Search

RCはり部材に対する曲げひび割れ進展挙動について，クリープ，収縮，コンクリートの硬化過程に伴う材料特性の変化と，鉄筋の付着性状を考慮した3次元有限要素解析を用いて解析的に評価を行った．鉄筋の付着性状を考慮することにより，荷重増加によるRCはり，PRCはりのひび割れ性状およびひび割れ幅について評価できることが示された．また，時間依存挙動を考慮することにより，持続荷重による全体挙動およびひび割れ進展挙動を，強度による材料特性の違いに依らず，妥当に評価できることが示された．さらに，本解析手法を用いて，乾燥収縮量や自己収縮量，乾燥領域，クリープがひび割れ進展挙動に及ぼす影響を検討した．, Analytical evaluation of crack propagation of reinforced concrete beam was performed. Creep, shrinkage, change of material characteristics depending on hardening and bond behavior were considered in 3-Dimensional finite element analysis. Crack initiation and crack width on increasing load were evaluated considering bond behavior. Time dependent propagation under constant load such as curvature and crack width was also evaluated for normal and high strength concrete. Moreover, the effect of dry shrinkage, autogenous shrinkage, creep and area of shrinkage in beam on crack propagation were investigated.

本研究では，RC部材の非線形有限要素解析における損傷評価手法の確立を目的として，コンクリートの圧縮破壊が支配的となるせん断圧縮破壊するRC部材の破壊基準としてのひずみ評価指標を検討した．面的なひずみ性状を計測可能なアクリル格子法を用い，損傷領域と損傷度を実験的に評価するとともに，3次元非線形有限要素解析による損傷評価を行った．その結果，平均化ひずみを用いることで要素寸法によらないひずみ分布性状が得られることを示し，ひずみによる損傷領域評価と破壊基準を提案した．また，提案手法を曲げ破壊するRC部材に適用し，その妥当性と適用性を示した．さらに，不静定構造物を対象とした検討の結果，構造全体の耐荷力以前における部材の破壊を評価でき，単一部材のみならず構造物中の部材の損傷評価に対する適用性を示した．, In this study, damaged areas of RC beams failed in shear compression were experimentally evaluated by means of acrylic lattice method which can measure planar strain distribution. Three-dimensional nonlinear finite element analysis was also conducted in order to verify the damage evaluation method and failure criteria of RC members failed in shear compression. As the result, damage region were evaluated by the averaged strain without mesh dependency and failure criterion for shear compression failure was proposed. It was confirmed that the proposed method was also applicable to RC beams, which has various dimension and specification, failed in both shear and flexural by the analyses. Moreover, it was shown that the proposed criterion was useful to evaluate the damage of a member in statically indeterminate structures.

ASR劣化した構造物における補強後のASR膨張挙動を対象として，補強された部材のASR膨張抑制効果について解析的な評価を行った．ASR膨張モデルを用いた有限要素解析の結果，鋼板巻立てやPC巻立てにより補強されたRC柱の補強後の膨張挙動を概ね評価可能であることを示した．また，並列バネモデルを用いて各種補強方法を対象としたパラメトリック解析を行い，膨張の抑制に及ぼす要因の評価と膨張抑制効果の定量的な評価を試みた．その結果，プレストレスのように力により膨張を拘束する方法は，補強材の拘束鋼材比を大きくする方法よりも，ASR膨張の抑制に対して効果的であることを示した．, In this study, the analytical evaluation was conducted in order to evaluate the mitigation effect resulting from various retrofitting methods on ASR expansion. Through the investigation by means of Finite Element Analysis, ASR expansion model proposed by authors was applicable to evaluate the ASR expansive behaviors of RC columns retrofitted by steel plate bonding method and PC confined method. The parametric analyses were also conducted in order to evaluate the mitigation effect retrofitting on ASR expansion. As the results, it was quantitatively confirmed that the introducing lateral force such as PC confined method was more effective for mitigating ASR expansion than the retrofitting with high reinforcement ratio.

Analytical model developed by the authors, using three-dimensional Rigid-Body-Spring-Method (RBSM) combined with a three-phase material corrosion-expansion model, was verified against experiments in the case of multi-rebar corrosion. The experiments of beams having multi-rebars were carried out by the other researchers using electric corrosion tests. The applicability of the analytical model was confirmed in terms of crack patterns, surface crack width and internal crack propagation due to multi-rebar corrosion. Moreover, a mechanism of crack propagation in concrete due to multi-rebar corrosion was investigated and compared with the case of single-rebar corrosion analytically. As a result, it was found that rebar spacing strongly affects crack patterns and crack propagation mechanism of concrete. Internal cracks are dominant rather than surface cracks and the propagation of internal cracks combined with surface cracks may cause de-lamination of the concrete cover.

