• Structural Engineering and Mechanics
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• v.75 no.5
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• pp.529-540
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• 2020

The mechanical properties of timber construction have drawn more attention after the 2013 Lushan earthquake. A strong desire to preserve this ancient architectural styles has sprung up in recent years, especially for residential buildings of the mountainous areas. In the column-and-tie timber construction, continuous-tenon joints are the most common structural form to connect the chuanfang (similar to the beam in conventional structures) and the column. To study the cyclic performance of the continuous-tenon joints in column-and-tie timber construction, the reversed lateral cyclic loading tests were carried out on three 3/4 scale specimens with different section heights of the chuanfang. The mechanical behavior was assessed by studying the ultimate bending capacity, deformation ductility and energy dissipation capacity. Test results showed that the slippage of chuanfang occurred when the specimens entered the plastic stage, and the slippage degree increased with the increase of the section height of chuanfang. An obvious plastic deformation of the chuanfang occurred due to the mutual squeezing between the column and chuanfang. A significant pinching was observed on the bending moment-rotation curves, and it was more pronounced as the section height of chuanfang increased. The further numerical investigations showed that the flexural capacity and initial stiffness of the continuous-tenon joints increased with the increase of friction coefficient between the chuanfang and the column, and a more obvious increasing of bending moment occurred after the material yielding. The compressive strength perpendicular to grain of the material played a more significant role in the ultimate bending capacity of continuous-tenon joints than the compressive strength parallel to grain.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.75-82
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• 2015

In this study, experimental research was carried out to evaluate steel reinforced ECC (Engineered Cementitious Composites) column, which exhibits excellent crack control property and highly ductile behavior. Ordinary portland cement and high volume fly ash were used as binding materials in the mixture proportions for the purpose of achieving a high level of multiple cracking property with the tightly controlled crack width. To compare with the cyclic behavior of steel reinforced ECC column specimen, a conventional reinforced concrete column was prepared and tested under reversed cyclic loading condition. Based on the cyclic load test, ECC column exhibited higher cyclic behavior, compared to the conventional RC column, in terms of load carrying capacity and energy dissipation capacity.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.129-132
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• 2008

Coupled shear wall system is the primary seismic load resisting system of buildings. The coupling beam of these buildings must exhibit excellent ductility and energy dissipation capacity. To achieve better ductility and energy dissipation, the steel coupling beam embedded in the reinforced concrete walls is proposed. Performance of the steel coupling beam is mainly effected by embedment length. ACI equation and BS equation were examined with 23 previous test results. The statistical study uses the values of mean value, standard deviation, correlation coefficient, normal distribution curve, and error analysis. Through the analytical program, the evaluation of the 2 equations was established.

• Earthquakes and Structures
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• v.8 no.3
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• pp.555-572
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• 2015

This paper presents an experimental study of three two-dimensional (2D/planar) steel reinforced concrete (SRC) T-shaped column-RC beam hybrid joints and six 3D SRC T-shaped column-steel beam hybrid joints under low cyclic reversed loads. Considering different categories of steel configuration types in column cross section and horizontal loading angles for the specimens were selected, and a reliable structural testing system for the spatial loading was employed in the tests. The load-displacement curves, carrying capacity, energy dissipation capacity, ductility and deformation characteristics of the test subassemblies were analyzed. Especially, the seismic performance discrepancies between planar hybrid joints and 3D hybrid joints were intensively compared. The failure modes for planar loading and spatial loading observed in the tests showed that the shear-diagonal compressive failure was the dominating failure mode for all the specimens. In addition, the 3D hybrid joints illustrated plumper hysteretic loops for the columns configured with solid-web steel, but a little more pinched hysteretic loops for the columns configured with T-shaped steel or channel-shaped steel, better energy dissipation capacity & ductility, and larger interlayer deformation capacity than those of the planar hybrid joints. Furthermore, it was revealed that the hysteretic loops for the specimens under $45^{\circ}$ loading angle are generally plumper than those for the specimens under $30^{\circ}$ loading angle. Finally, the effects of steel configuration type and loading angle on the seismic damage for the specimens were analyzed by means of the Park-Ang model.

• Journal of the Korea Concrete Institute
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• v.26 no.6
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• pp.695-705
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• 2014

Precast concrete (PC) beam-column connections using ductile rods are proposed for earthquake zone. An existing beam-column connection, two PC specimens designed by considering failure modes and a conventional RC specimen were tested under cyclic loading to evaluate the seismic performance. The specimens were designed to satisfy the requirements of current design code. The variables are the yield strength of longitudinal reinforcing bars of PC beams. The test results showed that the proposed system applying smaller yield strength of the longitudinal reinforcing bars at the PC beams than the ductile rods was satisfied with seismic criteria. The deformation capacity and energy dissipation capacity of the proposed PC beam-column connections were greater than those of the existing DDC system.

