• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.69-77
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• 2003

This paper presents test results on eight reduced beam section(RBS) steel moment connections. The testing program addressed bolted versus welded web connection and panel zone(PZ) strength as key variables, Specimens with medium PZ strength were designed to promote energy dissipation from both PZ and RBS regions such that the requirement for expensive doublet plates could be reduced. Both strong and medium PZ specimens with a welded web connection were able to provide satisfactory connection rotation capacity for special moment-resisting frames. On the other hand, specimens with a bolted web connection performed poorly due to premature brittle fracture of the beam flange of the weld access hole. If fracture within the beam flange groove weld was avoided using quality welding, the fracture tended to move into the beam flange base metal of the weld access hole. Plausible explanation of a higher incidence of base metal fracture in bolted web specimens was presented. The measured strain data confirmed that the classical beam theory dose not provide reliable shear transfer prediction in the connection. The practice of providing web bolts uniformly along the beam depth was brought into question. Criteria for a balanced PZ strength improves the plastic rotation capacity while reduces the amount of beam distortion ore also proposed.

• Tunnel and Underground Space
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• v.19 no.6
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• pp.498-506
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• 2009

The stability assessment of a concrete liner of a compressed air storage tunnel should be performed by an approach which is different from that commonly used for the liners of road tunnels, since the liner is exposed to high air pressure. In this study, the stability analysis method for the liner of compressed air storage tunnel is proposed based on the elastic and elasto-plastic solutions of the thick-walled cylinder problem. In case of elastic analysis, the yield initiation condition at the inner boundary is considered as the failure condition of the liner, while the condition which results in the extension of yielding zone to a certain depth is taken as a failure indicator of the liner in the elasto-plastic analysis taking Mohr-Coulomb criterion. The application of the proposed method revealed that the influence of the relative magnitude of boundary loads on the stability of liner is considerable. In particular, noting that the estimation of the outer boundary load may be relatively difficult, it is thought that the precise prediction of outer boundary load is very important in the analysis. Accordingly, the emphasis is put on the selection of the liner installation time, which may govern the magnitude of outer boundary load.

• Tunnel and Underground Space
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• v.24 no.3
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• pp.212-223
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• 2014

In this study, the stability analyses for metal mine roadways at a great depth were performed. In-situ stress measurements using hydrofracturing, numerous laboratory tests for rock cores and GSI & RMR classifications were conducted in order to find the physical properties of both intact rock and in-situ rock mass distributed in the studied metal mine. Through the scenario analysis and probabilistic assessment on the results of rock mass classification, the in-situ ground conditions of mine roadways were divided into the best, the average and the worst cases, respectively. The roadway stabilities corresponding to the respective conditions were assessed by way of the elasto-plastic analysis. In addition, the appropriate roadway shapes and the support patterns were examined through the numerical analyses considering the blast damaged zone around roadway. It was finally shown to be necessary to reduce the radius of roadway roof curvature and/or to install the crown reinforcement in order to enhance the stability of studied mine roadways.

• Steel and Composite Structures
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• v.27 no.3
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• pp.337-353
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• 2018

In previous weak-axis moment connection tests, brittle fracture always initiated near the edge of the beam flange groove weld due to force flow towards the stiffer column flanges, which is the opposite pattern as strong-axis moment connections. As part of the China NSFC (51278061) study, this paper tested two full-scale novel weak-axis reduced beam section moment connections, including one exterior frame connection specimen SJ-1 under beam end monotonic loading and one interior frame joint specimen SJ-2 under column top cyclic loading. Test results showed that these two specimens were able to satisfy the demands of FEMA-267 (1995) or ANSI/AISC 341-10 (2010) without experiencing brittle fracture. A parametric analysis using the finite element software ABAQUS was carried out to better understand the cyclic performance of the novel weak-axis reduced beam section moment connections, and the influence of the distance between skin plate and reduced beam section, a, the length of the reduced beam section, b, and the cutting depth of the reduced beam section, c, on the cyclic performance was analyzed. It was found that increasing three parametric values reasonably is beneficial to forming beam plastic hinges, and increasing the parameter a is conducive to reducing stress concentration of beam flange groove welds while increasing the parameters b and c can only reduce the peak stress of beam flange groove welds. The rules recommended by FEMA350 (2000) are suitable for designing the proposed weak-axis RBS moment connection, and a proven calculation formulation is given to determine the thickness of skin plate, the key components in the proposed weak-axis connections. Based on the experimental and numerical results, a design procedure for the proposed weak-axis RBS moment connections was developed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6C
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• pp.339-347
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• 2008

