• Title, Summary, Keyword: RC frame

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Strengthening of Non-ductile Reinforced Concrete (RC) frames with Expansive Joint Mortar and H-beam Frame (팽창형 접합부 모르타르와 H형강 프레임에 의한 비내진 상세를 갖는 철근콘크리트 골조의 내진보강)

  • Kim, Ji-Hyeon;Jang, Seok-Joon;Yun, Da-Ae;Kim, Dae-Young;Yun, Hyun-Do
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.3
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    • pp.127-135
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    • 2019
  • The seismic performance of non-ductile reinforced concrete (RC) frame retrofitted with H-beam frame and cast expansive mortar into joint between existing RC frame and H-beam frame is investigated experimentally and analytically. RC frames considered in the study contain non-ductile reinforcement details of low-rise school building constructed in Korea before 1988. The tests were conducted on half-scale specimens simulating the lower frame assemblages of a typical school building. Two one-bay, one-story RC frames with and without retrofitting with H-beam frame and expansive joint mortar were tested to failure. Test and analysis results indicated that seismic strengthening using H-beam and expansive joint mortar significantly improved the lateral strength and stiffness of non-ductile RC frame without installing anchor bolts to fit H-beam frame into existing RC frame. The effectiveness of seismic strengthening technology proposed in the study for non-ductile RC frame was verified experimentally and analytically.

Experimental study on RC frame structures strengthened by externally-anchored PC wall panels

  • Choi, Seung-Ho;Hwang, Jin-Ha;Lee, Deuck Hang;Kim, Kang Su;Zhang, Dichuan;Kim, Jong Ryeol
    • Computers and Concrete
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    • v.22 no.4
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    • pp.383-393
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    • 2018
  • Infill wall strengthening method has been widely used for seismic strengthening of deteriorated reinforced concrete (RC) frame structures with non-seismic details. Although such infill wall method can ensure sufficient lateral strengths of RC frame structures deteriorated in seismic performances with a low constructional cost, it generally requires quite cumbersome construction works due to its complex connection details between an infill wall and existing RC frame. In this study, an advanced seismic strengthening method using externally-anchored precast wall panels (EPCW) was developed to overcome the disadvantage inherent in the existing infill wall strengthening method. A total of four RC frame specimens were carefully designed and fabricated. Cyclic loading tests were then conducted to examine seismic performances of RC frame specimens strengthened using the EPCW method. Two specimens were fully strengthened using stocky precast wall panels with different connection details while one specimen was strengthened only in column perimeter with slender precast wall panels. Test results showed that the strength, stiffness, and energy dissipation capacity of RC frame specimens strengthened by EPCWs were improved compared to control frame specimens without strengthening.

Dynamic Behaviour of Masonry inFilled Reinforced Concrete Frames with Non-Seismic Details (진동대실험을 통한 비내진상세를 가지는 RC 골조의 조적채움벽 유무에 따른 동적 거동 평가)

  • Baek, Eun-Rim;Kim, Kyung-Min;Cheon, Ju-Hyun;Oh, Sang-Hoon;Lee, Sang-Ho
    • 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.

Probabilistic seismic demand assessment of self-centering concrete frames under mainshock-aftershock excitations

  • Song, Long L.;Guo, Tong;Shi, Xin
    • Steel and Composite Structures
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    • v.33 no.5
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    • pp.641-652
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    • 2019
  • This paper investigates the effect of aftershocks on the seismic performance of self-centering (SC) prestressed concrete frames using the probabilistic seismic demand analysis methodology. For this purpose, a 4-story SC concrete frame and a conventional reinforced concrete (RC) frame are designed and numerically analyzed through nonlinear dynamic analyses based on a set of as-recorded mainshock-aftershock seismic sequences. The peak and residual story drifts are selected as the demand parameters. The probabilistic seismic demand models of the SC and RC frames are compared, and the SC frame is found to have less dispersion of peak and residual story drifts. The results of drift demand hazard analyses reveal that the SC frame experiences lower peak story drift hazards and significantly reduced residual story drift hazards than the RC frame when subjected to the mainshocks only or the mainshock-aftershock sequences, which demonstrates the advantages of the SC frame over the RC frame. For both the SC and RC frames, the influence of as-recorded aftershocks on the drift demand hazards is small. It is shown that artificial aftershocks can produce notably increased drift demand hazards of the RC frame, while the incremental effect of artificial aftershocks on the drift demand hazards of the SC frame is much smaller. It is also found that aftershock polarity does not influence the drift demand hazards of both the SC and RC frames.

Analysis of behavior of bare and in-filled RC frames subjected to quasi static loading

  • Sandhu, Balvir;Sharma, Shruti;Kwatra, Naveen
    • Structural Engineering and Mechanics
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    • v.73 no.4
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    • pp.381-395
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    • 2020
  • Study on the inelastic response of bare and masonry infilled Reinforced Concrete (RC) frames repaired using Carbon Fibre Reinforced Polymers (CFRP) and Glass Fiber Reinforced Polymers (GFRP) subjected to quasi- static loading is presented in the work. The hysteresis behaviour, stiffness retention, energy dissipation and damage index are the parameters employed to analyze the efficacy of FRP strengthening of bare and brick in-filled RC frames. It is observed that there is a significant improvement in load carrying capacity of brick infilled frame over bare RC frame. Also FRP strengthened brick infilled frame performs much better than FRP repaired bare frame under quasi static loading. Repair and retrofitting of brick infilled RC frame shows an improved load carrying and damage tolerance capacity than control frame.

