• Journal of Korean Society of Steel Construction
• /
• v.29 no.4
• /
• pp.269-280
• /
• 2017

In this study, seismic performance was evaluated for the exposed column-base plate weak-axis connections of small size steel structures through cyclic loading tests. The primary test parameters are the thickness of base plate, the presence of rib plates, the number of anchor bolts and embedment length of anchor bolts. To investigate the effect of bond performance of anchor bolts on the seismic performance of column-base plate connections, L-shaped round bars and thread bars were used as the hooked anchor bolts in the test specimens. Test results showed that bond performance of anchor bolts and the thickness of base plate significantly affect the structural performance and energy dissipation capacity. In particular, it was found that even if the requirements for minimum thickness of the base plate that is satisfied, the base plate can yield before the capacity of steel column reaches the plastic moment resulting in decreasing the structural performance of the connections. However, the proposed details of the connections might be considered as the partially restrained, that is semi-rigid connections. Consequently, the L-shaped thread anchor bolts is applicable in the exposed column-base plate weak-axis connections of small-size steel structures.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.16 no.6
• /
• pp.134-142
• /
• 2012

This paper presents a study of system identification on the tilt response of the L-type retaining wall located at Tanhyun 11th ACE Apartment, Ilsan in order to understand mechanism how the structure behaves in operational conditions and to provide a reference tilt values for assessing structural abnormality. The retaining wall was extraordinarily tall (14m) in urban area so the long-term monitoring system had been installed with 3 tilts-meters and 9 temperature sensors operational from Oct 2004 upto Nov 2007. By using 5-months continuous data in which all the 12 channels were up and running, the two prediction models, 1) the linear model, and 2) the state-space equation (SSE) model, have been identified by finding the best fitness model among all possible 511 combinations of input temperatures out of the 9 temperatures. The linear model which was simple in the model structure achieved the validation fittness of 68% due to the fact that the static model wasn't able to represent thermal dynamics. The SSE model achieved the validation fitness of 90% which was quite accurate considering various unexpected noises happening in field measurements.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.14 no.3
• /
• pp.31-37
• /
• 2015

In this paper, newly proposed dual-band microstrip antennas using stacked inverted-L-shaped parasitic elements are presented for GPS $L_1(1.575GHz)$ and $L_2(1.227GHz)$ bands. For making dual band which has large interval, ${\lambda}/4$($L_1$ band) inverted-L-shaped parasitic elements were stacked at both side of radiation apertures on the half-wavelength($L_2$ band) patch antennas. The resonance in the parasitic elements occurs through coupling to the patch. Next, due to using circular polarization at GPS, ${\lambda}/4$($L_1$ band) inverted-L-shaped parasitic elements was stacked using sequential rotation technique on the patch and both side of the diagonal corners of the antenna were eliminated to make dual-band circular polarization. The designed circular polarized antenna's dimensions are $0.43{\lambda}L{\times}0.43{\lambda}L{\times}0.06{\lambda}L$ (${\lambda}L$ is the free-space wavelength at 1.227 GHz). Measured -10 dB bandwidths was 120 MHz(7.6%) and 82.5 MHz(6.7%) at GPS $L_1$ and $L_2$ bands. and 3 dB axial ration bandwidths are 172 MHz(10.9%) and 25 MHz(2.03%), respectively. All of these cover the respective required system bandwidths. Within each of the designed bands, broadside radiation patterns were observed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1994.10a
• /
• pp.225-230
• /
• 1994

본 연구에서는 진동특성을 개선하기 위한 방법으로서 구조물이 가지는 공간적인 좌표를 설계변수로 하여 감도를 구하고, 이를 이용하여 구조물의 길이와 높이에 대한 형상을 변경하는 최적구조변경법에 대해 예시하고자 한다. 먼저 모우드합성법을 이용하여 임의 치수의 L형 구조물의 진동특성을 해석하고, 진동 특성을 변경하기 위해 감도해석법으로 변경할 부분의 감도를 구하여 변경할 부분의 변경량을 계산한다. 그리고 변경한 후 재해석을 통해 결과를 비교함으로써 제시한 방법의 타당성을 고찰하고자 한다.

