• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.1 s.24
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• pp.11-20
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• 2007

The study proposes the method to cancel the scallop to avoid fracture of the circumstance of the scallop at H shape column-to-beam connection and reinforce at beam flange two faces with the cover plates and rib. A total of four specimens were tested to enhance seismic performance of building structure by reducing the frequency of stress concentration and preventing the brittle fracture of scallop. For this purpose, four full-scale test specimens were made and loaded with quasi-static reversed cyclic loading. The main analytical parameters are panel-zone-strength ratio, yield strengths, initial stiffness, total plastic rotation, contribution of each element to total plastic rotation and energy dissipation capability. For the specimens tested under repeated loading, the experimental result was satisfied with seismic performance requirement as the Special Moment Frames (SMF). The analysis results show that all of the test specimens were found to have good performance to 4% story drift and satisfied the criteria for the plastic roation capacity of SMFs that is 0.03 rad. according to the 1997 AISC seismic provision.

• Composites Research
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• v.30 no.2
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• pp.132-137
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• 2017

The purpose of this paper is to investigate failure characteristics of Carbon/BMI-Nomex honeycomb sandwich on design parameters. A total of 6 types sandwich specimens were manufactured according to core height, face thickness and density, and environmental condition were applied to evaluate temperature and humidity effects of one of these specimens. The test results show that the core shear buckling loads was commonly observed in all specimens except for the joint with density of $64kg/m^3$. After core shear buckling, however, the joint carried additional loads over the buckling loads and then finally failed in the upper face and lower face at the same time. In the case of specimen having high stiffness, the maximum failure load was low due to interfacial failure of the upper face and core without initial core shear buckling. The ETW1 and ETW2 conditions, which were carried out to evaluate the environmental condition of the sandwich specimen, show an initial failure mode which was significantly different from RTD condition. Also, the ETW2 condition with increased temperature under the same humidity shows that the core shear buckling load was 18% less than ETW1 condition.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.42-48
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• 2009

There are a number of factors affecting the continued airworthiness of composite structure. Unlike metal structure, damages made in manufacturing processes or maintenance repair procedures need to be considered. The different levels of degradation and damage, which may occur, must be considered for structural substantiation of static strength, stiffness, flutter, and damage tolerance. This can start with an evaluation of environmental effects for the particular composite material. Matrix-dominated composite properties, such as compressive strength, are most sensitive to moisture absorption and temperatures. Static strength substantiation includes the smaller damages that will not be detected in production or maintenance inspection while damage tolerance addresses larger damages that need to be repaired once discovered. In this paper, we intend to list the airworthiness regulations and advisory circular that are deemed closely related to the certification of composite airplanes.

• Journal of Korean Society of Steel Construction
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• v.22 no.2
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• pp.121-128
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• 2010

The current trends in steel construction involve the use of tapered sections to minimize the use of excess materials to the extent possible, by choosing cross-sections that are as economical as possible abandoning the classical approach of using prismatic members. In addition, snug-tightened connections, especially the end-plate type, have the advantage of fetching less construction costs and shorter assembly times as opposed to fully tightened joints. Although they have many merits, however, snug-tightened bolted end plates are extremely complex in their structural behavior. In this study, an experimental investigation of the snug-tightened flush end-plate connections of tapered beams were conducted. The primary test parameters were the torque for the clamping bolt, the loading pattern, the bolt type and the connection failure type. Using initial stiffness and load-carrying capacity as proposed by Silva et al. and AISC (2003), the moment-rotation curve of a linearly tapered member with a snug-tightened flush end-plate connection was predicted. Moreover, numerical and experimental data for moment-rotation curves were compared.

• Journal of Korean Society of Steel Construction
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• v.28 no.6
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• pp.427-438
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• 2016

This study is experimental research for the effect of gap at the end plate on the performance of extended end-plate type splice. For this research, simple beam type specimens by using extended end-plate type splice are planned. Main variables are the initial gap between end-plates, the installation of finger shim plate before the installation of high tension bolts, the final gap between end-plates, and the installation of finger shim plate after the installation of high tension bolts. The static loading tests results show that the maximum bending strength of splice is not dependent on the gap, but the vertical displacement, initial stiffness and elastic stiffness are affected by the gap. In addition to that, the possibility of brittle fracture is increased when the torque of high tension bolt is used to control the gap. Thus, careful consideration is needed in this case.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.103-112
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• 2005

