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論文（リポジトリ）
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山田, 義智 ; 伊良波, 繁雄 ; 富山, 潤 ; Yamada, Yoshitomo ; Iraha, Shigeo ; Tomiyama, Jun
概要:
科研費番号: 18560554
平成18年度～平成19年度科学研究費補助金(基盤研究(C))研究成果報告書 研究概要：(平成18年度時点)本研究は,フレッシュコンクリートの流動特性を理論的側面から具体的に説明・検証できる … よう,合理的な流動構成式の提案と,流動シミュレーションのための数値解析手法開発を目的としている。以下に,流動構成式を導くために行ったレオロジー試験の概要と,今回開発した数値解析手法の概要を示す。レオロジー試験は,流体内部の構造変化に起因する軟化特性や硬化特性,さらには履歴現象を表現できる構成式を定式化すべく,回転粘度計を用いて行った。ここでは,試験試料としてセメントペーストを用いている。セメントペーストがひずみ加速度に依存したレオロジー特性を示すことを考慮して,応力緩和曲線を用いた手法により,レオロジー特性を定式化した。この試験により,様々なひずみ加速度を受けている時のセメントペーストのレオロジー定数(降伏値,塑性粘度)を数式により表すことができた。次年度においてはこれを参考に,モルタルペースト,フレッシュコンクリートのレオロジー特性を定式化する予定である。フレッシュコンクリートの流動シミュレーションを目的として,本年度は二つの数値解析手法を開発した。一つは,マーカー粒子を用いたオイラー型粘塑性有限要素法。もう一つは,MPS(Moving Particle Semi-implicit)法によるものである。マーカー粒子を用いたオイラー型粘塑性有限要素法では,スランプおよびスランプフローについて解析を行い,既往の実験成果と比較したところ,定性的にも定量的にも良い結果を得た。また,MPS法においては,フレッシュコンクリートの流動モデルとして用いられるビンガムモデルに起因する材料非線形性を考慮した解析手法を提案し,L型フロー試験結果を説明できる解析結果を得ることができた。次年度は,これらの数値解析手法に本研究で提案する構成式を取り込んで解析を行い,実験結果と比較検討する予定である。 未公開：P.5以降(別刷論文のため) 研究報告書 続きを見る |
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松原, 仁 ; 伊良波, 繁雄 ; 富山, 潤 ; 矢川, 元基 ; Matsubara, Hitoshi ; Iraha, Shigeo ; Tomiyama, Jun ; Yagawa, Genki
概要:
In this paper, the solid tetrahedron element with drilling degrees of freedom is presented. This element has only four n
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odes. Each node has three translational components and three drilling ones. By using this element, the high level of analytical accuracy can be obtained. On the other hand, the free mesh method creates tetrahedron elements locally around every nodal point. Consequently, the element with intermediate nodes is not available to the free mesh method. However, the proposed solid tetrahedron element with drilling degrees of freedom is especially effective to the free mesh method, because it has no intermediate nodes. In this paper, the feature of accuracy of this element is shown through several numerical examples, and the effectiveness of the free mesh method is also described.
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富山, 潤 ; 伊良波, 繁雄 ; 松原, 仁 ; 山城, 建樹 ; 入部, 綱清 ; Tomiyama, Jun ; Iraha, Shigeo ; Matsubara, Hitoshi ; Yamashiro, Tateki ; Iribe, Tunakiyo
概要:
Recently, the computer technology has been used in many engineering fields. And numerical simulation has been applied to
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the analysis on mechanical behavior of concrete. However, it is assumed that the concrete is a homogeneous material, though it is a composite material, with coarse aggregates and mortar as the main components. Then we proposed the generation method of concrete model in consideration of the coarse aggregate. This method is a quite new model, so it is created from the shape of any actual aggregates. Also, in this paper, Voxel element with the drilling degrees of freedom is proposed, and the stress condition within the concrete that is made by proposed method is calculated by the Voxel analysis which used this element. The analytical result became excellent.
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仲座, 栄三 ; 津嘉山, 正光 ; 伊良波, 繁雄 ; 藤井, 智史 ; 鹿熊, 信一郎 ; 川満, 康智 ; 北村, 康司 ; Nakaza, Eizo ; Tsukayama, Seiko ; Iraha, Shigeo ; Fujii, Satoshi ; Kakuma, Shinichiro ; Kawamitsu, Yasutomo ; Kitamura, Yasushi
概要:
A project, to explore the sea environments of subtropical Okinawa, Japan, has been running with financial aid from the E
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ducation Agency of Japan. Surveys may reveal the characteristics of the currents around coral reefs and deep-sea water up-welling, induced by ocean currents like Kuroshio, which is well known around the world. This East Asian warm sea current originates in the mid-pacific along the equator. Based on the survey results, we ultimately hope to be able to propose an artificial deep-sea upwelling generation method. In the first survey of this project, the characteristics of the sea current around Zanpa cape are being explored.
