• Wind and Structures
• /
• 제12권3호
• /
• pp.205-217
• /
• 2009

Aerodynamic flutter control for long-span cable-supported bridges was investigated based on three basic girder sections, i.e. streamlined box girder section, box girder section with cantilevered slabs and two-isolated-girder section. Totally four kinds of aerodynamic flutter control measures (adding fairings, central-slotting, adding central stabilizers and adjusting the position of inspection rail) were included in this research. Their flutter control effects on different basic girder sections were evaluated by sectional model or aeroelastic model wind tunnel tests. It is found that all basic girder sections can get aerodynamically more stabled with appropriate aerodynamic flutter control measures, while the control effects are influenced by the details of control measures and girder section configurations. The control effects of the combinations of these four kinds of aerodynamic flutter control measures, such as central-slotting plus central-stabilizer, were also investigated through sectional model wind tunnel tests, summarized and compared to the flutter control effect of single measure respectively.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
• /
• pp.25-28
• /
• 2004

Many highway bridges in Korea need seismic retrofit because only one decade has passed since the seismic design criteria was introduced. In this experimental study, the effectiveness of base isolation bearings was discussed for the seismic retrofit of the highway bridges. Four real scale RC pier specimens were constructed for the test. These RC piers didn't have seismic details. Except for one RC pier for the pilot test, three types of bearings such as Pot bearing, Rubber bearing (RB), Lead-rubber bearing (LRB) were applied to the other RC piers respectively. The RC pier with Pot bearing means current state of the prototype bridge that is not retrofitted seismically. And two RC piers with RB or LRB mean assumed states of the prototype bridge that are retrofitted seismically. To simulate dynamic behavior of these RC piers under earthquake loads, Pseudo-dynamic test method was used.

• Wind and Structures
• /
• 제10권5호
• /
• pp.421-435
• /
• 2007

A two-dimensional flutter analysis method (2d-3DOF method) was developed to simultaneously investigate the relationship between oscillation parameters and aerodynamic derivatives of three degrees of freedom, and to clarify the coupling effects of different degrees of freedom in flutter instability. With this method, the flutter mechanism of two typical bridge deck sections, box girder section and two-isolated-girder section, were numerically investigated, and both differences and common ground in these two typical flutter phenomena are summarized. Then the flutter stabilization effect and its mechanism for long-span bridges with box girders by using central-slotting were studied by experimental investigation of aerodynamic stability and theoretical analysis of stabilizing mechanism. Possible explanation of new findings in the evaluation trend of critical wind speed through central vent width is finally presented.

• 한국습지학회지
• /
• 제22권1호
• /
• pp.31-38
• /
• 2020

보는 하천수량을 확보하고 낙차공은 하상안정을 위한, 그리고 교량은 차량 등의 이동을 위한 하천횡단시설물이다. 그러한 시설물의 안정성을 확보하기 위하여 하천설계기준에서는 시설물의 최소 규모에 관한 지침을 제시하고 있으나 실태 조사 결과에 의하면, 기존 보 및 낙차공의 물받이 및 바닥보호공의 규모는 설계기준을 만족시키지 못하는 경우가 대부분이고 교량의 교각은 일부만 만족시키는 것으로 나타났다. 기존 보 및 낙차공의 수리적 안정성을 제고하기 위해서는 설계기준에서 제시한 바닥보호공에 대한 물받이의 비율인 3.3을 최소값으로 확보해줄 필요가 있다. 표본하천 시설물 실태조사에 의하면 기존 보 및 낙차공을 자연형 여울공으로 개량할 경우 적용하는 종단경사는 1:20이 가장 적정한 것으로 나타났다. 또한, 교량의 철거 또는 재가설에 관한 결정에서 교각의 여유고 및 경간장 위배사항만 고려하고 있지만, 향후 교량 노후도 및 경간장 완화 규정 등을 종합적으로 검토하여 결정하는 것이 바람직하다. 본 연구에서는 설계기준, 하천실태 조사결과, 일본사례 등을 통하여 기존 보, 낙차공 및 교각의 수리적 안정성을 제고하는 종합적인 방안을 제시하였다. 하천횡단시설물의 안정화 노력은 정부 차원의 예산 지원과 적극적인 하천관리를 통하여 이룰 수 있으며, 이를 통하여 하천재해를 예방하고 건전한 하천 환경을 유지할 수 있을 것이다.

