本研究は，コンクリート構造物の環境作用に対する性能照査を信頼性理論に基づく限界状態設計法の枠組みの中で実現することを目的とした基礎的研究である．特に沿岸部などの塩害環境下に着目し，塩分の飛来から鉄筋腐食が発生するまでのモデル化に介在する種々の不確定性について，観測・実験データをもとに評価し，耐用期間内に鉄筋腐食が生じる損傷確率を定量化した．次いで，損傷確率を Monte Carlo ...法などにより算定することなく，要求レベルに漸近させるために必要な設計かぶりを評価する手法を提示した．これにより，塩害環境やコンクリートの品質に関わらず，鉄筋腐食に対してある一定の損傷確率を有する鉄筋コンクリート構造物の耐久設計が可能となることを示した．
According to the limit state design based on reliability theory, the verification of the durability of concrete structures against various deteriorating factors is examined in this fundamental study. ...Especially, verification of salt attack is considered. Various kinds of uncertainty in the modeling of airborne chlorides transportation to corrosion initiation of reinforcing bar are evaluated using the previous observation or experimental results, and the probabilities that the threshold chloride concentration is exceeded during service life are calculated for concrete structures exposed to marine environments. Without any calculation of probability such as Monte Carlo Simulation, safety factor and design procedure to specify cover ensuring that the probability of corrosion initiation of reinforcing bar is almost the same as a target value, is proposed.
According to the increasing of 2- or 3-plate girder systems and open-box girder ones in short- and medium-span highway bridges, the span lengths of concrete slabs have become longer than the one of ...ordinary multi-girder systems. As one of the method dealing with this problem, 2-way slabs supported by main girders and cross beams seem to be effective because of not only reducing the bending moment caused by wheel load, but also improving the durability by relaxing shear concentration by arranging main reinforcements parallel with moving wheel. Therefore, in order to certify the deterioration mechanism of the 2-way slabs, fatigue tests by using wheel-running machine were carried out Then, a FEM analysis modeling the cracks by gap elements with rotational and shear spring, was developed and the test results were evaluated with the relation between the influence of strength and repeating number of wheel load on the decreasing stiffness of the slab and the deterioration rate.
Reinforced concrete (RC) structures in a marine environment deteriorate with time due to chloride-induced corrosion of reinforcing bars. This paper presents reliability-based durability assessment of ...existing RC structure in a marine environment. A simple assessment criterion with partial factors that satisfy the target reliability level within the remaining life-time of existing RC structure is presented. A procedure to obtain the partial factors updated by the Sequential Monte Carlo Simulation is indicated. In this procedure, the chloride concentration distribution by coring test is used as observational data. Partial factors could be determined by taking into consideration the reduction of uncertainties associated with the prediction of chloride-induced corrosion. Partial factors for durability assessment of existing RC structures could be reduced compared with those for durability design of new RC structures.
Damage of marine structures due to salt attack is well known as one of major deterioration processes of reinforced concrete (RC) structures. In order to investigate diffusion characteristics of ...chloride ions in concrete piers of Sin-Kitakyusyu Airport Bridge, exposure tests of RC beams were carried out for six years. Results on chloride diffusion were studied in comparison with the continuous diffusion tests in a laboratory. Based on these results, a performance-based analysis on the salt attack of the piers is conducted to confirm the durability of the concrete piers.
PDF
