• Earthquakes and Structures
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• v.16 no.3
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• pp.265-277
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• 2019

Framed masonry wall structures represent a typical high-rise structural system that are also seismically vulnerable. During ground motions, they are excited in both in-plane and out-of-plane terms. The interaction between the frame and the infill during ground motion is a highly investigated phenomenon in the field of seismic engineering. This paper presents a numerical investigation of two distinct static out-of-plane loading methods for framed masonry wall models. The first and most common method is uniformly loaded infill. The load is generally induced by the airbag. The other method is similar to in-plane push-over method, involves loading of the frame directly, not the infill. Consequently, different openings with the same areas and various placements were examined. The numerical model is based on calibrated in-plane bare frame models and on calibrated wall models subjected to OoP bending. Both methods produced widely divergent results in terms of load bearing capabilities, failure modes, damage states etc. Summarily, uniform load on the panel causes more damage to the infill than to the frame; openings do influence structures behavior; three hinged arching action is developed; and greater resistance and deformations are obtained in comparison to the frame loading method. Loading the frame causes the infill to bear significantly greater damage than the infill; infill and openings only influence the behavior after reaching the peak load; infill does not influence initial stiffness; models with opening fail at same inter-storey drift ratio as the bare frame model.

• 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.

• Earthquakes and Structures
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• v.23 no.1
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• pp.23-34
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• 2022

This paper presents experimental studies on reinforced concrete moment resisting frames that have engineered cementitious composite (ECC) in plastic hinge length (PHL) of beam/column members and beam-column joints. A two-story frame structure reduced by a 1:3 scale was further tested through a shake-table (seismic simulator) using multiple levels of simulated earthquake motions. One model conformed to all the ACI-318 requirements for IMRF, whereas the second model used lower-strength concrete in the beam/column members outside PHL. The acceleration time history of the 1994 Northridge earthquake was selected and scaled to multiple levels for shake-table testing. This study reports the observed damage mechanism, lateral strength-displacement capacity curve, and the computed response parameters for each model. The tests verified that nonlinearity remained confined to beam/column ends, i.e., member joint interface. Calculated response modification factors were 11.6 and 9.6 for the code-conforming and concrete strength deficient models. Results show that the RC-ECC frame's performance in design-based and maximum considered earthquakes; without exceeding maximum permissible drift under design-base earthquake motions and not triggering any unstable mode of damage/failure under maximum considered earthquakes. This research also indicates that the introduction of ECC in PHL of the beam/column members' detailing may be relaxed for the IMRF structures.

• Structural Monitoring and Maintenance
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• v.8 no.4
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• pp.329-344
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• 2021

The use of structural control devices to minimize structural response to seismic/dynamic excitations has attracted increased attention in recent years. The use of magnetorheological (MR) dampers as a control device have captured the attention of researchers in this field due to its flexibility, adaptability, easy control, and low power requirement compared to other control devices. However, little attention has been paid to the effect of configuration and number of dampers installed in a structure on responses reduction. This study assesses the control of a five-story structure using one and two MR dampers at different stories to determine the optimal damper positions and configurations based on performance indices. This paper also addresses the fail-safe current value to be applied to the MR damper at each floor in the event of feedback or control failure. The model is mathematically simulated in SIMULINK/MATLAB environment. Linear control strategies for current at 0 A, 0.5 A, 1 A, 1.5 A, 2 A, and 2.5 A are implemented for MR dampers, and the response of the structure to these control strategies for different configurations of dampers is compared with the uncontrolled structure. Based on the performance indices, it was concluded that the dampers should be positioned starting from the ground floor, then the 2^nd floor followed by 1^st and rest of the floors sequentially. The failsafe value of current for MR dampers located in lower floors (G+1) should be kept at a higher value compared to dampers at top floors for effective passive control of multi-story structures.

• Journal of the Korean Wood Science and Technology
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• v.52 no.4
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• pp.375-382
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• 2024

The study focuses on evaluating the bending creep performance of laminated veneer lumber (LVL) formwork in timber concrete composite (TCC) structures. Timber-framed construction is highlighted for its environmental benefits and seismic resistance, but limitations such as poor tensile strength and brittle failure in bending hinder its use in high-rise buildings. Wood-concrete hybrid structures, particularly those using reinforced concrete slabs with TCC floors, emerge as a potential solution. The research aims to understand the time-dependent behavior of TCC components, considering factors like wood and concrete shrinkage and connection creep. The experiment was conducted in western Japan on the TCC floor designed for use in the Kama-city Inatsuki-higashi compulsory education school. The LVL formwork, measuring 9,000 mm by 900 mm, and concrete is loaded onto it for testing. The creep test periods are examined using concrete loading. It employs a comprehensive creep analysis, adhering to Japanese standards, involving deflection measurements and regression analysis to estimate the creep coefficient. Results indicate substantial deformation after shoring removal, suggesting potential reinforcement needs. The study recommends extending test periods for improved accuracy and recognizing regional climate impacts. Overall, the research provides valuable insights into the potential of LVL formwork in TCC structures, emphasizing safety considerations and paving the way for further experimentation under varied conditions to validate structural integrity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.18-28
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• 2015

The purpose of this study is to develop a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. The results were analyzed to find that the specimen with anchored connection experienced shear failure, while the other specimen with steel plate connection principally manifested flexural failure. The ultimate strength of the specimens was determined to be the weaker of the shear strength of top connection and flexural strength at the critical section of precast panel. In this setup of U-type panel specimens, if a push loading is applied to the reinforced concrete column on one side and push the precast concrete panel, a pull loading from upper shear connection is to be applied to the other side of the top shear connection of precast panel. Since the composite flexural behavior of the two members govern the total behavior during the push loading process, the ultimate horizontal resistance of this specimen was not directly influenced by shear strength at the top connection of precast panel. However, the RC column and PC wall panel member mainly exhibited non-composite behavior during the pull loading process. The ultimate horizontal resistance was directly influenced by the shear strength of top connection because the pull loading from the beam applied directly to the upper shear connection. The analytical result for the internal shear resistance at the connection pursuant to the anchor shear design of ACI 318M-11 Appendix-D, agreed with the experimental result based on the elastic analysis of Midas-Zen by using the largest loading from experiment.

