• Title/Summary/Keyword: seismic performance

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Hysteretic Behavior Evaluation of a RC Coupling Beam using a Steel Fiber and Diagonal Reinforcement (강섬유와 묶음철근 보강을 통한 고성능 연결보의 이력거동 평가)

  • Oh, Hae Cheol;Lee, Kihak;Han, Sang Whan;Shin, Myoungsu;Jo, Yeong Wook
    • Journal of the Korea Concrete Institute
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    • v.27 no.3
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    • pp.291-298
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    • 2015
  • In this paper, a bundled diagonal reinforcement using high performance steel fiber was proposed to enhance the construct ability and seismic performance. Experiments of coupling beam was composed of four specimens and the hysteretic behavior evaluated for reverse cyclic loading to specimens using high performance steel fiber. The main variables of the experiment is a amount of stirrup and bundled reinforcement, depending on whether the mix of steel fiber. Specimen which criteria was applied 100% of stirrup and bundled diagonal reinforcement of ACI318 criteria. With this, by appling same diagonal reinforcement, two specimens were created by adjusting stirrup of 75%, 50%. So, a total of four specimens were produced. When coupling beam was placed concrete, this experiment was mixed in a content of steel fiber 1%. All the specimens were produced by aspect ratio 3.5(l/h=1050/300) to a half-scale. In this result, two specimens as reduced to stirrup of 75%, 50% was no significant difference in the strength, stiffness and energy dissipation capacity, respectively compared to the stirrup of 100%.

Initial Stiffness of Beam Column Joints of PCS Structural Systems (PCS 구조 시스템 접합부의 초기 강성에 대한 연구)

  • Park, Soon-Kyu;Kim, Moo-Kyung
    • Journal of the Korea Concrete Institute
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    • v.20 no.3
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    • pp.271-282
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    • 2008
  • Specific joint devices composed of end-plates and through bolts are under development to assemble steel beams to PC columns efficiently by dry construction method for the PCS structural system, of which major structural components are precast concrete columns and steel beams. Seismic performance of the joint devices had been evaluated by experimental tests in the previous studies and it was showed that all the performance requirements regarding to strength deterioration, stiffness degradation and energy dissipation capacity were satisfied to the criteria of ACI requirements, but the initial stiffness was not. In order to find out possible causes of the insufficient rigidity of the joint devices and provide the proper measures to improve the performance of the joint accordingly, numerical analyses were carried out by using ABAQUS. Parameters, such as thickness of neoprene pad, conditions of surface between PC column and end-plate, magnitude of pretension forces of through bolts, stiffness of end-plate were taken into consideration. As the result, it was found that the rigidity of the PCS system was negatively affected by the magnitude of initial gaps between PC columns and end-plates, and insufficient stiffness of neoprene fillers and end plates. In order to improve the initial stiffness performance of the joints, measures such as increase of the magnitude of pretension forces on through bolts and increase of the stiffness of end-plate by reducing the bolt pitch and providing adequate stiffeners are recommended.

Hysteretic Behavior and Seismic Resistant Capacity of Precast Concrete Beam-to-Column Connections (프리캐스트 콘크리트 보-기둥 접합부의 이력거동 및 내진성능)

  • Choi, Hyun-Ki;Choi, Yun-Cheul;Choi, Chang-Sik
    • Journal of the Earthquake Engineering Society of Korea
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    • v.14 no.4
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    • pp.61-71
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    • 2010
  • Five half-scale beam-to-column connections in a precast concrete frame were tested with cyclic loading that simulated earthquake-type motions. Five half -scale interior beam-column assemblies representing a portion of a frame subjected to simulated seismic loading were tested, including one monolithic specimen and four precast specimens. Variables included the detailing used at the joint to achieve a structural continuity of the beam reinforcement, and the type of special reinforcement in the connection (whether ECC or transverse reinforcement). The specimen design followed the strong-column-weak-beam concept. The beam reinforcement was purposely designed and detailed to develop plastic hinges at the beam and to impose large inelastic shear force demands into the joint. The joint performance was evaluated on the basis of connection strength, stiffness, energy dissipation, and drift capacity. From the test results, the plastic hinges at the beam controlled the specimen failure. In general, the performance of the beam-to-column connections was satisfactory. The joint strength was 1.15 times of that expected for monolithic reinforced concrete construction. The specimen behavior was ductile due to tensile deformability by ECC and the yielding steel plate, while the strength was nearly constant up to a drift of 3.5 percent.

