When precast concrete structure is constructed, it may be concerned that the joint work takes much time and causes structural weaknesses. Therefore, in this study, two types of new rebar connection systems between precast members were proposed. These connections have special tools attached in the tops of rebars which protrude from adjacent precast members, and the whole of these tools and around it are combined by high performance mortar after their members are connected. This paper described the load carrying capacities with proposed joints by experimental approaches, such as tension test for the specimen extracting a pair of connection, and static load test for the specimen with joints modeling precast road bridge deck slab. These results revealed that one of new connection systems had sufficient load bearing performance.
Some performances of stainless steel in concrete had been estimated, and corrosion occurrence amounts for SUS304, SUS316 and SUS410 had been clarified. Also, it had been clear that a corrosion characteristic is different between a bend part and a straight part for carbon steel. However, there is no examination about corrosion of stainless steel with a bend part such as stirrup. Based on above backgrounds, three-steps experiments were conducted in this paper to clear the performance of stainless steel with a bend part. First, anode polarization curves of SUS304, SUS316 and SUS410 were measured in a saturated calcium hydroxide solution. Next anode polarization curves of stainless steels and carbon steel were measured in mortar using special divided steel bars. According to these tests, it could be confirmed that the anode reaction progress at a bend part was easier than that at a straight part even in stainless steels. Finally, the corrosion current density of stainless steels in concrete beam with main rebar and stirrup was evaluated. As a result, it could be confirmed that the corrosion rate of stainless steel was remarkably low in comparison with carbon steel. However, it was clarified that at even stainless steel, the corrosion rate was high at a bend part in stirrup. In addition, there was a special case in third test whose main rebar was made with carbon steel and stirrup was made with stainless steel. This was set because stainless steel with expensive cost used at only limited part which was most severe position. According to this special case, the corrosion rate of stirrup decreased compared to a case whose main rebar and stirrup were made with carbon steel.
Geosynthetic Reinforced Soil (GRS) integral bridge, which fixes the girder on the top of GRS abutment, provides high performance against traffic load and earthquake thanks to the unity of abut wall and GRS. On the other side this type of bridge is subject to statically indeterminate force caused by the abut wall and GRS restraining the girder from volumetric change. Especially, long-term deformation by shrinkage and creep tends to arise on concrete girders. The authors examine long-term behavior of the first constructed GRS integral bridge by site measurement and thermo-hygral multi scale analysis. The integrity of the bridge and GRS was verified by 4 years history of the geosynthetic's strain and the girder's longitudinal displacement. The reliability of the analysis, considering the effect of rainfall, was confirmed by comparison with measured displacement and rebar strain of the girder. Finally, the stability of GRS integral bridge against long-term volumetric change of concrete was verified up to 100 years of design life.