• Earthquakes and Structures
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• v.11 no.3
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• pp.483-503
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• 2016

This study aims to evaluate seismic performance of existing low and mid-rise reinforced concrete buildings by comparing their displacement capacities and displacement demands under selected ground motions experienced in Turkey as well as demand spectrum provided in 2007 Turkish Earthquake Code for design earthquake with 10% probability of exceedance in 50 years for soil class Z3. It should be noted that typical residential buildings are designed according to demand spectrum of 10% probability of exceedance in 50 years. Three RC building sets as 2-, 4- and 7-story, are selected to represent reference low-and mid-rise buildings located in the high seismicity region of Turkey. The selected buildings are typical beam-column RC frame buildings with no shear walls. The outcomes of detailed field and archive investigation including approximately 500 real residential RC buildings established building models to reflect existing building stock. Total of 72 3-D building models are constructed from the reference buildings to include the effects of some properties such as structural irregularities, concrete strength, seismic codes, structural deficiencies, transverse reinforcement detailing, and number of story on seismic performance of low and mid-rise RC buildings. Capacity curves of building sets are obtained by nonlinear static analyses conducted in two principal directions, resulting in 144 models. The inelastic dynamic characteristics are represented by "equivalent" Single-Degree-of- Freedom (ESDOF) systems using obtained capacity curves of buildings. Nonlinear time history analysis is used to estimate displacement demands of representative building models idealized with (ESDOF) systems subjected to the selected ground motion records from past earthquakes in Turkey. The results show that the significant number of pre-modern code 4- and 7-story buildings exceeds LS performance level while the modern code 4- and 7-story buildings have better performances. The findings obviously indicate the existence of destructive earthquakes especially for 4- and 7-story buildings. Significant improvements in the performance of the buildings per modern code are also obvious in the study. Almost one third of pre-modern code buildings is exceeding LS level during records in the past earthquakes. This observation also supports the building damages experienced in the past earthquake events in Turkey.

• Fire Science and Engineering
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• v.31 no.2
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• pp.9-16
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• 2017

In this study, fire resistance tests were conducted to evaluate the fire resistance performance of unprotected and non-welded CFT columns in relation to the shape and size of cross-sections. Unprotected slot-type CFT columns which were ${\square}300$ and ${\square}500$ in dimensions resisted fire for 125 minutes and more than 180 minutes, respectively. Strain analysis showed that slot-type CFT columns were more ductile than welded CFT columns. The temperatures of central parts measured when welded CFT columns and slot-type CFT columns had lost fire resistance performance were higher in the former than the latter. Therefore, slot connection does not a great influence on the temperatures inside the concrete.

• Steel and Composite Structures
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• v.36 no.4
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• pp.447-462
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• 2020

The paper aims to investigate the mechanical mechanism and seismic effect of stiffeners in blind bolt endplate connection to CFST column. A precise 3D finite element model with considering the cyclic properties of concrete and steel materials was established, and the efficiency was validated through monotonic and cyclic test data. The deforming pattern and the seismic performance of the unstiffened and stiffened blind bolt endplate connections were investigated. Then a parametric analysis was conducted to analyze the contribution of stiffeners and the joint working behaviors with endplate under cyclic load. The joint stiffness classifications were compared and a supplement stiffness classification method was proposed, and the energy dissipation ability of different class connections were compared and discussed. Results indicated that the main deformation pattern of unstiffened blind bolt endplate connections was the local bending of end plate. The vertical stiffeners can effectively alleviate the local bending deformation of end plate. And influence of stiffeners in thin endplate and thick endplate was different. Based on the stiffness of external diaphragm welded connection, a more detailed rigidity classification was proposed which included the pin, semi-rigid, quasi-rigid and rigid connection. Beam was the main energy dissipation source for rigid connection. For the semi-rigid and quasi-rigid connection, the extended endplate, stiffeners and steel beam would all participate in the energy dissipation.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.51-58
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• 2002

To reduce the story height for high-rise buildings, the TEC Beam is developed as a new composite beam composed of structural tee, precast concrete, stirrup, and site-in-cast reinforced concrete slab. The preliminary test of the proposed system was performed for simple beams and it showed a good behavior. However, for the field application of the system, it is required to develope a steel moment resisting connection using steel brackets on which upper rebars of the TEC BEAM are anchored. In this paper, three types of the proposed system are experimentally investigated. The parameters of the test are as follows: (1) the spacing of transverse bars, (2) the ratio of width of rebar's layer to bracket length. Specimens were classified as semi-rigid full strength by the Eurocode 4. It could be concluded that the proposed moment resisting system shows a good structural behavior and may be applicable in the filed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.48-58
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• 2014

