• 한국지진공학회논문집
• /
• 제12권1호
• /
• pp.67-77
• /
• 2008

내진기술의 한 방안으로서 지진격리받침을 설치하여 지진력을 감소시키고, 지진피해를 최소화하고자 하는 연구가 계속되고 있다. 이와 같은 지진격리시스템의 설계 및 시공을 위해서는 먼저 지진격리받침의 제작시 지진격리받침의 균일한 품질유지 및 내진에 대한 성능검증이 뒤따라야 한다. 이를 위해 본 연구에서는 지진격리받침인 납-적층고무받침(LRB)와 적층고무받침(RB)의 전단특성 평가시험을 실시하였으며. 온도변화에 따른 전단특성 변화를 파악하기 위해 온도의존성 시험도 실시하였다. 시험후 측정값을 설계 기준값과 비교하여 전단성능에서의 오차를 조사하고, 이를 도로교 설계기준의 허용한계와 비교 분석하였다. 시험결과 지진격리받침의 상당수가 도로교 설계기준의 허용한계를 넘거나 근접해 있는 것으로 나타났다. 그리고 공용중에 전단특성을 변화시키는 온도변화에 의한 영향도 매우 큰 것으로 파악되었는데, 제작 초기의 품질오차가 이런 영향과 중첩된다면 처음 설계값보다 50% 이상 큰 전단강성 변화를 보일 가능성도 있는 것으로 나타났다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2011년도 춘계학술대회 논문집
• /
• pp.389-394
• /
• 2011

Existing FPS(Friction Pendulum System) is isolation system which is possible to isolate structures by pendulum characteristic from ground vibration. Structural natural frequency could be decided by designing the radius of curvature of FPS. Thus, response vibration could be reduced by changing natural frequency of structures from FPS. But effective periods of recorded seismic wave were various and estimation of earthquake characteristic could be difficult. If effective periods of seismic wave correspond to natural frequency of structures with FPS, resonance can be occurred. Therefore, CFPBS(Cone-type Friction Pendulum Bearing System) was developed for controlling the response acceleration and displacement by the slope of friction surfaces. Structural natural frequency with CFPBS can be changed according to position of ball on the friction surface which was designed cone-type. Therefore, Divergence of response could be controlled by CFPBS which had constantly changing natural frequency with low modal participation factor in wide-range. In this study, Seismic performance of CFPBS was evaluated by numerical analysis and shaking table test.

• 한국소음진동공학회논문집
• /
• 제21권7호
• /
• pp.599-608
• /
• 2011

FPS(friction pendulum system) is an isolation system which is possible to isolate structures from earthquake by pendulum characteristic. Natural frequencies of the structures could be determined by designing the radius of curvature of FPS. Thus, response vibration could be reduced by changing natural frequency of structures from FPS. But effective periods of recorded seismic wave were various and estimation of earthquake characteristic could be difficult. If effective periods of seismic wave correspond to natural frequency of structures with FPS, resonance can be occurred. Therefore, CFPBS(cone-type friction pendulum bearing system) was developed for controlling the acceleration and displacement of structure by the slope of friction surfaces. Structural natural frequency with CFPBS can be changed according to position of ball on the friction surface which was designed cone-type. Therefore, superstructures on CFPBS could be isolated from earthquake. In this study, seismic performance of CFPBS was evaluated by numerical analysis and shaking table test.

• Earthquakes and Structures
• /
• 제19권6호
• /
• pp.427-444
• /
• 2020

The performance of an isolated horizontally curved continuous bridge with High Damping Rubber (HDR) Bearings has been investigated under seismic loading conditions. The effectiveness of response controls of the bridge by HDR bearings for various aspects viz. variation in ground motion characteristics, multi-directional effect, level of earthquake shaking, varying incidence angle, have been determined. Three recorded ground motions, representative of historical earthquakes along with near-field, far-field and forward directivity effects, have been considered in the study. The efficacy of the bearings with bidirectional effect considering interaction behavior of bearing and pier has also been investigated. Modeling and analysis of the bridge have been done by finite element approach. Sensitivity studies of the bridge response with respect to design parameters of the bearings for the considered ground motions have been performed. The importance of the nonlinearity of HDR bearings along with crucial design parameters has been identified. It has been observed that the HDR bearings performed well in different variations of ground motions, especially for controlling torsional moment. However, the deck displacement has been found to be increased significantly in case of Turkey ground motions, considering forward directivity effect, which needs to be paid more attention from designer point of view.

• Earthquakes and Structures
• /
• 제21권5호
• /
• pp.461-475
• /
• 2021

Strategic structures are a potential target of the growing terrorist attacks, so their performance under explosion hazard has been paid attention by researchers in the last years. In this regard, the aim of this study is to evaluate the blast-resistance performance of lead-rubber bearing (LRB) base isolation system based on a probabilistic framework while uncertainties related to the charge weight and standoff distance have been taken into account. A sensitivity analysis is first performed to show the effect of explosion uncertainty on the response of base-isolated buildings. The blast fragility curve is then developed for three base-isolated steel moment-resisting buildings with different heights of 4, 8 and 12 stories. The results of sensitivity analysis show that although LRB has the capability of reducing the peak response of buildings under explosion hazard, this control system may lead to increase in the peak response of buildings under some explosion scenarios. This shows the high importance of probabilistic-based assessment of isolated structures under explosion hazard. The blast fragility analysis shows effective performance of LRB in mitigating the probability of failure of buildings. Therefore, LRB can be introduced as effective control system for the protection of buildings from explosion hazard regarding uncertainty effect.

