• Advances in concrete construction
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• 제10권2호
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• pp.93-104
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• 2020

Basalt fiber is an eco-friendly fiber and comparatively newer to the world of fiber-reinforced polymer (FRP) composites. A limited number of studies have been reported in the literature on the strengthening of reinforced concrete (RC) beams with basalt fiber reinforced polymer (BFRP). The present experimental work explores the feasibility of using the BFRP strips for shear strengthening of the RC beams. The strengthening schemes include full wrap and U-wrap. A simple mechanical anchorage scheme has been introduced to prevent the debonding of U-wrap as well as to utilize the full capacity of the BFRP composite. The effect of varying shear span-to-effective depth (a/d) ratio on the behavior of shear deficient RC beams strengthened with BFRP strips under different schemes is examined. The RC beams were tested under a four-point loading system. The study finds that the beams strengthened with and without BFRP strips fails in shear for a/d ratio 2.5 and the enhancement of the shear capacity of strengthened beams ranges from 5% to 20%. However, the strengthened beams fail in flexure, and the control beam fails in shear for a higher a/d ratio, i.e., 3.5. The experimental results of the present study have been compared with the analytical study and found that the latter gives conservative results.

• Steel and Composite Structures
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• 제38권2호
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• pp.165-176
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• 2021

Existing research on confined concrete filled steel tubular (CCFT) columns has been mainly focused on static or cyclic loading. In this paper, square section CCFT and CFT columns were tested under both static and impact loading, using a 10,000 kN capacity compression test machine and a drop weight testing equipment. Research parameters included bonded and unbonded fiber reinforced polymer (FRP) wraps, with carbon, basalt and glass FRPs (or CFRP, BFRP, and GFRP), respectively. Time history curves for impact force and steel strain observed are discussed in detail. Experimental results show that the failure modes of specimens under impact testing were characterized by local buckling of the steel tube and cracking at the corners, for both CCFT and CFT columns, similar to those under static loading. For both static and impact loading, the FRP wraps could improve the behavior and increase the loading capacity. To analyze the dynamic behavior of the composite columns, a finite element, FE, model was established in LS-DYNA. A simplified method that is compared favorably with test results is also proposed to predict the impact load capacity of square CCFT columns.

• Advances in nano research
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• 제5권4호
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• pp.337-357
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• 2017

Knowledge of thin films mechanical properties is strongly associated to the reliability and the performances of Nano Electro Mechanical Systems (NEMS). In the literature, there are several methods for micro materials characterization. Bulge test is an established nondestructive technique for studying the mechanical properties of thin films. This study improve the performances of NEMS by investigating the mechanical behavior of Nano rectangular thin film (NRTF) made of new material embedded in Nano Electro Mechanical Systems (NEMS) by developing the bulge test technique. The NRTF built from adhesively-bonded layers of basalt fiber reinforced polymer (BFRP) laminate composite materials in Nano size at room temperature and were used for plane-strain bulging. The NRTF is first pre-stressed to ensure that is no initial deflection before applied the loads on NRTF and then clamped between two plates. A differential pressure is applying to a deformation of the laminated composite NRTF. This makes the plane-strain bulge test idea for studying the mechanical behavior of laminated composite NRTF in both the elastic and plastic regimes. An exact solution of governing equations for symmetric cross-ply BFRP laminated composite NRTF was established with taking in-to account the effect of the residual strength from pre-stressed loading. The stress-strain relationship of the BFRP laminated composite NRTF was determined by hydraulic bulging test. The NRTF thickness gradation in different points of hemisphere formed in bulge test was analysed.

• Smart Structures and Systems
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• 제14권3호
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• pp.307-325
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• 2014

A newly developed method based on energy is presented to study the damage pattern of FRP material. Basalt fiber reinforced polymer (BFRP) is employed to monitor the damage under fatigue loading. In this study, acoustic emission technique (AE) combined with scanning electronic microscope (SEM) technique is employed to monitor the damage evolution of the BFRP specimen in an approximate continuous scanning way. The AE signals are analyzed based on the wavelet transform, and the analyses are confirmed by SEM images. Several damage patterns of BFRP material, such as matrix cracking, delamination, fiber fracture and their combinations, are identified through the experiment. According to the results, the cumulative energy (obtained from wavelet coefficients) of various damage patterns are closely related to the damage evolution of the BFRP specimens during the entire fatigue tests. It has been found that the proposed technique can effectively distinguish different damage patterns of FRP materials and describe the fatigue damage evolution.

