• Steel and Composite Structures
• /
• v.45 no.4
• /
• pp.605-619
• /
• 2022

The tensile behavior of the Thread-fixed One-side Bolt (TOB) at high temperatures was studied using the Finite Element Modeling (FEM) to explore the structural responses that could not be measured in tests. The accuracy of the FEM was verified using the test results from the failure mode, load-displacement curve as well as yielding load. Three typical failure modes of TOB connected T-stubs were observed, which were the Flange Yielding (FY), the Bolt Failure (BF) and the Coupling Failure mode (CF). The influence of the flange thickness tb and the temperature θ on the tensile behavior of the T-stub were discussed. The initial stiffness and the yielding load decreased with the increase of the temperature. The T-stubs almost lost their resistance when the temperature exceeded 700℃. The failure modes of T-stubs were mainly decided by the flange thickness, which relates to the anchorage of the hole threads and the bending resistance of flange. The failure mode could also be changed by the high temperature. Design equations in EN 1993-1-8 were modified and verified by the FEM results. The results showed that these equations could predict the failure mode and the yielding load at different temperatures with satisfactory accuracy.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.7
• /
• pp.827-834
• /
• 2014

In this paper, a triple-band U-shaped monopole antenna with T-shaped stub for WLAN(Wireless Local Area Networks)/WiMAX(World interoperability for Microwave Access) applications. The proposed antenna is based on a planar monopole design, and composed of U-shaped of radiating patch, T-shaped strip in U-shaped, for triple-band operation. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and found the parameters that greatly effect antenna characteristics. Using the obtained parameters, the antenna is fabricated. The numerical and experiment results demonstrated that the proposed antenna satisfied the -10 dB impedance bandwidth requirement while simultaneously covering the WLAN and WiMAX bands. And characteristics of gain and radiation patterns are determined for WLAN/WiMAX application.

• Steel and Composite Structures
• /
• v.15 no.2
• /
• pp.131-150
• /
• 2013

This paper presents the experimental results of axially loaded stub columns of slender steel hollow square section (SHS) strengthened with carbon fiber reinforced polymers (CFRP) sheets. 9 specimens were fabricated and the main parameters were: width-thickness ratio (b/t), the number of CFRP ply, and the CFRP sheet orientation. From the tests, it was observed that two sides would typically buckle outward and the other two sides would buckle inward. A maximum increase of 33% was achieved in axial-load capacity when 3 layers of CFRP were used to wrap HSS columns of b/t = 100 transversely. Also, stiffness and ductility index (DI) were compared between un-retrofitted specimens and retrofitted specimens. Finally, it was shown that the application of CFRP to slender sections delays local buckling and subsequently results in significant increases in elastic buckling stress. In the last section, a prediction formula of the ultimate strength developed using the experimental results is presented.

• Earthquakes and Structures
• /
• v.15 no.4
• /
• pp.351-360
• /
• 2018

Energy-based methodology is utilized to design novel timber-steel hybrid core wall system. The timber-steel core wall system consists of cross laminated timber (CLT), steel columns, angled brackets and t-stub connections. The CLT wall panels are stiff and strong, and ductility is provided through the steel t-stub connections. The structural system was modelled in SAP2000 finite element program. The hybrid system is explained in detail and validated using first principles. To evaluate performance of the hybrid core system, a 7-story building was designed using both forced-based design and energy based design (EBD) approaches. Performance of the structure was evaluated using 10 earthquakes records selected for 2500 return period and seismicity of Vancouver. The results clearly served as a good example of the benefits of EBD compared to conventional forced based design approaches.

• Journal of Korean Society of Steel Construction
• /
• v.22 no.4
• /
• pp.355-363
• /
• 2010

The objective of this study is to examine the structural performance on the Rectangular Steel Tube Column-to-H Beam connections using one-side bolts and T-stub. Although a rectangular steel tube comparing with a H-shaped steel has many advantages and is more efficient, its application is limited due to the lack of experiences and connection details. Existing steel moment connections using the rectangular steel tube are mainly using through plate diaphragms. Its processing of construction is so complicated that it is hard to apply in the field. In this study, the structural performance and the earthquake capacity for T-stub connection with one-side bolts were investigated. And it is performed a comparative analysis of strength, rigidity, total rotation and energy absorption capacity for the various connection details.