ASRを生じた構造物の膨張挙動とそれに伴う損傷が構造性能に及ぼす影響を明らかにすることを目的として，実験と解析による検討を行った．ASR膨張試験の結果，ASR膨張は構造物の配筋状態等の影響により方向性を持つことを示した．また，はり供試体から採取したコア供試体の材料特性は，膨張の程度に従った異方性に影響を受けるため，構造全体挙動を評価する際は，コアの採取位置や方向に注意する必要があることを示した．一方，ASR膨張解析と荷重作用解析を行なった結果，はり供試体から実構造物に至るまでASR損傷状況を概ね評価できることを示した．本研究の結果，RC構造はASR膨張が比較的小さい場合においても構造性能が低下するのに対して，プレストレス構造はASR膨張に対する抑制の効果が大きく，構造性能への影響は少ないことを示した．, In this paper, experiments and finite element analyses were conducted in order to evaluate effects of ASR on structural performance of RC and PC structures. From the experimental results, it was confirmed that the ASR expansion was affected by the restraint of reinforcement and the magnitude of prestress. The material properties of concrete damaged by ASR had anisotropic characteristics depending on the degree of ASR expansion. Therefore, when the structural performance of RC and PC structures were evaluated by using the material properties of core concrete, the direction and place where cylinder specimens were cored should be considered. On the other hand, by means of proposed analytical method, ASR expansion behaviors of RC and PC beams and changing of their structural performance were evaluated. As the results, it was confirmed that PC structure had much advantage comparing with RC structure regarding the structural performance under ASR damage because of restraint by prestress against the ASR.

Autogenous healing of concrete structure was studied as a part of measures for reduction of the total life cycle cost. This study presents the measurement for autogenous healing ability by using the stiffness through three-point bending test. It shows the relation between autogenous healing ability and the initial loading age for three kinds of concrete, such as normal concrete, fly ash concrete and fly ash concrete with fiber. Furthermore, the size effect of specimens on autogenous healing is examined.

Cracking behavior due to rebar corrosion for concrete specimen with single rebar was evaluated analytically. The evaluation was performed by comparing with results of the electric corrosion test. Three-dimensional Rigid- Body-Spring-Method (RBSM) with three phase material corrosion expansion model was applied to simulate internal cracking patterns and surface crack width propagation. The effect of rebar local corrosion and penetration of corrosion products into cracks during the corrosion process were investigated and cracking behavior due to rebar corrosion was evaluated quantitatively.

The behavior of deep beams failed in shear with shear span ratio (a/d) of 0.5 was investigated using 3D-RBSM, which is a representative method of discrete method. The analytical results for the beam without web reinforcement were compared with the experimental ones and analysis capability of 3D-RBSM was confirmed. 3D effects were discussed by comparing the change of strut widths and high stress as well as 3D deformed shapes. Then, the effect of web reinforcement was investigated. It was confirmed that, there is no significant effect of web reinforcement in deep beams with a/d=0.5. Keywords: Rigid-Body-Spring-Model, deep beam, shear failure, 3D effect, web reinforcement

Ultra High Performance Strain Hardening Cementitious Composites (UHP-SHCC) is a new strain hardening composite with outstanding mechanical and protective performance. In this study, UHP-SHCC was applied to RC beams as a tensile strengthening material, and the beams were tested under four-point bending setup. It was clarified that strengthening by UHP-SHCCs significantly contributed to increasing the load carrying capacity. And stress-strain relation obtained from the tensile tests can well simulate the response of the strengthened beams.

Bond quality is an important factor that affects the performance of repaired members. In patching repair, interfacial cracking and delamination due to the shrinkage of repair materials are often observed. In this study, flexural bond strength tests using jointed specimens were carried out, and the tension softening diagrams were determined by using experimental load-CMOD curves. These tension softening diagrams were adopted as the bond properties in numerical analyses to predict shrinkage and cracking behavior. For crack injection repair, bond strength tests based on Japan Industrial Standard (JIS) were carried out under conditions that are different from those normally encountered in the field (i.e., the tests involved smaller specimens, smoother surfaces, and finer grained materials). The bond properties of crack injection materials were evaluated using tension softening diagrams. Size effect on flexural bond strength of repair materials was observed and clarified by numerical analysis with these tension softening diagrams. The analyses indicate size effect should be considered when evaluating the strength of larger structures in the field.

In this study, damage evaluation of RC column subjected to cyclic loading and evaluation of retrofitting effect were conducted by means of 3 dimensional finite element analysis. Damage area of RC column was evaluated by using averaged compressive strain which was calculated by average of strain within certain area. Bond deteriorated area, in which concrete and rebar behave independently, could also be considered as the damage index of RC column. By comparing with the test result, both averaged compressive strain and bond deteriorated area corresponded to repaired area. Structural behavior of repaired RC column was simulated. As the results, it was confirmed that the damage evaluation method and repairing procedure in this study were suitable to simulate the repaired RC column., 応用力学論文集Vol.15（特集）