• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.2
• /
• pp.67-74
• /
• 2010

A variation of temperature acting on a RC roof slab causes a change of stress in concrete since it expands during summer and is compressed during winter. This behavior repeats annually and makes an affection to the structural capacity of member for both serviceability and ultimate level. In this paper, a cyclic temperature loading variation is calculated by analyzing the weather data of Korea for 20 years. In addition, an experimental work is planned to find the long term effect of temperature variation. Six RC slab are made with same dimension. Test parameters are loading duration (10, 20, 30 year) and whether it has pre-damage or not. Observation of stiffness variations according to cyclic loading period shows that the serious stiffness drop happens after 10 year's cyclic loading at summer while after 30 year's loading at winter. From the fracture test about slabs damaged by long term cyclic loading, however, the capacity of member such as initial stiffness and maximum strength were not changed except yield strength according to the period of long term cyclic loading. The yield strength tends to decrease after 20 year's cyclic loading.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.12
• /
• pp.41-50
• /
• 2010

The behavior of laterally cyclic loaded piles is different from that of piles under monotonic loading and depends on soil and load characteristics. In this study, model pile load tests were performed using a calibration chamber to investigate the effects of load characteristics on the behavior of laterally cyclic loaded piles in sand. Results of the model tests show that the ultimate lateral load capacity of laterally cyclic loaded piles decreases linearly with increasing the number of cycles and increases slightly with increasing the magnitude of cyclic lateral loads. When the piles reach the ultimate state, the maximum bending moment developed in the piles decreases linearly with increasing the number of cycles and it occurs at a depth of 0.36 times pile embedded length for all the number of cycles. However, both the magnitude and depth of the maximum bending moment of piles in the ultimate state increase slightly as the magnitude of cyclic lateral loads increases. It is also observed that the cyclic lateral loading generates a decrease in the ultimate lateral load capacity and maximum bending moment for piles in the ultimate state. In addition, based on the model test results, a new empirical equation for the ultimate lateral load capacity of laterally cyclic loaded piles in dense sand is also proposed. A comparison between predicted and measured load capacities shows that the proposed equation reflects satisfactorily the model test results.

• 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.

• The Journal of Advanced Prosthodontics
• /
• v.11 no.6
• /
• pp.305-312
• /
• 2019

PURPOSE. The purpose of this study was to compare computer-aided design/computer-aided manufacturing (CAD/CAM) abutment and prefabricated abutment in Morse taper internal connection type implants after cyclic loading. MATERIALS AND METHODS. The study was conducted with internal type implants of two different manufacturers (Group Os, De). Fourteen assemblies were prepared for each manufacturer group and divided into 2 groups (n=7): prefabricated abutments (Os-P, De-P) and CAD/CAM abutments (Os-C, De-C). The amount of axial displacement and the removal torque values (RTVs) were measured before and after cyclic loading (10⁶ cycles, 3 Hz with 150 N), and the tensile removal force to dislodge the abutments was measured after cyclic loading. A repeated measures ANOVA and a pattern analysis based on the logarithmic regression model were conducted to evaluate the effect of cyclic loading on the axial displacement. The Wilcoxon signed-rank test and the Mann-Whitney test was conducted for comparison of RTV reduction% and tensile removal forces. RESULTS. There was no significant difference between CAD/CAM abutments and prefabricated abutments in axial displacement and tensile removal force; however, significantly greater RTV reduction% after cyclic loading was observed in CAD/CAM abutments. The correlation among the axial displacement, the RTV, and the tensile removal force was not significant. CONCLUSION. The use of CAD/CAM abutment did not significantly affect the amount of axial displacement and tensile removal force, but presented a significantly greater removal torque reduction% than prefabricated abutments. The connection stability due to the friction at the abutment-implant interface of CAD/CAM abutments may not be different from prefabricated abutment.

• Structural Engineering and Mechanics
• /
• v.75 no.6
• /
• pp.675-684
• /
• 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.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2002.10a
• /
• pp.483-488
• /
• 2002

In this paper numerical algorithm for the continuum large crack model is proposed based on the return-mapping formulation. The numerical test results show that the present algorithm works appropriately under cyclic loading. It is also shown that in continuum damage models a large crack model to prevent excessive tensile plastic strain should be used to have realistic cyclic loading simulation results.

• Proceedings of the KACD Conference
• /
• 2003.11a
• /
• pp.599-599
• /
• 2003

Endodontic rotary NiTi(Nickel-Titanium) files have several advantages, but they also have some problems. Fracture of instrument is the one of the problems. Cyclic fatigue fracture may not give a previous sign(ex, bending or distortion of the files) before it happen. It is affected by various factors. This study investigated time which takes for cyclic fatigue fracture to happen and fracture patterns with regard to different NiTi files and pecking motion.(omitted)

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.12 no.4
• /
• pp.219-226
• /
• 1983

Cyclic heating performance of 3 ton air-to-air unitary heat pump installed in a residence in the Washington, D.C. area was determined by applying the bin method to field test result. Cyclic degradation coefficient Cn of heat pump may be expressed in terms of heating load factor HLF as the following : $$C_D=\frac{1-HLF^m}{1-HLF}$$ where $$C_D{\ge}m$$ The less is the value of exponent m, the better is, the performance of a heat pump, depending upon the heat pump design.

• Steel and Composite Structures
• /
• v.8 no.6
• /
• pp.441-455
• /
• 2008

This paper presents an effective hysteretic model for the prediction and evaluation of steel reinforced concrete member seismic performance. This model adopts the load-deformation relationship acquired from monotonic load tests and incorporates the double-pivot behavior of composite members subjected to cyclic loads. Deterioration in member stiffness was accounted in the analytical model. The composite member performance assessment control parameters were calibrated from the test results. Comparisons between the cyclic load test results and analytical model validated the proposed method's effectiveness.

• Proceedings of the KSR Conference
• /
• 2002.10a
• /
• pp.620-625
• /
• 2002

In this study, the simulated cyclic train loading test was carried out in order to investigate the dynamic behavior in/at the block type reinforced earth retaining wall. The results in this test were compared with unreinforced and reinforced case, respectively. It was shown that we confirmed the correlation between earth pressure and displacement, the confining effect of wall displacement by the effect of geogrid.