• Advances in concrete construction
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• 제9권2호
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• pp.115-123
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• 2020

The performance of steel fiber reinforced geopolymer concrete beam column joints under cyclic loading was investigated. The volume fraction of fibers considered were 0.25% (19.62 kg/㎥), 0.5% (39.24 kg/㎥), 0.75% (58.86 kg/㎥) and 1% (78.48 kg/㎥). A total of fifteen specimens were prepared and tested under reverse cyclic loading. Test results were analyzed with respect to first crack load, ultimate load, energy absorption capacity, energy dissipation capacity, stiffness degradation and load deflection behavior. Test results revealed that the addition of steel fibers enhanced the performance of geopolymer concrete beam column joints significantly. The joints were analyzed using finite element software ANSYS. The analytical results were found to compare satisfactorily with the experimental values.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.851-856
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• 2000

When subjected to the strong earthquake ground motion, upper-wall lower-frame structures have high possibility of the weak-story failure in the lower frame part. Sufficient strength, energy dissipation capacity and ductility should be provided at the joint between the deep beam and the lower column. In this study, a typical structure was selected for a prototype and four 1:2.5 scaled models, representing the subassemblage including the exterior column and the deep beam, were constructed. The transverse reinforcement was designed according to ACI procedure¹ and the procedure proposed by Sheikh². The inelastic behavior of the subassemblages subjected to the cyclic lateral displacement were evaluated through investigation of the ultimate strength, ductility, load-deformation characteristics. From the test of 4 specimens, it is concluded that the specimens designed according to Sheikh's procedure revealed higher ductility than that by ACI procedure.

• Structural Engineering and Mechanics
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• 제75권6호
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• pp.675-684
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• 2020

An innovative retrofit method using pre-stressed steel strips and externally-bonded steel plates was presented in this paper. With the aim of exploring the seismic performance of the retrofitted RC interior joints, four 1/2-scale retrofitted joint specimens together with one control specimen were designed and subjected to constant axial compression and cyclic loading, with the main test parameters being the volume of steel strips and the existence of externally-bonded steel plates. The damage mechanism, force-displacement hysteretic response, force-displacement envelop curve, energy dissipation and displacement ductility ratio were analyzed to investigate the cyclic behavior of the retrofitted joints. The test results indicated that all the test specimens suffered a typical shear failure at the joint core, and the application of externally-bonded steel plates and that of pre-stressed steel strips could effectively increase the lateral capacity and deformability of the deficient RC interior joints, respectively. The best cyclic behavior could be found in the deficient RC interior joint retrofitted using both externally-bonded steel plates and pre-stressed steel strips due to the increased lateral capacity, displacement ductility and energy dissipation. Finally, based on the test results and the softened strut and tie model, a theoretical model for determining the shear capacity of the retrofitted specimens was proposed and validated.

• Journal of Welding and Joining
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• 제9권1호
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• pp.40-47
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• 1991

The most fatigue tests carried out under the either stress or strain control, but machines and structures had taken variable stress. This variable stress was treated as statistics based on p-type distributions. In this paper, the cumulative fatigue damage of SM45C round bar specimens having a center hole resulting from block loading with p-distributions in rotating bending conditions, is presented. The value of p was changed in the range from 0.25 to 1; 0.25, 0.5, 0.75, 1. The following conclusions were obtained through the constant stress amplitude experiments and the block loading experiments. (1) In constant loading test, fatigue life was affected by cyclic rate. From experimental data, N$_{f}$ (100cpm)/N$_{f}$(3000cpm)equal to 0.56. (2) In case of the cyclic rate 100cpm and 3000cpm, at the high stress amplitude level the crack propagation life N$_{*}$f is longer than the low stress amplitude level. (3) Miner's hypothesis may be valid for p=0.75 and prediction of fatigue life by Haibach's method agree with experimental data well for the case p=0.5, while the modified Miner's method agree with experimental data well for the case p=0.25.5.