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山川, 哲雄 ; 伊良波, 繁雄 ; 知念, 秀起 ; 今村, 大樹 ; Yamakawa, Tetsuo ; Iraha, Shigeo ; Chinen, Hideki ; Imamura, Hiroki
概要:
Fifteen R/C public apartment houses in Okinawa were investigated on their damage due to chloride attack. These buildings
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were built between 1961 and 1976. The main objective of this investigation is to estimate the percentage of damaged R/C buildings due to chloride attack in Okinawa main island and to clear the dominant cause. As a result of investigation, fourteen R/C public apartment houses have been damaged by chloride attack except for the oldest apartment house which was built in 1961. Among them thirteen apartment houses contain a lot of sodium chloride in the concrete. The amount of chloride ion is beyond the permission line according to Japanese government guide line. The oldest R/C public apartment house built in 1961 is not damaged by chloride attack. This is the reason why sea sand was not used. Most of R/C public housing built between 1966 and 1977 has been damaged by chloride attack. The chloride attack is caused by using sea sand without removing sodium chloride. The percentage of damaged R/C buildings due to chloride attack in Okinawa main island is about 30%. Nowadays, this problem is a big social problem in Okinawa.
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山川, 哲雄 ; 伊良波, 繁雄 ; 田中, 伸幸 ; 松永, 尚凡 ; Yamakawa, Tetsuo ; Iraha, Shigeo ; Tanaka, Nobuyuki ; Matsunaga, Takamina
概要:
An investigation on damage due to chloride attack on a reinforced concrete public housing was carried out before the hor
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izontal cyclic loading test. Chloride attack is caused by using sea sand without removing sodium chloride. The compressive strength of concrete, cover thickness and carbonation were examined. As a result of this investigation, the deterioration of the existing R/C public housing was recognized from the point of the durability for the R/C buildings.\nIn order to observe the overall seismic behavior of the existing R/C public housing damaged due to chloride attack, a horizontal cyclic loading test was carried out on the building site. This loading test indicated that the behavior of this building was not affected by the damage and deterioration. The horizontal loading capacity of this building was about four times the value determined using an elasto-plastic analysis of a pure frame structure. This fact is the cause of using partition or outer walls made of concrete block. However, the seismic capacity and ductility of this existing building were not high. Assurance of safety and serviceability are important for corrosion damaged buildings.
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山川, 哲雄 ; 伊良波, 繁雄 ; 玉城, 康哉 ; 中山, 耕一 ; Yamakawa, Tetsuo ; Iraha, Shigeo ; Tamaki, Yasuya ; Nakayama, Koichi
概要:
In order to investigate the damage affecting aseismatic behavior of R/C columns, R/C column specimens sustained damage b
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y electrolytic corrosion test were tested under a constant axial load and alternately repeated lateral loads by using the loading apparatus. Furthermore, R/C column specimens using FRP grid as hoops were tested in the similar manner. The other test specimens were offered to the exposure test in high salty environment in the semitropical and marine region at the coast in Okinawa. When the exposure test comes to an end several years after, these test specimens will be loaded laterally and vertically in order to discuss the damage affecting aseismatic behavior of R/C columns under chloride attack environment in the semitropical region.
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山川, 哲雄 ; 伊良波, 繁雄 ; 知念, 秀起 ; Yamakawa, Tetsuo ; Iraha, Shigeo ; Chinen, Hideki
概要:
The authors investigated damage and deterioration due to chloride attack in Awase, Tohashina and Ueda Prefectural Housin
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g, which were built with reinforced concrete (R/C) framed structure about 20 years ago in Okinawa. Such investigations have been carried out plentifully in Okinawa until today. According to these investigations, the following two major points have been already indicated. 1) Sea sand was used in the concrete of housing as the fine aggregate without removing salt. 2) Okinawa is located in the semitropical region under chloride attack environment. From above viewpoints, it is clarified that the damages and cracks due to corrosion of reinforcing steel bars are subjected to R/C structures in Okinawa. These facts are also confirmed through this investigation. Nowadays the durability of R/C structures in Okinawa has been surely improved, however it must be further improved.