In this study, quasi-static according to the displacement-controlled (strain control) method tests on RC columns for seismic reinforcement performance in accordance with the provisions of the seismic design and construction before 1992 design code for highway bridges in korea. Used reinforcement that improves the performance of Inorganic Helical Bar, a kind of alloy steel, circular columns were tested outside the seismic reinforcing. In the experiment, fracture behavior, lateral load-displacement relation, ductility and energy assessment evaluation was performed through tests. The variables in experimental are section force of reinforcement, spiral reinforcement spacing, reinforcement method. Improved seismic performance and effect were confirmed through quasi-static test experiments. The results of study confirmed determination the appropriate size of reinforcement, reinforcement forces, spacing and selection of the type required, furthermore, not only mechanical reinforcement but also substitution of high-strength concrete reinforced with concrete cover improved seismic performance.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.89-96
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• 2016

Compressive axial behavior of the variable cross-section soft ground reinforced foundation is investigated from the field load test results at ${\bigcirc}{\bigcirc}$ construction site in Incheon city. Variable cross-section soft ground reinforced foundation is a type of partial-displacement pile formed by mixing bidding material with in situ soils to obtain a rigid and strong variable cross-section column in a relatively soft ground. The foundations are usually constructed as a group; however in this study, only single foundation was installed and tested under compressive axial load on foundation head. For the comparison of the variable cross-section soft ground reinforced foundation axial behavior, behavior of typical Pretensioned spun high strength concrete (PHC) pile constructed on a relatively soft ground near the surface was analyzed. It was concluded that variable cross-section soft ground reinforced foundation efficiently resists against axial load with sufficient stiffness and strength within a considerable range of axial load magnitude.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.121-129
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• 2017

In this paper, the shake table test for the masonry infilled reinforced concrete frame with non-seismic details was carried out in order to evaluate its dynamic behaviour and damage under seismic condition. The tested specimens were the RC frame and the masonry infilled RC frame and the dynamic characteristics, such as a resonant period, acceleration response, displacement response and base shear force response, were compared between them. As a result of the shake table test, RC frame specimen had flexural cracks at the top and bottom of the column and shear cracks at the joints. In the case of masonry infilled RC frame, the damage of the frame was relatively minor but the sliding cracks and diagonal shear cracks on the masonry wall were severe at the final excitation. The resonant period of infilled RC frame specimen was shorter than that of the RC frame specimen because the masonry infill contributed to increase the stiffness. The maximum displacement response of the infilled RC frame specimen was decreased by about 20% than the RC frame specimen. It was analyzed that the masonry infill wall applied in this study contributed to increase the lateral strength of the RC frame with non - seismic detail by about 2.2 times and the stiffness by about 1.6 times.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.15-24
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• 2013

This paper presents the results from a systematic finite element study on the bending moment resisting capacity of double web-angle connection for a CFT(concrete filled tube) composite frame subjected to cyclic loading. The three-dimensional nonlinear finite element models are constructed to investigate the rotational stiffness, bending moment capacity, and failure modes of the partially restrained composite CFT connections. A wide scope of additional structural behaviors explain the different influences of the double web-angle connections parameters, such as the different thickness of connection angles and the gage distances of high strength steel connection bar. The moment-rotation angle relationships obtained statically from the finite element analysis are compared with those from Richard's theoretical equation.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.170-175
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• 2011

최근 고강도 콘크리트의 내화성능이 사회적 이슈로 부각되고 국토해양부에서 고강도 콘크리트의 내화성능 관리기준(안)이 고시되면서 국내에서도 고강도 콘크리트의 내화성능을 향상시키기 위한 연구가 활발히 진행되고 있다. 본 연구에서는 유기질 섬유인 폴리프로필렌섬유(PP섬유)와 강섬유를 하이브리드한 Fiber Cocktail를 혼입한 고강도 내화콘크리트 개발을 위한 연구를 수행하였다. PP섬유는 $160^{\circ}C$의 온도에서 용융되어 콘크리트 내부에 미세한 통로를 형성하여 고강도 콘크리트 부재 내의 수증기압 및 공극압을 효과적으로 배출하여 고강도 콘크리트의 폭렬발생을 억제시키는 데 효과적이며, 강섬유는 PP섬유가 용융된 후의 고강도 콘크리트 부재의 균열 발생을 억제하며 외부로부터 침투하는 열기를 차단할 수 있다. 100MPa 고강도 콘크리트의 내화실험을 실시하여 최적단면 조건을 도출하기 위해 철근온도를 분석한 결과, 단면이 커질수록 철근온도는 점차 낮아지는 경향이 나타났으며 $600{\times}600mm$, $800{\times}800mm$ 단면에서 내화성능을 확보할 수 있는 것으로 나타났으며, 이중 경제성을 고려할 경우 $600{\times}600mm$ 단면이 최적단면으로 도출되었다. 또한 도출된 $600{\times}600mm$ 단면에 대해서 철근의 온도를 분석한 결과 PP섬유 $1.5kg/m^3$와 강섬유 $40kg/m^3$를 배합한 Fiber Cocktail이 최적배합비로 나타났다.