Experimental Study on the Effect of Temperature on Modal Frequencies of Bridges

2018 ◽  
Vol 18 (12) ◽  
pp. 1850155 ◽  
Author(s):  
Limin Sun ◽  
Yi Zhou ◽  
Zhihua Min
Keyword(s):  
Boundary Conditions ◽  
Freezing Point ◽  
Concrete Bridges ◽  
Effect Of Temperature ◽  
Steel Cable ◽  
Temperature Changes ◽  
Continuous Beam Bridge ◽  
Bridge Model ◽  
Increasing Temperature ◽  
Beam Bridge

This study investigates the relationship between the temperature and the modal frequencies of bridges through a series of model experiments using a concrete continuous beam bridge model and a steel cable-stayed bridge model in a controlled-temperature chamber. The experimental results show that, for a given boundary condition and in the absence of freezing, a change in temperature affects the structural frequencies of the bridge as it alters the elastic modulus of the bridge materials. The structural frequency tends to linearly decrease with increasing temperature and with the decrease in the frequency of steel bridges smaller than that of concrete bridges. For the particular case of wet concrete bridges, the temperature dependencies of modal frequencies vary dramatically near the freezing point, which is attributable to the freeze–thaw process of concrete pore water. The effect of air humidity on structural frequency is less significant than that of temperature when the boundary conditions remain unchanged. Furthermore, temperature changes may alter the boundary conditions of bridges, thereby affecting the structural frequencies.

Frequency modification of continuous beam bridge based on co-integration analysis considering the effect of temperature and humidity

2018 ◽  
Vol 18 (2) ◽  
pp. 376-389 ◽  
Author(s):  
Haoxiang He ◽  
Wei Wang ◽  
Xiaofu Zhang
Keyword(s):  
Environmental Factors ◽  
Effect Of Temperature ◽  
Integration Theory ◽  
Frequency Model ◽  
Modified Method ◽  
Continuous Beam Bridge ◽  
Bridge Model ◽  
Temperature And Humidity ◽  
Beam Bridge ◽  
Integration Analysis

The variation of the temperature and humidity significantly affects the modal parameters of the structure, and the effect and the quantitative statistics of single environmental factors such as temperature on the frequency of bridge are intensively studied, but the study on the mechanism and the effective model considering the comprehensive effect of multi-environmental factors is relatively rare. The principle and analysis method of co-integration is introduced, and the frequency-modified method based on co-integration is presented. Through the monitoring of a three-span concrete bridge model in the natural environment, the effective monitoring data are analyzed to establish a long-term equilibrium model about “frequency–temperature–humidity” based on co-integration theory. The experimental results indicate that the model has a better fitting ability and accuracy, and it is can be used to predict the variation trend of frequency. Based on the mathematical model of co-integration analysis, the modified frequency model considering multi-environmental factors is proposed, which can eliminate the comprehensive effect of temperature and humidity on frequency, and the variation of dynamic characteristics due to the internal causes of structure is revealed. The extracted sequence can provide effective information for further safety assessment and damage detection of bridge.

Correlation Study on Modal Frequency and Temperature Effects of a Cable-Stayed Bridge Model

2012 ◽  
Vol 446-449 ◽  
pp. 3264-3272 ◽  
Author(s):  
Li Min Sun ◽  
Yi Zhou ◽  
Xue Lian Li
Keyword(s):  
Experimental Study ◽  
Boundary Conditions ◽  
Dynamic Properties ◽  
Bridge Engineering ◽  
Fe Model ◽  
Steel Cable ◽  
Transverse Beam ◽  
Expansion Joints ◽  
Cable Stayed Bridge ◽  
Bridge Model