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山川, 哲雄 ; 伊良波, 繁雄 ; 玉城, 康哉 ; 松永, 尚凡 ; 枇杷田, 篤 ; Yamakawa, Tetsuo ; Iraha, Shigeo ; Tamaki, Yasuya ; Matsunaga, Takamina ; Biwada, Atsushi
概要:
Numerous investigations on corrosion and corrosion protection of steel in concrete have been carried out until today. Ho
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wever, most of these studies are almost limited in the field of materials engineering, for example, main subjects are as follows.\n1) Mechanics and mechanisms of steel corrosion, and evaluation of corrosion data.\n2) Corrosion monitoring in field structures and corrosion protection.\n3) Prediction of service life and repair methods.
On the other hand, the influence of corrosion on flexural, shear and bond strength of reinforced concrete members has been discussed on beams and floor slabs. Japan is located in the seismic hazard zoning area. Therefore, in this paper the damage affecting aseismatic behavior of reinforced concrete structural members due to corrosion of steel reinforcing bars is discussed through experiments under the constant axial load and alternately repeated lateral loads. As the first step, structural walls were adopted as the test specimens. Because the coverage thickness, namely, the concrete protective covering for reinforcement is small and the corrosion area is large for reinforcing bars in structural walls. Furthermore, a new fiber reinforced composite material (NFM) instead of steel bars was used in order to investigate durability of the structural walls under chroride attack environment in the semitropical region. A wall panel size was 800x950mm and its thickness was 80mm. The rigid edge beams were attached to the top and bottom of the wall panel. The shear-span ratio M/Qd was 1.43. The weight of a test specimen was about 1tonf. The reinforcing bars, whose diameter was 6mm, were arranged as likely mesh by double layered reinforcement. The reinforcement ratio of the wall panel was 0.8%. In order to prevent from corrosion, epoxy coated steel bars were used in the top and bottom rigid edge beams. These test specimens were offered to the electrolytic corrosion test and exposure test in high salty environment in the semitropical and marine region at the coast in Okinawa Prefecture, Japan. The concrete cylinder average strength was about 250kgf/cm^2. The 11 test specimens were provided. The 8 ones contained the soldium chloride solution (NaCl 3.3% sol.). Now, among them the 6 test specimens, in which the 3 NFM test specimens are included, are exposed at the coast in Okinawa. These exposed test specimens will be loaded laterally by a set of hydraulic jacks after one or several years. The other 5 test specimens were tested under the constant gravity load and alternately repeated lateral forces. One of them was the standard test specimen. The 2 specimens were arranged by the new fiber reinforced composite mesh. An electrolytic corrosion test was applied to the other 2 specimens with the steel reinforcing bars contained the soldium chloride solution. In this case, a steel mesh wrapped in gelatin was adopted as an electrode. This electrode was the same size as a wall panel and was attached on it. The loading apparatus was a cantilever type. As a result of this experimental investigation, the following conclusions were obtained. 1) The failure mode of normal test specimen was a flexural compressive failure type. The maximum lateral capacity was kept until a drift ratio reached approximately 1.0%. Then some loss of the lateral load due to the crushing at the bottom corner of the wall panel occurred gradually.\n2) The ultimate lateral load of test specimens with electrochemical corrosion damages was obtained after the drift ratio reached over 0.5%. Especially. the ultimate loads were almost same regardless of corrosion damages. The cover concrete at the neighborhood of the bottom of wall panel spalled off and the buckling of the longitudinal reinforcing bars was observed at conclusion of loading. These test specimens, whose failure mode was similar to the brittle shear failure, resulted in the significant deterioration of the ductility.\n3) The ultimate lateral load of the test specimens, which were arranged by the new fiber reinforced composite material (NFM), was superior to the other test specimens with reinforcing steel bars. After drift ratio reached over 1.0%, the reinforcing bars made of NFM were partially broken. And the degradation of the lateral load capacity was observed in the hysteretic loops. The energy absorption capacity of these test specimens was slightly smaller than the other specimens because of lacking of the plastic range for the NFM. However, the durability of these test specimens will be expected in chloride attack environment. 紀要論文 続きを見る |
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論文（リポジトリ）
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伊良波, 繁雄 ; Iraha, Shigeo
概要:
A numerical method for tension fracture of materials which exhibit strain-softening is presented here by use of the hybr
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id stress model. When tension fracture occurs in the materials, the stress field has to satisfy the equation of stress-crack width relation on cracking surfaces. For numerical analysis, the equation has to be introduced into the principle of the hybrid complementary energy using Lagrange multipliers defined on cracking surfaces. This method is useful for tension fracture analysis because the size of total stiffness matrix does not increase even for calculation under the condion of cracking in the materials. The results of computer simulation on compact tension (CT) test by this method yield a good agreement with the experimental ones.
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