Long-term field test of temperature gradients on the composite girder of a long-span cable-stayed bridge

2019 ◽  
Vol 22 (13) ◽  
pp. 2785-2798 ◽  
Author(s):  
Jiang Liu ◽  
Yongjian Liu ◽  
Lei Jiang ◽  
Ning Zhang
Keyword(s):  
Temperature Distribution ◽  
Temperature Gradients ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Composite Girder ◽  
Depth Ratio ◽  
Cantilever Length ◽  
Composite Girders

Bridges are inevitably affected by daily, seasonal and annual air temperature and solar radiation. The thermal effects on bridges, especially for long-span cable-stayed bridges with composite girders, are significant and complicated. The evaluation of temperature distribution has been a primary concern to bridge engineers and researchers. This article presents a more than one-year temperature database of a long-span cable-stayed bridge with a small cantilever length-to-web depth ratio in the composite girder. Uniform temperature, linear temperature difference, thermal curvature, and self-equilibrated thermal stress are considered to imply the characteristics of the temperature distribution in such composite girders. Two profiles (profile 1 and profile 2) for positive vertical temperature gradient and one profile (profile 3) for negative vertical temperature gradient are proposed. The extreme temperature differences with a 100-year return period are determined for each profile with extreme value analysis. Among the three profiles, profile 2 is unique for composite girders with a small cantilever length-to-web depth ratio. Based on parametric studies, profile 2 is revised with the cantilever length-to-web depth ratio for wide applications. Finally, comparisons of vertical temperature gradients are made between the investigated composite girder and the recommendations in Chinese Specification.

Effects of Age and Overhead Illumination on Temperatures Preferred by Underyearling Rainbow Trout, Salmo gairdneri, in a Vertical Temperature Gradient

1978 ◽  
Vol 35 (11) ◽  
pp. 1430-1433 ◽  
Author(s):  
Wen-Hwa Kwain ◽  
Robert W. McCauley
Keyword(s):  
Rainbow Trout ◽  
Temperature Gradient ◽  
Temperature Gradients ◽  
Salmo Gairdneri ◽  
Vertical Temperature Gradient ◽  
Temperature Preference ◽  
Vertical Temperature ◽  
Preferred Temperature ◽  
Distribution Of Fish ◽  
Vertical Gradients

During their first 12 mo of life rainbow trout, Salmo gairdneri, preferred progressively cooler temperatures as they grew older; 19 °C was selected during the 1st mo and the selected temperature declined by intervals of 0.5 °C for each of the following months up to the 3rd mo. Fish swam higher in temperature gradients exposed to overhead illumination than in those in total darkness. This trend was reversed during the following 9 mo. These findings demonstrate the important role that age plays in the temperature preference of this species and the influence that overhead light may have on the distribution of fish in vertical gradients. Key words: preferred temperature, age, Salmo gairdneri, light gradients

scholarly journals Analysis of Sunshine Temperature Field of Steel Box Girder Based on Monitoring Data

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Hailin Lu ◽  
Jing Hao ◽  
Jiwei Zhong ◽  
Yafei Wang ◽  
Hongyin Yang
Keyword(s):  
Temperature Field ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Maximum Temperature ◽  
Temperature Model ◽  
Bridge Site ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Box Girder ◽  
Steel Box Girder

In this study, based on the recorded meteorological data of the bridge site, a spatial-temporal temperature model of a 3-span steel box girder is developed through applying the thermal analysis software TAITHERM. Firstly, the rationality and dependability of the proposed spatial-temporal temperature model are adequately verified by means of implementing the comparison with the measurement data. Then the temperature distribution of the steel box girder is analyzed and discussed in detail. The analytical results show that the time of the bottom of pavement reaching the daily maximum temperature lags behind the top of pavement by 2 or 3 hours due to the thermal insulation effect of pavement, and the maximum vertical temperature gradient of the structure exceeds the existing standards. Moreover, with the help of the analytical model, a parametric study of comprehensively meteorological factors is also performed. The results of the sensitivity analysis indicate that solar radiation is the most significant factor affecting the maximum vertical temperature gradient of the steel box girder, followed by air temperature and wind speed. After that, with the representative values of the extreme meteorological parameters during 100-year return period in Wuhan City in China being considered as the thermal boundary conditions, the temperature distribution of the steel box girder is further studied for investigation purpose. The results demonstrate that the heat conduction process of the steel box girder has distinct “box-room effect,” and it is of great necessity to consider both the actual weather conditions at the bridge site and the “box-room effect” of steel box girder when calculating thermal behaviors of bridge structures. Finally, it is related that the particular method proposed in this paper possesses a satisfactory application prospect for temperature field analysis upon various types of bridges in different regions.