Development of a Design Seismic Wave Time History Generation Technique Corresponding to the Recorded Seismic Wave-Based Design Response Spectrum (계측 지진파 기반 설계응답스펙트럼에 상응하는 설계 지진파 시간이력 생성 기법 개발)

  • Oh, Hyun Ju;Park, Hyung Choon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.41 no.6
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    • pp.687-695
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    • 2021
  • With the recent occurrence of large-scale earthquakes in Korea, the importance of seismic design has greatly increased. Seismic design standards stipulate that dynamic time history analysis be performed for important or special structures. In the seismic analysis and design of such structures, determining a rational design input seismic wave is a very important factor in ensuring the reliability of the analysis and design. In the seismic design standards, rational design seismic waves must reflect the characteristics of the area (fault) and satisfy the design response spectrum for each seismic performance level. This requirement can be partially satisfied by modifying the actual seismic wave measured in the area (fault) according to the design response spectrum. In this study, a method of correcting and generating seismic wave time histories according to the design response spectrum based on actual measured seismic waves using the harmonic wavelet transform was proposed. To examine the applicability of the proposed technique, the technique was applied to earthquakes of magnitude 5.8 and 5.4, respectively, that occurred in Gyeongju (2016) and Pohang (2017), and the seismic wave time histories corresponding to the design response spectrum were modified and generated.

Pullout Tests on M12&M20 Stainless Steel Post-Installed Expansion Anchor for Seismic Design in Cracked Concrete (균열 콘크리트에 설치된 M12, M20 내진용 스테인리스스틸 확장식 후설치 앵커 인장 실험)

  • Kim, Jin-Gyu;Chun, Sung-Chul;An, Yeong-Seung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.1
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    • pp.29-38
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    • 2022
  • Recently, seismic design for anchors is required, which are used for connecting structural members and non-structural and structural members. In this study, pull-out tests on the new expansion anchors which have been developed for cracked concrete. The anchors of 12 mm and 20 mm diameters were tested which are commonly used. Experiments were conducted on non-cracked concrete and cracked concrete to evaluate the seismic performance of the post-installed anchor. The experimental method complies with the specified test protocol (KCI, 2018). Three experimental variables are included in this study: presence of cracks, concrete compressive strength, and effective embedment depth. The strength of the anchors was evaluated with the characteristic capacity K5% determined from the test results incorporated with the safety of 5% fractile. The characteristic capacity K5% of the non-cracked and cracked concrete specified in KDS 14 20 54 are 9.8 and 7.0, respectively. Test results show that all groups except the three groups have higher characteristic capacity K5% than the KDS code and the nominal strengths of the tested anchors can be determined with the obtained characteristic capacity K5%.

A study for the performance evaluation of concrete block assembly wall without using mortar (무모르타르로 건식조립된 콘크리트블록 벽체의 성능평가 연구)

  • Lee, Joong-Won
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.7
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    • pp.203-210
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    • 2019
  • A recent earthquake on the Korean Peninsula caused much damage to masonry buildings, and research on performance evaluation has been underway. A masonry building is generally constructed using wet construction and is affected by temperature, which reduces the efficiency of the construction. In this study, we propose a dry construction technique for assembling concrete blocks without using mortar and evaluated its performance through experimental and analytical research. To evaluate the performance, experiments were carried out for the prismatic compressive strength, direct terminal strength, and diagonal tensile strength of the dry construction wall. The adequacy of the cross section shape was also reviewed through FEM analysis. The results show that the compressive strength and diagonal tensile strength could exert a certain intensity or higher. Furthermore, the H-type module of a key block acted as a shear key for the entire concrete block, which resulted in excellent shear strength performance. In addition, the shape and thickness of the main block have a major effect on the strength performance of each block. Therefore, an optimal shape and the proposed dry construction method could be applied to replace the wet method by studying the construction or seismic performance of the proposed method.

A Study on the Split Strength Characteristics of High Strength Concrete Sphere for Seismic Isolation (면진용 고강도 콘크리트 구의 할열강도 특성에 관한 연구)

  • Kim, Dong-Baek;Kim, In-Bae;Kim, Myung Gon;Park, Bong-Gwan
    • Journal of the Society of Disaster Information
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    • v.14 no.4
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    • pp.466-473
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    • 2018
  • Purpose: Nowadays, it is the trend that seismic isolation method and combined method are used for seismic retrofitting, if concrete sphere foundation(CSF) system is applied to mid and low rise RC structure for the seismic isolation, the characteristics of concrete sphere, etc split tensile strength will be need. Method: The various experiments are carried out to know the split strength of high strength concrete sphere(60Mpa) and the ratio of split strength of concrete sphere to standard cylinder specimen, the size effect of concrete sphere with diameter. Results: It was purposed that the split strength of concrete sphere with diameter 150mm will be lower than that of cylinder specimen but, the average value is 4.39 Mpa and the ratio is higher than that of cylinder specimens, each 3.8% and 13.7%, the reason of this result is thought that the internal stress action of spot load and line load are different. Conclusion: There is a standard method for split tensile strength of cylinder type specimen, but there are few studies for the tensile split of concrete sphere. And therefore, in this study, theoretical and experimental details of concrete sphere will be served for the concrete sphere foundation or other sequent studies.