• Structural Engineering and Mechanics
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• v.55 no.6
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• pp.1139-1155
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• 2015

In this study, a new retrofitting method for improving the seismic performance of reinforced concrete column was presented, in which prestressed steel strips were utilized as retrofitting stuff to confine the reinforced concrete column transversely. In order to figure out the seismic performance of concrete column specimen retrofitted by such prestressed steel strips methods, a series of quasi-static tests of five retrofitted specimens and two unconfined column specimen which acted as control specimens were conducted. Based on the test results, the seismic performance including the failure modes, hysteresis performance, ductility performance, energy dissipation and stiffness degradation of all these specimens were fully investigated and analyzed. And furthermore the influences of some key parameters such as the axial force ratios, shear span ratios and steel strips spacing on seismic performance of those retrofitted reinforced concrete column specimens were also studied. It was shown that the prestressed steel strips provided large transverse confining effect on reinforced concrete column specimens, which resulted in improving the shearing bearing capacity, ductility performance, deformation capacity and energy dissipation performance of retrofitted specimens effectively. In comparison to the specimen which was retrofitted by the carbon fiber reinforced plastics (CFRP) strips method, the seismic performance of the specimens retrofitted by the prestressed steel strips was a bit better, and with much less cost both in material and labor. From this research results, it can be concluded that this new retrofitting method is really useful and has significant advantages both in saving money and time over some other retrofitting methods.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.1
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• pp.8-14
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• 2020

The implosion phenomena of pressure vessels operating in deep water under extremely high external pressure have been well known. The drastic energy release to ambient field in the form of pressure pulse is accompanied with catastrophic collapse of shell structure. Such a proximity shock wave could be a serious threat to the structural integrity of adjacent submerged body and several suspected accidents have been reported. In this study, basic research for the occurrence and development of shock wave due to implosion was carried out. The mechanism of pressure pulse generation and energy dissipation were investigated, and a simplified kinematic model to approximate the collapse modes of circular tubes which can be generated by external pressure and implosion was examined. Using the simplified kinematic model, the process of energy dissipation was formulated, and the magnitude of released pressure shock wave was estimated quantitatively. To investigate the validity of developed kinematic model and shock wave estimation process, the results from a nonlinear FE analysis code and collapse test carried out using pressure chamber were compared with the results from the developed kinematic model.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.141-148
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• 2021

In this study, the technology to prevent lateral deformation of steel dampers was reviewed and applied to the clamp type dampers. As for the experimental method, the rocking behavior was applied as in the previous study. The evaluation variables are the existing research results (SV-260) without lateral deformation prevention details and the test results (V-1, V-1R) with lateral deformation prevention details. Where, V-1 is the lateral deformation prevention detail at the lower part of the damper, and V-1R is the lateral deformation prevention detail at the lower part and upper part of the damper. As a result of evaluating the moment, drift ratio, and energy dissipation capacity relative to SV-260 at the time of maximum load, the maximum moments of V-1 and V-1R were increased by 1.22 times and 1.36 times compared to SV-260, and the maximum drift ratio increased by 2.41 times and 2.92 times. In addition, the energy dissipation capacity also increased by 1.39 times and 1.52 times, respectively. Therefore, the application of lateral deformation prevention details to the steel damper was evaluated as appropriate.

• Earthquakes and Structures
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• v.17 no.2
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• pp.163-173
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• 2019

For Special Concentrically Braced Frame (SCBF), it is common that the damage concentrates at a certain story instead of spreading over all stories. Once the damage occurs, the soft-story mechanism is likely to take place and possibly to result in the failure of the whole system with more damage accumulation. In this study, we use a strongback column which is an additional structural component extending along the height of the building, to redistribute the excessive deformation of SCBF and activate more structural members to dissipate energy and thus avoid damage concentration and improve the seismic performance of SCBF. We tested one-third-scaled, three-story, double-story X SCBF specimens with static cyclic loading procedure. Three specimens, namely S73, S42 and S0, which represent different combinations of stiffness and strength factors ${\alpha}$ and ${\beta}$ for the strongback columns, were designed based on results of numerical simulations. Specimens S73 and S42 were the specimens with the strongback columns, and S0 is the specimen without the strongback column. Test results show that the deformation distribution of Specimen S73 is more uniform and more brace members in three stories perform nonlinearly. Comparing Drift Concentration Factor (DCF), we can observe 29% and 11% improvement in Specimen S73 and S42, respectively. This improvement increases the nonlinear demand of the third-story braces and reduces that of the first-story braces where the demand used to be excessive, and, therefore, postpones the rupture of the first-story braces and enhances the ductility and energy dissipation capacity of the whole SCBF system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.5
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• pp.339-347
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• 2019

The power circuit design of an on-board S-band transmitter for KSLV-II with derating(operation of a component at less than its maximum rated specification to enhance reliability) is investigated. The power circuit of the transmitter consists of linear voltage regulators, DC/DC converters for regulating the DC supply, and diodes for reverse voltage protection. After analyzing the load current of the components, derating requirements are explored. Furthermore, power dissipation and junction temperature rise are considered with respect to the load current. The analysis is compared to the results from an engineering model of the transmitter. The temperature of the components is derated by >$40^{\circ}C$ in an environment where the ambient temperature is $+60^{\circ}C$, which is the acceptance test specification of high temperature.