Spectrum of Small-Scale Oceanic Temperature Gradients

1976 ◽  
Vol 33 (10) ◽  
pp. 2296-2306 ◽  
Author(s):  
J. A. Elliott ◽  
N. S. Oakey
Keyword(s):  
Temperature Gradient ◽  
Thermal Diffusion ◽  
Temperature Gradients ◽  
Small Scale ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Spectral Maximum ◽  
Sharp Interfaces

The spectrum of the vertical temperature gradient is computed for a number of "typical" 50-m long profiles from the upper 200 m of the ocean. Most of the variance occurs in the microstructure range, between approximately 1 and 100 cycles/m; there is normally a spectral maximum near 10 cycles/m. The shape of the spectra for the range 10–100 cycles/m agrees well with that predicted for sharp interfaces that have been smoothed by thermal diffusion.

scholarly journals Temperature distribution in the chamber used for crystal growth of GaN under high pressure of nitrogen

1996 ◽  
Vol 1 ◽  
Author(s):  
S. Krukowski
Keyword(s):  
Finite Element ◽  
High Pressure ◽  
Crystal Growth ◽  
Temperature Distribution ◽  
Thermal Conditions ◽  
High Pressure Chamber ◽  
Vertical Temperature Gradient ◽  
Element Calculation ◽  
Vertical Temperature ◽  
Nitrogen Gas

The theoretical analysis of high pressure influence on the conditions of crystal growth of GaN is presented. High pressure influence on the transport and equilibrium properties of nitrogen is estimated using scaling approach. Nitrogen gas properties are used in the finite element calculation of the thermal conditions in the high pressure chamber. The temperature distribution during GaN growth in the vertical temperature-gradient configuration is obtained.

Effects of M.S. 222 Anesthetization on Temperature Selection in Lake Trout, Salvelinus namaycush

1974 ◽  
Vol 31 (1) ◽  
pp. 100-103 ◽  
Author(s):  
C. I. Goddard ◽  
J. W. Lilley ◽  
J. S. Tait
Keyword(s):  
Temperature Distribution ◽  
Temperature Gradient ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
Control Fish ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Temperature Selection

Yearling lake trout (Salvelinus namaycush) were anesthetized with a 150 ppm solution of M.S. 222 for 2 min at 10 C. When tested in a vertical temperature gradient, their behavior was abnormal for 5 days following anesthetization. Initially, they remained at the bottom of the gradient tank, as much as 63% of the time, and when they did swim up into the gradient, their temperature selection was much less precise than that of control fish. The percentage of fish on the bottom declined daily, and on the 6th day their temperature distribution did not differ from that of controls.

Effects of Stable Cable on Ultimate Load-Carrying Capacity of Long-Span Composite Girder Cable-Stayed Bridge with Three Pylons

2010 ◽  
Vol 163-167 ◽  
pp. 2337-2342 ◽  
Author(s):  
Long Fei Wang ◽  
Mu Yu Liu
Keyword(s):  
Carrying Capacity ◽  
Ultimate Load ◽  
Failure Load ◽  
Load Carrying Capacity ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Composite Girder ◽  
Load Carrying ◽  
Internal Forces ◽  
Ultimate Load Carrying Capacity

On the background of a long-span composite girder cable-stayed bridge with three pylons under construction for research, this paper establishes two models of the whole bridge by considering the structural geometric nonlinearity, material nonlinearity and interface slip effect in composite girder, one has stable cables between pylons but the other hasn’t, then comparatively studies the failure loads and structural internal forces of the two models to achieve effects of stable cable on the ultimate load-carrying capacity of the cable-stayed bridge. This research shows that the stable cables can strengthen the vertical stiffness of structure and obviously increase the failure load of the bridge, and the internal forces in main girder, middle pylon and stayed cables are smaller and their distributions are more reasonable under the failure load than those in the bridge with no stable cables, so the stable cables can effectively improve the ultimate load-carrying capacity of long-span composite girder cable-stayed bridges with three pylons.

