• Title/Summary/Keyword: retrofitting method

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Retrofitting of Reinforced Concrete Wall to Increase Axial Load Capacity (벽체의 축력 증진 방안 연구)

  • 신영수;홍기섭;최완철;홍영균;김상준
    • Proceedings of the Korea Concrete Institute Conference
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    • 1997.10a
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    • pp.673-678
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    • 1997
  • The main structural system of domestic apartments is the wall-slab system. In such structures, the lack of material strength of wall affects severely on the safety of structures. It is fond frequently that the wall in the apartment structures has lower strength in concrete than the specified. This paper presents the retrofitting method of the reinforced concrete wall with low concrete strength. The tests are performed to investigate the structural behavior and the effects of external reinforcing and thickness increasing on the axial load capacity of walls. Six specimens are tested. As the test results, the external reinforcing method is less effective than thickness increasing method.

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Use of a Genetic Algorithm to Predict the Stiffness Reductions and Retrofitting Effects on Structures Subjected to Seismic Loads (지진하중을 받은 구조물의 유전알고리즘 기반 강성저하 및 보강 효과 추정)

  • Lee, Jae-Hun;Ahn, Kwang-Sik;Lee, Sang-Youl
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.33 no.3
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    • pp.193-199
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    • 2020
  • This study examines a method for identifying stiffness reductions in structures subjected to seismic loads and retrofitting effects using a combination of the finite element method and an advanced genetic algorithm. The novelty of this study is the application of seismic loading and its response to anomalies in the tested structure. The technique described in this study may enable not only detection of damaged elements but also the identification of their locations and the extent of damage due to seismic loading. To demonstrate the feasibility of the method, the advanced genetic algorithm is applied to frame and truss bridge structures subjected to El Centro and Pohang seismic loads. The results reveal the excellent computational efficiency of the method and its ability to prevent severe damage from earthquakes.

Retrofit Method of Damaged Flexural Wall (피해가 발생된 휨벽체의 내진보강에 관한 연구)

  • 서수연;이용택;이현호;이리형;천영수;양지수
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.05a
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    • pp.811-816
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    • 2002
  • An experimental work is performed to evaluate the retrofit method of damaged flexural walls. For two flexural walls damaged up to almost failure, reinforcements yielded and concrete below height of 1d are replaced with new reinforcements and steel fiber concrete, respectively. In order to evaluate the effectiveness of Aramid sheet for retrofitting walls, Aramid sheet is also, attached to longitudinal direction and rolled horizontal direction of one wall specimen. Horizontal cyclic loads are applied to the top of the specimen with constant axial load. Test result showed that retrofitting with steel fiber concrete after replacing reinforcements can not afford to recover 100% of the wall capacity before damage. However, the capacity of walls could be sufficiently strengthened by using Aramid sheet.

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Study on Strengthening Effect and Failure Behavior of CFS Strengthened High Strength RC Columns after Cross -sectional Shape Modification (4각기둥의 단면형상 변형 후 CFS로 보강한 고강도 철근 콘크리트 기둥의 보강효과 및 파괴거동 연구)

  • Jun Kyung-Suk;Kim Jang-Ho;Park Seok-Kyun;Kim Jin-Keun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05a
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    • pp.259-262
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    • 2005
  • Numerous studies showed that safety and serviceability of many concrete infrastructures and buildings built in 1970's have capacity less than their design capacities and thereby require immediate retrofitting. Currently, these aged concrete structure are being repaired using many repair and strengthening methods developed in the past. Therefore, in this study, a repairing and strengthening method for retrofitting high strength concrete columns that can effectively improve the performance of high strength concrete columns is developed. The square high strength concrete column's cross-sectional shape is modified to octagonal shape by attaching precast members on the surface of the column. Then, the octagonal column surface is wrapped using Carbon Fiber Sheets (CFS). The method allowed the maximum usage of confinement effect of externally wrapped CFS, which resulted in improved strength and ductility of repaired high strength concrete columns.

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Strength Demand Calculation for Retrofitting Unreinforced Masonry Buildings Based on the Displacement Coefficient Method and the Preliminary Seismic Evaluation Procedure (변위계수법 및 약산식 내진성능평가에 기초한 비보강 조적조 건물의 내진보강 요구강도 산정)

  • Seol, Yun Jeong;Park, Ji-Hun;Kwak, Byeong Hun;Kim, Dae Ho
    • Journal of the Earthquake Engineering Society of Korea
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    • v.26 no.1
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    • pp.31-38
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    • 2022
  • Based on the nonlinear static analysis and the approximate seismic evaluation method adopted in "Guidelines for seismic performance evaluation for existing buildings, two methods to calculate strength demand for retrofitting individual structural walls in unreinforced masonry buildings are proposed." The displacement coefficient method to determine displacement demand from nonlinear static analysis results is used for the inverse calculation of overall strength demand required to reduce the displacement demand to a target value meeting the performance objective of the unreinforced masonry building to retrofit. A preliminary seismic evaluation method to screen out vulnerable buildings, of which detailed evaluation is necessary, is utilized to calculate overall strength demand without structural analysis based on the difference between the seismic demand and capacity. A system modification factor is introduced to the preliminary seismic evaluation method to reduce the strength demand considering inelastic deformation. The overall strength demand is distributed to the structural walls to retrofit based on the wall stiffness, including the remaining walls or otherwise. Four detached residential houses are modeled and analyzed using the nonlinear static and preliminary evaluation procedures to examine the proposed method.