• 발명특허
• /
• v.31 no.8 s.362
• /
• pp.64-67
• /
• 2006

'한강의 기적'이라는 말이 있듯 우리나라의 근대화, 산업화는 그 어느 나라에서도 유래를 찾아볼 수 없을 만큼 눈부신 성장속도를 자랑한다. 그러나 근대화, 산업화라는 명분 아래 우리에게 너무나도 고마운 존재인 자연환경에 대한 외면은 이미 수많은 부작용을 낳고 있다. 그 예로 우리 생활환경에 아주가까운 물인 하천은 심각하게 오염되고 더 이상 오염되어 가는 하천을 그냥 두고 볼 수 만은 없는 일이 되어 버렸다. 이러한 필요에 의해 몇 년 전부터 활발하게 이루어지고 있는 하천의 개보수공사는 석축 쌓기, L형 옹벽 및 돌망태, 견치석 등을 사용하고 있는데, 이는 하천의 생태계를 단절시키는 또 하나의 문제를 야기하고 있다. 또한 이런 과정을 통해 하천이 직선화되면서 홍수가 났을 경우 피해를 가중시키고, 자연석을 고갈시키는 등의 문제점이 대두되고 있다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1996.03b
• /
• pp.16-22
• /
• 1996

Two kinds of blank shapes, optimum and square, are adopted to investigate formbility. Optimum blank shape is determined to construct an L-shape cup with uniform height and without flange part. For this purpose , rigid-plastic FEM analysis is applied with backward tracing technique. Maximum cup detph and strain distribution are measured experimetally for the products of the two kinds of blank shapes, which are optimum and square.It is confirmed that deeper cup without severe thickness reduction can be obtained fro the optimum shape.

• Journal of Korea Foundry Society
• /
• v.5 no.2
• /
• pp.125-136
• /
• 1985

The most desirable method for the solution of solidification problems in castings must be the one which combines accuracy, simplicity, and low computer usage cost. The purpose of the present study is to develop a method which includes all these advantages. The purpose of the present research was approached by the introduction of two methods: (1) A pour-out test, employed with very high purity aluminum, for the purpose of obtaining accurate solidification data in L-sections; and (2) an numerical technique, using the cubic spline function for defining solidification curves.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2007.04a
• /
• pp.440-443
• /
• 2007

In this paper, microstrip antenna is designed for industrial-scientific-medical(ISM)band of S-Band. We proposed that radiation element of antenna, which is rectangle patch shape. The feeding structure used L-shaped structure. Center frequency and -l0dB bandwidth are investigated by change of length and width in patch plane. And maximum gain, front to back ratio and 3dB beam width is presented by simulation radiation pattern of antenna in frequency ISM Band. The center frequency is 2.45GHz, band width is $2.314{\sim}2.577GHz$ with 263MHz(11%). And the antenna maximum gain is 9.3dBi, 3dB beam width E-plane is $52.5^{\circ}$, H-plane is $64.7^{\circ}$.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.5A
• /
• pp.267-275
• /
• 2012

This paper describes the experimental study on the structural behavior of the joint plane between a RC(Reinforced Concrete) wall and a SC(Steel Plate Concrete) wall under out-of plane flexural loads and in-plane shear loads. The test specimens were produced with L and I shape to assess efficiently flexural and shear behavior of the structures. In order to consider dynamic loads such as earthquake, cyclic loading tests were carried out. As results of the out-of plane flexural tests, ductile failure mode of vertical bars was shown under a push load and the failure load was more than nominal strength of the specimen. And the latter test was performed to verify the variation which was composition presence of horizontal bars in the SC member. The test results showed that capacity of the specimens was more than their nominal strength regardless of composition presence of horizontal bars.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.37 no.2
• /
• pp.343-355
• /
• 2017

In this study, an Assembled Earth Retaining Wall (AER wall) is newly proposed. The AER wall combined stabilizing piles names as Back Supporting Beam is developed to improve stability and economics of existing retaining walls. For the verification of the AER wall, the field model tests and 3D numerical analyses were performed. As a result of the field tests, it can be confirmed that the earth pressure is considerably reduced compared with the L-shaped retaining wall. Also, the 3D numerical analyses show that AER wall is at least 29.85% more effective at lateral displacement than general L-shaped retaining wall. In other words, AER wall is expected to raise economical efficiency because of excellent mechanical stability of Back Supporting Beam.