• Computers and Concrete
• /
• 제33권4호
• /
• pp.385-398
• /
• 2024

As concrete dominates the construction industry, alternatives to traditionally used steel reinforcement are being sought. This study explored the suitability of carbon fiber-reinforced polymer (CFRP) as a substitute within rigid frames, focusing on its impact on section ductility and overall structural durability against seismic events. However, current design guidelines address quasi-static loads, leaving a gap for dynamic or extreme circumstances. Our approach included multiscale simulations, parametric study, and energy dissipation analyses, drawing upon a unique adaptation of modified compression field theory. In our efforts to optimize macro and microparameters to improve yield strength, manage brittleness, and govern failure modes, we also recognized the potential of CFRP's high corrosion resistance. This characteristic of CFRP could significantly reduce the frequency of required repairs, thereby contributing to enhanced durability of the structures. The research reveals that CFRP's durability and seismic resistance are attributed to plastic joints within compressed fibers. Notably, CFRP can impart ductility to structural designs, effectively balancing its inherent brittleness, particularly when integrated with quasi-brittle materials. This research challenges the notion that designing bendable components with carbon fiber reinforcement is impractical. It shows that creating ductile bending components with CFRP in concrete is feasible despite the material's brittleness. This funding overturns conventional assumptions and opens new avenues for using CFRP in structural applications where ductility and resilience are crucial.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
• /
• pp.23-28
• /
• 2001

Since the steel fiber used in concrete to improve shear and ductility capacity, a number of laboratory tests have been studied to define shear strengthening effect according steel fiber contents in concrete. This study investigates shear strengthening effect of steel fiber in RC columns according to compression strength of concrete. From the structural performance test, following conclusions can be made; the maximum enhancement of shear strengthening effect can be achieved at about 1.0 %~l.5 % of steel fiber contents in comparison with shear capacity ratio, and ductility capacity slightly improved as steel fiber contents increased.

• 열처리공학회지
• /
• 제33권3호
• /
• pp.117-123
• /
• 2020

Due to high corrosion resistance, Zinc has been widely used in the automobile, shipping or construction industries as a galvanizing material. Zinc is popular as a coating element, but its low mechanical strength impede the expansion of applications as a load-bearing structure. The mechanical strength of Zinc can be increased through zinc based alloy process, but the ductility is significantly reduced. In this study, the mechanical strength and ductility of Zinc-Magnesium alloys with respect to heat treatment hold time was investigated. In order to enhance the mechanical strength of Zinc, a Zinc-Magnesium alloy was fabricated by a melting process. The heat treatment process was performed to improve the ductility of Zinc-Magnesium alloy. The microstructure of the heat-treated alloy specimen was analyzed using SEM. The hardness and compressive strength of the specimen were measured by a micro-hardness tester and a nano-indenter, respectively.

• 한국분말재료학회지
• /
• 제13권5호
• /
• pp.340-350
• /
• 2006

Nanostructured materials exhibit attractive mechanical properties that are often superior to the performance of their coarse-grained counterparts. However, one major drawback is their low ductility, which limits their potential applications. In this paper, different strategies to obtain both high strength and enhanced ductility in nanostructured materials are reported for Ti-base and Zr-base alloys. The first approach consists of designing an in-situ composite microstructure containing ductile bcc or hop dendrites that are homogeneously dispersed in a nanostructured matrix. The second approach is related to refining the eutectic structure of a Ti-Fe-Sn alloy. For all these materials, the microstructure, mechanical properties, deformation and fracture mechanisms will be discussed.

• 산업기술연구
• /
• 제41권1호
• /
• pp.7-13
• /
• 2021

Fiber-reinforced polymer reinforcement or polyurea reinforcement techniques are applied to strengthen unreinforced masonry walls (UMWs). The out-of-plane reinforcing effect of sprayed glass fiber-reinforced polyurea (GFRPU), which is a composite elastomer made of polyurea and milled glass fibers on UMW, is experimentally verified. The out-of-plane strengths and ductile behaviors based on various coating shapes are compared in this study. An empirical formula to describe the degree of reinforcement on the out-of-plane strength of the UMW is derived based on the experimental results. It is reported that the peak load-carrying capacity, ductility, and energy absorption capacity gradually improve with an increase in the strengthening degree or area. Compared with the existing masonry wall reinforcement method, the GFRPU technique is a construction method that can help improve the safety performance along with ease of construction and economic efficiency.

• 대한건축학회논문집:구조계
• /
• 제35권1호
• /
• pp.21-28
• /
• 2019

This study investigates the applicability of composite polyurea to contain fiber reinforcement like fiber glass, steel fiber and carbon nanotube. Polyurea as elastomer is an excellent water-proofing material with many mechanical characteristics such as high tensile strength, ductility, high rate of expansion and contraction, and so on. The reinforcing fibers can be utilized for improving the load-carrying capacity of concrete structures. The polyurea plays a role to improve the ductility and toughness. Composite polyurea takes the mechanical advantages of the fibers and the polyurea. The test variables include the type of reinforcing fiber, its spraying thickness, and its weight ratio contained in the composite polyurea. It is observed that the load-carrying capacity, and the ductility and toughness are improved with the increase in the spraying thickness and the weight ratio contained in the composite polyurea. It is expected that the composite polyurea can be widely utilized in enhancing the structural and seismic performance.

