• Title/Summary/Keyword: Column retrofitted

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Structural Performance Enhancement of Seismic Retrofitted Column Using New Reinforcing Materials (신보강재로 보수 보강한 기둥의 구조 성능 개선)

  • Oh, Chang-Hak;Han, Sang-Whan;Lee, Li-Hyung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.2
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    • pp.121-128
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    • 2001
  • Reinforced concrete frame buildings in regions of low to moderate seismicity are typically designed only for gravity loads with non-seismic detailing provisions of the code. These buildings possess strong beam-weak column, which brings about the brittle structural performance like the column sidesway failure mechanism during the strong lateral load. The objective of this paper is to enhance the column strength and deformation capacity for reconfiguring the structural failure mode by averting a column soft-story collapse and moving to a more ductile beam-sides way mechanism suing new reinforcing materials. Aramid fiber sheet and reinforcing rod-composite materials was used for this purpose. The column was modeled by the 2/3 scale experimental specimen retested. According to the concept of the capacity design, the damaged column was strengthened by the column jacketing using new reinfocing materials such as rod-composite materials. In conclusion, the improvement of the flexural strength is observed and the capacity of the energy dissipation and the ductility is enhanced, too.

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Nonlinear model of reinforced concrete frames retrofitted by in-filled HPFRCC walls

  • Cho, Chang-Geun;Ha, Gee-Joo;Kim, Yun-Yong
    • Structural Engineering and Mechanics
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    • v.30 no.2
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    • pp.211-223
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    • 2008
  • A number of studies have suggested that the use of high ductile and high shear materials, such as Engineered Cementitious Composites (ECC) and High Performance Fiber Reinforced Cementitious Composites (HPFRCC), significantly enhances the shear capacity of structural elements, even with/without shear reinforcements. The present study emphasizes the development of a nonlinear model of shear behaviour of a HPFRCC panel for application to the seismic retrofit of reinforced concrete buildings. To model the shear behaviour of HPFRCC panels, the original Modified Compression Field Theory (MCFT) for conventional reinforced concrete panels has been newly revised for reinforced HPFRCC panels, and is referred to here as the HPFRCC-MCFT model. A series of experiments was conducted to assess the shear behaviour of HPFRCC panels subjected to pure shear, and the proposed shear model has been verified through an experiment involving panel elements under pure shear. The proposed shear model of a HPFRCC panel has been applied to the prediction of seismic retrofitted reinforced concrete buildings with in-filled HPFRCC panels. In retrofitted structures, the in-filled HPFRCC element is regarded as a shear spring element of a low-rise shear wall ignoring the flexural response, and reinforced concrete elements for beam or beam-column member are modelled by a finite plastic hinge zone model. An experimental study of reinforced concrete frames with in-filled HPFRCC panels was also carried out and the analysis model was verified with correlation studies of experimental results.

Damage detection of reinforced concrete columns retrofitted with FRP jackets by using PZT sensors

  • Tzoura, Efi A.;Triantafillou, Thanasis C.;Providakis, Costas;Tsantilis, Aristomenis;Papanicolaou, Corina G.;Karabalis, Dimitris L.
    • Structural Monitoring and Maintenance
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    • v.2 no.2
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    • pp.165-180
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    • 2015
  • In this paper lead zirconate titanate transducers (PZT) are employed for damage detection of four reinforced concrete (RC) column specimens retrofitted with carbon fiber reinforced polymer (CFRP) jackets. A major disadvantage of FRP jacketing in RC members is the inability to inspect visually if the concrete substrate is damaged and in such case to estimate the extent of damage. The parameter measured during uniaxial compression tests at random times for known strain values is the real part of the complex number of the Electromechanical Admittance (Conductance) of the sensors, obtained by a PXI platform. The transducers are placed in specific positions along the height of the columns for detecting the damage in different positions and carrying out conclusions for the variation of the Conductance in relation to the position the failure occurred. The quantification of the damage at the concrete substrate is achieved with the use of the root-mean-square-deviation (RMSD) index, which is evaluated for the corresponding strain values. The experimental results provide evidence that PZT transducers are sensitive to damage detection from an early stage of the experiment and that the use of PZT sensors for monitoring and detecting the damage of FRP-retrofitted reinforced concrete members, by using the Electromechanical Admittance (EMA) approach, can be a highly promising method.

