• Journal of the Earthquake Engineering Society of Korea
• /
• v.24 no.4
• /
• pp.189-196
• /
• 2020

In this study, two full-scale gravity load-designed reinforced concrete corner beam-column joints were tested by being subjected to uniand bi-directional cyclic lateral loading. The test variable was loading type: uni- or bi-directional loading. To investigate the effect of the loading type on the cyclic behavior of joint specimens, damage progression, force-deformation relation, contribution of joint deformation to total drift, joint stress-strain response, and cumulative energy dissipation were investigated. The test data suggest that bidirectional loading can amplify damage accumulation in the joint region.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.2 s.257
• /
• pp.166-173
• /
• 2007

Fatigue fracture behavior of a hybrid bolted joint was evaluated in comparison to the case of static fracture. Two kinds of specimens were fabricated for the mechanical tests; a hybrid bolted joint specimen for the shear test and a hybrid joint part specimen applied in the real tilting car body for the bending test. Characteristic fracture behaviors of those specimens under cyclic toads were obviously different from the case under static loads. For the hybrid bolted joint specimen, static shear loading caused the fracture of the bolt body itself in a pure shear mode, whereas cyclic shear loading brought about the fracture at the site of local tensile stress concentration. For the hybrid joint part specimen, static bend loading caused the shear deformation and fracture in the honeycomb core region, while cyclic bend loading did the delamination along the interface between composite skin and honeycomb core layers as well as the fracture of welded joint part. Experimental results obtained by static and fatigue tests were reflected in modifications of design parameters of the hybrid joint structure in the real tilting car body.

• Structural Engineering and Mechanics
• /
• v.23 no.2
• /
• pp.129-145
• /
• 2006

This paper provides an insight into the response of non-seismic reinforced concrete (RC) building frames to excitations of different frequencies through experimental investigation. The results of cyclic loading tests of six full-scale RC beam-column sub-assemblies are presented. The tested specimens did not have any transverse reinforcement inside the joint core, and they were subjected to quasi-static and dynamic loading with frequencies as high as 20 Hz. Some important differences between the cyclic responses of non-seismic and ductile RC frames are highlighted. The effect of excitation frequency on the behavior of non-seismic joints is also discussed. In the quasi-static tests, shear deformation of the joint panel accounted for more than 50% of the applied story drift. The test results also showed that higher-frequency excitations are less detrimental than quasi-static cyclic loads, and non-seismic frames can withstand a higher load and a larger deformation when they are applied faster.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.6
• /
• pp.68-75
• /
• 2021

In this study, the anchoring performance of 57mm headed bars anchored at the external beam-column joint under cyclic loading was evaluated. A total of 6 external beam-column joint test specimens were planned, and anchorage performance was evaluated by setting concrete compressive strength, side covering thickness, lateral reinforcement ratio, and fracture type as major experimental variables. As result of cyclic loading test, it was found that the factors that had the greatest influence on the anchoring capacity of the large-diameter headed bar anchored at the joint were the side cover thickness and the transverse reinforcing bar. It was confirmed that the 57mm large-diameter headed bar anchored at the external beam-column joint showed sufficient anchoring capacity even under cyclic loading.

• The Journal of Korean Academy of Prosthodontics
• /
• v.46 no.6
• /
• pp.561-568
• /
• 2008

STATEMENT OF PROBLEM: Currently, many implant systems are developed and divided into two types according to their joint connection: external or internal connection. Regardless of the connection type, screw loosening is the biggest problem in implant-supported restoration. PURPOSE: The purpose of this study is to assess the difference in stability of abutment screws between the external and internal hexagonal connection types under cyclic loading. MATERIAL AND METHODS: Each of the 15 samples of external implants and internal abutments were tightened to 30 N/cm with a digital torque gauge, and cemented with a hemispherical metal cap. Each unit was then mounted in a $30^{\circ}$ inclined jig. Then each group was divided into 2 sub-groups based on different periods of cyclic loading with the loading machine (30 N/ cm - 300 N/cm,14 Hz: first group $1{\times}10^6$, $5{\times}10^6$ cyclic loading; second group $3{\times}10^6$, $3{\times}10^6$ for a total cyclic loading of $6{\times}10^6$) The removal torque value of the screw before and after cyclic loading was checked. SPSS statistical software for Windows was used for statistical analysis. Group means were calculated and compared by ANOVA, independent t-test, and paired t-test with ${\alpha}$=0.05. RESULTS: In the external hexagonal connection, the difference between the removal torque value of the abutment screw before loading, the value after $1{\tims}10^6$ cyclic loading, and the value after $1{\times}10^6$, and additional $5{\times}10^6$ cyclic loading was not significant. The difference between the removal torque value after $3{\times}10^6$ cyclic loading and after $3{\times}10^6$, and additional $3{\times}10^6$ cyclic loading was not significant. In the internal hexagonal connection, the difference between the removal torque value before loading and the value after $1{\times}10^6$ cyclic loading was not significant, but the value after $1{\times}10^6$, and additional $5{\times}10^6$ cyclic loading was reduced and the difference was significant (P < .05). In addition, in the internal hexagonal connection, the difference between the removal torque value after $3{\times}10^6$ cyclic loading and the value after $3{\times}10^6$, and additional $3{\times}10^6$ cyclic loading was not significant. CONCLUSION: The external hexagonal connection was more stable than the internal hexagonal connection after $1{\times}10^6$, and additional $5{\times}10^6$ cyclic loading (t = 10.834, P < .001). There was no significant difference between the two systems after $3{\times}10^6$, and additional $3{\times}10^6$ cycles.