• Earthquakes and Structures
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• 제3권1호
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• pp.37-57
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• 2012

The behavior of beam-column joints in moment resisting frame structures is susceptible to damage caused by seismic effects due to poor performance of the joints. A good number of researches were carried out to understand the complex mechanism of RC joints considered in current seismic design codes. The traditional construction detailing of transverse reinforcement has resulted in serious joint failures during earthquakes. This paper introduces a new design philosophy involving the use of additional diagonal bars within the joint particularly suitable for low to medium seismic effects in earthquake zones. In this study, ten full-scale interior beam-column specimens were constructed with various additional reinforcement details and configurations. The results of the experiment showed that adding additional bars is a promising approach in reinforced concrete structures where earthquakes are eminent. In terms of overall cracking observation during the test, the specimens with additional bars (diagonal and straight) compared with the ones without them showed fewer cracks in the column. Furthermore, concrete confinement is certainly an important design measure as recommended by most international codes.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.599-604
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• 2000

The analytical studies for the test results are presented. From experimental envelope curve, hysteretic behaviors under cyclic loading are modelled for beam-column subassemblages. Modelled curves show relatively good reproduction or experimental curves. finally, seismic performances are investigated for 7 story plain framed structure by nonlinear dynamic analysis. The resulting responses are different by each beam-column joint design.

• Earthquakes and Structures
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• 제11권4호
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• pp.665-680
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• 2016

This paper focuses on the study of seismic behavior of steel reinforced concrete special-shaped column-beam joints. Six specimens, which are designed according to the principle of strong-member and weak-joint core, are tested under low cyclic reversed load. Key parameters include the steel form in column section and the ratio of column limb height to thickness. The failure mode, load-displacement curves, ductility, stiffness degradations, energy dissipation capacity and shear deformation of joint core of the test subassemblies are analyzed. The results indicate that SRC special-shaped column-beam joints have good seismic behavior. All specimens failed due to the shear failure of the joint core, and the failure degree between the two sides of joint core is similar for the exterior joint but different for the corner joint. Compared to the joints with channel steel truss, the joints with solid web steel skeleton illustrate better ductility and energy dissipation capacity, but the loading capacity and stiffness are roughly close. With the increasing of the ratio of column limb height to thickness, the joints illustrate higher loading capacity and stiffness, better energy dissipation capacity, but worse ductility.

• Earthquakes and Structures
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• 제21권6호
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• pp.653-667
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• 2021

In this study, cyclic loading tests were conducted on the precast concrete (PC) wide beam (WB)-column joints. Two beam-column joint specimens were fabricated with the arrangement and anchorage details of the reinforcing bars penetrating the beam and column as variables. Through a cyclic loading test, the lateral load-story drift ratio responses, seismic performance characteristics (e.g., ductility, overstrength factor), energy dissipation, strength and stiffness degradations of each specimen were compared and analyzed based on the various indices and the current structural codes (ACI 318-19 and ACI 374.1-05 report). In addition, the shear lag effect was confirmed through the gauge values of the PC beam, and the differences in seismic performance between the specimens were identified on that basis.

• 한국지진공학회논문집
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• 제18권1호
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• pp.63-71
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• 2014

This study presents an experimental study of the structural behavior for steel plate-concrete column-to-steel girder connections. Experiments were carried out to investigate the moment-rotation characteristics, failure behavior and ultimate moment capacity of these connections. The results of this experimental study involving three welded moment-resisting connections subjected to cyclic loading are presented. The specimens were fabricated at full scale to evaluate their hysteretic behavior. A description of the test specimens, the details of the joint, the test system and the testing methods are described. The test results showed that the structural behavior of these composite connections was influenced by the connection details.

• Steel and Composite Structures
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• 제27권4호
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• pp.495-508
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• 2018

In this paper, cyclic loading tests on composite frame inner joints of steel-reinforced recycled concrete (SRRC) column-steel beam were conducted. The main objective of the test was to obtain the shear behavior and analyze the shear strength of the joints. The main design parameters in the test were recycled coarse aggregate (RCA) replacement percentage and axial compression ratio. The failure process, failure modes, hysteresis curves and strain characteristics of the joints were obtained, and the influences of design parameters on the shear strength of the joints have been also analysed in detail. Results show that the failure modes of the joints area are typical shear failure. The shear bearing capacity of the joints maximally decreased by 10.07% with the increase in the RCA replacement percentage, whereas the shear bearing capacity of the joints maximally increased by 16.6% with the increase in the axial compression ratio. A specific strain analysis suggests that the shear bearing capacity of the joints was mainly provided by the three shear elements of the recycled aggregate concrete (RAC) diagonal compression strut, steel webs and stirrups of the joint area. According to the shear mechanism and test results, the calculation formulas of the shear bearing capacity of the three main shear elements were deduced separately. Thus, the calculation model of the shear bearing capacity of the composite joints considering the adverse effects of the RCA replacement percentage was established through a superposition method. The calculated values of shear strength based on the calculation model were in good agreement with the test values. It indicates that the calculation method in this study can reasonably predict the shear bearing capacity of the composite frame inner joints of SRRC column-steel beam.