• Elastomers and Composites
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• v.58 no.3
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• pp.128-135
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• 2023

To improve the adhesive strength of natural rubber (NR) for a seismic isolation damper, citraconic acid-g-NR (CCA-g-NR) was synthesized via the melt grafting of citraconic acid (CCA) onto NR using an azobisisnomerobutyronitrile (AIBN) initiator. Subsequently, the influence of CCA and AIBN concentrations on the graft ratio G/R (%) and graft efficiency G/E (%) of the CCA-g-NR was investigated. The optimum CCA and AIBN concentrations required to achieve the desired G/R (3.49%) and G/E (49.8%) were found to be 7 phr and 0.13 phr, respectively. Additionally, we studied the influence of CCA-g-NR concentration on the mechanical properties (tensile strength, elongation at break, and modulus at 300%), adhesive strength, and cure characteristics of the rubber compound in the seismic isolation damper. As the concentration of CCA-g-NR increased, the elongation at break and adhesive strength of the compound increased, whereas its tensile strength and modulus at 300% decreased. Moreover, as the concentration increased, the maximum torque decreased and the scorch time was delayed to obtain an optimal vulcanization time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.492-498
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• 2017

This study examined the bending performance of high strength and seismic purpose reinforcing bars experimentally with various parameters. For the experimental approach on the bending performance, the specimens were prepared with parameters, such as steel grades, diameters of reinforcing bars, and bending angles of reinforcing bars. Tensile strength tests on the reinforcing bars, the bending tests and re-bending tests, and the second tensile strength tests on the re-bended reinforcing bars were conducted. According to the test results on high strength and seismic purpose reinforcing bars, defects did not appear when the yield strength of the reinforcing bar was 500 MPa or less and the diameter was D13 or less, even when the first bending process was performed with a $135^{\circ}$ bending angle and a $2d_b$ inner radius. The bending performance decreased asthe strength and diameter of the reinforcing bars was increased. In addition, there was no significant difference between the general reinforcing bars and seismic purpose-reinforcing bars.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.741-748
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• 2006

Seismic performance evaluation was conducted for four wind-designed concentrically braced steel highrise buildings in order to check the feasibility of designing steel highrise buildings per elastic seismic design criterion (or strength and stiffness solution) in the regions of strong wind and moderate seismicity. The pushover analysis results revealed that the wind-designed highrise buildings possess significantly increased elastic seismic capacity due to the overstrength resulting from the wind serviceability criterion. The strength demand-to-capacity study showed that, due to the wind-induced overstrength, highrise buildings with a slenderness ratio of larger than four or five can withstand elastically even the maximum considered earthquake at the performance level of immediate occupancy. Based on the analytical results of this study, practical elastic seismic design procedure for steel highrise buildings in the regions of moderate seismicity is proposed.

• Steel and Composite Structures
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• v.34 no.5
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• pp.743-767
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• 2020

Due to the impressive flexural performance, enhanced compressive strength and more constrained crack propagation, Fibre-reinforced concrete (FRC) have been widely employed in the construction application. Majority of experimental studies have focused on the seismic behavior of FRC columns. Based on the valid experimental data obtained from the previous studies, the current study has evaluated the seismic response and compressive strength of FRC rectangular columns while following hybrid metaheuristic techniques. Due to the non-linearity of seismic data, Adaptive neuro-fuzzy inference system (ANFIS) has been incorporated with metaheuristic algorithms. 317 different datasets from FRC column tests has been applied as one database in order to determine the most influential factor on the ultimate strengths of FRC rectangular columns subjected to the simulated seismic loading. ANFIS has been used with the incorporation of Particle Swarm Optimization (PSO) and Genetic algorithm (GA). For the analysis of the attained results, Extreme learning machine (ELM) as an authentic prediction method has been concurrently used. The variable selection procedure is to choose the most dominant parameters affecting the ultimate strengths of FRC rectangular columns subjected to simulated seismic loading. Accordingly, the results have shown that ANFIS-PSO has successfully predicted the seismic lateral load with R² = 0.857 and 0.902 for the test and train phase, respectively, nominated as the lateral load prediction estimator. On the other hand, in case of compressive strength prediction, ELM is to predict the compressive strength with R² = 0.657 and 0.862 for test and train phase, respectively. The results have shown that the seismic lateral force trend is more predictable than the compressive strength of FRC rectangular columns, in which the best results belong to the lateral force prediction. Compressive strength prediction has illustrated a significant deviation above 40 Mpa which could be related to the considerable non-linearity and possible empirical shortcomings. Finally, employing ANFIS-GA and ANFIS-PSO techniques to evaluate the seismic response of FRC are a promising reliable approach to be replaced for high cost and time-consuming experimental tests.

• Journal of Korean Association for Spatial Structures
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• v.18 no.1
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• pp.109-116
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• 2018

As the number of high-rise buildings increases, a mid-story isolation system has been proposed for high-rise buildings. Due to structural problems, an appropriate isolation layer displacement is required for an isolation system. In this study, the mid-story isolation system was designed and the seismic response of the structure was investigated by varying the yield strength and the horizontal stiffness of the seismic isolation system. To do this, a model with an isolation layer at the bottom of $15^{th}$ floor of a 20-story building was used as an example structure. Kobe(1995) and Nihonkai-Chubu(1983) earthquake are used as earthquake excitations. The yield strength and the horizontal stiffness of the seismic isolation system were varied to determine the seismic displacement and the story drift ratio of the structure. Based on the analytical results, as the yield strength and horizontal stiffness increase, the displacement of the isolation layer decreases. The story drift ratio decreases and then increases. The displacement of the isolation layer and the story drift ratio are inversely proportional. Increasing the displacement of the isolation layer to reduce the story drift ratio can cause the structure to become unstable. Therefore, an engineer should choose the appropriate yield strength and horizontal stiffness in consideration of the safety and efficiency of the structure when a mid-story isolation system for a high-rise building is designed.

