• Earthquakes and Structures
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• v.11 no.2
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• pp.371-386
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• 2016

During the last decades, many destructive earthquakes occurred in Algeria, particularly in the northern part of the country (Chlef (1980), Constantine (1985), Tipaza (1989), Mascara (1994), Ain-Benian (1996), Ain Temouchent (1999), Beni Ourtilane (2000), and recently $Boumerd{\acute{e}}s$ (2003), causing enormous losses in human lives, buildings and equipments. In order to reduce this risk and avoid serious damages to the strategic existing buildings, the authorities of the country, aware of this risk and in order to have the necessary elements that let them to know and estimate the potential losses in advance, with an acceptable error, and to take the necessary countermeasures, decided to invest into seismic upgrade, strengthening and retrofitting of those buildings. To do so, seismic vulnerability study of this category of buildings has been considered. Structural analysis is performed based on the site investigation (inspection of the building, collecting data, materials characteristics, general conditions of the building, etc.), and existing drawings (architectural plans, structural design, etc.). The aim of these seismic vulnerability studies is to develop guidelines and a methodology for rehabilitation of existing buildings. This paper presents the methodology, based on non linear and seismic analysis of existing buildings, followed in this study and summarizes the vulnerability assessment and strengthening of one of the strategic buildings according to the new Algerian code RPA 99/version 2003. As a direct application of this methodology, both, static equivalent method and non linear dynamic analysis, of composite concrete masonry existing building in the city of "CONSTANTINE", located in the east side of ALGERIA, are presented in this paper.

• Journal of Environmental Health Sciences
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• v.37 no.2
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• pp.141-149
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• 2011

This study aimed for developing a two stage dual media filtration system. It has a sand and activated carbon layer above the under-drain system, and a sand layer above the middle-drain system for pretreatment. When retrofitting an old sand filter bed or designing a new one, this technology can substitute the existing sand filter bed without requiring a new plant site. The removal rate of total particle is 93, and 3~7 ${\mu}m$ and 5~15 ${\mu}m$ particles are all 97%. These high removal efficiencies of each pollutant due to adsorption and biological oxidation in activated carbon filter layer. The best backwashing method of two stage dual media filtration system is ascertained by air injection, air + water injection and water injection sequence. In this study, a pilot plant of two stage and dual filtration system was operated for 4 months in water treatment plant. The stability of turbidity was maintained below 1 NTU. The TOC, THMFP and HAAFP were removed about 90% by two stage and dual media filtration system, which is almost 2 times higher than existing water treatment plant.

• Structural Engineering and Mechanics
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• v.61 no.3
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• pp.407-417
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• 2017

RC shear walls are considered one of the main lateral resisting members in buildings. In recent years, FRP has been widely utilized in order to strengthen and retrofit concrete structures. A number of experimental studies used CFRP sheets as an external bracing system for retrofitting of RC shear walls. It has been found that the common mode of failure is the debonding of the CFRP-concrete adhesive material. In this study, behavior of RC shear wall was investigated with three different micro models. The analysis included 2D model using plane stress element, 3D model using shell element and 3D model using solid element. To allow for the debonding mode of failure, the adhesive layer was modeled using cohesive surface-to-surface interaction model at 3D analysis model and node-to-node interaction method using Cartesian elastic-plastic connector element at 2D analysis model. The FE model results are validated comparing the experimental results in the literature. It is shown that the proposed FE model can predict the modes of failure due to debonding of CFRP and behavior of CFRP strengthened RC shear wall reasonably well. Additionally, using 2D plane stress model, many parameters on the behavior of the cohesive surfaces are investigated such as fracture energy, interfacial shear stress, partial bonding, proposed CFRP anchor location and using different bracing of CFRP strips. Using two anchors near end of each diagonal CFRP strips delay the end debonding and increase the ductility for RC shear walls.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.1 s.41
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• pp.9-16
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• 2005

The purpose of this paper is to present a design procedure of a friction damper for controlling elastic and inelastic responses of building structures under earthquake excitation. The equivalent damping and period increased by the friction damper are estimated using ATC-40 and ATC-55 procedures which provide equivalent linear system for bilinear one, and then a design formula to achieve target performance response level by the friction damper is presented. It is identified that there exists error between the responses obtained by this formula and by performing nonlinear analysis and the features of the error vary according to the hardening ratio, yield strength ratio, and structural period. Equations for compensating the error are proposed based on the least square method, and the results from numerical analysis indicate that the error is significantly reduced. The proposed formula can be used without much error for designing a friction damper for retrofitting a structure showing elastic or inelastic behavior.

