• Title/Summary/Keyword: Deflection limit

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Deflection Limit on Vibration Serviceability of High-speed Railway Bridges Considering the Exposed Time Duration (진동지속시간을 고려한 고속철도교량의 진동 사용성 처짐 한계)

  • Jeon, Bub-Gyu;Kim, Nam-Sik;Kim, Sung-Il
    • Proceedings of the KSR Conference
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    • 2010.06a
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    • pp.1444-1451
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    • 2010
  • This paper aims for proposed the deflection limit on vibration serviceability of high-speed railway bridges considering the exposed time duration when a train passes a railway bridge. For this purpose, bridge-train transfer function was derived and bridge-train interaction analysis was performed by using the derived function. The vertical acceleration signals of passenger cars obtained from bridge-train interaction analysis were compared with them from the bridge-train transfer function by moving constant force analysis. Therefore it was estimated possible to induce the comfort deflection limit of railway bridge by using bridge-train transfer function. The deflections by moving force of single span bridge and continuous bridge were assumed as sine and haversine wave. The deflection limit on vibration serviceability of high-speed railway bridges considering the exposed time duration can be expanded using bridge-train transfer function and bridge comfort limit considering serviceability due to bridge vibration. And it was compared to other allowable deflection limits of railway bridge design specifications.

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Handling Deflection Limit in Open-Loop-Onset-Point PIO Analysis (Open-Loop-Onset-Point PIO 해석의 변위한계)

  • Park, Sang-Hyuk
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.2
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    • pp.135-140
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    • 2010
  • A new treatment is proposed to handle a deflection limit in the open-loop-onset-point (OLOP), which is commonly used in the prediction of pilot in-the-loop oscillation (PIO) due to a rate saturation. The new approach is motivated by the frequency response of a stand-alone actuator in that, unlike the suggestion by the original OLOP procedure, the rate limit onset is not delayed to a higher frequency by a deflection limit. Indeed, if a feedback control loop is closed, the rate limit onset can be shifted to a lower frequency since the controller tends to react with larger commands when deflection limited. The amplitude of the command at this onset frequency is combined with the deflection limit to estimate the associated gain reduction in the open-loop-onset-point in the final step of the OLOP process. The comparison of the new approach with the previous method reveals that an inaccurate optimism which can occur in the previous method is corrected by the proposed treatment.

Comparison of Reliability of PSSC Girder Bridge for Different Limit States (PSSC 거더 교량의 한계상태별 신뢰도 비교)

  • Hwang, Chul-Sung;Paik, In-Yeol
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.11 no.1
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    • pp.171-180
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    • 2007
  • Reliability analysis of prestressed steel and concrete(PSSC) girders is conducted for deflection, stress and moment strength limit state. PSSC girder has strong advantages in terms of construction cost and vertical clearance for the span length of over 40 meters. In this paper, example PSSC girders with different span lengths, section dimensions and design stress levels are designed and analyzed to calculate the midspan deflection, stress and the section moment strength. Deflection limit state, stress limit state and strength limit state functions are assumed and the reliability indexes are obtained by Monte-Carlo simulation and Rackwitz-Fiessler procedure. The results show that the reliability of PSSC girder for deflection limit state is appropriately higher than the stress limit state and the reliability for moment strength is significantly conservative.

Bending Properties of Parallel Chord Truss with Steel-Web Members

  • Hyung Woo LEE;Sang Sik JANG
    • Journal of the Korean Wood Science and Technology
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    • v.51 no.3
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    • pp.197-206
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    • 2023
  • A truss is a structure in which the members are connected and arranged such that they are primarily subjected to axial loading. A truss has the advantage that it can be used for a longer span because the structure distributes the applied force to its members well, and the load is transmitted only in the axial direction of the members. Trusses manufactured using timber have more advantages than those made of other materials. In this study, the properties of parallel chord trusses composed of timber chord and steel-web members were evaluated. We constructed truss specimens with various lengths by using upper and lower chords of 2 × 4 inch spruce-pine-fir lumber and steel-web members manufactured by S and P companies. The specimens were tested in accordance with KS F 2150. The test results showed that the load at the deflection limit and the deflection limit itself increased from L/180 to L/360 regardless of the length of the specimens. For specimens of the same length, the load at the deflection limit increased as the height of the parallel timber chord truss specimens increased from 200 to 300 mm. Successive installations of the steel-web members (SST) showed almost 2 times the load at each deflection limit compared to that of SAT specimens (alternate installation of the steel-web members). When comparing the three load-deflection limits in terms of the manufacturer of the steel-web members, the load at each deflection limit for SST specimens was higher than that for PST specimens.

The Mechanical Behavior and the Anatomical Changes of Wood due to Variation of Deflection Rates

  • Kang, Chun Won
    • Journal of the Korean Wood Science and Technology
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    • v.33 no.5 s.133
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    • pp.7-12
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    • 2005
  • The objective of this study is to estimate the mechanical behavior in bending and the anatomical changes of wood under several deflection rates. Sample specimens of water-saturated Japanese cedar (Cryptomeria japonica) were stressed to rupture under several deflection rates. Mechanical properties of wood such as modulus of elasticity, modulus of rupture and stress at proportional limit, and anatomical changes affected by deflection rates were estimated. Microscopic observations on compression side of the test specimens when the specimen was loaded to rupture were carried out by the SEM (scanning electron microscopy). The results are summarized as follows: 1. The mechanical properties of wood were affected by variations of the deflection rates. The modulus of elasticity (MOE), modulus of rupture (MOR) and stress at proportional limit were in proportion to the logarithm of deflection rates. 2. The deflection of wood at rupture in bending increased as deflection rates decreased. 3. The variations of the microscopic deformations of sample specimens were closely related to the deflection of wood at rupture. In case of largely deflected wood by maximum bending load, severe and abundant microscopic deformations were observed.