A Study on the Operational Plan and Acquisition Method for CO2 Carrier by Retrofitting Existing Vessels and New Ship-Building (중고선 개조와 신조에 의한 CO2 운송선 확보 및 운용방안에 관한 연구)

  • Shin, Myung-Soo;Park, Beom Jin;Ki, Min Suk;Lee, Dae Hak
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.18 no.1
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    • pp.15-21
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    • 2015
  • This paper presents the feasibility study on $CO_2$ carrier for carbon dioxide marine geological storage. Conceptual design was carried out to acquire $CO_2$ carriers by retrofitting existing vessels and new ship-building. Based on conceptual design, the acquisition cost of $CO_2$ carriers was estimated. Finally, necessary expense and number of ships were estimated based on operational plans for the assumed scenario.

Seismic Retrofit Design of RHS Column-to-H Beam Connections (RHS 기둥-H형강보 접합부의 내진보강 설계)

  • Kim, Young Ju;Oh, Sang Hoon
    • 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.

Vibrational characteristic of FG porous conical shells using Donnell's shell theory

  • Yan, Kai;Zhang, Yao;Cai, Hao;Tahouneh, Vahid
    • Steel and Composite Structures
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    • v.35 no.2
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    • pp.249-260
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    • 2020
  • The main purpose of this research work is to investigate the free vibration of conical shell structures reinforced by graphene platelets (GPLs) and the elastic properties of the nanocomposite are obtained by employing Halpin-Tsai micromechanics model. To this end, a shell model is developed based on Donnell's theory. To solve the problem, the analytical Galerkin method is employed together with beam mode shapes as weighting functions. Due to importance of boundary conditions upon mechanical behavior of nanostructures, the analysis is carried out for different boundary conditions. The effects of boundary conditions, semi vertex angle, porosity distribution and graphene platelets on the response of conical shell structures are explored. The correctness of the obtained results is checked via comparing with existing data in the literature and good agreement is eventuated. The effectiveness and the accuracy of the present approach have been demonstrated and it is shown that the Donnell's shell theory is efficient, robust and accurate in terms of nanocomposite problems.

Cost-effective method for reducing local failure of floodwalls verified by centrifuge tests

  • Chung R. Song;Binyam Bekele;Brian D. Sawyer;Ahmed Al-Ostaz;Alexander Cheng;Vanadit-Ellis Wipawi
    • Geomechanics and Engineering
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    • v.33 no.2
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    • pp.155-165
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    • 2023
  • Hurricane Katrina swept New Orleans, Louisiana, USA, in 2005, causing more than 1,000 fatalities and severe damage to the flood protection system. Recovery activities are complete, however, clarifying failure mechanisms and devising resilient and cost-effective retrofitting techniques for the flood protection system are still of utmost importance to enhance the general structural integrity of water retaining structures. This study presents extensive centrifuge test results to find various failure mechanisms and effective retrofitting techniques for a levee system. The result confirmed the rotational failure and translational failure mechanisms for the London Ave. Canal levee and 17th St. Canal levee, respectively. In addition, it found that the floodwalls with fresh waterstop in their joints perform better than those with old/weathered waterstop by decreasing pore water pressure build-up in the levee. Structural caps placed on the top of the joints between I-walls could also prevent local failure by spreading the load to surrounding walls. At the same time, the self-sealing bentonite-sand mixture installed along the riverside of floodwalls could mitigate the failure of floodwalls by blocking the infiltration of seepage water into the gap formed between levee soils and floodwalls.

Evaluation of Shear Strength of Unreinforced Masonry Walls Retrofitted by Fiber Reinforced Polymer Sheet (FRP로 보강한 비보강 조적 벽체의 전단강도 산정)

  • Bae, Baek-Il;Yun, Hyo-Jin;Choi, Chang-Sik;Choi, Hyun-Ki
    • Journal of the Korea Concrete Institute
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    • v.24 no.3
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    • pp.305-313
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    • 2012
  • Unreinforced masonry buildings represent a significant portion of the existing and historical buildings around the world. Recent earthquakes have shown the need for seismic retrofitting for these types of buildings. Various types of retrofitting materials (i.e., shotcrete, ECC and Fiber Reinforced Polymer sheets (FRPs)) for unreinforced masonry buildings (URM) have been developed. Engineers prefer to use FRPs, because these materials enhance the shear strength of the wall without expansion of wall sectional area and adding weight to the total structure. However, the complexity of the mechanical behavior of the masonry wall and the lack of experimental data from walls retrofitted by FRPs may cause problems for engineers to determine an appropriate retrofitting level. This paper investigate in-plane behavior of URM and retrofitted masonry walls using two different types of FRP materials to determine and provide information for the retrofitting effect of FRPs on masonry shear walls. Specimens were designed to idealize the wall of a low-rise apartment which was built in 1970s in Korea with no seismic reinforcements with an aspect ratio of 1. Retrofitting materials were carbon FRP and Hybrid sheets which have different elastic modulus and ultimate strain capacities. Consequently, this study evaluated the structural capacity of masonry shear walls and the retrofitting effect of an FRP sheet for in-plane behavior. Also, the results were compared to the results obtained from the evaluation method for a reinforced concrete beam retrofitted with FRPs.