A simplified evaluation method of skeleton curve for RC frame with URM infill

  • Jin, Kiwoong;Choi, Ho
    • Earthquakes and Structures
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    • v.13 no.3
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    • pp.309-322
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    • 2017
  • In this paper, a simplified evaluation method of the skeleton curve for reinforced concrete (RC) frame with unreinforced masonry (URM) infill is proposed in a practical form, based on the previous studies. The backbone curve for RC boundary frame was modeled by a tri-linear envelope with cracking and yielding points. On the other hand, that of URM infill was modeled by representative characteristic points of cracking, maximum, and residual strength; also, the interaction effect between RC boundary frame and the infill was taken into account. The overall force-displacement envelopes by the sum of RC boundary frame and URM infill, where the backbone curves of the infill from other studies were also considered, were then compared with the previous experimental results. The simplified estimation results from this study were found to almost approximate the overall experimental results with conservative evaluations, and they showed much better agreement than the cases employing the infill envelopes from other studies.

Performance Analysis of SMART Frame Applied to RC Column-Beam Structures (RC 라멘조에 SMART Frame 적용 시 효용성 분석)

  • Cho, Wonhyun;Lim, Chaeyeon;Jang, Duk Bea;Kim, Sunkuk
    • Proceedings of the Korean Institute of Building Construction Conference
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    • pp.168-169
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    • 2015
  • SMART Frame is a composite precast concrete structure system to deliver the advantages of both steel frame and reinforced concrete. Many studies have established to date that SMART Frame is more advantageous than conventional frame-type structure in terms of structural stability, constructability, economic viability as well as reduction of construction schedule. However, such studies have focused primarily on wall-type or flat slab-type apartment housing structures, failing to include Rahmen structures in their scope. Accordingly, this study aims to analyze the benefits of potential application of SMART Frame to RC Rahmen structures. As the structural stability and constructability of SMART Frame is already proven, this study reviews its benefits from the perspective of cost reduction. Conclusion of this study will be used subsequently in predicting the benefits of SMART Frame when it is adapted to RC Rahmen structures.

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Seismic performance of RC-column wrapped with Velcro

  • Kwon, Minho;Seo, Hyunsu;Kim, Jinsup
    • Structural Engineering and Mechanics
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    • v.58 no.2
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    • pp.379-395
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    • 2016
  • A seismic strengthening method using Velcro is proposed to improve the seismic performance of columns in RC frame structures. The proposed method was evaluated experimentally using three fabricated RC specimens. Velcro was wrapped around the columns of the RC-frame specimen to prevent concrete spall falling. The reinforcing performance of the Velcro was determined from comparison of results on seismic performance (i.e., strength, displacement, failure mode, displacement ductility capacity and amount of dissipated energy). As the displacement of the reinforced specimens was increased, the amount of dissipated energy increased drastically, and the displacement-ductility-capacity of the reinforced specimens also increased. The final failure mode of RC frame structure was changed. As a result, it was concluded that the proposed seismic strengthening method using Velcro could be used to increase the displacement ductility of RC columns, and could be used to change the final failure mode of RC-frame structures.

Effect of staircase on seismic performance of RC frame building

  • Kumbhar, Onkar G.;Kumar, Ratnesh;Adhikary, Shrabony
    • Earthquakes and Structures
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    • v.9 no.2
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    • pp.375-390
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    • 2015
  • Staircase is a vertical transportation element commonly used in every multistoried structure. Inclined flights of staircase are usually casted monolithically with RC frame. The structural configuration of stairs generally introduces discontinuities into the typical regular reinforced concrete frame composed of beams and columns. Inclined position of flight transfers both vertical as well as horizontal forces in the frame. Under lateral loading, staircase in a multistory RC frame building develops truss action creating a local stiffening effect. In case of seismic event the stiff area around staircase attracts larger force. Therefore, special attention is required while modeling and analyzing the building with staircase. However, in general design practice, designers usually ignore the staircase while modeling either due to ignorance or to avoid complexity. A numerical study has been conducted to examine the effect of ignoring staircase in modeling and design of RC frame buildings while they are really present in structure, may be at different locations. Linear dynamic analysis is performed on nine separate building models to evaluate influence of staircase on dynamic characteristics of building, followed by nonlinear static analysis on the same models to access their seismic performance. It is observed that effect of ignoring staircase in modeling is severe and leads to unsafe structure. Effect of location and orientation of staircase is also important in determining seismic performance of RC frame buildings.

Infill wall effects on the dynamic characteristics of RC frame systems via operational modal analysis

  • Komur, Mehmet A.;Kara, Mehmet E.;Deneme, Ibrahim O.
    • Structural Engineering and Mechanics
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    • v.74 no.1
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    • pp.121-128
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    • 2020
  • This paper presents an experimental study on the dynamic characteristics of infilled reinforced concrete (RC) frames. A 1/3-scaled, one-bay, three-storey RC frame was produced and tested by using operational modal analysis (OMA). The experiments were performed on five specimens: one reference frame with no infill walls and four frames with infill walls. The RC frame systems included infill walls made of hollow clay brick, which were constructed in four different patterns. The dynamic characteristics of the patterns, including the frequency, mode shapes and damping ratios in the in-plane direction, were obtained by 6 accelerometers. Twenty-minute records under ambient vibration were collected for each model, and the dynamic characteristics were determined using the ambient vibration testing and modal identification software (ARTeMIS). The experimental studies showed that the infill walls significantly affected the frequency value, rigidity and damping ratio of the RC frame system.