• 대한토목학회논문집
• /
• 제30권6A호
• /
• pp.513-523
• /
• 2010

I-거더 형식의 연속교 교각 부근에서는 큰 부모멘트가 작용하게 되며 이로 인하여 소성힌지가 생성된다. 소성힌지가 형성됨에 따라 교각 부근의 부모멘트는 감소하게 되며, 정모멘트부의 휨모멘트는 반대로 증가하게 된다. 이러한 모멘트 재분배가 원활히 발생하기 위해서는 소성힌지가 충분한 휨연성 혹은 단면회전 능력을 가지고 있어야 한다. 하지만 고강도 강재에 있어 재료연성이 다소 떨어지는 경향이 있고, 재료의 항복응력이 증가할수록 I-거더의 탄성 변형량은 이에 비례하여 증가하므로, 소성변형 능력 및 휨연성이 감소하는 것으로 알려져 있다. 따라서, 고강도 강재를 I-거더 형식의 연속교에 적용할 때 동일한 수준의 휨연성을 확보할 수 있는 방안에 대한 연구가 필요하다. 본 연구에서는 유한요소해석 및 실험 연구를 통하여 항복강도 680 Mpa급 강재 적용 I-거더의 휨연성 평가 및 휨연성 확보 방안에 대하여 연구를 수행하였다. 연구 결과 재료의 인장 강도가 증가함에 따라 탄성 변형이 증가하며 소성 변형 능력이 저하됨으로 I-거더의 휨연성이 현저하게 감소하는 것으로 나타났으며, I-거더의 휨연성 확보를 위하여 부등간격으로 가로보를 배치하는 방안을 제안하였다. 최종적으로 가로보부등배치가 I-거더의 휨연성에 미치는 영향을 실험적으로 검증하였다.

• Structural Engineering and Mechanics
• /
• 제83권3호
• /
• pp.305-326
• /
• 2022

To realize the recycling utilization of waste concrete and alleviate the shortage of resources, 11 specimens of steel reinforced recycled concrete (SRRC) filled circular steel tube columns were designed and manufactured in this study, and the cyclic loading tests on the specimens of columns were also carried out respectively. The hysteretic curves, skeleton curves and performance indicators of columns were obtained and analysed in detail. Besides, the finite element model of columns was established through OpenSees software, which considered the adverse effect of recycled coarse aggregate (RA) replacement rates and the constraint effect of circular steel tube on internal RAC. The numerical calculation curves of columns are in good agreement with the experimental curves, which shows that the numerical model is relatively reasonable. On this basis, a series of nonlinear parameters analysis on the hysteretic behaviors of columns were also investigated. The results are as follows: When the replacement rates of RA increases from 0 to 100%, the peak loads of columns decreases by 7.78% and the ductility decreases slightly. With the increase of axial compression ratio, the bearing capacity of columns increases first and then decreases, but the ductility of columns decreases rapidly. Increasing the wall thickness of circular steel tube is very profitable to improve the bearing capacity and ductility of columns. When the section steel ratio increases from 5.54% to 9.99%, although the bearing capacity of columns is improved, it has no obvious contribution to improve the ductility of columns. With the decrease of shear span ratio, the bearing capacity of columns increases obviously, but the ductility decreases, and the failure mode of columns develops into brittle shear failure. Therefore, in the engineering design of columns, the situation of small shear span ratio (i.e., short columns) should be avoided as far as possible. Based on this, the calculation model on the skeleton curves of columns was established by the theoretical analysis and fitting method, so as to determine the main characteristic points in the model. The effectiveness of skeleton curve model is verified by comparing with the test skeleton curves.

• Steel and Composite Structures
• /
• 제28권5호
• /
• pp.527-539
• /
• 2018

The use of reinforced concrete (RC) shear wall with concrete filled steel tube (CFST) columns and steel fiber reinforced concrete (SFRC) shear wall has aroused widespread attention in recent years. A new shear wall, named SFRC shear wall with CFST columns, is proposed in this paper, which makes use of CFST column and SFRC shear wall. Six SFRC shear wall with CFST columns specimens were tested under cyclic loading. The effects of test parameters including steel fiber volume fraction and concrete strength on the failure mode, strength, ductility, rigidity and dissipated energy of shear wall specimens were investigated. The results showed that all tested shear wall specimens exhibited a distinct shear failure mode. Steel fibers could effectively control the crack width and improve the distribution of cracks. The load carrying and energy dissipation capacities of specimens increased with the increase of steel fiber volume fraction and concrete strength, whilst the ductility of specimens increased with the increase of steel fiber volume fraction and the decrease of concrete strength.

• Structural Engineering and Mechanics
• /
• 제16권2호
• /
• pp.127-139
• /
• 2003

Reinforced concrete buildings with shearwalls are very efficient to resist earthquake disturbances. In general, reinforced concrete frames are governed by flexure and shearwalls are governed by shear. If a structure included both frames and shearwalls, it is generally governed by shearwalls. However, the ductility of ordinary reinforced concrete is very limited. To improve the ductility, a series of tests on framed shearwalls made of corrugated steel was performed previously and the experimental results were compared with ordinary reinforced concrete frames and shearwalls. It was found that ductility of framed shearwalls could be greatly improved if the thickness of the corrugated steel wall is appropriate to the surrounding reinforced concrete frame. In this paper, an analytical model is developed to predict the horizontal load-displacement relationship of hybrid reinforced concrete frame-steel wall systems according to the analogy of truss models. This analytical model is based on equilibrium and compatibility conditions as well as constitutive laws of corrugated steel. The analytical predictions are compared with the results of tests reported in the previous paper. It is found that proposed analytical model can predict the test results with acceptable accuracy.