In recent years, structural health monitoring has been paid more and more attention in bridge engineering community. Previous researches showed that ambient temperature was one of principal factors affecting structural modal parameters in long-term. In this paper, an experimental study on correlation between dynamic properties of a cable-stayed bridge and its structural temperature was performed under temperature controlled laboratory environment. Using hammer impacting method, a dynamic testing was conducted based on a steel cable-stayed bridge model which had a span layout of 0.9+1.9+0.9m. During the experiment, the first six vertical bending modes under the environmental temperature of 0, 20 and 40°C were identified with the consideration of three kinds of boundary conditions at the deck’s ends as to two degrees of freedom, i.e. the longitudinal translation (UX) and the rotation about the transverse beam (RotZ). The above boundary conditions are UX & RotZ not constrained, UX constrained only and UX & RotZ constrained, attempting to simulate the different conditions of the bridge expansion joints. The efforts were paid to explain the physical mechanism of the results based on the updated FE model. This experimental study indicates a tendency that the frequency of the cable-stayed bridge model decreases with the increase of temperature. And furthermore, the relative difference of frequencies between 0 and 40 °C is affected by boundary conditions; in other words, when the deck is free to expand, the variation of model’s frequencies is smaller than that when the deck is restrained to expand, which is similar to the condition of the bridge’s expansion joints cannot work as normal. This experimental study can give some reference to the research of SHM and damage identification for cable-stayed bridges.

scholarly journals Temperature changes alter the acute toxicity responses of cypermethrin in Zebrafish

2018 ◽  
Vol 29 (1) ◽  
pp. 64-70 ◽  
Author(s):  
MH Uddin ◽  
MS Alim ◽  
SMM Islam ◽  
H Rashid ◽  
M Shahjahan
Keyword(s):  
Blood Glucose ◽  
Acute Toxicity ◽  
Probit Analysis ◽  
Effect Of Temperature ◽  
Temperature Changes ◽  
Temperature Regimes ◽  
Higher Temperature ◽  
T1 And T2 ◽  
Increasing Temperature ◽  
The Impact

The study was carried out to determine the effect of temperature changes on acute toxicity of pyrethroid pesticide cypermethrin in zebrafish. A two-day renewal bioassay system for 96h was conducted to find out LC50 value of cypermethrin at two temperature regimes i.e. 25°C and 30°C considering as T1 and T2, respectively. During the determination of LC50 in both temperatures, blood glucose (mg/dL) levels were measured at lower concentration (0.25 µg/L) of cypermethrin. The results of acute toxicity test at 96h LC50 values were calculated through probit analysis. It was found that 96h LC50 for T1 and T2 groups were about 2.1 and 1.4 µg/L, respectively. Significantly lower LC50 of cypermethrin at T2 compared to T1 showed that higher temperature increased the toxicity of cypermethrin. There was a significant increase (P<0.05) in blood glucose level (mg/dL) in 0.25 µg/L compared to 0 µg/L concentration of cypermethrin at both treatments. Dissolved oxygen decreased and free CO2 increased significantly (P<0.05) with increasing temperature, while the pH of the water was almost unchanged throughout the study period. The present study indicated the impact of increased temperature on pesticide toxicity in the aquatic ecosystem.Progressive Agriculture 29 (1): 64-70, 2018 

The interaction of rearing temperature and food supply on the life history of two species of Simuliidae (Diptera)

1981 ◽  
Vol 59 (2) ◽  
pp. 158-163 ◽  
Author(s):  
M. H. Colbo ◽  
G. N. Porter
Keyword(s):  
Maximum Growth ◽  
Effect Of Temperature ◽  
Feeding Rates ◽  
Temperature Changes ◽  
Simulium Vittatum ◽  
Development Times ◽  
Preimaginal Stages ◽  
Proportional Change ◽  
History Of ◽  
Increasing Temperature

The effect of rearing the preimaginal stages of Simulium vittatum and Simulium verecundum at 15, 20, and 25 °C and at four feeding rates was examined. The results showed that flies reared on all diets were larger at the coolest temperature. The decrease in size in S. vittatum between 20 and 15 °C and 25 and 20 °C was not proportional, with the decrease in size being very much larger with a temperature increase from 20 to 25 °C. This was reflected in the fecundity of the autogenous females. The changes in development times were, however, almost proportional. With S. verecundum size changes approached a proportional change but the development times did not, being markedly elongated at 15 °C. Therefore the nature of the effect of temperature changes can not be predicted from one species of simuliid to another. An examination of growth in relation to quantity of food availability and temperature indicated that the quantity of food required for maximum growth increased exponentially with increasing temperature.

