• Earthquakes and Structures
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• v.9 no.4
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• pp.735-752
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• 2015

The effectiveness of seismic retrofitting of RC-frame buildings by converting selected bays into new walls through infilling with RC walls was studied experimentally using a full-scale four-storey model tested with the pseudo-dynamic (PsD) method. The frames were designed and detailed for gravity loads only using different connection details between the walls and the bounding frame. In order to simulate the experimental response, two numerical models were formulated differing at the level of modelling. The purpose of this paper is to illustrate the capabilities of these models to simulate the experimental nonlinear behaviour of the tested RC building strengthened with RC infill walls and comment on their effectiveness. The comparison between the capacity, in terms of peak ground acceleration, of the strengthened frame and the one of the bare frame, which was obtained numerically, has shown a five-fold increase.

• Computers and Concrete
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• v.10 no.5
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• pp.435-455
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• 2012

In the recent years, rehabilitation of structures, strengthening and increasing the ductility of them under seismic loads have become so vital that many studies has been carried out on the retrofit of steel and concrete members so far. Bridge piers are very important members concerning rehabilitation, in which the plastic hinging zone is very vulnerable. Pier is usually confined by special stirrups predicted in the design procedure; moreover, fiber-reinforced polymers (FRP) jackets are used after construction to confine the pier. FRP wrapping of the piers is one of the most effective ways of increasing moment and ductility capacity of them, which has a growing application due to its relative advantages. In many earthquake-resistant bridges, reinforced concrete columns have a major defect which could be retrofitted in different ways like using FRP. After rehabilitation, it is important to check the strengthening adequacy by dynamic nonlinear analysis and precise modeling of material properties. If the plastic hinge properties are simplified for the strengthened members, as the simplified properties which FEMA 356 proposes for non-strengthened members, static nonlinear analysis could be performed more easily. Current paper involves this matter and it is intended to determine the plastic hinge properties for static nonlinear analysis of the FRP-strengthened circular columns.

• Smart Structures and Systems
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• v.4 no.2
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• pp.247-259
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• 2008

The potential use of Cu-based shape memory alloys (SMA) in retrofitting historical monuments is investigated in this paper. This study is part of the ongoing work conducted in Tunisia within the framework of the FP6 European Union project (WIND-CHIME) on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The present investigation consists of a finite element simulation, as a preliminary to an experimental study where a cantilever masonry wall, representing a part of a historical monument, is subjected to monotonic and quasi-static cyclic loadings around a horizontal axis at the base level. The wall was retrofitted with an array of copper SMA wires with different cross-sectional areas. A new model is proposed for heat-treated copper SMAs and is validated based on published experimental results. A series of nonlinear finite element analyses are then performed on the wall for the purpose of assessing the SMA device retrofitting capabilities. Simulation results show an improvement of the wall response for the case of monotonic and quasi-static cyclic loadings.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.529-537
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• 2008

The objective of this paper is to propose retrofit design methods of theRHS column-to-H beam connections with floor slabs. Referring to previous studies on the retrofitting of moment connections, it is clear that connections retrofitted with a stiffened RBS (SR) or a lengthened horizontal stiffener (LH) has an effect on decreasing the stress/strain concentration. A new design procedure using these two retrofitting methods was thus presented. In addition, this paper addressed various design or detailing options and recommended a procedure for designing the improved retrofitting method of steel moment connections. Finally, a pilot test was conducted to verify the design procedure.

• Structural Engineering and Mechanics
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• v.71 no.3
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• pp.233-244
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• 2019

Steel jacketing technique is a retrofitting method often employed for static and seismic strengthening of existing reinforced concrete columns. When no continuity is given to angle chords as they cross the floor, the jacket is considered "indirectly loaded", which means that the load acting on the column is transferred partially to the external jacket through interface shear stresses. The evaluation of load transfer mechanism between core and jacket is not straightforward to be modeled, due to the absence of knowledge of a proper constitutive law of the concrete-to-steel interface and to the difficulties in taking into account the mechanical nonlinearities of materials. This paper presents an incremental analytical/numerical approach for evaluating the compressive response of RC columns strengthened with indirectly loaded jackets. The approach allows calculating shear stresses at the interface between core and jacket and predicting the axial capacity of retrofitted columns. A proper constitutive law is proposed for modelling the interaction between the steel and the concrete. Based on plasticity rules and the non-linear behaviour of materials, the column is divided into portions. After a detailed parametric analysis, comparisons are finally made by theoretical predictions and experimental results available in the literature, showing a good agreement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.51-61
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• 2007

A series of three shear wall specimens were tested under constant axial stress and reversed cyclic lateral loading to evaluate the capacity of seismic retrofit proposed for the shear wall with the opening induced by remodeling. One specimen was tested in the as-built condition and the others were retrofitted prior to testing. The retrofit involved the use of carbon fiber sheets and steel plates (thickness ; 3mm) over the entire face of the wall. Specimens were 1/2-scale representations of a one-story wall in a Korean apartment building that was built in 1980. The test results showed that failure mechanism of specimens governed by shear fracture and the strength of specimens was varied with according to the retrofitting strategies.

