• Title/Summary/Keyword: reinforced joints

Search Result 416, Processing Time 0.023 seconds

Modelling beam-to-column joints in seismic analysis of RC frames

  • Lima, Carmine;Martinelli, Enzo;Macorini, Lorenzo;Izzuddin, Bassam A.
    • Earthquakes and Structures
    • /
    • v.12 no.1
    • /
    • pp.119-133
    • /
    • 2017
  • Several theoretical and analytical formulations for the prediction of shear strength in reinforced concrete (RC) beam-to-column joints have been recently developed. Some of these predictive models are included in the most recent seismic codes and currently used in practical design. On the other hand, the influence of the stiffness and strength degradations in RC joints on the seismic performance of RC framed buildings has been only marginally studied, and it is generally neglected in practice-oriented seismic analysis. To investigate such influence, this paper proposes a numerical description for representing the cyclic response of RC exterior joints. This is then used in nonlinear numerical simulations of RC frames subjected to earthquake loading. According to the proposed strategy, RC joints are modelled using nonlinear rotational spring elements with strength and stiffness degradations and limited ductility under cyclic loading. The proposed joint model has been firstly calibrated against the results from experimental tests on 12 RC exterior joints. Subsequently, nonlinear static and dynamic analyses have been carried out on two-, three- and four-storey RC frames, which represent realistic existing structures designed according to old standards. The numerical results confirm that the global seismic response of the analysed RC frames is strongly affected by the hysteretic damage in the beam-to-column joints, which determines the failure mode of the frames. This highlights that neglecting the effects of joints damage may potentially lead to non-conservative seismic assessment of existing RC framed structures.

Seismic resistance and mechanical behaviour of exterior beam-column joints with crossed inclined bars

  • Bakir, P.G.
    • Structural Engineering and Mechanics
    • /
    • v.16 no.4
    • /
    • pp.493-517
    • /
    • 2003
  • Attempts at improving beam-column joint performance has resulted in non-conventional ways of reinforcement such as the use of the crossed inclined bars in the joint area. Despite the wide accumulation of test data, the influence of the crossed inclined bars on the shear strength of the cyclically loaded exterior beam-column joints has not yet been quantified and incorporated into code recommendations. In this study, the investigation of joints has been pursued on two different fronts. In the first approach, the parameters that influence the behaviour of the cyclically loaded beam-column joints are investigated. Several parametric studies are carried out to explore the shear resisting mechanisms of cyclically loaded beam-column joints using an experimental database consisting of a large number of joint tests. In the second approach, the mechanical behaviour of joints is investigated and the equations for the principal tensile strain and the average shear stress are derived from joint mechanics. It is apparent that the predictions of these two approaches agree well with each other. A design equation that predicts the shear strength of the cyclically loaded exterior beam-column joints is proposed. The design equation proposed has three major differences from the previously suggested design equations. First, the influence of the bond conditions on the joint shear strength is considered. Second, the equation takes the influence of the shear transfer mechanisms of the crossed inclined bars into account and, third, the equation is applicable on joints with high concrete cylinder strength. The proposed equation is compared with the predictions of the other design equations. It is apparent that the proposed design equation predicts the joint shear strength accurately and is an improvement on the existing code recommendations.

Strengthening of non-seismically designed beam-column joints by ferrocement jackets with chamfers

  • Li, Bo;Lam, Eddie Siu-Shu;Cheng, Yuk-Kit;Wu, Bo;Wang, Ya-Yong
    • Earthquakes and Structures
    • /
    • v.8 no.5
    • /
    • pp.1017-1038
    • /
    • 2015
  • This paper presents a strengthening method that involves the use of ferrocement jackets and chamfers to relocate plastic hinge for non-seismically designed reinforced concrete exterior beam-column joints. An experimental study was conducted to assess the effectiveness of the proposed strengthening method. Four half-scale beam-column joints, including one control specimen and three strengthened specimens, were prepared and tested under quasi-static cyclic loading. Strengthening schemes include ferrocement jackets with or without skeleton reinforcements and one or two chamfers. Experimental results have indicated that the proposed strengthening method is effective to move plastic hinge from the joint to the beam and enhance seismic performance of beam-column joints. Shear stress and distortion within the joint region are also reduced significantly in strengthened specimens. Skeleton reinforcements in ferrocement provide limited improvement, except on crack control. Specimen strengthened by ferrocement jackets with one chamfer exhibits slight decrease in peak strength and energy dissipation but with increase in ductility as compared with that of two chamfers. Finally, a method for estimating moment capacity at beam-column interface for strengthened specimen is developed. The proposed method gives reasonable prediction and can ensure formation of plastic hinge at predetermined location in the beam.