• Steel and Composite Structures
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• v.24 no.4
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• pp.441-453
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• 2017

In Y-shaped eccentrically braced frame fabricated with high strength steel (Y-HSS-EBF), link uses conventional steel while other structural members use high strength steel. Cyclic test for a 1:2 length scaled one-bay and one-story Y-HSS-EBF specimen and shake table test for a 1:2 length scaled three-story Y-HSS-EBF specimen were carried out to research the seismic performance of Y-HSS-EBF. These include the failure mode, load-bearing capacity, ductility, energy dissipation capacity, dynamic properties, acceleration responses, displacement responses, and dynamic strain responses. The test results indicated that the one-bay and one-story Y-HSS-EBF specimen had good load-bearing capacity and ductility capacity. The three-story specimen cumulative structural damage and deformation increased, while its stiffness decreased. There was no plastic deformation observed in the braces, beams, or columns in the three-story Y-HSS-EBF specimen, and there was no danger of collapse during the seismic loads. The designed shear link dissipated the energy via shear deformation during the seismic loads. When the specimen was fractured, the maximum link plastic rotation angle was higher than 0.08 rad for the shear link in AISC341-10. The Y-HSS-EBF is a safe dual system with reliable hysteretic behaviors and seismic performance.

• Earthquakes and Structures
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• v.9 no.4
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• pp.699-718
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• 2015

The effect of reinforcing concrete members with high strength steel bars with yield strength up to 600 MPa on the overall seismic behavior of concrete moment frames was studied experimentally and numerically. Three geometrically identical plane frame models with two bays and two stories, where one frame model was reinforced with hot rolled bars (HRB) with a nominal yield strength of 335 MPa and the other two by high strength steel bars with a nominal yield strength of 600 MPa, were tested under simulated earthquake action considering different axial load ratios to investigate the hysteretic behavior, ductility, strength and stiffness degradation, energy dissipation and plastic deformation characteristics. Test results indicate that utilizing high strength reinforcement can improve the structural resilience, reduce residual deformation and achieve favorable distribution pattern of plastic hinges on beams and columns. The frame models reinforced with normal and high strength steel bars have comparable overall deformation capacity. Compared with the frame model subjected to a low axial load ratio, the ones under a higher axial load ratio exhibit more plump hysteretic loops. The proved reliable finite element analysis software DIANA was used for the numerical simulation of the tests. The analytical results agree well with the experimental results.

• Land and Housing Review
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• v.8 no.3
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• pp.211-221
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• 2017

This study proposed hybrid coupled shear wall in the steel plate insertion method, which is capable of reinforcing the shear strength of the entire wall without increasing wall thickness in the wall-slab apartment buildings. The proposed hybrid coupled shear wall was tested for its effectiveness, shear strength and seismic behavior in experiment. As a test result, the shear strength improvement by the proposed hybrid coupled shear was found effective. Integral-type of steel plate insertion was found more effective than separate-type steel plate insertion. In this case, if the stud enforcement method proposed in this study was used, the shear strength of hybrid coupled shear wall was recommended to calculate using the KBC2016 0709.4.1(3) method. The steel plate inserted in the proposed method was found to have no significant impact on the final fracture behavior and bending strength of hybrid coupled shear wall. The shear strength at the final destruction of the wall was merely about 1/50 of the entire design shear strength. Thus, it is deemed that the wall was over excessively designed regarding the shear force in the existing design method. This finding indicates further study on wall designing to ensure effective and economic designing based on appropriate strength estimation under the destruction mechanism.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.318-326
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• 2008

Recently, a new seismic probe, called "MudFork", has been developed and can be utilized for accurate and easy measurements of shear wave velocities of soft soils. To expand its use to estimate undrained shear strength and density, correlations between those and shear wave velocity were being attempted. Cone penetration tests and a seismic test, using MudFork, were performed at a soft ground site near Incheon, Korea. Also, undisturbed samples were obtained and shear wave velocities of the samples were measured as well as undrained shear strength, using triaxial compression test and bender elements. A simple linear relationship between shear strength and shear wave velocity was obtained, and a tentative relationship between density and shear wave velocity was also defined.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.57-66
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• 2000

The ductility is an important consideration in the design of reinforced concrete structures. In the seismic design of reinforced concrete columns, it is necessary to allow for relatively large ductilities that the seismic energy be absorbed without shear failure of significant strength degradation after the reinforcement yielding in columns. Therefore, prediction of the ductility should be as accurate as possible. This research investigate the ductile behavior of rectangular reinforced high-strength concrete columns like as bridge piers with confinement steel. The effects on the ductility of axial load, lateral reinforcement ratio, longitudinal reinforcement ratio, shear span ratio, and compressive strength of concrete were investigated analytically using layered section analysis. as the results, it was proposed the proper relationship between ductility and variables and formulated into equations.