• Geophysics and Geophysical Exploration
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• v.20 no.3
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• pp.146-162
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• 2017

Multibeam and seismic data in the northwestern part of the Ulleung Basin were analyzed to study stratigraphy and evolutionary history of submarine canyon. A detailed analysis reveals that the sedimentary sequences in this area consist of four stratigraphic units separated by erosional unconformities. On the continental slope, these units are dominated by well-stratified facies with some slope failures, whereas these units show well-stratified and chaotic facies toward the basin floor. Generally, the sediment thickness is relatively thin on the slope, whereas thick sediment accumulation occurs on the base of slope and basin floor. Based on seismic characteristics and distribution, the deposition of each units are well correlated with the evolutionary history of the submarine canyon. Unit 1 directly overlying the acoustic basement has thin sediment layer on the slope, whereas its thickness gradually increase toward the basin floor. Compared to other units, Unit 2 is relatively thick accumulations on the slope and contains some slope failures related to faults systems. The mass transport sediments due to slope failures, mainly deposited on the base of slope as a submarine fan. The width and depth of submarine canyon increase due to dominant of the erosional process rather than the sediment deposition. Unit 3 is thin accumulation on the slope around the submarine canyon. Toward the basin floor, its thickness gradually increases. Unit 4 is characterized by thin layers including slides and slumps on the slope, whereas it formed thick accumulations at the base of slope as a submarine fan. The increase in the width and depth of submarine canyon results from the dominant of the erosional process and slope failures around the submarine canyon. Consequently, the formation of sedimentary units combined with the development of submarine canyon in this area is largely controlled by the amounts of sediment supply originated from slope failures, regional tectonic effects and sea-level fluctuations.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.793-805
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• 2004

The main objective of this paper is to evaluate the ductility and strength factors that are key components of the response modification factor for special steel moment-resistant frames. The ductility factors for special steel moment-resistant frames were calculated by multiplying the ductility factor for SDOF systems and the MDOF modification factors. Ductility factors were computed for elastic and perfectly plastic SDOF systems undergoing different levels of inelastic deformation and periods when subjected to a large number of recorded earthquake ground motions. Based on the results of the regression analysis, simplified expressions were proposed to compute the ductility factors. Based on previous studies, the MDOF modification factors were also proposed to account for the MDOF systems. Strength factors for special steel moment resisting frames were estimated from the results of the nonlinear static analysis. A total of 36 sample steel frames were designed to investigate the ductility and strength factors considering design parameters such as number of stories (4, 8, and 16 stories), seismic zone factors (Z = 0.075, 0.2, and 0.4), framing system (Perimeter Frames, PF and Distributed Frames, DF), and failure mechanism (Strong-Column Weak Beam, SCWB, and Weak-Column Strong-Beam, WCSB). The effects of these design parameters on the ductility and strength factors for special steel moment-resisting frames were investigated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.120-128
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• 2019

It is very important to verify the seismic performance and stability of the power plant fixture in the domestic power plant, because earthquakes have increased in frequency around the world which resulted in the frequent occurrence of power plant damage caused by the failure of electric power facilities. In this study, through the on-site inspection of power plant fixation unit installed in domestic power plants, we carried out structural performance evaluation of the fixation unit anchor bolts installed on the concrete slabs. The field survey showed M12 J hook anchor bolts were used. Anchor bolt pullout and shear performance evaluation were performed based on ASTM E 488-96 standard. Moreover, artificial crack with the width of 0.5 mm was applied during the experiment based on ATM355.4 and ETAG 001. The comparison of M12 J hook anchor bolt pullout and shear test result to design value required in domestic and international design standard, show a satisfactory result. M12 J hook anchor pullout and shear performance was found to be about 35% and 7%, respectively, higher than the required design value.

• The Korean Journal of Petroleum Geology
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• v.9 no.1_2 s.10
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• pp.16-23
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• 2001

The study area in the East Sea is located on the northeastern margins of the Ulleung Basin near the Kita-Yamato Bank. The research area provides the important clue to the development of Miocene basins which are characterized by the normal faults and volcanic activities related to rifting in the continental crust. Kita-Yamato Bank is a small sediment-filled graben which was formed by failed rifting in the Early Miocene. The basins rapidly vary the bathymetry, depth of acoustic basement and thickness of sedimentary layer. The tension in the study area caused the extensional lithospheric deformation before/during the Early Miocene. In consequence, tectonic forces resulted in the depression or subsidence of basement from continental rifting in the Kita-Yamato Bank followed by the opening of the Ulleung Basin, and caused the onset of graben or half-graben structure bounded by large blocked syn-rift faults. Afterward no significant tectonic deformation exists, with the consequence that post-rift normal faults with small heave were formed and reactivated by the resultant forces such as tectonic subsidence, sediment loading and volcanic activity. The Cenozoic sediment layer has a maximum thickness of 1.0 s along the center of the graben or half-graben, which overlies the consolidated acoustic basement. Seismic units V and IV supposed to be syn-rift sedimentary rocks are deformed by both the volcanic activities and numerous basement-involved normal faults induced from extension. In the uppermost layer, slump scars resulted from the slope failure are recognized.