Critical Influence of Rivet Head Height on Corrosion Performance of CFRP/Aluminum Self-Piercing Riveted Joints

  • Karim, Md Abdul;Bae, Jin-Hee;Kam, Dong-Hyuck;Kim, Cheolhee;Park, Yeong-Do
    • Corrosion Science and Technology
    • /
    • v.18 no.3
    • /
    • pp.92-101
    • /
    • 2019
  • This study investigates how rivet head height affects the corrosion performance of carbon fiber reinforced plastic (CFRP) to aluminum alloy self-piercing riveted joints. Specimens with two different head heights were prepared. A rivet head protruding out of the top CFRP laminate forms the proud head height while a rivet head penetrating into the top CFRP generates the flush head height. The salt spray test evaluated corrosion performance. The flush head joints suffered from severe corrosion on the rivet head. Thus, the tensile shear load of flush head joints was substantially reduced. Electrochemical corrosion tests investigated the corrosion mechanisms. The deeper indentation of the flush head height damaged the CFRP around the rivet head. The exposure of damaged fibers from the matrix increased the cathodic potential of local CFRP. The increased potential of damaged CFRP accelerated the galvanic corrosion of the rivet head. After the rivet head coating material corroded, a strong galvanic couple was formed between the rivet head base metal (boron steel) and the damaged CFRP, further accelerating the flush rivet head corrosion. The results of this study suggest that rivet head flushness should be avoided to enhance the corrosion performance of CFRP to aluminum alloy self-piercing riveted joints.

Seismic Evaluation of Beam-Column Joint Specimens of RC Special Moment Frames (철근콘크리트 특수모멘트골조의 보-기둥 접합부 실험체의 내진성능평가)

  • Lee, Ki-Hak;Seok, Keun-Yung;Jung, Chan-Woo;Shin, Young-Shik;Kang, Joo-Won
    • Journal of Korean Association for Spatial Structures
    • /
    • v.8 no.2
    • /
    • pp.85-93
    • /
    • 2008
  • This study summarizes the results of a research project aimed at investigating the inelastic rotation capacity of beam-column joints of reinforced concrete special moment frames. All of the test specimens were classified as special moment frame (SMF), based on the design and detailing requirements of the ACI 318-02 provisions. The acceptance criteria, originally defined for steel moment frame connections in the 1997 edition of the AISC Seismic provisions, were used to evaluate the beam-column joints of the reinforced concrete moment frames. A total of 39 test specimens were examined in detail. Most of the joints that satisfy the design requirements for special moment frame structures were found to be ductile up to a plastic rotation of 3% without any major degradation in strength. This is mainly due to the stringent ACI 318-02 requirements for special moment frame joints. The presence of transverse beams increases confinement and shear resistance of joints, which results in better performance than for joints without transverse beams. All of the SMF connections that satisfy the ACI 318-02 limitations on joint shear stress turned out to meet the acceptance criteria.

  • PDF

Seismic Performance Evaluation of Reinforced Concrete Buildings Strengthened by Embedded Steel Frame (내부 매입형 철골조로 보강된 철근콘크리트 건물의 내진 성능평가)

  • Kim, Seonwoong;Lee, Kyungkoo
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.24 no.1
    • /
    • pp.29-37
    • /
    • 2020
  • This study is to investigate the effect of a retrofitted reinforced concrete frame with non-seismic details strengthened by embedded steel moment frames with an indirect joint, which mitigates the problems of the direct joint method. First, full-scale experiments were conducted to confirm the structural behavior of a 2-story reinforced concrete frame with non-seismic details and strengthened by a steel moment frame with an indirect joint. The reinforced concrete frame with non-seismic details showed a maximum strength of 185 kN at an overall drift ratio of 1.75%. The flexural-shear failure of columns was governed, and shear cracks were concentrated at the beam-column joints. The reinforced concrete frame strengthened by the embedded steel moment frames achieved a maximum strength of 701 kN at an overall drift ratio of 1.5% so that the maximum strength was about 3.8 times that of the specimen with non-seismic details. The failure pattern of the retrofitted specimen was the loss of bond strength between the concrete and the rebars of the columns caused by a prying action of the bottom indirect joint because of lateral force. Furthermore, methods are proposed for calculation of the specified strength of the reinforced concrete frame with non-seismic details and strengthened by the steel moment frame with the indirect joint.

