• Earthquakes and Structures
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• 제15권3호
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• pp.307-317
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• 2018

The current study explores the soil-structure interaction (SSI) effect on the potential seismic damage of mid-rise non-seismically designed reinforced concrete frames retrofitted by Fibre Reinforced Polymer (FRP). An 8-storey reinforced concrete frame poorly-confined due to transverse reinforcement deficiency is selected and then retrofitted by FRP wraps to provide external confinement. The poorly-confined and FRP retrofitted frames with/without SSI are modelled using hysteretic nonlinear elements. Inelastic time history and damage analyses are performed for these frames subjected to different seismic intensities. The results show that the FRP confinement significantly reduces one or two damage levels for the poorly-confined frame. More importantly, the SSI effect is found to increase the potential seismic damage of the retrofitted frame, reducing the effectiveness of FRP retrofitting. This finding, which is contrary to the conventionally beneficial concept of SSI governing for decades in structural and earthquake engineering, is worth taking into account in designing and evaluating retrofitted structures.

• 한국공간구조학회논문집
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• 제23권4호
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• pp.43-50
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• 2023

This study aims to assess the seismic performance of retrofitted reinforced concrete columns using a Replaceable Steel Brace (RSB) system, subjected to combined axial, lateral, and torsional loadings. Through experimental testing, one non-retrofitted concrete column specimen and two retrofitted specimens with variable sliding slot lengths were subjected to eccentric lateral loads to simulate realistic seismic loading. The retrofitted specimens with RSBs exhibited enhanced resistance against shear cracking, effective torsional resistance, and demonstrated the feasibility of easy replacement. The RSB system substantially improved seismic performance, achieving approximately 1.7 times higher load capacity and 3.5 times greater energy dissipation compared to non-retrofitted column, thus validating its efficacy under combined loading conditions.

• Structural Engineering and Mechanics
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• 제55권6호
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• pp.1139-1155
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• 2015

In this study, a new retrofitting method for improving the seismic performance of reinforced concrete column was presented, in which prestressed steel strips were utilized as retrofitting stuff to confine the reinforced concrete column transversely. In order to figure out the seismic performance of concrete column specimen retrofitted by such prestressed steel strips methods, a series of quasi-static tests of five retrofitted specimens and two unconfined column specimen which acted as control specimens were conducted. Based on the test results, the seismic performance including the failure modes, hysteresis performance, ductility performance, energy dissipation and stiffness degradation of all these specimens were fully investigated and analyzed. And furthermore the influences of some key parameters such as the axial force ratios, shear span ratios and steel strips spacing on seismic performance of those retrofitted reinforced concrete column specimens were also studied. It was shown that the prestressed steel strips provided large transverse confining effect on reinforced concrete column specimens, which resulted in improving the shearing bearing capacity, ductility performance, deformation capacity and energy dissipation performance of retrofitted specimens effectively. In comparison to the specimen which was retrofitted by the carbon fiber reinforced plastics (CFRP) strips method, the seismic performance of the specimens retrofitted by the prestressed steel strips was a bit better, and with much less cost both in material and labor. From this research results, it can be concluded that this new retrofitting method is really useful and has significant advantages both in saving money and time over some other retrofitting methods.

• Steel and Composite Structures
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• 제29권3호
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• pp.287-299
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• 2018

The purpose of this study is to investigate the effectiveness of damped cable systems (DCS) to mitigate the earthquake-induced responses of a building frame structure. The seismic performance of the DCS is investigated using the fragility analysis and life cycle cost evaluation of an existing building retrofitted with the DCS, and the results are compared with the structure retrofitted with conventional fluid viscous dampers. The comparison of the analysis results reveals that, due to the self-centering capability of the DCS, residual displacement approximately reaches to zero for the structure retrofitted with the DCS. The fragility analysis shows that the structure retrofitted with the DCS has the least probability of reaching the specific limit states compared to the bare structure and the structure with the conventional fluid viscous damper (VD), especially under the severe ground motions. It is also observed that both the initial and the life cycle costs of the DCS seismic retrofitting technique is lesser compare to the structure retrofitted with the VD.

• Earthquakes and Structures
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• 제12권1호
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• pp.79-89
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• 2017

As a new type of energy dissipation component with excellent mechanical performance, the Buckling-Retrained Braces (BRBs) were gradually applied in retrofitting and improving seismic performance of reinforced concrete structures in China. In order to investigate the seismic performance of reinforced concrete structures retrofitted with BRBs, quasi-static test of two single-bay and 3-story reinforced concrete frames specimens was conducted and introduced in this paper. Two 1/2 scaled specimens were designed to reflect real prototype structure. For comparison, one control specimen was designed without BRBs, and the other specimen was retrofitted with BRBs. And particularly, for the specimen retrofitted with BRBs, the BRBs were eccentric layout instead of usually concentric or x-shaped layout, aiming to be more suitable for large-span frames. In the test, the failure mode, carrying capacity, deformability, ductility and energy dissipation ability of both two specimens were investigated. Based on the test results of the measured hysterical curves, skeleton curves, the seismic performances such as bearing capacity, plastic deformability, energy dissipation ability and ductility of two specimens were fully studied. And from the test results, it was indicated that the specimen retrofitted with BRBs showed much better seismic performance than the control specimen without BRBs, and the BRBs could effectively improve the seismic performance of the reinforced concrete frame. For the specimen retrofitted with BRBs, the BRBs firstly yielded before the beam-ends and the column-ends, and an expected yielding process or yielding mechanism as well as good seismic performance was obtained. For the specimens without BRBs, though the beam-ends yielded prior to the column-ends, the seismic performance was much poor than that of the specimen with BRBs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.559-564
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• 2001

