Design restoration method for existing reinforced concrete slab bridges

• Material Type: 博士論文
• Title: Design restoration method for existing reinforced concrete slab bridges
• Author/Editor: Tarekegn, Abrahaam Gebre
• Author Heading: Tarekegn, Abrahaam Gebre
• Publication Date: 2013-09-26
• Publication Date (W3CDTF): 2013-09-26
• Alternative Title: 既設RCスラブ橋の復元設計法
• Degree grantor/type: 横浜国立大学
• Date Granted: 2013-09-26
• Date Granted (W3CDTF): 2013-09-26
• Dissertation Number: 甲第1578号
• Degree Type: 博士(学術)
• Conferring No. (Dissertation): 甲第1578号
• Text Language Code: eng
• NDLC: UT51
• Target Audience: 一般
• Note (General): Bridges constructed several decades ago have been deteriorated due to many reasons and hence their capacity is reduced. Capacity performance assessment is one of the major tasks to be performed in bridge management and should be exercised with care. Original design documents, drawings and plans are important to perform such an activity. In cases of older bridges, assessing as much design information as possible is difficult. In the absence of these data, assessing bridge’s performance will be a common problem bridge engineers face. For bridges where necessary details, such as reinforcement in the concrete bridge, are not available, design restoration should be performed. Design restoration is a process of accurately describing the initial condition (design values) of a structure from its current condition (actual values). On the other hand, if deflection is used as additional data, it reflects the present actual values. A literature review on distributions of Ethiopian bridges shows that reinforced concrete bridges are dominant, which comprises 84% of the country’s bridge and they are in various state of deterioration. Almost 46% of the bridges are found in fair and bad conditions, about 44% of them are constructed before 40-110 years ago and considerable numbers of bridges were constructed in the years 1935-1945, by Italians. For restoration of initial conditions of bridges constructed in the specified period of time, detailed study on the Italian and AASHTO LRFD Bridge Design Specifications were carried out. For capacity assessment of RC bridges, classification and identification of damages are of great importance. Wide variety of failures is due to old bridge failures and design deficiency leading to bridge collapse. The literature survey also shows that the principal causes of the major defects of RC bridges in Ethiopia are excessive loading, poor design and aging. Concrete testing with a test hammer and from core test and detection of position of reinforcing bars using a magnetic device are the most frequently used non-destructive testing methods. For multi-layer reinforcement arrangement, however, if the gap between the reinforcement layers is small, only the first layer of the reinforcement can be detected using the radar method. In this study, a design restoration method for RC slab bridges is proposed. In the method, the unknown parameters are computed using a nonlinear deflection equation. Moreover, using this method, reinforcing area and position of any layer can be estimated. In the computation, variations in the neutral axis depth profile and the moment of inertia expression with parabolic functions are assumed. In line with this, new closed-formexplicit equations for the computation of slope and deflection of RC beams by considering variation in neutral axis depth profile are proposed. For the probabilistic design restoration, a Latin Hypercube Sampling (LHS) of random variables and experimental investigations under a control of achieved concrete cover thickness and dimensions for RC slab bridges is presented to take into account the statistical variations in the design parameters and to obtain the mean values and the confidence limits for mean of the restored design data. This LHS method is used to improve the computational efficiency in the estimation of actual values. The confidence interval to the mean tells us the accuracy (reliability) of the design restoration. With the present method, the current values can be obtained using the dimensional data and the deflections by load test only. In considering the statistical variations, the allowable limits of dimensional measurements by AASHTO Bridge Construction Specification are considered. A standard RC slab bridge is designed as per AASHTO LRFD Bridge Design Specification and simulated using FEM. In the simulation, the mesh consists of rectangular elements of 0.05m in size with 4 nodes and SBETA material model is used. The FEM simulation helps to predict deflection of bridges. For the derivation of empirical formula for the estimation of yield strength of steel by considering the effects of material constants and dimensional data is considered. Based on the FEM simulation results, current and initial conditions are restored. The design restoration results of the present method give better accuracy than the conventional method. The verification of the present method is shown using the experimental data. Test specimens of RC slab and beam are used to verify analytical results. For these test specimens, the coefficients of variations for dimensions obtained from experimental investigation are used. In addition, the result which is obtained from FEM simulation is verified by using the proposed method. Uncertainty and sensitivity analysis of random variables affecting the design restoration are performed. Cross-sectional area of steel bar and cover thickness are the most influencing factors in the estimation process. Based on the current results obtained, the initial condition of bridges; material strengths, dimensions, cross-sectional area of steel bar and position of reinforcing bars are estimated. The performance rating of RC bridge is performed and the probabilistic distributions of the rating factors for inventory loadings and posting analysis based on the current values are shown. The present design restoration scheme proposed for RC slab bridges can be extended for RC T-girder bridges, arch bridges and composite structures. By using sufficiently accurate displacement transducers, the present design restoration method can also be applicable to restore RC sections with multi-layer reinforcement arrangement.
• Persistent ID (NDL): info:ndljp/pid/10168231; https://dl.ndl.go.jp/pid/10168231
• Collection: 障害者向け資料
• Collection (Materials For Handicapped People:1): テキストデータ
• Collection (particular): 国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文; https://dl.ndl.go.jp/collections/A00014
• Acquisition Basis: 博士論文（自動収集）
• Date Accepted (W3CDTF): 2016-08-04T09:59:51+09:00
• Date Created (W3CDTF): 2016-09-16
• Format (IMT): application/pdf
• Access Restrictions: 国立国会図書館内限定公開
• Service for the Digitized Contents Transmission Service: 図書館・個人送信対象外
• Availability of remote photoduplication service: 可
• Periodical Title (URI): http://hdl.handle.net/10131/8488; https://ynu.repo.nii.ac.jp/records/4631
• Data Provider (Database): 国立国会図書館 : 国立国会図書館デジタルコレクション; https://dl.ndl.go.jp