impact load test on the composite beam reinforced with CFST were done. It was confirmed that toughness (deformability) was improved by using CFST for compression reinforcements.3. Static bending load and axial force were applied on steel-tube and concrete composite column. The hole of the bored steel-tube becomes a defect, when the column is subjected to cyclic load.4. Static load tests were done on a half-size model to simulate the real structure, i.e. rockshed.研究課題/領域番号:09650520, 研究期間(年度):1997 – 1998出典：研究課題「RCおよびPC製構造部材のCFSTによるエネルギー吸収能の向上と評価方法の確率 」課題番号09650520（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/report/KAKENHI-PROJECT-09650520/096505201998kenkyu_seika_hokoku_gaiyo/）を加工して作

Oberlin partial ulnar nerve transfer for restoration in obstetric brachial plexus palsy of a newborn: case report

An 8 month old male infant with Erb's birth palsy was treated with two peripheral nerve transfers. Except for rapid motor reinnervations, elbow flexion was obtained by an Oberlin's partial ulnar nerve transfer, while shoulder abduction was restored by an accessory-to-suprascapular nerve transfer. The initial contraction of the biceps muscle occurred two months after surgery. Forty months after surgery, elbow flexion reached M5 without functional loss of the ulnar nerve. This case demonstrates an excellent result of an Oberlin's nerve transfer for restoration of flexion of the elbow joint in Erb's birth palsy. However, at this time partial ulnar nerve transfer for Erb's birth palsy is an optional procedure; a larger number of cases will need to be studied for it to be widely accepted as a standard procedure for Erb's palsy at birth

Experiments on Rockfall Protection Embankments with Geogrids and Cushions

There are various protection measures against rockfalls. An embankment is effective in rockfall hazard mitigation at a dangerous slope end. The slope rockfall tests on full-scale embankments have been carried out. These embankments are made of sandy soil reinforced with geogrids. The cushioning layers which are made of geocells filled with crushed stones of 5-13 mm in diameter are also placed on the mountain side of the embankment. A boulder, i.e., RC block rolls down the test-site slope, and hits against the embankment. A new system of measuring instruments is employed in order to evaluate the impact force and the impact energy. One of important observations is a possibility that a rolling boulder carries it toward the top of an embankment because of its rolling momentum. The experimental results, especially the relationship between impact force and impact energy is discussed in this paper. © 2011, International Journal of GEOMATE

Prototype of a wire-rope rockfall protective fence developed with three-dimensional numerical modeling

This study uses a numerical procedure, previously validated with data from full-scale experiments, to investigate the performance of a modified prototype wire-rope fence to provide protection against rockfall. The cost-reducing modifications are increased post spacing and fewer wire netting layers. The numerical procedure provides the nonlinear response of the prototype under various impact conditions and insights into each component\u27s role in dissipating impact energy. A simple but effective method to increase fence capacity is also developed. Finally, the use of two units of the prototype to protect a wide area is investigated employing the numerical procedure. © 2013 Elsevier Ltd

Experiments and Dynamic Finite Element Analysis of a Wire-Rope Rockfall Protective Fence

The imperative need to protect structures in mountainous areas against rockfall has led to the development of various protection methods. This study introduces a new type of rockfall protection fence made of posts, wire ropes, wire netting and energy absorbers. The performance of this rock fence was verified in both experiments and dynamic finite element analysis. In collision tests, a reinforced-concrete block rolled down a natural slope and struck the rock fence at the end of the slope. A specialized system of measuring instruments was employed to accurately measure the acceleration of the block without cable connection. In particular, the performance of two energy absorbers, which contribute also to preventing wire ropes from breaking, was investigated to determine the best energy absorber. In numerical simulation, a commercial finite element code having explicit dynamic capabilities was employed to create models of the two full-scale tests. To facilitate simulation, certain simplifying assumptions for mechanical data of each individual component of the rock fence and geometrical data of the model were adopted. Good agreement between numerical simulation and experimental data validated the numerical simulation. Furthermore, the results of numerical simulation helped highlight limitations of the testing method. The results of numerical simulation thus provide a deeper understanding of the structural behavior of individual components of the rock fence during rockfall impact. More importantly, numerical simulations can be used not only as supplements to or substitutes for full-scale tests but also in parametric study and design. © 2012 Springer-Verlag Wien

高張力PC 鋼材の高強度コンクリートへの適用に関する実験的研究

[研究概要

Seismic response analysis and damage verification of notojima bridge during noto peninsula earthquake

Noto Peninsula earthquake of magnitude 6.7 occurred near Noto Peninsula in Japan on March 25 2007. Notojima Bridge across Nanao Bay which was completed in 1982 is located about 30 km east-southeast of the epicenter. It is 1050 m long multi-span bridge consisting of 21 spans in which the 10 and 8 spans are simply supported PC girder bridges and the central three spans are a rigid frame PC bridge with pin-connection at the mid-span. Notojima Bridge sustained considerable damage in many RC piers bearing supports and expansion joints. Especially the piers of P10 and P13 in the central portion of the bridge sustained damage asymmetrically in spite of the symmetrical figure of the superstructure and piers. In order to verify unexpected damage the central portion is investigated based on seismic response analysis taking account of the inelastic hysteretic property of piers and the strong-motion data observed near the bridge. It is found that the difference of steel pipe piles between P10 and P13 might affect the asymmetrical damage