The objective of this experimental research is to assess the seismic performance of circular RC bridge pier specimens retrofitted with fibers which were designed as a prototype of Hagal bridge in the city of Suwon, Korea. Pseudo-dynamic test has been done for two nonseismic test specimens which were nonseismic designed by the related provisions of the Highway Design Specification, and four nonseismic test specimens retrofitted with fibers in the plastic hinge region. Important test parameters were load patterns, and retrofit. The seismic behavior has been analyzed through the displacement ductility, energy analysis, and capacity spectrum. Approximate 7.0 displacement ductility was observed for nonseismic test specimens retrofitted with fibers. It is concluded that these retrofitting test specimens could have sufficient seismic capacity in the region of moderate seismic zone.

• Earthquakes and Structures
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• 제6권3호
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• pp.237-250
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• 2014

This paper experimentally investigates the seismic performance of RC columns retrofitted with Super Reinforcement with Flexibility (SRF), which is a polyester fiber reinforced polymer. A total of three specimens with a scale factor of 1/2 were constructed and tested in order to assess the structural behavior of the retrofitted RC columns. One specimen was a non-seismically designed column without any retrofit, while others were retrofitted with either one or two layers of the polyester belt with urethane as the adhesive. Static cyclic testing with a constant axial load was conducted to assess the seismic performance of the retrofitted RC columns. It is concluded that the SRF retrofitting method increases the strength and ductility of the RC columns and can also impact on the failure mode of the columns.

• Earthquakes and Structures
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• 제15권5호
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• pp.499-511
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• 2018

This paper aims to investigate the seismic performance of the prestressed steel strips retrofitted RC beam-column joints. Two series of joint specimens were conducted under compression load and reversed cyclic loading through quasi-static tests. Based on the test results, the seismic behavior of the strengthened joints specimens in terms of the failure modes, hysteresis response, bearing capacity, ductility, stiffness degradation, energy dissipation performance and damage level were focused. Moreover, the effects of the amount of the prestressed steel strips and the axial compression ratio on seismic performance of retrofitted specimens were analyzed. It was shown that the prestressed steel strips retrofitting method could significantly improve the seismic behavior of the RC joint because of the large confinement provided by prestressed steel strips in beam-column joints. The decrease of the spacing and the increase of the layer number of the prestressed steel strips could result in a better seismic performance of the retrofitted joint specimens. Moreover, increasing the axial compression ration could enhance the peak load, stiffness and the energy performance of the joint specimens. Furthermore, by comparison with the specimens reinforced with CFRP sheets, the specimens reinforced with prestressed steel strips was slightly better in seismic performance and cost-saving in material and labor. Therefore, this prestressed steel strips retrofitting method is quite helpful to enhance the seismic behavior of the RC beam-column joints with reducing the cost and engineering time.

• Structural Engineering and Mechanics
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• 제67권1호
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• pp.1-8
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• 2018

Shake table tests performed on five 1:3 reduced scale two story RC moment resisting frames having construction defects, have shown severe joint damageability in deficient RC frames, resulting in joint panels' cover spalling and core concrete crushing. Haunch retrofitting technique was adopted herein to upgrade the seismic resistance of the deficient RC frames. Additional four deficient RC frames were built and retrofitted with steel haunch; both axially stiffer and deformable with energy dissipation, fixed to the beam-column connections to reduce shear demand on joint panels. The as-built and retrofitted frames' seismic response parameters are calculated and compared to evaluate the viability of haunch retrofitting technique. The haunch retrofitting technique increased the lateral stiffness and strength of the structure, resulting in the increase of structure's overstrength. The retrofitting increased response modification factor R by 60% to 100%. Further, the input excitation PGA was correlated with the lateral roof displacement to derive structure response curve that have shown significant resistance of retrofitted models against input excitations. The technique can significantly enhance the seismic performance of deficient RC frames, particularly against the frequent and rare earthquake events, hence, promising for seismic risk mitigation.

• 콘크리트학회논문집
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• 제14권2호
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• pp.180-189
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• 2002

이 연구의 목적은 유사동적실험에 의한 섬유보강 원형철근콘크리트교각의 내진성능평가를 위한 연구로서 수원시에 위치한 내진설계된 교량인 하갈교를 대상모델로 하였다. 도로교설계기준의 내진설계규정이 적용되지 않은 비내진실험체 2개 및 내진설계 규정에 따라 설계된 내진실험체 2개 그리고 내진성능향상을 위해 비내진실험체를 보강한 섬유보강실험체 4개 즉 총 8개에 대하여 유사동적실험을 수행하였다. 보강공법으로는 유리섬유 및 탄소섬유 보강공법을 사용하였으며, 실험변수로는 내진 및 비내진설계, 하중형식, 섬유보강유무로 하였다. 내진성능평가 방법은 소산에너지, 변위연성도 그리고 능력스펙트럼이 분석되었다. 실험결과로 유리 및 탄소섬유로 보강된 비내진실험체의 변위연성도는 KHC인공지진파에 대하여 7.7~8.7정도의 값으로서 충분한 내진성능을 확보하고 있는 것으로 평가되었다.