• Title, Summary, Keyword: retrofitting

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Modal parametric changes in a steel bridge with retrofitting

  • Walia, Suresh Kumar;Vinayak, Hemant Kumar;Kumar, Ashok;Parti, Raman
    • Steel and Composite Structures
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    • v.19 no.2
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    • pp.385-403
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    • 2015
  • This paper presents the status improvement of an old damaged deck type rural road steel truss bridge through the modal parametric study after partial retrofitting. The dynamic and static tests on bridge were carried out as in damaged state and after partial retrofitting. The dynamic testing on the steel bridge was carried out using accelerometers under similar environmental conditions with same speed of the moving vehicle. The comparison of the modal parameters i.e., frequency, mode shape mode shape curvature, modal strain energy, along with the deflection parameter are studied with respect to structural analytical model parameters. The status up gradation for the upper and downstream truss obtained was different due to differential level of damage in the bridge. Also after retrofitting the structural elemental behavior obtained was not same as desired. The damage level obtained through static tests carried out using total station indicated further retrofitting requirement.

Combined seismic and energy upgrading of existing reinforced concrete buildings using TRM jacketing and thermal insulation

  • Gkournelos, Panagiotis D.;Bournas, Dionysios A.;Triantafillou, Thanasis C.
    • Earthquakes and Structures
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    • v.16 no.5
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    • pp.625-639
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    • 2019
  • The concept of the combined seismic and energy retrofitting of existing reinforced concrete (RC) buildings was examined in this paper through a number of case studies conducted on model buildings (simulating buildings of the '60s-'80s in southern Europe) constructed according to outdated design standards. Specifically, seismic and thermal analyses have been conducted prior to and after the application of selected retrofitting schemes, in order to quantify the positive effect that retrofitting could provide to RC buildings both in terms of their structural and energy performance. Advanced materials, namely the textile reinforced mortars (TRM), were used for providing seismic retrofitting by means of jacketing of masonry infills in RC frames. Moreover, following the application of the TRM jackets, thermal insulation materials were simultaneously provided to the RC building envelope, exploiting the fresh mortar used to bind the TRM jackets. In addition to the externally applied insulation material, all the fenestration elements (windows and doors) were replaced with new high energy efficiency ones. Afterwards, an economic measure, namely the expected annual loss (EAL) was used to evaluate the efficiency of each retrofitting method, but also to assess whether the combined seismic and energy retrofitting is economically feasible. From the results of this preliminary study, it was concluded that the selected seismic retrofitting technique can indeed enhance significantly the structural behaviour of an existing RC building and lower its EAL related to earthquake risks. Finally, it was found that the combined seismic and energy upgrading is economically more efficient than a sole energy or seismic retrofitting scenario for seismic areas of south Europe.

New Technique on the Improvement of Earthquake-Resistant Performance for the Retrofitting of Existing Reinforced Concrete Beam-Column Joints (철근콘크리트 보-기둥 접합부의 내진성능 개선 보강 신기술)

  • 하기주
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.2
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    • pp.73-81
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    • 2004
  • In this study, experimental research was carried out to improve earthquake-resistant performance for the retrofitting of reinforced concrete beam-column joints using carbon fiber materials in existing reinforced concrete building. Six reinforced concrete beam-column joints were constructed and tested to evaluate the retrofitting effect of test variables, such as the retrofitting materials and retrofitting region(plastic hinge, beam-column joint) under load reversals. Test results show that retrofitting specimen(RPC-CP2, RPC-CR, RJC-CP, RJC-CR), using new materials(carbon fiber plate, carbon fiber rod and carbon fiber sheet), designed by the improvement of earthquake-resistant performance and ductility, attained more load-carrying capacity and stable hysteretic behavior.

Blast analysis of concrete arch structures for FRP retrofitting design

  • Nam, Jin-Won;Kim, Ho-Jin;Yi, Na-Hyun;Kim, In-Soon;Kim, Jang-Ho Jay;Choi, Hyung-Jin
    • Computers and Concrete
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    • v.6 no.4
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    • pp.305-318
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    • 2009
  • Fiber Reinforced Polymer (FRP) is widely used for retrofitting concrete structures for various purposes. Especially, for the retrofitting of concrete structures subjected to blast loads, FRP is proven to be a very effective retrofitting material. However, a systematic design procedure to implement FRP for concrete structure retrofitting against blast loads does not exist currently. In addition, in case of concrete structures with inarticulate geometrical boundary conditions such as arch structures, an effective analysis technique is needed to obtain reliable results based on minimal analytical assumptions. Therefore, in this study, a systematic and efficient blast analysis procedure for FRP retrofitting design of concrete arch structure is suggested. The procedure is composed of three sequential parts of preliminary analysis, breach and debris analysis, and retrofit-material analysis. Based on the suggested procedure, blast analyses are carried out by using explicit code, LS-DYNA. The study results are discussed in detail.

Improvement and Evaluation of Seismic Performance of Reinforced Concrete Exterior Beam-Column Joints using Hybrid Retrofitting with AFRP Sheets and Embedded FRP Reinforcements (AFRP 쉬트와 매입형 FRP 보강재를 복합 보강한 R/C 외부 보-기둥 접합부의 내진성능 평가 및 개선)

  • Ha, Gee-Joo;Yi, Dong Ryul;Kang, Hyun-Wook
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.34 no.12
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    • pp.35-40
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    • 2018
  • In this study, experimental research was carried out to evaluate the seismic performance of reinforced concrete exterior beam-column joint regions using hybrid retrofitting with AFRP sheets and embedded CFRP reinforcements in existing reinforced concrete building. Therefore it was constructed and tested three specimens retrofitting the beam-column joint regions using such retrofitting materials. Specimens, designed by retrofitting the beam-column joint regions of existing reinforced concrete structure, were showed the stable failure mode and increase of load-carrying capacity due to the effect of crack control at the times of initial loading and confinement of retrofitting materials during testing. Specimens RBCJ-SRA3 designed by the retrofitting of AFRP sheets and embedded CFRP reinforcements in reinforced exterior beam-column joint regions were increased its maximum load carrying capacity by 1.86 times and its energy dissipation capacity by 1.65 times in comparison with standard specimen RBCJ for a displacement ductility of 5.

