• Steel and Composite Structures
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• 제50권3호
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• pp.319-336
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• 2024

Ultra-high-performance concrete (UHPC) has attracted increasing attention in prefabricated steel-concrete composite beams as achieving the onsite construction time savings and structural performance improvement. The inferior replacement and removal efficiency of conventional prefabricated steel-UHPC composite beams (PSUCBs) has thwarted its sustainable applications because of the widely used welded-connectors. Single embedded nut bolted shear connectors (SENBs) have recently introduced as an attempt to enhance demountability of PSUCBs. An in-depth exploration of the mechanical behavior of SENBs in UHPC is necessary to evidence feasibilities of corresponding PSUCBs. However, existing research has been limited to SENB arrangement impacts and lacked considerations on SENB geometric configuration counterparts. To this end, this paper performed twenty push-out tests and theoretical analyses on the shear performance and design recommendation of SENBs. Key test parameters comprised the diameter and grade of SENBs, degree and sequence of pretension, concrete casting method and connector type. Test results indicated that both diameters and grades of bolts exerted remarkable impacts on the SENB shear performance with respect to the shear and frictional responses. Also, there was limited influence of the bolt preload degrees on the shear capacity and ductility of SENBs, but non-negligible contributions to their corresponding frictional resistance and initial shear stiffness. Moreover, inverse pretension sequences or monolithic cast slabs presented slight improvements in the ultimate shear and slip capacity. Finally, design-oriented models with higher accuracy were introduced for predictions of the ultimate shear resistance and load-slip relationship of SENBs in PSUCBs.

• Journal of the Korean Geotechnical Society
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• 제26권2호
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• pp.5-14
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• 2010

In this study, cyclic triaxial tests were performed under anisotropically consolidated condition by using irregular earthquake loading to consider in-situ condition and seismic wave. Jumunjin sand with a relative density 50 percent was used in the tests. The consolidation pressure ratio (K) was changed from 0.5 to 1.0. The Ofunato and Hachinohe wave were applied as irregular earthquake loadings and liquefaction resistance strengths of each specimen were estimated from the excess pore water pressure (EPWP) ratio. As a results of the cyclic triaxial tests, EPWP ratio increased with increased K value. It shows that isotropically consolidated sand is more susceptible to liquefaction than anisotropically consolidated sand under equal confining pressure and dynamic loadings. From the test results, the relationship between K and EPWP ratio normalized by effective confining pressure and deviator stress was proposed. And a new factor which corrects the liquefaction resistance strength for the in-situ stress condition is proposed.

• Magazine of the Korea Concrete Institute
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• 제10권6호
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• pp.241-252
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• 1998

The objective of the research stated herein is to observe the actual responses of a low-rise nonseismic moment-resisting reinforced concrete frame subjected to varied levels of earthquake ground motions. First, the reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used and the model was manufactured according to the similitude law. This model was, then, subjected to the shaking table motions simulating Taft N21E component earthquake ground motions, whose peak ground accelations (PGAs) were modified to 0.12g, 0.2g, 0.3g, and 0.4g. The lateral accelerations and displacements at each story and local deformations at the critical reginos of the structure were measured. The base shear was measured by using self-made load cells. Before and after each earthquake simulation test, free vibration tests were performed to find the change in the natural period and damping ratio of the model. The test data on the global and local behaviors are interpreted. The model showed the linear elastic behavior under the Taft N21E motion with the PGA if 0.12g, which represents the design earthquake in Korea. The maximum base shear was 1.8tf, approximately 4.7 times the design base shear. The model revealed fairly good resistance to the higher level of earthquake simulation tests. The main components of its resistance to the high level of earthquakes appeared to be 1) the high overstrength, 2) the elongation of the fundamental period, and 3) the minor energy dissipation by inelastic deformations. The drifts of the model under these tests were approximately within the allowable limit.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.241-248
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• 2000

In order to evaluate the limit earthquake resistance of multi-story steel frames influenced by the strength and stiffness ratios of members a series inelastic response analysis were carried out. From the analysis results the damage distribution rules of multi-story steel frames were proposed. Conclusions are summarized as follows. 1)As the stiffness ratio of beam and column becomes small damage concentrate on the lower end of columns of the first story. 2) Considering the strength and stiffness ratios of beam and column with weak beam type mechanism the equations predicting the damage distribution of multi-story steel frames were proposed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 한국지진공학회 2002년도 춘계 학술발표회 논문집
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• pp.135-142
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• 2002

This paper introduces the technologies related to seismic resistance assessment of nuclear power plant structures by seismic fragility analysis(SFA). The inelastic energy absorption factor is considered in SFA to represent the effects due to the nonlinear behavior of structures and has a significant effect on the seismic fragility that is a probability of failure of structures by earthquake. Several practical methods to evaluate the inelastic energy absorption capacity of structures are investigated. The capacities determined by those methods are compared with each other. And an improved method that uses the inelastic demand capacity diagram is presented. Conclusively, some comments on each method for practical application are made.

