• Computers and Concrete
• /
• 제29권 5호
• /
• pp.279-283
• /
• 2022

The seismic analytic collapse fragility of soil nail wall structures with a shotcrete concrete covering is investigated in this paper. The finite element modeling process has been well described. The fragility function evaluates the link between ground motion intensities and the likelihood of reaching a specific level of damage. The soil nail wall has been subjected to incremental dynamic analysis (IDA) from medium to strong ground vibrations. The nonlinear dynamic analysis of the soil nail wall uses a set of 20 earthquake ground motions with varying PGAs. PGD is utilized as an intensity measure, the numerical findings demonstrate that the soil nailing wall reaction is particularly sensitive to earthquake intensity measure (IM).

• 터널과지하공간
• /
• 제7권4호
• /
• pp.267-273
• /
• 1997

Rock fragmentation with plasma blasting technique has advantageous properties in contrast to the conventional blasting method in controlling of flying rocks and ground vibrations, when residents are complaining or surrounding structures stay in protection from blasting operations. The experiences show in urban construction works that the plasma blasting is the most possible method to prevent damages and minimize adverse environmnetal impacts. The fragmentation energy level is evaluated by numerical simulation using PFC-2D for various drill hole pattern and tested accordingly to get the feasibility. The energy output of plasma blasting system has been improved to a level of 1 MJ, which can break a 2~3 ㎥ granite boulder or 1.5 m height bench face. Measurements are carried out to get the ground vibration level and propagation equation, so that the control of the blasting operations can be performed more precisely and safely.

• 한국공작기계학회논문집
• /
• 제16권3호
• /
• pp.88-95
• /
• 2007

Generally, the integrated system using ion beam consists of 4 major parts, which are SEM, FIB, nano stage, and chamber. Among them, the nano stage and the chamber are designed and manufactured. The whole systems are integrated. Also, FE models are built to perform modal analyses of each part and the whole integrated system with a commercial program. Through these analyses, it is found that each part and the integrated system are very safe against vibrations including external excitations from ground and any others, because their natural frequencies are much larger than frequencies of external excitations. Also, isolation of ground induced vibration is considered.

• Structural Engineering and Mechanics
• /
• 제74권1호
• /
• pp.129-143
• /
• 2020

This study proposes a new shape memory alloy-tuned mass damper (SMA-TMD) and investigates the effectiveness of this damper in reducing and controlling the vibrations of a transmission tower-line system under various seismic excitations. Based on a practical transmission line system and considering the geometric nonlinearity of this system, the finite element (FE) software ANSYS is used to create an FE model of the transmission tower-line system and simulate the proposed SMA-TMD. Additionally, the parameters of the SMA springs are optimized. The effectiveness of a conventional TMD and the proposed SMA-TMD in reducing and controlling the vibrations of the transmission tower-line system under seismic excitations is investigated. Moreover, the effects of the ground motion intensity and frequency ratio on the reduction ratio (η) of the SMA-TMD are studied. The vibration reduction effect of the SMA-TMD under various seismic excitations is superior to that of the conventional TMD. Changes in the ground motion intensity and frequency ratio have a significant impact on the η of the SMA-TMD. As the ground motion intensity and frequency ratio increase, the η values of the SMA-TMD first increase and then decrease. Studying the vibration reduction effects of the SMA-TMD can provide a reference for the practical engineering application of this damper.

• Smart Structures and Systems
• /
• 제23권6호
• /
• pp.653-667
• /
• 2019

Using cross-ties to connect cables together when forming a cable network is regarded as an efficient method of mitigating cable vibrations. Cross-ties have been extended and fixed on bridge decks or towers in some engineering applications. However, the dynamics of this kind of system need to be further studied, and the effects of extending cross-links to bridge decks/towers on the modal response of the system should be assessed in detail. In this paper, a system of two cables connected by an inter-supported cross-link with another lower cross-link extended to the ground is proposed and analyzed. The characteristic equation of the system is derived, and some limiting solutions in closed form of the system are derived. Roots of cable system with special configurations are also discussed, attention being given to the case when the two cables are identical. A predictable mode behavior was found when the stiffness of inter-connection cross-link and the cross-link extended to the ground were the same. The vector of mode energy distribution and the degree of mode localization index are proposed so as to distinguish global and local modes. The change of mode behaviors is further discussed in the case when the two cables are not identical. Effects of cross-link stiffness, cross-link location, mass-tension ratio, cable length ratio and frequency ratio on $1^{st}$ mode frequency and mode shape are addressed.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2010년도 추계학술대회 논문집
• /
• pp.201-207
• /
• 2010

In this study, the SIP (Soil-cement Injected precast Pile) method among the Low-vibration & Low-noise pile driving methods was decided into study compensation. Ground vibrations by the SIP methods step by step divide and were analyzed. Quantitative response values and ground vibration equations with reliability were presented from findings of this study. Also, vibration responses that are occurred by the SIP method of construction were compared as quantitative with vibration responses by general method of construction that are presented in existent study. Ground vibration values by the SIP method correspond to level of 17 ~ 57% of values that are assumed by the Attewell & Famer's equation, respectively, and these result compares in reliability 50% and separated distance 10 ~ 50 m. Also, those values were analyzed that correspond to level of 14 ~ 96% of ground vibration values by the Prof. Park's equation, respectively. Construction limit extents, separation distances from vibration occurs position, were presented that can satisfy domestic criteria for vibration control for the SIP methods. Those presented in this paper were divided newly according to reliability.

