• Steel and Composite Structures
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• 제48권2호
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• pp.131-143
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• 2023

The CFRP bar was used to achieve more ductile and durable headed-stud shear connectors in composite components. Three series of push-out tests were firstly conducted, including specimens reinforced with pure steel fibers, steel and CFRP bars. The distributed stress was measured by the commercial PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) optical fiber sensor with high spatial resolution. A series of numerical analyses using non-linear FE models were also made to study the shear force transfer mechanism and crack response based on the test results. Test results show that the CFRP bar increases the shear strength and stiffness of the large diameter headed-stud shear connection, and it has equivalent reinforcing effects on the stud shear capacity as the commonly used steel bar. The embedded CFRP bar can also largely improve the shear force transfer mechanism and decrease the tensile stress in the transverse direction. The parametric study shows that low content steel fibers could delay the crack initiation of slab around the large diameter stud, and the CFRP bar with normal elastic modulus and the standard reinforcement ratio has good resistance to splitting crack growth in headed stud shear connectors.

• Structural Engineering and Mechanics
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• 제50권6호
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• pp.741-754
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• 2014

The conventional PHC pile-footing connection is the weak part because the surface area and stiffness are sharply changed. The Composite PHC pile reinforced with the transverse shear reinforcing bars and infilled-concrete, hereafter ICP pile, has been developed for improving the flexural and shear performance. This paper investigates the cyclic behavior and performance of the ICP pile-footing connection. To investigate the behavior of the connection, one PHC and two ICP specimens were manufactured and then a series of cyclic loading tests were performed. From the test results, it was found that the ICP pile-footing connection exhibited higher cyclic behavior and connection performance compared to the conventional PHC pile-footing connection in terms of ductility ratio, stiffness degradation and energy dissipation capacity.

• Steel and Composite Structures
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• 제12권3호
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• pp.261-273
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• 2012

This study proposes and examines a circular composite bridge pier for seismic resistance. The axial and flexural strengths of the proposed bridge pier are provided by the longitudinal reinforcing bars and the concrete, while the transverse reinforcements used in the conventional reinforced concrete pier are replaced by the steel tube. The shear strength of this composite pier relies on the steel tube and the concrete. This system is similar to the steel jacketing method which strengthens the existing reinforced concrete bridge piers. However, no transverse shear reinforcing bar is used in the proposed composite bridge pier. A series of experimental studies is conducted to investigate the seismic resistant characteristics of the proposed circular composite pier. The effects of the longitudinal reinforcing bars, the shear span-to-diameter ratio, and the thickness of the steel tube on the performance of strength, ductility, and energy dissipation of the proposed pier are discussed. The experimental results show that the strength of the proposed circular composite bridge pier can be predicted accurately by the similar method used in the reinforced concrete piers with minor modification. From these experimental studies, it is found that the proposed circular composite bridge pier not only simplifies the construction work greatly but also provides excellent ductility and energy dissipation capacity under seismic lateral force.

• Computers and Concrete
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• 제18권3호
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• pp.297-317
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• 2016

Current codes recommend large amounts of shear reinforcement for reinforced concrete beam-column joints that causes significant bar congestion. Increase in congestion of shear reinforcement in joint core (connection zone), leads to increase accomplishment problems. The congestion may also lead to diameter limitations on the beam bars relative to the joint dimensions. Using double headed studs instead of conventional closed hoops in reinforced concrete beam-column joints reduces congestion and ensures easier assembly of the reinforcing cage. The purpose of this research is evaluating the efficiency of the proposed reinforcement. In this way, 10 groups of exterior beam-column joints are modeled. Each group includes 7 specimens by different reinforcing details in their joint core. All specimens are modeled by using of ABAQUS and analyzed subjected to cyclic loading. After verification of analytical modeling with an experimental specimen, 3D nonlinear specimens are modeled and analyzed. Then, the effect of amount and arrangement of headed studs on ductility, performance, ultimate strength and energy absorption has been studied. Based on the results, all joints reinforced with double headed studs represent better performance compared with the joints without shear transverse reinforcement in joints core. The behavior of the former is close to joints reinforced with closed hoops and cross ties according to the seismic design codes. By adjusting the arrangement of double-headed studs, the decrease in ductility, performance, ultimate moment resistant and energy absorption reduce to 2.61%, 0.90%, 0.90% and 1.66% respectively compared with the joints reinforced by closed hoops on the average. Since the use of headed studs reduces accomplishment problems, these amounts are negligible. Therefore, use of double-headed studs has proved to be a viable option for reinforcing exterior beam-column joints.