Study on Ultimate Load-Carrying Capacity of Long-Span Composite Girder Cable-Stayed Bridge with Three Pylons

2011 ◽  
Vol 243-249 ◽  
pp. 1952-1956
Author(s):  
Long Fei Wang
Keyword(s):  
Bearing Capacity ◽  
Carrying Capacity ◽  
Failure Modes ◽  
Ultimate Load ◽  
Load Carrying Capacity ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Composite Girder ◽  
Load Carrying ◽  
Ultimate Load Carrying Capacity

Taking a long-span composite girder cable-stayed bridge with three pylons under construction as the object of research, this paper establishes a three-dimensional finite element model of a bridge considering the geometric nonlinearity, material nonlinearity and interface slip effect in composite girder, and analyzes the failure loads and failure modes of the structure at bearing capacity limited state. The results show that the ultimate load-carrying capacity is high at bearing capacity limited state, load case whose live load acts on one main span is more unfavorable, and according to the structural failure modes, increasing the ability of the middle pylon to resist bending moment can improve the ultimate load-carrying capacity of the whole bridge quickly.

Investigation of temperature actions on flat steel box girders of long-span bridges with temperature monitoring data

2018 ◽  
Vol 21 (14) ◽  
pp. 2099-2113 ◽  
Author(s):  
Yang Deng ◽  
Aiqun Li ◽  
Yang Liu ◽  
Suren Chen
Keyword(s):  
Temperature Distribution ◽  
Effective Temperature ◽  
Ambient Air ◽  
Temperature Gradients ◽  
Box Girders ◽  
Expansion Joints ◽  
Long Span Bridges ◽  
Long Span ◽  
Flat Steel

The worldwide application of streamlined flat steel box girder on long-span bridges calls for more knowledge of its temperature distribution. The rapid development of structural health monitoring techniques offers a great opportunity to address this issue. A comprehensive approach of installing monitoring equipment, collecting data, and applying long-term temperature monitoring data to study the temperature distribution of flat steel box girders is developed. As demonstrated through the analysis of 1-year data of a suspension bridge, first, a mapping relation between effective temperature and ambient air temperature is established. Such a relation enables identifying the optimal time to finally join the flat steel box girders at the designed effective temperature based on the easy-to-obtain ambient air temperature. Second, the cycling variation of effective temperature is presented to provide information for design and assessment of expansion joints and bearings, including not only the maximum design displacements but also cumulative displacements related to the long-term durability and remaining life of expansion joints and bearings. Finally, both vertical and transverse temperature gradients are studied to provide some new insights about the temperature characteristics of flat steel box girders. The study suggests that the transverse and vertical temperature gradients should be applied to the bridge cross section individually since the data analysis supports that the two gradients are independent.

scholarly journals Analysis of the occurrence of natural convection in a bed of bars in vertical temperature gradient conditions

2013 ◽  
Vol 34 (1) ◽  
pp. 71-83
Author(s):  
Rafał Wyczółkowski ◽  
Dorota Musiał
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Treatment ◽  
Natural Convection ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Free Convection ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Rayleigh Criterion

Abstract The reason for undertaking this study was to determine the possible involvement of natural convection in the global heat transfer, that occurs in the heated steel rods bed. This problem is related to the setting of the effective thermal conductivity of the bars bed. This value is one of the boundary conditions for heating modeling of steel rods bundles during heat treatment. The aim of this study was to determine for which geometry of the bed bars, there will be no free convection. To analyze the problem the Rayleigh criterion was used. It was assumed that for the value of the number Ra < 1700 convection in the bed bars does not occur. For analysis, the results of measurements of the temperature distribution in the unidirectionally heated beds of bars were used. It has been shown, that for obtained, during the test, differences of temperature between the surfaces of adjacent rods, convection can occur only when the diameter of the rod exceeds 18 mm.

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