• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.1
• /
• pp.79-86
• /
• 2007

The Magnus effect measurement apparatus was designed and built for spinning wind tunnel model which would simulate the rotation of projectiles. Prior to the high speed test, the ground functional test and the low speed test were carried out in the Agency for Defense Development's Low Speed Wind Tunnel(ADD-LSWT) at spin rates from about 6,000 to 10,000 rpm. Magnus force and moment were measured on the spinning projectile model at velocity of 100 m/s. It was shown that the Magnus force and moment were linear function of spin parameter. The test results were compared with Magnus test run on the same configuration in the Arnold Engineering Development Center's Propulsion Tunnel 4T(AEDC-4T).

• Journal of Korea Foundry Society
• /
• v.24 no.5
• /
• pp.273-280
• /
• 2004

Vibrational motions of the compaction table were investigated to select the optimal operation conditions of sand filling and compaction for the EPC process. Their modes were measured at the nine points of the table with changing the relative rotation angles between the two eccentric mass vibrators which were attached parallel beneath the table. Well-defined vibration modes were measured at the center of the table but those of left and right sides of the table were distorted regardless of rotational angle differences. The distortion of vibration modes at both sides of the table were caused by the moment generated by offset positions of two eccentric masses. It was found that the uniform vibration modes would be gathered by controlling the relative distances between the rotating axis and the center of gravity in the compaction system at the various conditions of vibration modes and rotational angle differences.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.8 no.1
• /
• pp.1-15
• /
• 2004

Dynamic analyses were carried out to study the seismic response of high-rise steel moment-resisting frames in sixteen story buildings. The frames are intentionally designed by three different design procedures; strength controlled design. strong column-weak beam controlled design. and drift controlled design. The seismic performances of the so-designed frames with vertical mass irregularities were discussed in view of drift ratio. plastic hinge rotation, hysteretic energy input and stress demand. A demand curve of hysteretic energy inputs was also presented with two earthquake levels in peak ground accelerations for a future design application.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.09a
• /
• pp.913-922
• /
• 2009

Fourteen model pile load tests using a calibration chamber and instrumented model pile were preformed to investigate the variation of the behaviors of driven piles in sands with soil and lateral cyclic loading conditions. Results of the model tests showed that the first loading cycle generated more than 70% of the pile head rotation developed for 50 lateral loading cycles. Lateral cyclic loading also made an increase of the ultimate lateral load capacity of piles for $K_0$=0.4 and an decrease for $K_0$ higher than 0.4. Higher portion of the increase or decrease in the ultimate lateral load capacity by lateral cyclic loading was generated for the first loading cycle due to densification of loosening of the soil around the pile by lateral cyclic loading. It was also observed that a two-way cyclic loading caused higher ultimate lateral load capacity of driven piles than a one-way cyclic loading. When the pile was in the ultimate state, the maximum bending moment developed in the pile increased with increasing $K_0$ value of soil and was insensitive to the magnitude and number of lateral cyclic loading.

• The Transactions of the Korea Information Processing Society
• /
• v.3 no.6
• /
• pp.1636-1645
• /
• 1996

In this paper we proposed a new scheme for conditional two dimensional (2-D)moment-based classification of patterns on the basis of Gibbs random fields which are will suited for representing spatial continuity that is the characteristic of the most images. This implementation contains two parts: feature extraction and pattern classification. First of all, we extract feature vector which consists of conditional 2-D moments on the basis of estimated Gibbs parameter. Note that the extracted feature vectors are invariant under translation, rotation, size of patterns the corresponding template pattern. In order to evaluate the performance of the proposed scheme, classification experiments with training document sets of characters have been carried out on 486 66Mhz PC. Experiments reveal that the proposed scheme has high classification rate over 94%.

• Steel and Composite Structures
• /
• v.18 no.5
• /
• pp.1177-1195
• /
• 2015

Six specimens are tested to investigate the cyclic behavior of beam-to-column abnormal joints in steel moment-resisting frames, which are designed according to the principle of strong-member and weak-panel zone. Key parameters include the axial compression ratio of column and the section depth ratio of beams. Experimental results indicate that four types of failure patterns occurred during the loading process. The $P-{\Delta}$ hysteretic loops are stable and plentiful, but have different changing tendency at the positive and negative direction in the later of loading process due to mechanical behaviors of specimens. The ultimate strength tends to increase with the decrease of the section depth ratio of beams, but it is not apparent relationship to the axial compression ratio of column, which is less than 0.5. The top panel zone has good deformation capacity and the shear rotation can reach to 0.04 rad. The top panel zone and the bottom panel zone don't work as a whole. Based on the experimental results, the equation for shear strength of the abnormal joint panel zone is established by considering the restriction of the bottom panel zone to the top panel zone, which is suitable for the abnormal joint of H-shaped or box column and beams with different depths.