• Earthquakes and Structures
• /
• 제24권5호
• /
• pp.333-343
• /
• 2023

Various seismic isolation and reduction devices have been applied to suppress the longitudinal vibration of continuous girder bridges. As representative devices, lead rubber bearing (LRB) and fluid viscous damper (FVD) might suffer from deterioration during the long-term service. This study aims to evaluate the impact of device deterioration on the seismic responses of continuous girder bridges and investigate the seismic behavior of deteriorated LRBs and FVDs. Seismic performance of a simplified bridge model was investigated, and the influence of device deterioration was evaluated by the coefficient of variation method. The contribution of LRB and FVD was assessed by the Sobol global sensitivity analysis method. Finally, the seismic behaviors of deteriorated LRBs and FVDs were discussed. The result shows that (i) the girder-pier relative displacement is the most sensitive to the changes in the deterioration level, (ii) the deterioration of FVD has a greater effect on the structural responses than that of LRB, (iii) FVD plays a major role in energy dissipation with a low degradation level while LRB is more essential in dissipating energy when suffering from high degradation level, (iv) the deteriorated devices are more likely to reach the ultimate state and thus be damaged.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 춘계학술대회논문집
• /
• pp.383-386
• /
• 2005

Low frequency heavy-weight impact noise is the most irritating noise in Korean high-rise reinforced concrete apartment buildings. This low frequency noise is generated by foot traffic due to the fact that Koreans do not wear shoes at home. The transmission of the noise is facilitated by a load bearing wall structural system without beams and columns which is used in these buildings. In order to control low frequency heavy-weight impact noise, floating floors using isolation materials such as glass-wool mat and poly-urethane mat are used. However, it was difficult to control low frequency heavy-weight impact sound using isolation material. In this study, reinforcement of concrete slab using beams and plate was conducted. Using the FEM analysis, the effect of concrete slab reinforcement using FRP(fiber-glass reinforced plastic) on the bang machine impact vibration acceleration level and sound were conducted at the standard floor impact sound test building. The $3{\sim}4dB$ floor impact vibration acceleration level and impact sound pressure level were reduced and the natural frequency of slabs were changed.

• Earthquakes and Structures
• /
• 제11권4호
• /
• pp.701-721
• /
• 2016

Base isolation is a well-established passive strategy for seismic response control of buildings. In this paper, an efficient framework is proposed for reliability-based design optimization (RBDO) of isolated buildings subjected to uncertain earthquakes. The framework uses reduced function evaluations method, as an efficient tool for structural reliability analysis, and an efficient optimization algorithm for optimal structural design. The probability of failure is calculated considering excessive base displacement, superstructure inter-storey drifts, member stress ratios and absolute accelerations of floors of the isolated building as failure events. The behavior of rubber bearing isolators is modeled using nonlinear hysteretic model and the variability of future earthquakes is modeled by applying a probabilistic approach. The effects of pulse component of stochastic near-fault ground motions, fixity-factor of semi-rigid beam-to-column connections, values of isolator parameters, earthquake magnitude and epicentral distance on the performance and safety of semi-rigidly connected base-isolated steel framed buildings are studied. Suitable RBDO examples are solved to illustrate the results of investigations.

• Smart Structures and Systems
• /
• 제17권5호
• /
• pp.691-708
• /
• 2016

Recently, number of smart material are investigated and widely used in civil construction and other industries. Present study investigates the application of smart semi-active piezoelectric friction damper (PFD) made with piezoelectric material for the seismic control of the horizontally curved bridge isolated with lead rubber bearing (LRB). The main aim of the study is to investigate the effectiveness of hybrid system and to find out the optimum parameters of PFD for seismic control of the curved bridge. The selected curved bridge is a continuous three-span concrete box girder supported on pier and rigid abutment. The PFD is located between the deck and abutments or piers in chord and radial directions. The bridge is excited with four different earthquake ground motions with all three components (i.e. two horizontal and a vertical) having different characteristics. It is observed that the use of semi-active PFD with LRB is quite effective in controlling the response of the curved bridge as compared with passive system. The incorporation of the smart damper requiring small amount of energy in addition with an isolation system can be used for effective control the curved bridge against the dynamic loading.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집A
• /
• pp.609-615
• /
• 2001

A turbo-fan is easily exposed to noise and vibration as against other industrial machines and the majority of them is subject to be damaged by vibration. The most usual problem of vibration in a turbo-fan is resonance so the case of being composed of iron sheet structure with low strength like a turbo-fan should be taken seriously. In this paper, FFT(Fast Fourier Transform) and Order tracking method were used to analyze factors of vibration in a turbo-fan and hereby with proper selection of vibration isolator, we wanted to reduce vibration of base. After Order tracking, we knew resonance occurred in rotational frequency 23 Hz(1400 rpm) at the casing and the bearing. After the test of base vibration using vibration isolators, the spring isolator was more effective than the robber isolator in the base vibration and the vibration isolating is more effective in the case that the isolating pad is adhered to the bottom of the isolating spring.