Analysis of unreinforced masonry (URM) walls and evaluation of retrofitting schemes for URM structures

  • Mehta, Sanjay;Saadeghvaziri, M.A.
    • Structural Engineering and Mechanics
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    • v.6 no.7
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    • pp.801-815
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    • 1998
  • An overview of an analytical model to predict mortar joint failure in unreinforced masonry (URM) structures is presented. The validity of the model is established by comparison with experimental results at element level as well as structure level. This model is then used to study the behavior of URM walls and two commonly used retrofitting schemes. Finally, effectiveness of the two retrofitting schemes in increasing strength and stiffness of existing URM walls is discussed.

Development of New Retrofitting Technology of RC Beams using High-Performance Carbon Fiber Bar and Strengthening Metal Fittings (고성능 탄소섬유봉과 보강철물을 이용한 철근콘크리트 보의 보강 신기술 개발)

  • 하기주;신종학;박연동;전찬목;이영범;김기태
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.805-810
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    • 2002
  • An experimental study was carried out to evaluate the structural performance of new retrofitting technology using high performance carbon fiber bar and strengthening metal fittings. Experimental programs were accomplished to evaluate the structural performance of test specimens, such as load-displacement relationship, crack propagation, ductility, and strain of retrofitting materials etc.. Specimens(BCR2, BCR2-AF1) designed with the new retrofitting technology using high-performance carbon fiber bar and strengthening metal fittings showed much higher load-carrying capacity and ductility compared to specimens(BC1P, BC2P, BS30) designed with the conventional retrofitting method.

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Fiber method analysis of rc beam retrofitted with turnbuckle external post-tensioning

  • Lejano, Bernardo A.
    • Computers and Concrete
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    • v.17 no.1
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    • pp.67-86
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    • 2016
  • Strengthening as well as correcting unsightly deflections of reinforced concrete (RC) beam may be accomplished by retrofitting. An innovative way to do this retrofitting that is proposed in this study utilizes turnbuckle to apply external post-tensioning. This Turnbuckle External Post-Tensioning (T-EPT) was experimentally proven to improve the serviceability and load carrying capacity of reinforced concrete beams. The T-EPT system comprises a braced steel frame and a turnbuckle mechanism to provide the prestressing force. To further develop the T-EPT, this research aims to develop a numerical scheme to analyze the structural performance of reinforced concrete beams with this kind of retrofitting. The fiber method analysis was used as the numerical scheme. The fiber method is a simplified finite element method that is used in this study to predict the elastic and inelastic behavior of a reinforced concrete beam. With this, parametric study was conducted so that the effective setup of doing the T-EPT retrofitting may be determined. Different T-EPT configurations were investigated and their effectiveness evaluated. Overall, the T-EPT was effective in improving the serviceability condition and load carrying capacity of reinforced concrete beam.

Seismic response and retrofitting proposals of the St. Titus Chruch, Heraklion, Crete, Greece

  • Tzanakis, Michael J.;Papagiannopoulos, George A.;Hatzigeorgiou, George D.
    • Earthquakes and Structures
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    • v.10 no.6
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    • pp.1347-1367
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    • 2016
  • The purpose of this work is to investigate the seismic behavior of St. Titus Church in Heraklion, Crete, Greece as well as the need of its seismic retrofitting. A numerical model of the Church is constructed using shell finite elements and it is then seismically examined using response spectrum and linear time-history analyses. Effects of soil-structure interaction have been also taken into account. The Church without retrofit is expected to exhibit extensive tensile failures and many compressive ones. Aiming to maintain the architectural character of the structure as well as to increase its seismic resistance, a retrofitting procedure involving injection of cement grout in conjunction with reinforced concrete jacketing to the internal side of the masonry walls is proposed. A numerical implementation of the proposed seismic retrofitting is performed and its effect is evaluated by response spectrum and linear time-history analyses. From the results of these analyses, it is shown that compressive failures are eliminated while only few tensile failures of local character take place.

Aseismic protection of historical structures using modern retrofitting techniques

  • Syrmakezis, C.A.;Antonopoulos, A.K.;Mavrouli, O.A.
    • Smart Structures and Systems
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    • v.4 no.2
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    • pp.233-245
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    • 2008
  • For historical masonry structures existing in the Mediterranean area, structural strengthening is of primary importance due to the continuous earthquake threat that is posed on them. Proper retrofitting of historical structures involves a thorough understanding of their structural pathology, before proceeding with any intervention measures. In this paper, a methodology is presented for the evaluation of the actual state of historical masonry structures, which can provide a useful tool for the seismic response assessment before and after the retrofitting. The methodology is mainly focused on the failure and vulnerability analysis of masonry structures using the finite element method. Using this methodology the retrofitting of historical structures with innovative techniques is investigated. The innovative technique presented here involves the exploitation of Shape Memory Alloy prestressed bars. This type of intervention is proposed because it ensures increased reversibility and minimization of interventions, in comparison with conventional retrofitting methods. In this paper, a case study is investigated for the demonstration of the proposed methodologies and techniques, which comprises a masonry Byzantine church and a masonry Cistern. Prestressed SMA alloy bars are placed into the load-bearing system of the structure. The seismic response of the non-retrofitted and the retrofitted finite element models are compared in terms of seismic energy dissipation and displacements diminution.