Finite element models of reinforced ECC beams subjected to various cyclic deformation

  • Frank, Timothy E.;Lepech, Michael D.;Billington, Sarah L.
    • Computers and Concrete
    • /
    • v.22 no.3
    • /
    • pp.305-317
    • /
    • 2018
  • Steel reinforced Engineered Cementitious Composite (ECC) components have been proposed for seismic structural applications, for example in coupling beams, infill panels, joints, columns, and flexural members. The development of strain in the steel reinforcement of cementitious components has been shown to vary based on both the steel reinforcement ratio and the applied deformation history. Strain in the steel reinforcement of reinforced ECC components is an important structural response metric because ultimate failure is often by fracture of the steel reinforcement. A recently proposed bond-slip model has been successfully calibrated to cyclically tested reinforced ECC beams wherein the deformation history contained monotonically increasing cycles. This paper reports simulations of two-dimensional finite element models of reinforced ECC beams to determine the appropriateness and significance of altering a phenomenological bond-slip model based on the applied deformation history. The numerical simulations with various values of post-peak bond-slip softening stiffness are compared to experimental results. Varying the post-peak bond-slip softening stiffness had little effect on the cracking patterns and hysteretic response of the reinforced ECC flexural models tested, which consisted of two different steel reinforcement ratios subjected to two different deformation histories. Varying the post-peak bond-slip softening stiffness did, however, affect the magnitude of strain and the length of reinforcing bar that strain-hardened. Overall, a numerical model with a constant bond-slip model represented well various responses in reinforced ECC beams with multiple steel reinforcement ratios subjected to different deformation histories.

Prediction of premature separation of bonded CFRP plates from strengthened steel beams using a fracture criterion

  • Lenwari, A.;Thepchatri, T.;Watanabe, E.
    • Structural Engineering and Mechanics
    • /
    • v.14 no.5
    • /
    • pp.565-574
    • /
    • 2002
  • This paper presents a method for predicting premature separation of carbon fiber reinforced plastic (CFRP) plates from strengthened steel beams. The fracture criterion based on material-induced singularity is formulated in terms of a singular intensity factor. Static test on double strap joints was selected to provide the critical stress intensity factor in the criterion because good degree of accuracy and consistency of experimental data can be expected compared with the unsymmetrically loaded single lap joints. The debond/separation loads of steel beams with different CFRP lengths were measured and compared with those predicted from the criterion. Good agreement between the test results and the prediction was found.

Seismic Behavior of RC Beam-Column Exterior Joints with Unbonded Tendons and High Strength Concrete (비부착 강연선과 고강도 콘크리트를 적용한 철근콘크리트 외부 접합부의 내진 거동)

  • Kwon, Byung Un;Kang, Thomas H.-K.
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.19 no.6
    • /
    • pp.283-292
    • /
    • 2015
  • In the moment frame subjected to earthquake loads, beam-column joint is structurally important for ductile behavior of a system. ACI Committee 352 proposed guidelines for designing beam-column joint details. The guidelines, however, need to be updated because of the lack of data regarding several factors that may improve the performance of joints. The purpose of this study is to investigate the seismic performance of reinforced concrete exterior joints with high-strength materials and unbonded tendons. Three specimens with different joint shear demand-to-strength ratios were constructed and tested, where headed bars were used to anchor the beam bars into the joint. All specimens showed satisfactory seismic behavior including moment strength of 1.3 times the nominal moment, ductile performance (ductility factor = at least 2.4), and sufficiently large dissipated energy.

A Study on Residual Stress of SiC Whisker Reiforced AI Alloy/$ZrO_2$ Joints (SiC 휘스커강화 금속복합재료와 지르코니아 접합체의 잔류응력 해석에 관한 연구)

  • 주재황;박명균
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.4 no.6
    • /
    • pp.18-26
    • /
    • 1996
  • A two dimensional thermo elasto-plastic finite element stress analysis was performed to study residual stress distributions in AI composites reinforced by SiC whisker and $ZrO_2$ ceramic joints. The influences on the residual stress distributions due to the difference of the reinforcement volume fraction and interlayer material property were investigated. Specifically, stress distributions between AI interlayer material property were investigated. Specifically, stress distributions between AI interlayer and $ZrO_2$ ceramic and between the AI interlayer and AI composite were computationally analzed.

  • PDF