• Geomechanics and Engineering
• /
• v.13 no.5
• /
• pp.809-823
• /
• 2017

This paper describes lab test results of artificial rock-like material samples having a plane joint. Cyclic shear tests were performed under different normal loads and different shear displacement amplitudes. For this purpose, multi-stage normal loading tests (30 kN, 60 kN, 90 kN, 180 kN, 360 kN and 480 kN) with cyclic excitation at frequency of 1.0 Hz and different shear displacement amplitudes (0.5 mm, 1.0 mm, 2.0 mm, 4.0 mm, 5.0 mm, and 8.0 mm) were conducted using the big shear box device GS-1000. Experimental results show, that shear forces increase with the increase of normal forces and quasi-static friction coefficient is larger than dynamic one. With the increase of normal loads, approaching the peak value of shear forces needs larger shear displacements. During each cycle the normal displacements increase and decrease (rotational behavior in every cycle). Peak angle of inclination increases with the increase of normal load. A phase shift between maximum shear displacement and maximum shear force is observed. The corresponding time shift decreases with increasing normal load and increases with increasing shear displacement amplitudes.

• Journal of the Korean Wood Science and Technology
• /
• v.41 no.2
• /
• pp.123-133
• /
• 2013

This paper presents experimental and numerical tests on a recently developed timber column concealed base joint. This joint was designed to replace the wood-wood connection found in the post-and-beam structure of Hanok, the traditional Korean timber house. The use of metallic connectors provides an increased ductility and energy dissipation for a better performance under reversed loading, especially seismic. In this study, we investigate the performance of the joint under pseudo-static reversed cyclic moment loading through the study of its ductility and energy dissipation. We first perform experimental tests. Results show that the failure occurs in the metallic connector itself because of stress concentrations, while no brittle fracture of wood occur. Subsequent numerical simulations using a refined finite element model confirm these conclusions. Then, using a practical modification of the joint configuration with limited visual impact, we improve the ductility and energy dissipation of the joint while retaining a same level of rotational strength as the originally designed configuration. We conclude that the joint has a satisfying behavior under reversed moment loading for use in earthquake resistant timber structure in low to moderate seismicity areas like Korea.

• Earthquakes and Structures
• /
• v.20 no.4
• /
• pp.417-430
• /
• 2021

Due to functional requirements, SRC column-RC beam abnormal joints with characteristics of strong beam weak column, variable column section, unequal beam height and staggered height exist in the Steel reinforced concrete (SRC) frame-bent main building structure of thermal power plant (TPP). This paper presents the experimental results of these abnormal joints through cyclic loading tests on five specimens with scaling factor of 1/5. The staggered height and whether adding H-shaped steel in beam or not were changing parameters of specimens. The failure patterns, bearing capacity, energy dissipation and ductile performance were analyzed. In addition, the stress mechanism of the abnormal joint was discussed based on the diagonal strut model. The research results showed that the abnormal exterior joints occurred shear failure and column end hinge flexural failure; reducing beam height through adding H-shaped steel in the beam of abnormal exterior joint could improve the crack resistance and ductility; the abnormal interior joints with different staggered heights occurred column ends flexural failure; the joint with larger staggered height had the higher bearing capacity and stiffness, but lower ductility. The concrete compression strut mechanism is still applicable to the abnormal joints in TPP, but it is affected by the abnormal characteristics.

• Structural Engineering and Mechanics
• /
• v.9 no.4
• /
• pp.375-382
• /
• 2000

Experimental investigation into the cyclic behaviour of sand plast brick masonry was performed on forty two square panels. The panels were subjected to cyclic uniaxial compression for two cases of loading: normal to bed joint and parallel to bed joint. Experimental data were used to plot the unloading-reloading curves for the entire range of the stress-strain curve. Mathematical expressions to predict the reloading and unloading stress-strain curves at various values of residual strain are proposed. A simple parabola and an exponential type formula are found adequate to model the unloading and reloading curves respectively. The models account for the potential effects of residual strain on these curves. Comparison of test results with the proposed mathematical expression shows good correspondence.

• Tunnel and Underground Space
• /
• v.9 no.4
• /
• pp.350-363
• /
• 1999

The precision cyclic shear test system was established to investigate the mechanical characteristics of rough rock joints under cyclic loading conditions. Laboratory cyclic shear tests were conducted for saw-cut joints and artificial rough rock joints using Hwangdeung granite and Yeosan marble. Surface roughness and aperture characteristics of specimens were examined by measuring surface topography using the laser profilometer. Peak shear strength, phase difference during loading and unloading, and anisotropic shear behavior were investigated throughout the cyclic shear test results. These features and their subsequent variations in each loading cycle are significantly dependent upon the second order asperities and the strength of intact rock. It was observed that degradation of asperities for rough rock joints under cyclic shear loading followed the exponential degradation laws of asperity angle and that the mechanism for asperity degradation would be different depending upon the normal stress level, roughness of joint surface and the loading stage.