• 한국구조물진단유지관리공학회 논문집
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• 제28권4호
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• pp.13-20
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• 2024

이 연구에서는 전단벽과 같은 면내 전단을 받는 경우에 대해, 종방향 보강근비를 2.96%로 일정하게 하고, 횡방향 보강근비를 0.30에서 2.98%까지 변화시켰을 때, CFRP 보강근을 사용한 콘크리트 부재의 거동특성을 MCFT 이론에 기반하여 평가하고, 철근을 사용한 콘크리트 부재의 경우와 비교하여 분석하고자 하였다. 보강근비 0.30에서 1.19% 사이에서는 CFRP 보강근을 사용한 경우가 철근을 사용한 경우보다 높은 전단강도를 보였으며, 그 이상의 1.79% 및 2.98%에서는 상대적으로 낮은 전단강도를 나타내었다. 최대전단변형률은 낮은 보강근비에서 철근을 사용한 경우가 더 크게 나타났으며, 0.97% 이상에서는 CFRP 보강근을 사용한 경우에 더 크게 나타났으며 보강근비가 커질수록 철근 대비 전단변형률 증가율이 더 크게 나타났다. 철근 및 CFRP 보강근의 기계적 성질 차이로 인해 발생하는 보강근에서의 변형률 차이 및 요소에서의 주변형률 차이 분석을 통해 보강근비 변화에 따른 철근 및 CFRP 보강근을 사용한 경우의 전단강도 및 전단변형률 변화를 비교하여 분석할 수 있었다.

• Steel and Composite Structures
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• 제35권4호
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• pp.475-494
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• 2020

Presented are experimental results from 24 full-scale push test specimens to study the behaviour of composite beams with trapezoidal profiled sheeting laid transverse to the beam axis. The tests use a single-sided horizontal push test setup and are divided into two series. First series contained shear loading only and the second had normal load besides shear load. Four parameters are studied: the effect of wire mesh position and number of its layers, placing a reinforcing bar at the bottom flange of the deck, normal load and its position, and shear stud layout. The results indicate that positioning mesh on top of the deck flange or 30 mm from top of the concrete slab does not affect the stud's strength and ductility. Thus, existing industry practice of locating the mesh at a nominal cover from top of the concrete slab and Eurocode 4 requirement of placing mesh 30 mm below the stud's head are both acceptable. Double mesh layer resulted in 17% increase in stud strength for push tests with single stud per rib. Placing a T16 bar at the bottom of the deck rib did not affect shear stud behaviour. The normal load resulted in 40% and 23% increase in stud strength for single and double studs per rib. Use of studs only in the middle three ribs out of five increased the strength by 23% compared to the layout with studs in first four ribs. Eurocode 4 and Johnson and Yuan equations predicted well the stud strength for single stud/rib tests without normal load, with estimations within 10% of the characteristic experimental load. These equations highly under-estimated the stud capacity, by about 40-50%, for tests with normal load. AISC 360-16 generally over-estimated the stud capacity, except for single stud/rib push tests with normal load. Nellinger equations precisely predicted the stud resistance for push tests with normal load, with ratio of experimental over predicted load as 0.99 and coefficient of variation of about 8%. But, Nellinger method over-estimated the stud capacity by about 20% in push tests with single studs without normal load.

• Earthquakes and Structures
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• 제18권1호
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• pp.113-127
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• 2020

In this study, the behavior of external beam-column joints reinforced by plain and deformed bars with non-seismic reinforcement details is investigated and compared. The beam-column joints represented in this study include a benchmark specimen by seismic details in accordance with ACI 318M-11 requirements and four other deficient specimens. The main defects of the non-seismic beam-column joints included use of plain bar, absence of transverse steel hoops, and the anchorage condition of longitudinal reinforcements. The experimental results indicate that using of plain bars in non-seismic beam-column joints has significantly affected the failure modes. The main failure mode of the non-seismic beam-column joints reinforced by deformed bars was the accumulation of shear cracks in the joint region, while the failure mode of the non-seismic beam-column joints reinforced by plain bars was deep cracks at the joint face and intersection of beam and column and there was only miner diagonal shear cracking at the joint region. In the other way, use of plain bars for reinforcing concrete can cause the behavior of the substructure to be controlled by slip of the beam longitudinal bars. The experimental results show that the ductility of non-seismic beam-column joints reinforced by plain bars has not decreased compared to the beam-column joints reinforced by deformed bars due to lack of mechanical interlock between plain bars and concrete. Also it can be seen a little increase in ductility of substructure due to existence of hooks at the end of the development length of the bars.