Seismic Behavior Evaluation of Embedded Kagome Damping Device (콘크리트에 매립된 카고메 감쇠시스템의 내진거동평가)

  • Hur, Moo-Won;Lee, Sang-Hyun;Kim, Jong-Ho;Hwang, Jae-Seung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.2
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    • pp.84-91
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    • 2019
  • Recently, there has been a tendency to improve seismic performance of building structure by installing a steel hysteretic damping device which is economically efficient and easy to install and maintain. However, for a reinforced concrete building, a set of complicated connecting hardware and braces to fix the steel hysteretic damping device yields deteriorated reliability in damping performance. Therefore, this study presents a method of directly embedding a Kagome damper, which was investigated in previous researches, into a concrete structure without additional connecting hardware. Moreover, in this study, a series of experiments conducted to provide a basis of the Kagome damper by confirming the seismic behavior for various embedded lengths. As a result, in a group of the embedded length of $1.0l_d$, the dampers were pulled out, while concrete breakout occurs. In a group of $2.0l_d$, neither pull-out nor concrete breakout occurred, while the dampers show stable behavior. Moreover, the buried length of $2.0l_d$ has 1.3 times better energy dissipation capacity. The system presented in this study can reduce the cost and period for installing, omitting making additional hardware.

Seismic Performance of Concrete Masonry Unit (CMU) Infills in Reinforced Concrete Moment Framing System (철근콘크리트 모멘트 골조시스템에서 조적 끼움벽의 내진성능)

  • Hong, Jong-Kook
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.1
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    • pp.19-26
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    • 2019
  • The masonry infill walls are one of the most popular components that are used for dividing and arranging spaces in building construction. In spite of the fact that the masonry infills have many advantages, the system needs to be used with caution when the earthquake load is to be considered. The infills tend to develop diagonal compression struts during earthquake and increase the demand in surrounding RC frames. If there are openings in the infill walls, the loading path gets even complicated and the engineering judgements are required for designing the system. In this study, a masonry infill system was investigated through finite element analysis (FEA) and the results were compared with the current design standard, ASCE 41. It is noted that the equivalent width of the compression strut estimated by ASCE 41 could be 32% less than that using detailed FEA. The global load resisting capacity was also estimated by 28% less when ASCE 41 was used compare to the FEA case. Rather than using expensive FEA, the adapting ASCE 41 for the analysis and design of the masonry infills with openings would provide a good estimation by about 25% conservatively.

Cyclic Seismic Testing of Cruciform Concrete-Filled U-Shape Steel Beam-to-H Column Composite Connections (콘크리트채움 U형합성보-H형강기둥 십자형 합성접합부의 내진성능)

  • Park, Chang-Hee;Lee, Cheol-Ho;Park, Hong-Gun;Hwang, Hyeon-Jong;Lee, Chang-Nam;Kim, Hyoung-Seop;Kim, Sung-Bae
    • Journal of Korean Society of Steel Construction
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    • v.23 no.4
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    • pp.503-514
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    • 2011
  • In this research, the seismic connection details for two concrete-filled U-shape steel beam-to-H columns were proposed and cyclically tested under a full-scale cruciform configuration. The key connecting components included the U-shape steel section (450 and 550 mm deep for specimens A and B, respectively), a concrete floor slab with a ribbed deck (165 mm deep for both specimens), welded couplers and rebars for negative moment transfer, and shear studs for full composite action and strengthening plates. Considering the unique constructional nature of the proposed connection, the critical limit states, such as the weld fracture, anchorage failure of the welded coupler, local buckling, concrete crushing, and rebar buckling, were carefully addressed in the specimen design. The test results showed that the connection details and design methods proposed in this study can well control the critical limit states mentioned above. Especially, the proposed connection according to the strengthening strategy successfully pushed the plastic hinge to the tip of the strengthened zone, as intended in the design, and was very effective in protecting the more vulnerable beam-to-column welded joint. The maximum story drift capacities of 6.0 and 6.8% radians were achieved in specimens A and B, respectively, thus far exceeding the minimumlimit of 4% radians required of special moment frames. Low-cycle fatigue fracture across the beam bottom flange at a 6% drift level was the final failure mode of specimen A. Specimen B failed through the fracture of the top splice plate of the bolted splice at a very high drift ratio of 8.0% radian.