This study examines the stability of Sungsu bridge which was issued nine years ago because of its collapse accident and now is on the progress of extension work in each construction stage by construction monitoring system. From this study, the measured value in each construction stage of anchorage truss and suspended truss shows the agreement with the analytical values up to 60~110 percents, and the elements' stresses emanating from the pre-loading stage, are also similar to the analytical value. Regarding these results, it is expected that each member has enough stiffness and the construction condition is satisfactory. In addition, it is expected that the transverse members and sway bracing bolts integrate completely the existing truss and new attached truss as a one body from the result of the vibration test to find out the integration rates.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.11-19
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• 2022

In this study, in order to improve the splice performance of mechanical couplers, two new mechanical couplers with different connection modes were developed with rebar(SD400). The stress analysis of mechanical couplers with two different connection modes was carried out. Uniaxial tensile tests were carried out with type of steel, connection mode and the slope length of internal fastener as variables to analyze the influence on the maximum tensile strength. Building upon this previous work, the specimens that met the code in uniaxial tensile test were fabricated and static loading test and cyclic loading test were performed on the basis of Korean code(KS D 0249). The results of this research are as follows; (1) The tensile strength of steel and the slope length of internal fasteners have a certain influence on the maximum tensile strength. (2) The connection mode has some influence on the stiffness, slip and stiffness reduction rate of the connecting rebars. The results verify the feasibility of the proposed enhanced mechanical coupler in the field.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.10-21
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• 2014

The joint of prefabricated steel grid composite deck is composed of concrete shear key and high-tension bolts. The flexural and shear strength of the joint were experimentally evaluated only by the bending and push-out test of the joint element. In this study the lateral load transfer behavior of the joint in deck structure system is experimentally evaluated. Several decks connected by the joint are prefabricated and loaded centrically and eccentrically. In the case of centrically loaded specimens, the analysis results show that for the same loading step the rotation angle of the joint with 4 high-tension bolts is larger than the case of the joint with 9 high-tension bolts. Consequently, flexural stiffness of deck and lateral load transfer decrease in the case of specimen with 4 high-tension bolts. But, in the case of eccentrically loaded specimens, it is found that there are no significant differences in the load transfer behavior. The further analysis results about the structural behavior of the joint show that lateral load transfer can be restricted by the load bearing capacity of the joint as well as punching shear strength of the slab. Furthermore, considering that high-tension bolts in the joint didn't reach to the yielding condition until the punching shear failure, increase in the number of high-tension bolts from 4 to 9 has a greater effect on the flexural stiffness of the joint and deck system than the strength of them.

• Journal of Bio-Environment Control
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• v.29 no.4
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• pp.473-479
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• 2020

In this study, the structural experiment was conducted with two types of specimens to investigate the mechanical behavior of the column-rafter-purlin connection of an arch-type greenhouse under monotonic loading. Based on the experimental results, the flexural performance was analyzed for two types of connections, and connection classification was attempted. Type B showed 77% of flexural performance compared to Type A, and both types showed that the rigidity and flexural strength did not reach the level of the full rigid. The behavior of the column-rafter-purlin connection was dominated by local buckling due to deformation of the weld and fasteners. As a result of connection classification by AISC standard, both Type A and B connections showed a result that did not meet the rigid connection performance assumed during design, and were classified as simple connection. Therefore, the connection performance evaluation and classification results show that the greenhouse design should be made in consideration of connection performance and in order to design a reliable greenhouse structure, a study on establishing clear design standards for the greenhouse connection is necessary.

• Journal of Korean Society of Steel Construction
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• v.28 no.6
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• pp.459-465
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• 2016

In this paper, it was performed the fatigue test to examine the effect of cyclic loading for the simple T-joint. Axial force of bolt by clamping and the change of the force by applied load were measured in the joint. And the bolt force, the failure mode and the fatigue strength under cyclic loading were investigated. The parameters of the tension joint were set to be the flange thickness and the diameter of bolt to a different stiffness of the joint in response to the combination. From the fatigue test, failure mode of tensile joints under cyclic loading could be evaluated using a static ultimate load of the specific failure mode in EC3. The fatigue strength of the tension joints was considerably higher than the fatigue strength of the EC3(36) that does not consider a lever action. However, the additional axial force by lever action occurs to an increase in the axial force of the bolt it requires a careful evaluation of the fatigue strength.