Deflection Limit for a Maglev Railway Guideway Considering Ride Comfort (승차감을 고려한 자기부상철도 가이드웨이 구조물의 처짐 한계)

  • Lee, Jin Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.33 no.6
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    • pp.367-374
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    • 2020
  • A standard for the vibration magnitude of a maglev train is presented herein to ensure a comfortable ride for the passengers. The vibration magnitude is determined from the vertical acceleration of the car body. A parameter analysis of the maglev train system is then performed considering the vehicle-structure interaction, and a deflection limit of L/1300 is proposed to satisfy the standard for the vertical acceleration. The proposed deflection limit is applied to the dynamic analysis of the actual maglev train system to assess applicability. Compared with the existing standard for the guideway structure, the proposed deflection limit is expected to enable economical design and construction.

Estimation of Stiffness Limit for Railway Bridge Vibration Serviceability (진동사용성을 고려한 철도교량구조물의 강성한계 분석)

  • Park, Kyung-Rock;Jeon, Bub-Gyu;Kim, Nam-Sik;Kim, Sung-Il
    • Proceedings of the KSR Conference
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    • 2008.06a
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    • pp.80-85
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    • 2008
  • In general, deflection limit criteria of bridge design specifications have been considered based on static serviceability and structural stability. Dynamic serviceability induced from bridge vibration actually has not been included in the criteria. Thus, it is necessary for comfort limit to be considered in order to check dynamic serviceability on bridge vibration. In this study, the comfort limit of bridge structures based on the RMQ and VDV considering the signal fluctuation effectively and the time duration exposed has been constructed. The comfort limit developed in time domain was verified by using vibration signals directly measured from the existing bridges. Comparing the developed comfort limit with the conventional ones defined in frequency domain, it is shown that the comfort limit developed in time domain would be more feasible for evaluating quantitatively the serviceability due to bridge vibration. Using the Bridge-train interaction analysis program, dynamic response of the bridge by the stiffness change were obtained for several railway bridges. And, a stiffness limit satisfying the bridge vibration serviceability was estimated by compared with comport limit. From the results, a new deflection limit on bridge structures satisfying the vibration serviceability could be proposed by comparing with the conventional deflection limit criteria.

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Limit Span/Depth Ratio for Indirect Deflection Control in Reinforced Concrete Flexural Members (철근콘크리트 휨부재의 처짐 간접제어를 위한 한계 지간/깊이-비 연구)

  • Choi, Seung-Won;Kim, Woo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.1A
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    • pp.35-41
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    • 2011
  • In concrete structural design provisons, two methods are normally provided to control deflection; direct method and indirect method. It is more efficient to use the indirect deflection control by which the span/depth ratio is limited not to exceed an allowable deflection limit. Because actual deflections are affected by many causes, it is complicated to evaluate actual deflections. In this study, limit span/depth ratios are derived from the deflection calculated directly at the serviceability limit state in RC members. The deflection is obtained from using average curvature, which depends on materials model used. The main variables examined are tension stiffening effect, concrete strength, cross section size and compressive steel ratio. It could be appeared that more analytical consistency is secured to use the 2nd order form of tension stiffening effect. And the limit span/depth ratio is dependent on material strength, tensile and compressive steel ratio but it is independent on cross-section size.

The Experimental Study for inferring the Safety-Factor of the Limit of Span-Deflection in Standard Specifications for Highway Bridges for Setting the Standard of the Measurement Criteria in RC Girder (철근콘크리트 거더의 관리기준치 설정을 위한 도로교설계기준 처짐 제한치의 안전계수 추정에 관한 실험적 연구)

  • Joo, Bong-Chul;Park, Ki-Tae;Hwang, Yoon-Koog;Lee, Woo-Sang
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.13 no.1 s.53
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    • pp.145-151
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    • 2009
  • The span deflection among the monitoring items of bridge measurement system in real time is representative behaviour and important index of superstructure condition. the limit of span deflection in Standard Specifications for Highway Bridge in Korea has been applied to the method that is making the management-criteria for span deflection in bridge measurement system. But the limit concern mainly serviceability of divers. So it is difficult to find the safety factor of the limit from the viewpoint of bridge safety. This study estimated the safety factor of the limit of span-deflection in Standard Specifications for Highway Bridge in Korea from the viewpoint of bridge safety by the indoor structural test.

Evaluation of Comfort Limit on High Speed Railway Bridge Vibration Considering Passenger's Comfort (승차감을 고려한 고속철도 교량 진동사용성 평가)

  • Chin, Won-Jong;Kwark, Jong-Won;Choi, Eun-Suk;Kang, Jae-Yoon;Kim, Sung-Tae;Yoon, Hye-Jin;Kim, Nam-Sik
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.829-835
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    • 2011
  • This paper aims for proposed the deflection limit on vibration serviceability of high-speed railway bridges considering passenger's comfort when a train passes a railway bridge. The vertical acceleration signals of passenger cars obtained from test were compared with them from the bridge-train transfer function by riding KTX. The deflections by KTX of seven high speed railway bridges were assumed as sine and haversine wave. The deflection limit on vibration serviceability of high-speed railway bridges considering passenger's comfort when a train passes a railway bridge duration can be expanded using bridge-train transfer function and bridge comfort limit considering serviceability due to bridge vibration. And it was compared to other allowable deflection limits of railway bridge design specifications.

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