• Wind and Structures
• /
• 제30권6호
• /
• pp.633-648
• /
• 2020

The objective of this work was to investigate the interference effects of two-parallel bridge decks on aerodynamic coefficients, vortex-induced vibration, flutter instability and flutter derivatives. The two bridges have significant difference in cross-sections, dynamic properties, and flutter speeds of each isolate bridge. The aerodynamic static tests and aeroelastic tests were performed in TU-AIT boundary layer wind tunnel in Thammasat University (Thailand) with sectional models in a 1:90 scale. Three configuration cases, including the new bridge stand-alone (case 1), the upstream new bridge and downstream existing bridge (case 2), and the downstream new bridge and the upstream existing bridge (case 3), were selected in this study. The covariance-driven stochastic subspace identification technique (SSI-COV) was applied to identify aerodynamic parameters (i.e., natural frequency, structural damping and state space matrix) of the decks. The results showed that, interference effects of two bridges decks on aerodynamic coefficients result in the slightly reduction of the drag coefficient of case 2 and 3 when compared with case 1. The two parallel configurations of the bridge result in vortex-induced vibrations (VIV) and significantly lower the flutter speed compared with the new bridge alone. The huge torsional motion from upstream new bridge (case 2) generated turbulent wakes flow and resulted in vertical aerodynamic damping H1^* of existing bridge becomes zero at wind speed of 72.01 m/s. In this case, the downstream existing bridge was subjected to galloping oscillation induced by the turbulent wake of upstream new bridge. The new bridge also results in significant reduction of the flutter speed of existing bridge from the 128.29 m/s flutter speed of the isolated existing bridge to the 75.35 m/s flutter speed of downstream existing bridge.

• 한국지진공학회논문집
• /
• 제11권1호
• /
• pp.21-27
• /
• 2007

본 연구에서는 교량의 내진보강을 위하여 기존 교량에 지진격리장치를 추가하는 접근법을 제안하였다. 기존 받침을 지진 격리받침으로 완전히 대체하는 접근법도 이미 제안되어 있지만 본 연구에서는 경제성과 안전성을 고려하여 기존 받침을 제거하지 않고 활용하도록 하였다. 이는 지진격리받침이 상부 수직하중을 분담하지 않고, 수평방향의 지진운동에 대한 주기 이동과 감쇠 역할만 한다. 이 접근법의 실험적 검증을 위해 실제 교량을 대상으로 납-적층고무받침(LRB)을 설계하고 실물크기로 기존 받침과 LRB를 제작하였다. 이 지진격리시스템의 가상 지진입력에 대한 응답은 유사동적실험으로 구하였다. 아울러 범용해석프로그램을 통한 지진응답해석과 비교하여 실험결과의 신뢰성을 확인하였다. 실험결과 제안된 지진격리시스템은 지진시 안정적인 거동을 보였다.

• Earthquakes and Structures
• /
• 제16권6호
• /
• pp.641-654
• /
• 2019

This paper investigates the seismic response of a typical non-navigable continuous girder bridge isolated with friction sliding bearings of the Hong Kong-Zhuhai-Macao link projects in China. The effectiveness of the friction pendulum system (FPS) and accuracy of the numerical model were evaluated by a 1/20 scaled bridge model using shaking table tests. Based on the hysteretic properties of friction pendulum system (FPS), double concave friction pendulum (DCFP), and triple friction pendulum system (TFPS), seismic response analyses of isolated bridges with the three sliding-type bearings are systematically carried out considering soil-pile interaction under offshore soft clay conditions. The fast nonlinear analysis (FNA) method and response spectrum are employed to investigate the seismic response of isolated offshore bridge structures. The numerical results show that the implementation of the three sliding-type bearings effectively reduce the base shear and bending moment of the reinforced concrete pier, at the cost of increasing the absolute displacement of the bridge superstructure. Furthermore, the TFPS and DCFP bearings show better isolation effect than FPS bearing for the example continuous girder bridge.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
• /
• pp.482-489
• /
• 2000

The cyclic extrusion damper, Lead Extrusion Damper, was invented by the W H Robinson in order to produce the isolated buildings and bridges the damping force. Recently, LED was applied to reduce the vibration of the tall building. In this study, to verify the dynamic characteristics of LED, the tests to find out the dependences on the velocity, displacement, repeated cycle, and temperature were performed at structural lab of Unison Industrial Co. Ltd. Through the result of the dynamic characteristics. we`ll define the design parameters and apply the appropriate parts.

• 한국해양공학회지
• /
• 제20권5호
• /
• pp.63-69
• /
• 2006

An isolated bridge using a laminated rubber bearing provides an elastic support of continuous span and prevents the transmission of excessive seismic force from the substructure of the bridge, which uses a metal bearing, as this permits a relative displacement between the super-and substructure. Hawever, this kind of bridge is caused long periodic, as a result of enlargingtotal thickness of the rubber, since it corresponds to temperature change and increases the horizontal displacement of the superstructure. This paper uses a numerical study to describe the pounding problem between adjacent decks when subjected to a strong earthquake. Furthermore, numerical results are clarified for the buffer rubber used to mitigate the pounding force between adjacent decks.

• 한국지진공학회논문집
• /
• 제2권3호
• /
• pp.51-60
• /
• 1998

Base isolation is an innovative design strategy that provides a practical alternative for the seismic design of structures. Base isolators, mainly employed to isolate large structures subjected to earthquake ground excitations and to rehabilitate structures damaged by past earthquakes, deflect and absorb the seismic energy horizontally transmitted to the structures. This study demonstrated that the base isolation system may offer effective performance for bridges during severe seismic events through shaking table tests. Two base isolation systems using laminated rubber bearings with and without hydraulic dampers are tested. The test results strongly show that the laminate rubber bearings cause the natural period of the bridge structure increased considerably, which results in the deck acceleration and the shear forces on the deck acceleratino and the shear forces on the piers reduced significantly. The results also demonstrate that the hydraulic dampers enhance the system's capacity in dissipating energy to reduce the relative displacement between the bridge deck and the pier.