• Journal of Korean Society of Steel Construction
• /
• v.27 no.5
• /
• pp.423-433
• /
• 2015

A double split tee connection, which is a beam-column moment connection, shows different behavioral characteristics under the influences of the thickness of a T-stub flange, a high-strength bolt gauge distance, and the number and diameter of a high-strength bolt. A double split tee connection is idealized and designed that a flexural moment normally acting on connections can be resisted by a T-stub and a shear force by a shear tap. However, where a double split tee connection is adopted to a low-and medium-rise steel structure, a small-sized beam member can be adopted. Then, a shear tab may not be bolted to the web of a beam. This study was conducted to suggest the details of a connection to secure that a double split tee connection with a geometric shape has a sufficient capacity to resist a shear force. To verify this, this study was conducted to make a three-dimensional nonlinear finite element analysis on a double split tee connection.

• ETRI Journal
• /
• v.34 no.3
• /
• pp.454-457
• /
• 2012

A miniaturized planar digital video broadcasting terrestrial (DVB-T) antenna, which is composed of a patterned helical line, an open stub, and an impedance matching circuit on an FR4 (${\varepsilon}_r$=4.4) substrate for portable media player applications, is presented in this letter. The antenna has monopole-like, omni-directional radiation characteristics and a wide impedance bandwidth (VSWR<3) in the DVB-T band from 174 MHz to 230 MHz at the VHF band.

• Structural Engineering and Mechanics
• /
• v.24 no.4
• /
• pp.463-478
• /
• 2006

The design of structural frameworks for buildings is constantly evolving and is dependent on regional issues such as loading and constructability. One of the most promising recent developments for low to medium rise construction in terms of efficiency of construction, robustness and aesthetic appearance utilises concrete-filled steel tubular sections as the columns in a moment-resisting frame. These are coupled to rigid or semi-rigid connections to composite steel-concrete beams. This paper includes the results of a pilot experimental programme leading towards the development of economical, reliable connections that are easily constructed for this type of frame. The connections must provide the requisite strength, stiffness and ductility to suit gravity loading conditions as well as gravity combined with the governing lateral wind or earthquake loading. The aim is to develop connections that are stiffer, less expensive and easier to construct than those in current use. A proposed fabricated T-stub connection is to be used to connect the beam flanges and the column. These T-stubs are connected to the column using "blind bolts" with extensions, allowing installation from the outside of the tube. In general, the use of the extensions results in a dramatic increase in the strength and stiffness of the T-stub to column connection in tension, since the load is shared between membrane action in the tube wall and the anchorage of the bolts through the extensions into the concrete.

• Journal of Korean Society of Steel Construction
• /
• v.24 no.5
• /
• pp.511-520
• /
• 2012

The double split Tee connection, a type of full strength-partially restrained connection, has adequate flexural strength according to the changes in the thickness of the T-stub flange and the gauge distance of the high-strength bolts. Moreover, the double split Tee connection is designed and constructed with seismic connections that have enough ductility capacity applicable to ordinary moment frame and special moment frame by grade of steel, size of beam and column and geometric connection shape. However, such a domestic research and a proposal of a suitable design formula about the double split Tee connection are insufficient. Thus, many experimental and analytical studies are in need for the domestic application of the double split Tee connection. Therefore, this study aimed to examine and suggest feasibility of a design formula of the double split Tee connection of FEMA.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.222-222
• /
• 2007

RF circuit을 구현하는데 있어서 기판의 전기적 특성을 정확하게 아는 것은 원하는 결과를 추출하기 위해 매우 중요하다. 본 연구에서는 현재 사용되고 있는 PI 기판의 전기적인 특성인 유효 유전율과 loss tangent 값을 T-resonator률 이용해 정확하게 측정하고자 했다. T-resonator는 microstrip 구조로 구현 되었으며 conductor material은 Cu를 사용하였다. PI 기판의 두께는 25um, Cu의 두께는 PI 기판의 종류에 따라 12um 와 18um, T-resonator line width는 50um로 구현하였다. 또한 공진 주파수에 따라 stub 길이가 다른 10개의 T-resonator를 제작하였다. PI 기판의 유효 유전율을 구하기 위해 stub 길이의 open-end effect와 T-junction effect를 고려하였으며 수식을 통해 정확한 유효 유전률을 추출하였다. 또한 PI 기판의 loss tangent 추출에 필요한 dielectric loss를 추출하기 위해 unload quality factor를 분석하였다. Unload quality factor는 dielectric loss, conductor loss, radiation loss를 구성되며 conductor loss와 radiation loss를 수식에 의해 구하고 dielectric loss를 추출 하였다. 추출 된 dielectric loss를 통해 각각의 T-resonator의 loss tangent 값을 구하였다. T-resonator를 이용한 PI 기판의 측정은 비교적 복잡한 수식에 의해 이루어지지만 정확한 data를 얻을 수 있고 다른 재료의 전기적 특성을 추출하는데 응용이 가능하다.