Consideration of the temperature factor of atmospheric air when determining standard consumption of fuel and energy resources for train traction

2018 ◽  
Vol 77 (6) ◽  
pp. 375-381
Author(s):  
K. M. Popov
Keyword(s):  
Statistical Processing ◽  
Specific Consumption ◽  
Energy Resources ◽  
Effect Of Temperature ◽  
Influence Coefficient ◽  
Specific Work ◽  
Specific Flow ◽  
Temperature Changes ◽  
Work Area ◽  
Physical Laws

Abstract. Influence of air temperature on the consumption of fuel and energy resources (FER) on train traction is due to a number of physical laws. The extent of this effect is specified in the Rules for Traction Settlement (RTS). At the same time, when rationing FER consumption for train traction, a specialized methodical base is used, which involves a different approach to accounting for the effect of temperature on FER consumption for train traction. At the same time in different documents of this base, the effects of low temperature on the absolute and specific consumption of fuel and energy resources on train traction are taken into account in a different way, which is due to the lack of consensus among specialists on the way this factor is taken into account. Specialists of JSC “VNIIZhT” carried out an analysis of a significant amount of driver’s routes data, results of which showed that the dependence of the specific flow rate on temperature, on the basis of which the corresponding influence coefficient is determined, needs to be periodically updated. In addition, when technically standardizing the consumption of fuel and energy resources (for the locomotive crew work site), the temperature effect coefficients need to be calculated for a specific work area and direction of motion on it, while using the average network coefficient values will lead to errors. When calculating additional flow of fuel and energy from the effect of temperature for electric multiple units (EMU), the equations of regression dependencies should be used, obtained by statistical processing of data on temperature changes and specific consumption of fuel and energy resources for EMU and determined for each series of EMU when working on a particular suburban area.

scholarly journals Review of annual progress of bridge engineering in 2019

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Renda Zhao ◽  
Yuan Yuan ◽  
Xing Wei ◽  
Ruili Shen ◽  
Kaifeng Zheng ◽  
...  
Keyword(s):  
High Performance ◽  
Concrete Bridges ◽  
Bridge Engineering ◽  
Research Progress ◽  
Steel Bridge ◽  
Wind Resistance ◽  
Main Research ◽  
Bridge Model ◽  
Bridge Evaluation ◽  
Bridge Structures

AbstractBridge construction is one of the cores of traffic infrastructure construction. To better develop relevant bridge science, this paper introduces the main research progress in China and abroad in 2019 from 13 aspects, including concrete bridges and the high-performance materials, the latest research on steel-concrete composite girders, advances in box girder and cable-supported bridge analysis theories, advance in steel bridges, the theory of bridge evaluation and reinforcement, bridge model tests and new testing techniques, steel bridge fatigue, wind resistance of bridges, vehicle-bridge interactions, progress in seismic design of bridges, bridge hydrodynamics, bridge informatization and intelligent bridge and prefabricated concrete bridge structures.

scholarly journals Influence of Bearing on Pier Failure Considering the Separation Condition under Near-Fault Earthquake

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 692
Author(s):  
Wenjun An ◽  
Guquan Song
Keyword(s):  
Expansion Method ◽  
Transient Wave ◽  
Earthquake Excitation ◽  
Near Fault ◽  
Continuous Beam Bridge ◽  
Wave Function Expansion Method ◽  
Earthquake Action ◽  
Stiffness And Damping ◽  
Beam Bridge ◽  
Bending Failure

To study the influence of the near-fault vertical earthquake, the beam-spring-damper-pier model is used to simulate the double-span continuous beam bridge. The transient wave function expansion method and the indirect mode function method are used to calculate the seismic response of the bridge. The theoretical solutions of the contact force and displacement response of the bridge under vertical earthquake excitation near-fault are derived. By using piers with three different heights, the influence of vertical separation on pier-bending failure is analyzed reasonably. The results show that under the near-fault earthquake action, the split has a certain influence on the pier failure. Moreover, the stiffness and damping of the bearing have an influence on the pier failure, and the change of the maximum pier height has different effects. Therefore, for bridges of different sizes, it is of great significance to select the appropriate stiffness and damping bearings to reduce pier failure.