• 한국지반공학회논문집
• /
• 제16권4호
• /
• pp.71-82
• /
• 2000

본 연구에서는 교량구간에서 경량전철의 주행에 의한 지반진동해석방법을 제안하였다. 경량전철의 주행시 교각에 작용하는 동하중을 열차와 교량의 상호작용을 고려하여 구하였으며, 경량전철 동하중에 의한 인근의 지반진동을 평면내 파동 전파와 축대칭 파동전파 해법을 사용하여 구한 후 비교/분석하였다. 또한, 축대칭 진동해석결과를 선형조합한 보다 엄밀한 교량구간에서의 지반진동해석법을 제시하였으며, 이를 통해 인접교각이 지반진동에 미치는 영향을 고찰하였다. 아울러 경량전철의 운행에 따른 환경진동의 문제를 평가하기 위하여 상판재료와 지반조건 등 제반사항의 변화에 따른 지반진동의 변화를 살펴보았다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제13권1호통권53호
• /
• pp.125-134
• /
• 2009

이 논문은 직시각형 단면을 갖는 원호형 등단면 띠기초의 자유진동에 관한 연구이다. 띠기초를 지지하는 지반을 두 변수 탄성지반으로 모형화하였다. 두 변수 탄성지반으로 지지된 원호형 띠기초의 휨-비틀림 자유 진동을 지배하는 미분방정식을 유도하고 이를 수치해석하여 고유진동수 및 진동형을 산정하였다. 띠기초의 경계조건은 자유-자유로 하여 최저저차 4개의 고유진동수를 산정하였다. 수치해석의 결과로, 중심각, 깊이비, 접촉비, 탄성계수비, 지반변수 등 5개의 변수가 고유진동수에 미치는 영향을 보고하였다. 변위 및 합응력의 진동형을 그림으로 나타내었다. 실험을 통하여 이 연구의 결과를 검증하였다.

• 한국철도학회논문집
• /
• 제18권4호
• /
• pp.289-300
• /
• 2015

철도 전동 소음은 철도에서 발생하는 대표적인 소음으로서 차륜과 레일의 음향 조도에 의해 가진 된 차륜 및 레일의 진동으로부터 발생한다. 철도 전동 소음 해석 시 레일 방사 소음은 자유 공간에 놓인 레일의 음향 방사 파워를 이용해 원거리에서 계산하므로, 일반적으로 소음원 모델에 지면 반사를 고려하지 않는다. 그러나 레일 주위의 근접 음장을 해석하고 저감 대책을 적용하기 위해서는 지면에 의한 음파의 반사를 고려해야 한다. 본 논문에서는 파수유한요소/경계요소법을 이용해 지면에 의해 발생하는 레일 소음의 변화와 그 특성을 살펴보았다. 해석은 먼저 레일이 강체 지면에 부착된 경우와 레일 패드 높이만큼 강체 지면에서 이격된 경우에 대해 방사효율을 구하고 그 결과를 비교하였다. 이를 통해 레일과 강체 지면의 이격 여부에 따라 레일 방사 소음에 크게 변화함을 확인하였다. 둘째로는 지면에 임피던스 경계조건을 부여하고 레일에서 방사되는 음향 파워 및 지향 특성의 변화를 살펴보았다.

• 한국소음진동공학회논문집
• /
• 제18권7호
• /
• pp.775-782
• /
• 2008

In this study, ground vibrations and aero space noises that is produced by the PRD(percussion rotary drill) were analyzed by work processes. Ground vibration equations were suggested by $2.798(SD)^{-0.793}$, $3.485(SD)^{-0.793}$, $3.705(SD)^{-0.793}$, according to experiment result, and these equations have reliability of 50%, 90%, 95%, respectively. Ground vibration values by the PRD method correspond to level of $5{\sim}34%$ of values that are assumed by the Attewell & Farmer's equation, and these result compares in reliability 50%. Also, those values were analyzed that correspond to level of $12{\sim}26%$ of ground vibration values by the Prof. Park etc.'s equations. But, the aero space noise was evaluated that is assumed by 88.9 dB(A) at separated distance 50m and is not satisfied even 85dB(A) that is the most negative noise value that present in domestic noise standard. The PRD method was analyzed that noise decrease effect exists hardly comparing with general pile driving method of construction. When is based in these results, the PRD method is judged that it is desirable that classify by the Low-vibration method more than the Non-violation noise method.