• Earthquakes and Structures
• /
• v.14 no.6
• /
• pp.525-535
• /
• 2018

This study presents a new beam-column model comprising material nonlinearity and joint flexibility to predict the nonlinear response of reinforced concrete structures. The nonlinear behavior of connections has an outstanding role on the nonlinear response of reinforced concrete structures. In presented research, the joint flexibility is considered applying a rotational spring at each end of the member. To derive the moment-rotation behavior of beam-column connections, the relative rotations produced by the relative slip of flexural reinforcement in the joint and the flexural cracking of the beam end are taken into consideration. Furthermore, the considered spread plasticity model, unlike the previous models that have been developed based on the linear moment distribution subjected to lateral loads includes both lateral and gravity load effects, simultaneously. To confirm the accuracy of the proposed methodology, a simply-supported test beam and three reinforced concrete frames are considered. Pushover and nonlinear dynamic analysis of three numerical examples are performed. In these examples the nonlinear behavior of connections and the material nonlinearity using the proposed methodology and also linear flexibility model with different number of elements for each member and fiber based distributed plasticity model with different number of integration points are simulated. Comparing the results of the proposed methodology with those of the aforementioned models describes that suggested model that only uses one element for each member can appropriately estimate the nonlinear behavior of reinforced concrete structures.

• Earthquakes and Structures
• /
• v.8 no.3
• /
• pp.591-617
• /
• 2015

Standards for seismic assessment and retrofitting of buildings provide deformation limit states for structural members and connections. However, in order to perform fully consistent performance-based seismic analyses of soil-structure systems; deformation limit states must also be available for foundations that are vulnerable to nonlinear actions. Because such limit states have never been established in the past, a laboratory testing program was conducted to study the rotational capacity of small-scale foundation models under combined axial load and moment. Fourteen displacement-controlled monotonic and cyclic tests were performed using a cohesionless soil contained in a $2.0{\times}2.0{\times}1.2m$ container box. It was found that the foundation models exhibited a stable hysteretic behavior for imposed rotations exceeding 0.06 rad and that the measured foundation moment capacity complied well with Meyerhof's equivalent width concept. Simplified code-based soil-structure analyses of an 8-story building under an array of strong ground motions were also conducted to preliminary evaluate the implication of finite rotational capacity of vulnerable foundations. It was found that for the same soil as that of the experimental program foundations would have a deformation capacity that far exceeds the imposed rotational demands under the lateral load resisting members so yielding of the soil may constitute a reliable source of energy dissipation for the system.

• Wind and Structures
• /
• v.23 no.3
• /
• pp.171-189
• /
• 2016

An adjustable, louver-type wind barrier was introduced in this study for improving the running safety and ride comfort of train on the bridge under the undesirable wind environment. The aerodynamic characteristics of both train and bridge due to this novel wind barrier was systematically investigated based on the wind tunnel tests. It is suggested that rotation angles of the adjustable blade of the louver-type wind barrier should be controlled within $90^{\circ}$ to achieve an effective solution in terms of the overall aerodynamic performance of the train. Compared to the traditional grid-type wind barrier, the louver-type wind barrier generally presents better aerodynamic performance. Specifically, the larger decrease of the lift force and overturn moment of the train and the smaller increase of the drag force and torsional moment of the bridge resulting from the louver-type wind barrier were highlighted. Finally, the computational fluid dynamics (CFD) technique was applied to explore the underlying mechanism of aerodynamic control using the proposed wind barrier.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.25 no.4
• /
• pp.153-160
• /
• 2021

The connection of the steel structure serves to transmit external forces to the main components. The same is true for the behavior of modular systems composed mainly of steel or composite members. In this study, the joint performance of the composite and steel modules proposed was evaluated. The analytical models of the two joint types were constructed and were subjected to cyclic loading to assess the safety and the energy dissipation capacity of the joint types. The analysis results of the joints showed that the joints of the modular systems remain stable when the joint rotation reached the seismic performance limit state of the 0.02 rad required for steel intermediate moment frame. It was also observed that the joint of the composite modular system showed higher energy dissipation capacity compared with the steel modular system.