scholarly journals Study on the Effect and Mechanism of Aerodynamic Measures for the Vortex-Induced Vibration of Separate Pairs of Box Girders in Cable-Stayed Bridges

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Han Xin He ◽  
Jia Wu Li
Keyword(s):  
Experimental Result ◽  
Box Girders ◽  
Vortex Induced Vibration ◽  
Optimum Angle ◽  
Low Wind Speed ◽  
Catastrophic Failures ◽  
Opening Ratio ◽  
Ratio Set ◽  
Inclined Angle ◽  
Cable Stayed Bridges

Although not always resulting in catastrophic failures, vortex-induced vibration (VIV) response can seriously impact the fatigue life and functionality of bridges, especially for separate pairs of box girders in cable-stayed bridges. This study investigates the effects of three aerodynamic measures: grating, inclined web plate, and the baffles on separated box girders in the cable-stayed bridges. The experimental result indicates that the grating of different opening ratios can control the vortex-induced vibration effectively, and the optimized grating opening ratio set in this paper is 40%. Increasing the angle of inclined web plate has a great control on mitigation of the vortex-induced vibration. However, there is an optimum angle where the amplitude of vortex-induced vibration is the smallest at low wind speed. The amplitude of vortex-induced vibration becomes larger with the increase of the web inclined angle that exceeds the optimum angle. Comparatively, the baffles installed on both sides of the inclined webs are more effective to restrain the vortex-induced resonance. The Computational Fluent Dynamics (CFD) software is utilized to investigate the mechanism of the experimental results.

Porous Titanium Fabricated by a Combination of Vacuum Distillation and Sintering Process

2018 ◽  
Vol 933 ◽  
pp. 78-85
Author(s):  
Xiao Tong Lu ◽  
Hong Jie Luo ◽  
Wei Yin ◽  
Lin Li Wu ◽  
Qi Le He
Keyword(s):  
Vacuum Distillation ◽  
Volume Fraction ◽  
Porous Titanium ◽  
Raw Material ◽  
Anhydrous Ethanol ◽  
Experimental Result ◽  
Sintering Process ◽  
Magnesium Powder ◽  
Opening Ratio ◽  
And Function

As a new type of material combined with special structure and function, the porous titanium was prepared through vacuum distillation and sintering process, by which the titanium powder was used as raw material, magnesium particles and its powder as space holder, anhydrous ethanol as binder. The porosity of porous titanium obtained by this method is between 35% and 75% and its opening ratio runs up to 95%. The experimental result showed that magnesium existed in the compacted precursor was evaporated rapidly in vacuum when temperature reached 750°C and removed completely within 20 minutes. The suitable sintering temperature was between 1050°C and 1250°C, but the porosity of porous titanium decreased from 76.2% to 61.3% with temperature elevated. The precursor uniformity was improved by addition of anhydrous ethanol and its formability and density was also done by addition of magnesium powder. The relative density of precursor increased from 82% to 98% with magnesium powder volume fraction varied from 30 vol.% to 80 vol.%.

Temperature variation in steel box girders of cable-stayed bridges during construction

2015 ◽  
Vol 112 ◽  
pp. 80-92 ◽  
Author(s):  
Sang-Hyo Kim ◽  
Se-Jun Park ◽  
Jiaxu Wu ◽  
Jeong-Hun Won
Keyword(s):  
Temperature Variation ◽  
Box Girders ◽  
Cable Stayed Bridges

Resilience Property of Spacer Fabric Compounded PU Foam Composites

2014 ◽  
Vol 910 ◽  
pp. 218-221
Author(s):  
Jia Horng Lin ◽  
Ting Ting Li ◽  
Yu Chun Chuang ◽  
Chen Hung Huang ◽  
Ching Wen Lou
Keyword(s):  
Experimental Result ◽  
Foam Density ◽  
Saving Energy ◽  
Pu Foam ◽  
Spacer Fabric ◽  
Foam Composite ◽  
Opening Ratio

For purpose of saving energy and avoiding injuries, foam composite with excellent resilience property was successfully prepared consisting of inflame-retarding nonwoven, spacer fabric and PU/additive foam. Effects of foam density, additives (vermiculite, perlite) content and opening ratio of spacer fabric on resilience rate were explored respectively. Experimental result shows that 50 kg/m3foam density of PU foam had the lower resilience rate when containing 10 wt%-20 wt% vermiculites. Perlite P2 addition produced optimal resilience property comparing other types of additives in PU foam. Resilience rate decreased with increase of opening ratio of spacer fabric when containing 5 wt% additions.

Investigation of vortex-induced vibration of a suspension bridge with two separated steel box girders based on field measurements

2011 ◽  
Vol 33 (6) ◽  
pp. 1894-1907 ◽  
Author(s):  
Hui Li ◽  
Shujin Laima ◽  
Jinping Ou ◽  
Xuefeng Zhao ◽  
Wensong Zhou ◽  
...  
Keyword(s):  
Field Measurements ◽  
Suspension Bridge ◽  
Box Girders ◽  
Vortex Induced Vibration

Investigation and control of vortex-induced vibration of twin box girders

2013 ◽  
Vol 39 ◽  
pp. 205-221 ◽  
Author(s):  
Shujin Laima ◽  
Hui Li ◽  
Wenli Chen ◽  
Fengchen Li
Keyword(s):  
Box Girders ◽  
Vortex Induced Vibration ◽  
And Control

scholarly journals Prediction of Vortex-Induced Vibration of Flexible Riser Using an Improved Wake-Oscillator Model

2009 ◽  
Author(s):  
Wein-min Chen ◽  
Liwu Zhang ◽  
Min Li
Keyword(s):  
Analytical Model ◽  
Flow Distribution ◽  
Experimental Result ◽  
Oscillator Model ◽  
Flexible Riser ◽  
Vortex Induced Vibration ◽  
Wake Oscillator Model ◽  
Wake Oscillator ◽  
Uniform Current ◽  
Lock In

Based on improving the wake-oscillator model, an analytical model for vortex-induced vibration (VIV) of flexible riser under non-uniform current is presented, in which the variation of added mass at lock-in and the nonlinear relationship between amplitude of response and reduced velocity are considered. By means of empirical formula combining iteration computation, the improved analytical model can be conveniently programmed into computer code with simpler and faster computation process than CFD so as to be suitable to application of practical engineering. This model is validated by comparing with experimental result and numerical simulation. Our results show that the improved model can predict VIV response and lock-in region more accurately. At last, illustrative examples are given in which the amplitude of response of flexible riser experiencing VIV under action of non-uniform current is calculated and effects of riser tension and flow distribution along span of riser are explored. It is demonstrated that with the variation of tension and flow distribution, lock-in region of mode behaves in different way, and thus the final response is a synthesis of response of locked modes.

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