• 한국구조물진단유지관리공학회 논문집
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• 제27권6호
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• pp.47-54
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• 2023

본 연구에서는 GFRP, BFRP와 CFRP 보강근으로 보강된 콘크리트 시험체의 인장 거동 특성을 실험적으로 분석하였다. FRP 보강근의 인장강도는 설계강도와 유사하게 나타났으나, 탄성계수는 다소 낮게 측정되었다. 또한 인장강화 시험체는 OPC와 SFRC를 사용하여 150(W)×150(B)×1000(H) mm의 크기로 제작하였다. 균열간격은 탄성계수가 낮고 표면이 보다 매끄러운 GFRP 보강근이 가장 크게 나타났으며, 표면이 다소 거친 BFRP와 탄성계수가 높은 CFRP 보강근의 균열간격은 비슷하게 분석되었다. 하중-변형률관계에서도 GFRP보강근은 균열후 다소 급격한 거동을 보인것에 반하여 BFRP와 CFRP 보강근은 균열발생시 다소 안정적인 거동후 일정수준은 인장강화 효과를 유지하였다. 인장강화지수의 경우 직경이 증가할수록 인장강화지수는 다소 작게 분석되었으며, BFRP보다 GFRP의 경우가 인장강화지수는 높게 분석되었다.

• 한국구조물진단유지관리공학회 논문집
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• 제24권6호
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• pp.153-160
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• 2020

지진동 하의 구조 시스템에서 기둥은 가장 중요한 구조 요소 중 하나이다. 이러한 관계로, 철근콘크리트(RC) 기둥의 내진 성능에 FRP 보강이 미치는 영행을 평가하기 위하여 광범위한 실험 연구가 이루어졌다. 이 중 상당수는 CFRP 또는 GFRP로 보강된 원형 단면 또는 정사각형 단면의 RC 기둥의 지진 거동에 집중하였다. 단면의 형태가 FRP 보강으로 인한 구속 효과에 영향을 미치기 때문에, 보강 효과와 최종 파괴 패턴이 형상에 따라 상이할 수 있다. 본 연구에서는 현무암 섬유를 함유한 BFRP 시트와 복합섬유 패널로 보강한 직사각형 단면을 가진 RC 기둥의 지진 거동을 살펴보기 위하여 반복하중 실험을 수행하였다. 실험 결과는 보강 효과가 크지 않았음을 보여주는데, BFRP 시트와 복합섬유 패널에 의한 구속 효과의 증가가 미미했음을 의미하며, 이는 기둥 단면 형상에 일부 기인하는 것으로 판단된다.

• Advances in concrete construction
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• 제6권2호
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• pp.199-220
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• 2018

In this study, the effects of sulphuric acid on the mechanical performance and the durability of Engineered Cementitious Composites (ECC) specimens were investigated. The carbon fiber reinforced polymer (CFRP) and basalt fiber reinforced polymer (BFRP) fabrics were used to evaluate the performances of the confined and unconfined ECC specimens under static and cyclic loading in the acidic environment. In addition, the use of CFRP and BFRP fabrics as a rehabilitation technique was also studied for the specimens exposed to the sulphuric acid environment. The polyvinyl alcohol (PVA) fiber with a fraction of 2% was used in the research. Two different PVA-ECC concretes were produced using low lime fly ash (LCFA) and high lime fly ash (HCFA) with the fly ash-to-OPC ratio of 1.2. Unwrapped PVA-ECC specimens were also produced as a reference concrete and all concrete specimens were continuously immersed in 5% sulphuric acid solution ($H_2SO_4$). The mechanical performance and the durability of specimens were evaluated by means of the visual inspection, weight change, static and cyclic loading, and failure mode. In addition, microscopic changes of the PVA-ECC specimens due to sulphuric acid attack were also assessed using scanning electron microscopy (SEM) to understand the macroscale behavior of the specimens. Results indicated that PVA-ECC specimens produced with low lime fly ash (LCFA) showed superior performance than the specimens produced with high lime fly ash (HCFA) in the acidic environment. In addition, confinement of ECC specimens with BFRP and CFRP fabrics significantly improved compressive strength, ductility, and durability of the specimens. PVA-ECC specimens wrapped with carbon FRP fabric showed better mechanical performance and durability properties than the specimens wrapped with basalt FRP fabric. Both FRP materials can be used as a rehabilitation material in the acidic environment.

