• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.141-146
• /
• 2000

Crack closure and growth behavior of physically short fatigue cracks under random loading are investigated by performing narrow- and wide-band random loading tests for various stress ratios. The importance of the crack closure phenomenon is examined by predicting the growth lives of short cracks using obtained crack opening behavior. Artificially prepared two-dimensional, short through-thickness cracks are used. The crack opening load of short cracks is much lower under random loading than under constant-amplitude loading corresponding to the largest load cycle in a random load history. This result indicates that the largest load cycle in a random load history has an effect to enhance crack opening of short cracks. Most of the life prediction ratios are within the factor of 2 scatter band except several data at very short crack sizes, indicating that crack growth predictions based on the measured crack opening data are excellent. From the results obtained in this study, it can be concluded that crack closure is the primary factor governing fatigue crack growth of short cracks under random loading as well as under constant-amplitude loading.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.457-460
• /
• 2004

This study is an experimental study to investigate the shear behavior of reinforced concrete shear walls with openings and to determine the shear strength of those walls. This paper compares rigidities of walls with opening by different opening types. The experimental results, as expected, show that the crack load, yield load, and limited load are inferior for specimen with larger opening area. The magnitude of axial stress and shear stress had a significant effect on the deformability of shear walls with opening.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.6
• /
• pp.1576-1582
• /
• 1990

To examine small fatigue crack behavior, the crack opening displacement (COD) was measured for surface cracks in the range of few tens to hundreds .mu.m using the computerized Interferometric Strain/Displacement Gage (ISDG) which could measure the relative displacement with a resolution of 0.02 .mu.m. The load-COD record is stored and analyzed after the test to determined the opening load. Single-edge notched specimens, 2.3mm thick, of Al 2024-T3 were precracked at load ratios of 0.0, -1.0 and -2.0 to make small fatigue cracks. The opening loads were measured these small cracks and compared with those of long cracks. The opening load ratios for the short cracks are about 10% smaller than those for long cracks at positive R-ratios, but are about 100% smaller at negative R-ratios.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.9 s.180
• /
• pp.2283-2291
• /
• 2000

The neural network method is applied to automatically measure the crack opening load under random loading. The crack opening results obtained are compared with the visual measured results. Fatigue crack growth under random loading is predicted using the crack opening data measured by the neural network method, and the prediction results are compared with experimental ones. It is found that the neural network method can be successfully applied to consistently measure the crack opening load under random loading and also gives some results different from the results by visual measurement.

• Steel and Composite Structures
• /
• v.50 no.1
• /
• pp.1-13
• /
• 2024

The objective of this research is to study experimentally and numerically the behavior of steel beam columns with openings. Although the presence of openings in the beam columns is inevitable, finding ways to maintain strength is crucial. The studied parameters are opening shape, the ratio between opening height to specimen height, the percentage of opening location from support to beam column length, and web slenderness. Experimental tests are conducted including twelve specimens to study the effect of these parameters and record failure load, load deflection curve, and stress strain curve. Two failure modes are observed: local and flexural buckling. Interaction curves plotted from finite element model analysis are also used to expand the parametric study. Changing the location of the opening can decrease failure load by up to 7% and 60% in both normal and moment ratios respectively. Increasing the opening dimension can lead to a drop in the axial ratio by up to 29% and in the moment ratio by up to 74%. The weakest beam column behavior is noticed in specimens with rectangular openings which results from uneven and concentrated stresses around the opening. The main results of this research illustrate that the best location for opening is at 40% - 50% from beam column support. Also, it is advisable to use circular openings instead of rectangular openings in specimens having slender webs because moment ratios are raised by 85% accompanied by a rise in normal ratios by 9%.

• KIEAE Journal
• /
• v.8 no.2
• /
• pp.41-46
• /
• 2008

Owing to a space covered by glass, atrium is an attractive space with a possibility as an inner public space but a typical building type with a high-energy load. From the aspect of global environmental issues, to reduce energy load is an important assignment to solve. Contriving a planning guideline of an opening is considered as the most effective environment adjustment method, to offer a highly assessed amenity space and secure openness to outside, keep the energy load to a minimum, and apply the natural energy such as daylight to a maximum at the same time. Users' assessment of environment was performed by questionnaire survey, then the structure of users' assessment was analyzed and design condition was regulated by multiple regression analysis. The opening design guideline to offer a highly assessed space was proposed with concrete environment adjustment method.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.67-72
• /
• 2001

The LBB behavior and the crack opening displacement after a crack penetrated wall thickness of statically indeterminate piping system were investigated in this study, compared with statically determinate piping system. The reduction of ultimate strength caused by a crack was relatively small in the statically indeterminate piping system. The statically indeterminate piping system has more safety margin for LBB behavior than the statically determinate piping system. The crack opening displacement could be evaluated by using the plastic rotation angle proposed to evaluate the crack opening displacement after crack penetration in pipe with a non-penetrating crack.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.447-452
• /
• 2001

An automated system is developed to perform fatigue crack growth tests under constant effective stress intensity factor range ${\Delta}K_{eff}$. In the system, crack length and crack opening load are measured in real-time by using the unloading elastic compliance method. The system consists of two personal computers, an analogue electrical subtraction circuit, a stepping motor, a stepping motor driver, a PIO board, and the application software used to integrate the whole system. The performance of the developed system was tested and discussed performing constant ${\Delta}K_{eff}$ crack growth tests on a CT specimen of 7075-T6 aluminum alloy. The performance of the system is found to be strongly dependent on the accuracy of measurements of crack opening load. Besides constant ${\Delta}K_{eff}$ testing, the system is expected to be successfully applied for automation of various fatigue tests.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.11
• /
• pp.1092-1100
• /
• 2004

This paper presents the effect of opening configuration on the thermal behavior and air pattern of earth tube system. The earth tube system is a fresh air load reduction system by using underground double floor space for air-conditioning. In order to analyze the effect of opening configuration on thermal performance of this system and air pattern in underground double floor space quantitatively, we used a model dealing with tree-dimensional profile of wind velocity and temperature in underground double floor space. In conclusion, it is confirmed that heat exchange of a fresh air is mainly performed with upper and lower wall in underground double floor space, and that heat exchange area increased by installing the opening near the wall.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2008.04a
• /
• pp.313-318
• /
• 2008

The blast load is caused by gas or bomb explosions. In this study blast load was simulated using the computer code CONWEP and nonlinear analysis was performed on three-story steel moment frames. It was observed from the analysis results that the response of the structures varied depending on the opening area and the explosive weight.