• Journal of the Korea Furniture Society
• /
• v.20 no.4
• /
• pp.358-373
• /
• 2009

Probability based design(PBD)method has some advantages against current design methods. First, it can provide the quantitative values for the structural safety or capacity through the reliability index, $^{\beta}$. That presented the certainty on the corresponding structure for the designer or user, also that permitted the broad consideration in the safety of structures. In addition, it can give the quantitative lifetime of the related structure in the calculation process of target reliability index. Also, incidental economical efficiency can be expected because decrease of required structural material can be obtained by using the practical material data. Unlikely current deterministic structural design methods, main advantage is the reflection of real condition in the structural design process by application of the data with not small clear specimen but structural size material. Advanced countries, namely America, Canada, Europe, Australia and New Zealand already converted from allowable stress design(ASD) method to PBD method and used as a standard wooden structures code in the late 1980s and 1990s. Other domestic constructions standards such as the steel or concrete constructions accepted and used the PBD methods already. Accordingly, wooden structural design method also should be converted from deterministic ASD to probabilistic LRFD(Load and resistance factor design) in order to keep pace with worldwide demands for PBD. Hence, to suggest the reason of introduction the PBD in domestic wooden structural design and analysis, a brief example was used to show the different reliability index by using the different design methods. Definition, merits and demerits of deterministic ASD and probabilistic LRFD were followed. Also the three examples were presented to show the similarity and differences between ASD and LRFD. Finally, connection problems that might cause a disputation in wooden structural design and analysis were broadly examined.

• Earthquakes and Structures
• /
• v.17 no.3
• /
• pp.297-306
• /
• 2019

The extension of existing RC buildings is a challenging process, which requires efficient connection between existing and new materials to guarantee load transferring between the lap-spliced longitudinal columns' reinforcement. Therefore, the length of the columns' starter bars is a crucial factor, which decisively affects the seismic response of the new columns. In particular, when the length of the starter bars is short, then the length of the lap splices of reinforcement is inadequate to ensure load transfer between steel bars and concrete, with an indisputable detrimental impact on the seismic behaviour of the columns. Moreover, in most of the existing RC buildings the column starter bars are of particularly short length, while they have probably been bent, cut or corroded. In the present study, the effectiveness of both welded rebar and mechanical splices of reinforcement in ensuring load transferring between the starter bars and the longitudinal reinforcement of the new column was experimentally evaluated. Four cantilever column subassemblages were constructed and subjected to earthquake-type loading. Three of the specimens were used to examine different types of shielded metal arc welding (SMAW), while in the fourth subassemblage mechanical splices were tested. The hysteretic response of the columns was evaluated and compared to the behaviour of a fifth specimen with continuous reinforcement, tested by Kalogeropoulos and Tsonos (2019). Test results clearly demonstrated that the examined types of SMAW were equally satisfactory in ensuring the ductile seismic performance of the columns, while the mechanical splices found to be more susceptible to exhibit slipping of the bars.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.2
• /
• pp.111-122
• /
• 2017

In this paper, the applicability of a 1900mm-deep concrete-filled U-shaped composite beam to composite ordinary moment frames (C-OMFs) was investigated based on existing test results from smaller-sized specimens and supplemental numerical studies since full-scale seismic testing of such a huge sized beam is practically impossible. The key issue was the web local buckling of concrete-filled U section under negative bending. Based on 13 existing test results compiled, the relationship between web slenderness and story drift capacity was obtained. From this relationship, a 1900mm-deep mega beam, fabricated with 25mm-thick plate was expected to experience the web local buckling at 2% story drift and eventually reach a story drift over 3%, thus much exceeding the requirements of C-OMFs. The limiting width to thickness ratio according to the 2010 AISC Specification was shown to be conservative for U section webs of this study. The test-validated supplemental nonlinear finite element analysis was also conducted to further investigate the effects of the horizontal stiffeners (used to tie two webs of a U section) on web local buckling and flexural strength. First, it is shown that the nominal plastic moment under negative bending can be developed without using the horizontal stiffeners, although the presence of the stiffeners can delay the occurrence of web local buckling and restrain its propagation. Considering all these, it is concluded that the 1900mm-deep concrete-filled U-shaped composite beam investigated can be conservatively applied to C-OMFs. Finally, some useful recommendations for the arrangement and design of the horizontal stiffeners are also recommended based on the numerical results.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.55 no.2
• /
• pp.121-128
• /
• 2019

Various artificial reefs provide the fish habitat and nursery, and contribute the improvement of fisheries productivity. The evaluation methods of fishery resources in the artificial reefs have been done by fishing, scuba diving, underwater camera, and scientific echo sounder/sonar. There are a number of studies using echosounders on the quantitative and qualitative evaluations of artificial reefs in various seas around the world. This study focused on the spatial distribution of fishes around artificial reefs and the influential area of reefs off Bukchon, Jeju Island. Not only acoustic data but also various properties of artificial reefs were used in the geographic information system to extract relevant results. As a result, the major material of reefs on this study site was concrete and the number of reefs with that material was the most. The volume of reefs consisted of steel only and steel with riprap was considerably large compared to other reefs. The average NASC in the vertical distribution of fishes in artificial reefs was $31.6m^2/nm^2$ in April, and that was $61.3m^2/nm^2$ in June. The distance between the fish school and their nearest reef in June morning had a wide range from 750 to 3250 m. On the basis of the influence ray of artificial reefs, it had a tendancy of NASC to decrease with distance from the reef in the June morning. It is a preliminary study to present the geospatial analysis example to understand a better way of comprehensive artificial reef environments.