• Earthquakes and Structures
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• 제14권5호
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• pp.379-388
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• 2018

This study aims to identify the effect of both longitudinal reinforcement details and damage level on making a decision of repairing pre-damaged bridge columns using basalt fiber reinforced polymer (BFRP) jackets. Two RC bridge columns with improper details of the longitudinal and/or transverse reinforcement were tested under the effect of a constant axial load and increasing lateral cyclic loading. Test results showed that the lap-splice column exhibited an inferior performance where it showed rapid degradation of strength before achieving the theoretical strength and its deformation capacity was limited; however, quick restoration is possible through a suitable rehabilitation technique. On the other hand, expensive repair or even complete replacement could be the decision for the column with the confinement failure mode. After that, a rehabilitation technique using external BFRP jacket was adopted. Performance-based design details guaranteeing the enhancement in the inelastic performance of both damaged columns were addressed and defined. Test results of the repaired columns confirmed that both reparability and the required repairing time of damage structures are dependent on the reinforcement details at the plastic hinge zone. Furthermore, lap-splice of longitudinal reinforcement could be applied as a key design-tool controlling reparability and restorability of RC structures after massive actions.

• 콘크리트학회논문집
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• 제22권1호
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• pp.93-102
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• 2010

최근, 토목 분야에서의 RC 구조물의 보강을 위한 FRP 사용이 증대되고 있다. 특히, FRP로 보강된 구조물의 폭발저항성능에 대한 관심이 증가하면서 폭발하중에 대한 FRP의 보강 효과에 대한 검토가 필요하게 되었다. 폭발하중을 받는 FRP의 보강 효과를 측정하기 위해 9개의 $1,000{\times}1,000{\times}150\;mm$의 RC 패널 시편을 제작하였으며, 각 시편에는 탄소섬유복합재(CFRP), 폴리우레아, 폴리우레아와 CFRP의 동시 보강한 경우와 현무암 섬유 복합재(BFRP, basalt fiber reinforced polymer)로 보강하여 각 보강 섬유의 폭발 저항 성능을 검토하고자 하였다. 폭발하중은 ANFO 15.88 kg의 장약량을 1.5 m 이격거리로 적용하였으며, 측정하고자 한 데이터는 초기 압력폭발압력하중 뿐만 아니라, 반사압력, 충격량, 중앙부의 처짐, 철근, 콘크리트 및 FRP의 변형률를 측정하였다. 각 시편의 파괴모드는 control 시편인 일반 강도 시편과 비교하였다. 실험을 통해 보강 재료에 따른 방폭 성능을 파악하였으며, 이 실험 결과는 구조물에 요구되는 방호 성능 및 방호도에 따라 보강 재료를 선택하는 기초자료로 활용될 수 있다.

• Steel and Composite Structures
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• 제16권5호
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• pp.491-506
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• 2014

Buckling-restrained braces (BRBs) have excellent hysteretic behavior while buckling-restrained braced frames (BRBFs) are susceptible to residual lateral deformations. To address this drawback, a novel self-centering (SC) BRB with Basalt fiber reinforced polymer (BFRP) composite tendons is presented in this work. The configuration and mechanics of proposed BFRP-SC-BRBs are first discussed. Then an 1840-mm-long BFRP-SC-BRB specimen is fabricated and tested to verify its hysteric and self-centering performance. The tested specimen has an expected flag-shaped hysteresis character, showing a distinct self-centering tendency. During the test, the residual deformation of the specimen is only about 0.6 mm. The gap between anchorage plates and welding ends of bracing tubes performs as expected with the maximum opening value 6 mm when brace is in compression. The OpenSEES software is employed to conduct numerical analysis. Experiment results are used to validate the modeling methodology. Then the proposed numerical model is used to evaluate the influence of initial prestress, tendon diameter and core plate thickness on the performance of BFRP-SC-BRBs. Results show that both the increase of initial prestress and tendon diameters can obviously improve the self-centering effect of BFRP-SC-BRBs. With the increase of core plate thickness, the energy dissipation is improved while the residual deformation is generated when the core plate strength exceeds initial prestress force.