In-plane seismic performance of masonry wall retrofitted with prestressed steel-bar truss

  • Hwang, Seung-Hyeon;Kim, Sanghee;Yang, Keun-Hyeok
    • Earthquakes and Structures
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    • v.19 no.6
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    • pp.459-469
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    • 2020
  • An external prestressed steel-bar truss unit was developed as a new strengthening technology to enhance the seismic performance of an in-plane masonry wall structure while taking advantage of the benefits of a prestressed system. The presented method consists of six steel bars: two prestressed vertical bars to introduce a prestressing force on the masonry wall, two diagonal bars to resist shear deformation, and two horizontal bars to maintain the configuration. To evaluate the effects of this new technique, four full-scale specimens, including a control specimen, were tested under combined loadings that included constant-gravity axial loads and cyclic lateral loads. The experimental results were analyzed in terms of the shear strength, initial stiffness, dissipated energy, and strain history. The efficiency of the external prestressed steel-bar truss unit was validated. In particular, a retrofitted specimen with an axial load level of 0.024 exhibited a more stable post behavior and higher energy dissipation than a control specimen with an observed complete sliding failure. The four vertical bars of the adjacent retrofitting units created a virtual column, and their strain values did not change until they reached the peak shear strength. The shear capacity of the masonry wall structure with external prestressed steel-bar truss units could be predicted using the model suggested by Yang et al.

Assessment of seismic retrofitting for soft-story buildings using gapped inclined brace system

  • Tohamy, Mohamed. A.;Elsayed, Mostafa. M.;Akl, Adel. Y.
    • Earthquakes and Structures
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    • v.22 no.3
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    • pp.319-330
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    • 2022
  • Retrofit of soft-story buildings due to seismic loads using Gap-Inclined-Brace (GIB) system is considered a new retrofit technique that aims to maintain both strength and stiffness of structure. In addition, it provides more ductility and less P-delta effect, and subsequently better performance is observed. In this paper, the effect of the eccentricity between GIB and the retrofitted column due to installation on the efficiency of the retrofitting system is studied. In addition, a modification in the determination method of GIB properties is introduced to reduce the eccentricity effect. Also, the effect of GIB system on the seismic response of mid-rise buildings with different heights considering soft-story at various heights has been studied. A numerical model is developed to study the impact of such system on the response of retrofitted soft-story buildings under the action of seismic loads. To achieve that goal, this model is used to perform a numerical investigation, by considering five case study scenarios represent several locations of soft-story of two mid-rise reinforced concrete buildings. At first, Non-linear static pushover analysis was carried out to develop the capacity curves for case studies. Then, Non-linear time history analyses using ten earthquake records with five peak ground accelerations is performed for each case study scenario before and after retrofitting with GIB. The results show that large GIB eccentricity reduce the ultimate lateral resistance and deformation capacity of the retrofitting system. Moreover, the higher the retrofitted building, the more deformation capacity is observed but without significant increase in ultimate lateral resistance.

An Experimental Comparison Study on the Strength and Earthquake-resistant Capacity of Reinforced Concrete Columns Retrofitted with Fiber-Steel Composite Plate (복합플레이트로 보강된 RC 기둥의 내진성능에 대한 연구)

  • Park Tae Man;Park Weon Su;Park Seong Min;Yoon Jeong Bae
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.05a
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    • pp.724-729
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    • 2004
  • The purpose of this study is to investigate the strength and ductility improvement of columns retrofitted with Fiber-Steel Composite Plate, compared with Steel Plate, and Carbon Fiber Sheet. Test specimens strengthened with 3 different materials--- carbon fiber sheet, steel plate and fiber-steel composite plate --- were tested under cyclic lateral force and a constant axial load equal to $20\%$ of the column's axial load capacity. The hypothetical equivalent value of the strengthening among three materials is introduced to evaluate.

