This paper presents the behavior characteristics of steel-concrete interface and analysis method to simulate interface behavior by using push-out results for steel-concrete composite members. In order to analyze the partial-interaction behavior of steel-conc rete interface, the interface is idealized by a number of interface elements. A total of 9 push-out specimens were tested and the test results were utilized to provide the properties of interface element in the analysis. To validate the present study, using a commercial structural analysis program, nonlinear structural analysis were performed for the push-out specimens, and the results of analysis were compared with the test data. The results of this study have shown that the nonlinear, slip-softening, as well as linear-elastic behaviors of steel-concrete interface can be efficiently and accurately simulated by the method of analysis presented in this paper.

This paper presents the structural performance of steel-concrete composite decks with profiled steel sheeting. The main objective of this study is to develop a longspan composite deck that weighs, less than the conventional cast-in-place concrete deck. The proposed deck system is composed of profiled sheeting that is perpendicular to the steel girder with perfobond rib shear connectors welded to the sheeting. For a prototype two-cell steel-box girder bridge, a composite deck profile was designed. A total of eight fullscale deck specimens with different shear span ratios were tested under a static monotonic loading to examine the structural performance of the proposed deck system. The test results were compared with those obtained by finite element analysis and analytical equation. The load-deflection behaviors of the proposed deck system were also compared with those of the cast-in-place concrete deck. The results have indicated that the strength and behavior of the composite deck proposed in this study are govened by the horizontal shear interaction between the sheeting and the concrete. The flexural strength of the proposed deck system under positive bending is approximately 2.5 times greater than that of a typically designed cast-in-place concrete deck with the deck weighing 30% less.

In this paper, for the case of “service life extension” with the same capacity for wind turbines, a structural safety evaluation was carried out to determine whether to extend the service life of the aged foundation. As a result of this study, it was found that the aged foundation satisfies the structural safety of material strength, ultimate strength, fatigue life, and serviceability up to the present. Although the in-service period has been over 16 years, it has been shown that the material properties of concrete have exceeded the design strength, and no significant material deterioration has occurred. Also, structural safety could be evaluated more realistically based on actual concrete properties. In particular, it has been shown that it has a fatigue life of 40 years or more, so service life can be extended. It is expected that the methodology used in this paper will be useful not only for structural safety evaluation of the foundation in service, but also for decision-making for extending the service life. Furthermore, a more technical approach should be explored by many researchers in the future.

This paper presents the results of wave force tests conducted on three types of offshore support structures considering eight waves and three sea levels to investigate the corresponding wave forces. As a result of this study, it is found that the occurrence of shoaling in shallow water induces a significant increase of the wave force. Most of the test models at the shallow water undergo a nonlinear increase of the wave force with higher wave height increasing. In addition, the larger the diameter of the support structure within the range of this study, the larger the diffraction effect is, and the increase in wave force due to shoaling is suppressed. Under an irregular wave at the shallow water, the wave force to the long-period wave tends to be slightly higher than that of the short period wave since the higher wave height component included in the irregular wave has an influence on the shoaling. In addition, it is found that the influence of shoaling under irregular wave becomes more apparent in the long period.

Many recent studies in the development of floating concrete structures focused on a connection system made of modules. In the connection system, the modules are designed to be attached by pre-stressing (PS) while floating on the water, which exposes them to loads on the surface of the water. Therefore, the development of a pre-connection material becomes critical to ensure successful bonding of floating concrete modules. Micro-silica mixed aqua-epoxy (MSAE) was developed for this task. To find the proper MSAE mix proportion, 0% to 4% micro-silica was mixed in a standard mixture of aqua-epoxy for material testing. Also, the effect of micro-silica on the viscosity of the aqua epoxy was evaluated by controlling the epoxy silane at proportions of 0%, ±5%, and ±10%. After completion of the performance tests of the MSAE, we evaluated the effect of MSAE in a connected structure. The plain unreinforced concrete module joint specimens applied with MSAE at thicknesses of 5, 10, and 20 mm were prepared to be tested. Finally, we evaluated the performance of MSAE-applied reinforced concrete (RC) module specimens connected by PS tendons, and these were compared with those of continuous RC and non-MSAE-applied beams. The results showed that the mix of micro-silica in the aqua-epoxy changed the performance of the aqua-epoxy and the mix ratio of 2% micro-silica gave a stable failure behavior. The flexural capacity of concrete blocks bonded with MSAE changed according to the bond thickness and was better than that of concrete blocks bonded with aqua-epoxy without micro-silica. Even though MSAE insignificantly increases the load-carrying capacity of the attached concrete module structure, the stress concentration reduction effect stabilized the failure of the structure.