• Structural Engineering and Mechanics
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• v.89 no.5
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• pp.507-524
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• 2024

Since the cost of reconstruction is very high and the structure may have been damaged by an earthquake, we must retrofit the structure. Therefore, the importance of studying this issue is very high in order to achieve the desired resistance against the regulations. The present study involved the numerical and experimental analysis of nine concrete frames, consisting of three concrete frames, three concrete frames with bracing, and three concrete frames with a TADAS damper. The purpose of this study is to strengthen the damaged concrete frame using braces and TADAS dampers. Observations were made of the frames as they were subjected to controlled displacement. Also, ABAQUS software was used to compare numerical and experimental results. According to the results, the software was sufficiently capable of modeling the studied frames. Additionally, a parametric study was conducted on the thickness and number of bending plates. Thickness increases from 8 mm to 12 mm, 8 mm to 15 mm, and 8 mm to 20 mm, increasing the base shear by about 6.7%, 11.1%, and 25%, respectively. Furthermore, increasing the number of plates from 4 to 5, 4 to 6, and 4 to 7 increased base shears by about 4.5%, 8.4%, and 14%, respectively.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.419-428
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• 2013

In this study, experimental research was carried out to evaluate the constructability and seismic performance of high strength R/C exterior beam-column joints regions, with or without the shear reinforcement, using high ductile fiber-reinforced mortar. Five specimens of retrofitted the exterior beam-column joint regions using high ductile fiber-reinforced mortar are constructed and tested for their retrofit performances. Specimens designed by retrofitting the exterior beam-column joint regions (BCJNSP series) of existing reinforced concrete building showed a stable mode of failure and an increased its maximum load-carrying capacity by 1.09~2.03 times in comparison with specimen of BCJNS due to the effect of enhancing dispersion of crack control at the time of initial loading and bridging of fiber from retrofitting new high ductile materials during testing. Specimens of BCJNSP series attained its maximum load carrying capacity by 0.92~0.96 times and increased its energy dissipation capacity by 1.62 times when compared to standard specimen of BCJC with a displacement ductility of 4.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.753-760
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• 2012

In this study, experimental research was carried out to evaluate and improve the constructability and seismic performance of high strength R/C interior beam-column joints regions, with or without the shear reinforcement, using high ductile fiber-reinforced mortar. Six specimens of retrofitted the beam-column joint regions using high ductile fiber-reinforced mortar are constructed and tested for their retrofit performances. Specimens designed by retrofitting the interior beam-column joint regions (IJNS series) of existing reinforced concrete building showed a stable mode of failure and an increase in load-carrying capacity due to the enhancement of crack dispersion by fiber bridging from using new high ductile materials for retrofitting. Specimens of IJNS series, designed by the retrofitting of high ductile fiber-reinforced mortar in beam-column joint regions increased its maximum load carrying capacity by 96~102.8% and its energy dissipation capacity by 0.99~1.11 folds when compared to standard specimen of SIJC with a displacement ductility of 5.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.41-54
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• 1999

Because of relatively heavy dead weight of concrete itself and unavoidable heat of massive concrete in bridge piers, circular hollow columns are widely used in Korean highway bridges. Since the occurrence of 1995 Kobe earthquake, there have been much concerns about seismic design for various infrastructures, inclusive of bridge structures. It is, however, understood that there are not much research works for nonlinear behavior of circular hollow columns subjected to eqrthquake motions. The objective of this experimental research is to investigate nonlinear behavior of circular hollow reinforced concrete bridge piers under the quasi-static cyclic load, and then to enhance their ductility by strengthening the plastic hinge region with glassfiber sheets. Particularly for this test, constant 10 cyclic loads have been repeatedly actuated to investigate the magnitude of strength degradation for the displacement ductility factor. Important test parameters are seismic design, confinement steel ratio, axial force and load pattern. It is observed from quasi-static tests for 7 bridge piers that the seismically designed columns and the retrofitted columns show better performance than the nonseismically designed colums, i.e. about 20% higher for energy dissipation capacity and about 70% higher for curvatures.