When steel structures exposed to atmospheric environment are repainted, corrosion product containing chloride tends to be left on the surface. As a results, under-film corrosion will occur in an early stage after the repainting. In author's previous studies, an anticorrosive method with Al-Zn sacrificial anode material and fiber sheet which has functions of continual water absorption and retention has been developed as anticorrosive method without a high quality surface preparation. The purpose of this research is to investigate the anticorrosive effect and practicability of the developed anticorrosive method. Tensile strength tests were carried out on deteriorated Al-Zn sacrificial anode plates to clarify the mechanical properties. In addition, atmospheric exposure tests were conducted on the model specimens with the anode plate holes of various diameter and arrangement to quantitatively evaluate the influence of alloy composition of casting plate and water-absorbing route on current efficiency of the anode material. Furthermore, the practicability was also investigated by applying the method to hot-rolled H-section steel that simulated an actual structure and a steel I-section girder bridge of which almost paint coating has deteriorated and disappeared.
An estimation of a rail tilting under the design load is an important factor in a rational design of rail fastening systems. A rail tilting has been estimated by the practical solution based on the torsion theory. However, the recent study has reported that the rail tilting estimated by the conventional solution does not agree well with the experimental values. The purpose of this study is to establish a practical and high-accuracy solution for a rail tilting. First, a FEM model for a rail tilting was proposed and the validity of the model was examined by comparing the analytical values with the experimental values. As a result, a rail tilting estimated by the model was in good agreement with the experimental values. Therefore, it is found out that the model is available for predicting the response of a rail and its fastenings. Secondly, the model was applied to determining the loading condition of the performance test of rail fastening systems. Thereby, it is made possible to evaluate the performance of rail fastenings with high accuracy as compared with the conventional evaluation.
Decomposing the earthquake motion phase into the linear delay part and the fluctuation part from it, we investigate the stochastic characteristics of the phase difference in the fluctuation part. The probability density function of the Newton's difference quotient of phase (approximation of the group delay time), which is defined as the quotient of phase difference with respect to the discrete circular frequency interval, is expressed by a unique stable distribution for any arbitrary circular frequency intervals. Because the variance of the stable distribution cannot be defined it is analytically derived that the group delay time, as well as the phase difference, are the discontinuous function with respect to the circular frequency. The earthquake motion phase, therefore, is the continuous but undifferentiable function with respect to the circular frequency. We propose a new type of stochastic process being able to represent these stochastic characteristics of phase difference by the use of Lebesgue-Stieltjes type integral formula. In which the Kernel plays a role to realize the self-affine and auto correlation nature of phase difference and the integration function represents the main stochastic characteristics of earthquake motion phase. Comparison of several numerical simulations with observed earthquake motion phase differences results in the efficiency of the newly proposed stochastic process to simulate a realistic earthquake motion phase.
It is important to evaluate the amount of airborne sea salt adhered to each member of a bridge accurately and quantitatively for effective maintenance and management, because airborne sea salt have large influence on their durability especially at coastal regions. On the other hand, local governments have to maintenance and manage many bridges simultaneously. Therefore, it is preferable to obtain corrosion environment of each bridge without any on-site observation and/or monitoring to conserve their budget. First, in this paper, the authors calculated wind speed, wind direction and airborne sea salt concentrations using the meso-scale atmospheric model WRF. Second, the study bridge and the simplified surrounding topography were realized in computational domains to calculate steady flows in each approaching wind direction using the CFD technique. Finally, in addition to these results, on the basis of the proposed quantitative evaluation method of the amount of airborne sea salt on a surface, the authors evaluated the salinity amount in vicinity to each member of the study bridge. The authors achieved a certain result to regard with the WRF simulation and the evaluation of the salt amount, and expect that more accurate estimation will be realized with some improvements.
In this study, the structural design of railing post affecting road landscape was investigated. Bridge beam-type railing post is often made of aluminum-alloy because it has high durability and the extrusion process is possible to produce an arbitrary shape. The optimization of extruded shape was performed by a genetic algorithm using multiple objective functions of mechanical performance and economy. By changing dimensional parameters used in the optimization, the effect of each parameter on the optimization was examined. Based on the optimization results of separated extrusion models, the shape optimized for bulk extrusion models that require the latest developed extrusion machine was also examined.
In this research, a method which is able to analyze corrosion damage condition such as local thickness reduction or formation of rust layer of steel members of steel members at same time has been investigated. Considering eddy current testing which uses especially low frequency eddy current such as 1~1000Hz, corrosion damage condition analysis method which performs inspection from only one side of steel members has investigated to become easy non-destructive testing method. Firstly, differences of dynamic magnetic field characteristics due to damage form was clarified using numerical simulation, and further data analyzing method to obtain the differences was investigated. Then sweep wave and frequency step wave were designed as induced wave and analysis using both detected voltage and wavelet coefficient was performed. Based on results of all process, a corrosion damage condition analysis method was proposed. Finally, in the applicability of proposed method was clarified by experiment.
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