The penetration of the probe produces the excess pore pressure due to the disturbance. The objective of this study is to evaluate the disturbance zone by using the dissipation of the excess pore water pressure, which was generated due to the penetration of the penetrometer with different size. The CPT, DMT and FVP (Field Velocity Probe) are adopted for in-situ tests. The tests are carried out in the construction site of north container pier of Busan new port, Korea where is accelerating the consolidation settlement using plastic board drains (PBD) and surcharges by crushed gravels. The coefficient of consolidation $(C_h)$ and soil properties are deduced by the laboratory test. The in-site tests are performed after the predrilling the surcharge zone at the point of 90% degree of consolidation. To minimize the penetration effect, the horizontal distance between penetration tests is 3m, the change of the pore pressure is monitored at the fixed depth of 24m. The coefficient of consolidation $(C_h)$ and the $t_{50}s$ are calculated based on the laboratory test and the in-situ data, respectively. The equvalent radi based on the $t_{50}$ shows that the FVP and the DMT produce the smallest and the greatest equivalent radi, respectively.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.6
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• pp.431-450
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• 2011

When a circular vertical shaft is constructed below the groundwater level, additional forces caused by groundwater flow besides horizontal effective stresses will act on the wall. The inward direction of the groundwater flow will be inclined to the vertical wall and its direction will change depending on the wall depth. In this paper, to figure out the effect of seepage forces acting on the circular vertical shaft, the slope of the inclined flow varying with the depth is divided into vertical and horizontal components to derive the coefficient of earth pressure considering the seepage pressure and to obtain the vertical stress by taking the seepage pressure into account. The control volume in this study is assumed to be the same with that of the dry ground condition within which the earth pressure is acting on the wall by the creation of the plastic zone during shaft excavation. An example study shows that the vertical stress increases by about 1.4 times and the horizontal earth pressure increases up to 2.5 times compared to the dry ground condition. The estimated values from the proposed equation considering seepage forces and the calculated values from numerical analysis with "effective stress plus seepage force" show similar values, which verifies appropriateness of the proposed equation to estimate the earth pressure under the seepage condition.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.337-347
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• 2011

In this study, seismic resistance of concrete encased U-shaped steel beam-to-steel H-shaped column connections was evaluated. Three specimens of the beam-to-column connection were tested under cyclic loading. The composite beam was integrated with concrete slab using studs. Re-bars for negative moment were placed in the slab. The primary test parameter was the details of the connections, which are strengthening and weakening strategies for the beam end and the degree of composite action. The depth of the composite beams was 600mm including the slab thickness. The steel beam and the re-bars in the slab were weld-connected to the steel column. For the strengthening strategy, cover plates were weld-connected to the bottom and top flanges of the steel beam. For the weakening strategy, a void using styrofoam box was located inside the core concrete at the potential plastic hinge zone. The test results showed that the fully composite specimens exhibited good strength, deformation, and energy dissipation capacities. The deformation capacity of the beam exceeded 4% rotation angle, which is the requirement for the Special Moment Frame.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.3 no.2
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• pp.129-136
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• 1970

As an attempt to determine if the morphological differences between the southern and western oysters are due simply to the local ecological factors or are based on their fundamental genetic nature, oyster seeds produced in 1968 at Tong-Young, Ye-Chun, and Ko-Hung on the south coast and at Kan-Wol-Do on the west coast were cross-transplanted during May of 1969 to compare their growth. The spats were placed in plastic baskets which permitted free water flow through and the baskets hung from a wooden rack located at a tidal zone of less than I hour exposure at a depth chosen to keep the baskets submerged in water at all times. Twice a month the growth of the spats were measured along with the air and water temperature and salinity. The early summer spats, which were $17-240\%$ larger, in size, than the late summer spats at the time of cross-transplantation, grew more slowly than the late summer spats when exposed to identical environmental conditions, shortening the initial gap to a $5-20\%$ level as the first year of the growth phase came to an end in December. The growth of the Kan-Wol-Do spats lagged considerably behind the southern spats at all localities tested, whereas there were no significant differences among the latter groups. This suggests that the morphological differences between southern and western Pacific oysters in Korea are a manifestation of genetic variety and that Pacific oysters cultured along the south coast are of an identical variety as they are commonly believed to be. The seasonal changes in temperature and salinity even during rainy season in both the southern and western coastal areas are well within the range suitable for successful spawning, and spat fall. However, since the results were based on twice-a-month measurements with no data covering the critical period before and after spawning, they can only serve to indicate at best the general pattern of changes in the environmental conditions of each growing area.