• Steel and Composite Structures
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• v.23 no.2
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• pp.187-194
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• 2017

To reuse a broken plain concrete (PC) arch, a retrofitting method was proposed to ensure excellent structural performances, in which carbon fiber reinforced polymers (CFRPs) were applied to repair and strengthen the damaged PC arch through bonding and wrapping techniques. Experiments were carried out to reveal the deformation and the load carrying capacity of the retrofitted composite arch. Based on the experiments, repairing and strengthening effects of the CFRP retrofitted broken arch were revealed. Simplified analysing model was suggested to predict the peak load of the CFRP retrofitted broken arch. According to the research, it is confirmed that absolutely broken PC arch can be completely repaired and reinforced, and even behaves more excellent than the intact PC arch when bonded together and strengthened with CFRP sheets. Using CFRP bonding/wrapping technique a novel efficient composite PC arch structure can be constructed, the comparison between rebar reinforced concrete (RC) arch and composite PC arch reveals that CFRP reinforcements can replace the function of steel bars in concrete arch.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.1-9
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• 2014

Improving the earthquake resistance of buildings through seismic retrofitting using steel braces can result in brittle failure at the connection between the brace and the building, as well as buckling failure of the braces. In this study, a non-compression cross-bracing system using the Carbon Fiber Composite Cable (CFCC), which consists of CFCC bracing and bolt connection was proposed to replace the conventional steel bracing. This paper presented the seismic resistance of a reinforced concrete frame strengthened using CFCC X-bracing. Cyclic loading tests were carried out, and the maximum load carrying capacity and ductility were investigated, together with hysteresis of the lateral load-drift relations. Test results revealed that the CFCC X-bracing system installed RC frames enhanced markedly the strength capacity and no buckling failure of the bracing was observed.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.323-331
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• 2012

This paper presents a new strengthening method on concrete column against seismic loads for structural performance tests. An X-bracing using high performance carbon fiber threads called the "Carbon fiber anchor X-bracing system" is used to connect RC frames internally. The carbon fiber sheet is wrapped around the column to fix the top and bottom of the column after Super anchor was installed by drilling hole on the column. The structural performance was evaluated experimentally and analytically. Two types of columns specimens were made; flexure fracture scaled model and shear fracture scaled model. For the performance evaluation, cyclic loading tests were conducted on moment and shear resisting columns with and without X bracing. Test results confirmed that the bracing system installed on RC columns enhanced the strength capacity and provided adequate ductility.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.3
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• pp.287-294
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• 2008

This study proposes a novel method for in service evaluation of tension force of a prestressed 7-wire strand which is frequently employed for retrofitting bridge superstructure. The smart strand is made by replacing the straight king wire of the strand with an instrumented steel tube in which the FBG sensor is embedded. Since the strain of the smart strand can easily be measured using the sensor, it is possible to monitor tension force of the strand during the service. For the sake of demonstrating effectiveness of the proposed strand, we came up with a 7.0m long prototype with 2 FBG sensors, and it is applied as an external tendon to a 6.4m long and 0.6 high RC T-shaped beam. A loading-unloading test has been carried out, and estimated tension forces using the smart strand are compared with measured forces by load cell. The comparison showed that the proposed smart tendon is useful and accurate for monitering tension force of the prestressed tendon.

• Structural Engineering and Mechanics
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• v.75 no.6
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• pp.675-684
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• 2020

An innovative retrofit method using pre-stressed steel strips and externally-bonded steel plates was presented in this paper. With the aim of exploring the seismic performance of the retrofitted RC interior joints, four 1/2-scale retrofitted joint specimens together with one control specimen were designed and subjected to constant axial compression and cyclic loading, with the main test parameters being the volume of steel strips and the existence of externally-bonded steel plates. The damage mechanism, force-displacement hysteretic response, force-displacement envelop curve, energy dissipation and displacement ductility ratio were analyzed to investigate the cyclic behavior of the retrofitted joints. The test results indicated that all the test specimens suffered a typical shear failure at the joint core, and the application of externally-bonded steel plates and that of pre-stressed steel strips could effectively increase the lateral capacity and deformability of the deficient RC interior joints, respectively. The best cyclic behavior could be found in the deficient RC interior joint retrofitted using both externally-bonded steel plates and pre-stressed steel strips due to the increased lateral capacity, displacement ductility and energy dissipation. Finally, based on the test results and the softened strut and tie model, a theoretical model for determining the shear capacity of the retrofitted specimens was proposed and validated.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.6
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• pp.311-319
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• 2019

The number of aged bridges is increasing so that bridges over 30 years old account for about 11% of all bridges. Consequently, the development of a seismic performance evaluation method that considers the effects of ageing is essential for a seismic retrofitting process for improvement of the seismic safety of existing old bridges. Assessment of the damage situation of bridges after the recent earthquakes in Korea has been limited to the bearings, anchor, and concrete mortar on piers. The purpose of this study is to evaluate the seismic responses of PSC box girder bridges by considering the ageing effect of rubber bearings (RBs) and lead-rubber bearings (LRBs). The modification factor proposed by AASHTO is used to take into account the ageing effect in the bearings. PSC box girder bridges with RBs and LRBs were 3D modeled and analyzed with the OpenSEES program. In order to evaluate the ageing effect of RBs and LRBs, 40 near fault and 40 far field records were used as the input earthquakes. When considering the effect of ageing, the displacement responses and shear forces of bridge bearings (RBs and LRBs) were found to increase mostly under the analytical conditions. It was shown that the effect of ageing is greater in the case of RBs than in the case of LRBs.