Tokyo Gas has introduced the super-dense real-time monitoring earthquake system, SUPREME, composed of ultra high density seismographs for the purpose of prevention of secondary disasters at the time of earthquake. SUPREME collects seismic observation information promptly, identifies blocks to be stopped immediately, plays an important role to predict damage to the pressure gas conduit and supports supply stop judgment according to the degree of damage. In this study, the authors investigate the damage of low pressure gas pipelines in the Great East Japan Earthquake by classifying it according to the characteristics of damage by analyzing considering the influence of terrain and reviewing the composition of the damage prediction equations.
In this study, to examine the effect of the mechanical properties of the expanded material on the performance of the multi-layered absorbing system, a scaled model of the absorbing system composed of sand, RC plate, and expanded material was designed and manufactured. Weight drop impact tests were performed by changing the type of expanded material, layer configuration, and input energy due to impact loading. The results showed that the larger the compressive strength of the expanded material, the larger the weight impact force and transmitted impact force, and the smaller the weight penetration and the degree of damage to the expanded material. Also, the shear stress acting on the RC plate increases as the compressive strength of the expanded material increases, and the tendency of punching shearing of the RC plate appears more strongly. It has been found that it has twice as much energy absorption performance as the input energy in design.
For the painted steel structures exposed to highly corrosive environments, especially where under the air-borne sea salt deposition, most of the localized corrosion initiates from coating flaws and defects. These corrosion cases would often progress with the mutual interaction between adjacent defects, because of the occurrence of the electrical short circuit around the multiple coating defects due to the stagnated rainwater or dew. This study focused on those regions in steel structure where the rainwater accumulated, and wetdry cycles repeated caused by dew. The objective is to investigate the electrochemical properties of corrosion between adjacent coating defects during the initial stage. Therefore, the model specimens embedded with a plurality of electrodes were fabricated to simulate coating defects, and the time-dependent macrocell currents were monitored between the electrodes. Based on the test results, an estimation method of the corrosion current density was proposed by investigating the electrochemical properties of the three coating defects in the water stagnated environment. Additionally, for the cyclic wet-dry environment, it was clear that the corrosion occurred in small-area defect would be easier to progress than that of a large-area defect.
A cover anticorrosion method is expected to have the effect of suppressing inflow of environmental factors from outside, and is an anticorrosion method capable of improving corrosion environment. However, there are few studies on evaluation of corrosion environment in enclosed girder space. In this study, a sandwich panel was attached to a steel plate girder bridge which is constructed in coastal area of subtropical zone, and corrosion environment in internal space is evaluated by measurement and analysis. In addition to evaluation of environmental factors such as salinity, temperature, humidity, time of wet and exposure test, thermal fluid simulation was carried out for dew condensation phenomenon observed sporadically on deck plate in internal space. Furthermore, exposure tests were conducted at vicinity of the bridge, and the environmental improvement effect of cover anticorrosion method was confirmed by comparing with the environment inside and outside the girder.