• Journal of the Korean Society of Safety
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• 제30권2호
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• pp.27-34
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• 2015

Nowadays, remodeling cases for some apartment like Hyundai through the support of government are reported. Conventionally, balcony and aisle are extended for additional private area or balcony which is supported by new frame is extended. In extension work at site, dowel bar is conventionally inserted in old concrete slab for connection with old and new slab, however, an examination for structural safety is rarely performed prior to construction, if ever, vertical load is only considered for structural analysis. When conventionally connected structures are exposed to earthquake, the old and new structures have individual earthquake behavior with different mode, which may lead the elimination of resistance to earthquake in new structures. As of this reason, new detailing connection system which can have light weight and sufficient ductility performance is developed for application to domestic extension works. Additionally, user manual and specification are also developed for fertilization of application for the developed technology.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.356-363
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• 2001

The friction pendulum type seismic isolation system (FPS) using the PTFE based materials has been developed to provide a simple and effective way to achieve earthquake resistance for buildings. PTFE matrials are soft and apt to be deformed easily after a few working cycles. Instead of the usual PTFE materials, the Polyimide material was used in this research. Polyimide is harder than PTFE, but has smaller friction coefficient and longer duration fur usage. In this paper, various kinds of PTFE materials were tested to define the frictional characteristics compared with the Polyimide material. FPS was manufactured with fine surface roughness and used with Polyimide material to show the seismic isolation efficiency, and life duration when applied to a rigid mass model and a 5 stole frame model.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 한국지진공학회 1997년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
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• pp.159-166
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• 1997

The purpose of this thesis is to derive a theoretical model of the hysteretic resistance of the visco-elastic damper based on test results of harmonic excitation and to investigate of the basis of theory and experiment the effect of vibration control and response characteristics of portal frames degree vibration systems provided with the damper. The behaviour of a visco-elastic degree under dynamic loading is idealized by a model of the theory of visco-elasticity, i.e. a four-parameter model formed as a parallel combination of Maxwell fluid and Kelvin-Voigh models and its constitutive equation is derived. The model parameters are determined for a tested damper from the datas of harmonic excitation tests. The theoretical model of the damper is incorporated in equation fo motion of single degree of freedom. A computer program for solving the equation is written using Runge-kuttas's numerical integration scheme. Using this analysis program test cases of the earthquake excitation are simulated and the results of the simulation are the results of the simulation are the results of the simulation are compared with the test results.

• International journal of steel structures
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• 제18권4호
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• pp.1420-1430
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• 2018

Earthquakes of 5.8 and 5.4 Richter scale recently occurred one after another in Korea, changing the Korean peninsula from an earthquake safe zone but 'earthquake danger zone'. Therefore, seismic reinforcements must expand to include structures with low seismic resistance in order to prepare for earthquakes on a larger scale in the future. This study investigated the performances of various seismic reinforcement systems such as X-braced steel rod reinforcement, steel shear wall with circular opening reinforcement, and slit damper reinforcement using shaking table test and computational analyses of seismic data in order to establish a proper seismic reinforcement plan. These three seismic reinforcement systems could increase the stiffness and strength of existing structures and reduce maximum drift ratio in the event of an earthquake.

• Journal of Korean Association for Spatial Structures
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• 제13권3호
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• pp.73-81
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• 2013

In paper after the strong earthquake of recently the Korea neighborhood, the Korean government survey show that the 86% of school buildings in Korea are in potential damage risk and only 14% of them are designed as earthquake-resistance buildings. Earthquake Reinforcing projects of school have been a leading by the ministry of education, however their reinforcing methods done by not proved a engineering by experiment which results in uneconomical and uneffective rehabilitation for the future earthquake. An experimental and analytical study have been conducted for the shear reinforcing method of column by axis and horizontal axis load using attaching composite beam. Based on the previous research, in this study, Design examples are given to show the performance evaluation for the column reinforcing of old school buildings using nonlinear analysis is going to be conducted and strengthening method is going to be on the market after their performance is proved by the test.