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Experimental Study on Compressive Strength of Concrete Column Retrofitted by Carbon FRP Sheet (탄소섬유시트로 보강된 콘크리트 기둥의 압축성능 평가를 위한 실험연구)

  • Yoo, Youn-Jong;Lee, Kyoung-Hun;Kim, Heecheul;Lee, Young-Hak;Hong, Won-Kee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.3
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    • pp.119-126
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    • 2008
  • In 1980 and 1990's most of residential buildings were constructed with relatively low strength concrete of 18 MPa. And, columns were designed considering only vertical loads. In this study, compressive strength tests for low strength RC columns retrofitted by carbon fiber sheets were carried out. Carbon fiber sheet provides constructability and high tensile strength as well as good corrosion resistance characteristics. A pair of carbon sheets were wrapped with ${\pm}60^{\circ}$ angle with respect to longitudinal direction of RC column to increase structural capacity against axial and lateral load simultaneously. Strength and strain patterns and failure modes of specimens were analyzed and prediction equation of increased compressive strength of RC column confined by carbon fiber sheet was proposed based on regression analysis.

Single and multi-material topology optimization of CFRP composites to retrofit beam-column connection

  • Dang, Hoang V.;Lee, Dongkyu;Lee, Kihak
    • Computers and Concrete
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    • v.19 no.4
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    • pp.405-411
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    • 2017
  • Carbon Fiber Reinforced Plastic (CFRP) has commonly been used to strengthen existing RC structures. Wrapping the whole component with CFRP is an effective method and simple to execute. Besides, specific configuration of CFRP sheets (L, X and T shape) has also been considered in some experiments to examine CFRP effects in advance. This study aimed to provide an optimal CFRP configuration to effectively retrofit the beam-column connection using continuous material topology optimization procedure. In addition, Moved and Regularized Heaviside Functions and penalization factors were also considered. Furthermore, a multi-material procedure was also used to compare with the results from the single material procedure.

Seismic retrofitting and fragility for damaged RC beam-column joints using UHP-HFRC

  • Trishna, Choudhury;Prem P., Bansal
    • Earthquakes and Structures
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    • v.23 no.5
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    • pp.463-472
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    • 2022
  • Reinforced concrete (RC) beam column joints (BCJ) have mostly exhibited poor seismic performance during several past earthquakes, typically due to the poor-quality concrete or lack of reinforcement detailing typical of pre-code design practice. The present study is motivated towards numerical simulation and seismic fragility assessment of one such RC-BCJ. The BCJ is loaded to failure and strengthened using Ultra High Performance-Hybrid Fiber Reinforced Concrete (UHP-HFRC) jacketing. The strengthening is performed for four different BCJ specimens, each representing an intermediate damage state before collapse. viz., slight, moderate, severe, and collapse. From the numerical simulation of all the BCJ specimens, an attempt is made to correlate different modelling and design parameters of the BC joint with respect to the damage states. In addition, seismic fragility analysis of the original as well as the retrofitted damaged BCJ specimens show the relative enhancement achieved in each case.

Pseudo Dynamic Test Study on Seismic Performance Evaluation of RC Columns Retrofitted by PolyUrea (내진보강용 폴리우레아로 보강된 철근콘크리트 기둥의 내진성능 평가에 대한 유사동적실험 연구)

  • Cho, Chul Min;Lee, Doo Sung;Kim, Tae Kyun;Kim, Jang-Ho Jay
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.37 no.2
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    • pp.289-301
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    • 2017
  • As earthquakes have frequently happened all over the world, huge losses of human life and property have occurred. Therefore, retrofitting and strengthen technologies of non-seismically designed structures in Korea are urgent. Also, there has been a growing interest about seismic retrofitting, where researches on the topic have been actively pursued in Korea. The study results showed that ductility inducing retrofitting method is more superior stiffness inducing method. In Japan, Super Reinforcement with Flexibility (SRF) was introduced. Therefore, in this study, seismic performance evaluation was performed through pseudo dynamic test and uniaxial compression test for RC column retrofitted by PolyUrea for ductility inducing retrofitting material. Uniaxial compression test results showed that strength of all specimens retrofitted by PolyUrea was higher than that of RC specimens. Also, all specimens retrofitted by PolyUrea also showed ductile fracture behavior. In pseudo dynamic test, by appling real earthquake record, the seismic behavior of RC column reinforced by PolyUrea was evaluated through relative displacement, reinforcement strain, displacement ductility, and dissipation energy. The results showed that PolyUrea helped to enhance seismic performance of RC columns.