scholarly journals Theoretical Effect of Temperature on Threshold in the Hodgkin-Huxley Nerve Model

1966 ◽  
Vol 49 (5) ◽  
pp. 989-1005 ◽  
Author(s):  
Richard Fitzhugh
Keyword(s):  
Relaxation Time ◽  
Relaxation Times ◽  
Giant Axon ◽  
Temperature Curve ◽  
Effect Of Temperature ◽  
Threshold Temperature ◽  
Ionic Conductances ◽  
And Shifts ◽  
The Right ◽  
Increasing Temperature

In the squid giant axon, Sjodin and Mullins (1958), using 1 msec duration pulses, found a decrease of threshold with increasing temperature, while Guttman (1962), using 100 msec pulses, found an increase. Both results are qualitatively predicted by the Hodgkin-Huxley model. The threshold vs. temperature curve varies so much with the assumptions made regarding the temperature-dependence of the membrane ionic conductances that quantitative comparison between theory and experiment is not yet possible. For very short pulses, increasing temperature has two effects. (1) At lower temperatures the decrease of relaxation time of Na activation (m) relative to the electrical (RC) relaxation time favors excitation and decreases threshold. (2) For higher temperatures, effect (1) saturates, but the decreasing relaxation times of Na inactivation (h) and K activation (n) factor accommodation and increased threshold. The result is a U-shaped threshold temperature curve. R. Guttman has obtained such U-shaped curves for 50 µsec pulses. Assuming higher ionic conductances decreases the electrical relaxation time and shifts the curve to the right along the temperature axis. Making the conductances increase with temperature flattens the curve. Using very long pulses favors effect (2) over (1) and makes threshold increase monotonically with temperature.

Flow Behaviors of High Acyl Gellan Aqueous Solutions as Affected by Temperature, and Calcium and Gellan Concentrations

2008 ◽  
Vol 4 (5) ◽  
Author(s):  
Yiqun Huang ◽  
Pawan Singh Takhar ◽  
Juming Tang ◽  
Barry G Swanson
Keyword(s):  
Shear Rate ◽  
Aqueous Solutions ◽  
Apparent Viscosity ◽  
Flow Resistance ◽  
Effect Of Temperature ◽  
Temperature Changes ◽  
Influence Of Temperature ◽  
Rheological Behaviors ◽  
Low Concentrations ◽  
Influence Of Temperature On

Rheological behaviors of high acyl (HA) gellan are not well understood partially because of its relatively late commercialization compared to low acyl gellan. The objective of this study was to investigate the effect of temperature (5-30 °C), calcium (0, 1 and 10 mM) and gellan concentrations (0.0044-0.1000% w/v) on the flow behaviors of high acyl gellan aqueous solutions using rheological tests. Gellan solutions with 0 or 1 mM added Ca++ exhibited shear thinning behavior at gellan concentrations above 0.0125%. The influence of temperature on apparent viscosity (shear rate, 100 s-1) of gellan solutions can be described with an Arrhenius relationship. The apparent viscosity of gellan solution at low concentrations was more sensitive to temperature changes. The addition of Ca++ led to a decrease in flow resistance for a dilute gellan solution (<0.0125%), but an increased resistance for a relatively concentrated gellan solution (>0.0125%).

scholarly journals Buckling and vibration analysis of shape memory laminated composite beams under axially heterogeneous in-plane loads in the glass transition temperature region

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Nilesh Tiwari ◽  
A. A. Shaikh
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Boundary Conditions ◽  
Shape Memory ◽  
Transition Region ◽  
Shape Memory Polymer ◽  
Shear Deformation Theory ◽  
Effect Of Temperature ◽  
Glass Transition Region

AbstractBuckling and vibration study of the shape memory polymer composites (SMPC) across the glass transition temperature under heterogeneous loading conditions are presented. Finite element analysis based on C° continuity equation through the higher order shear deformation theory (HSDT) is employed considering non linear Von Karman approach to estimate critical buckling and vibration for the temperature span from 273 to 373 K. Extensive numerical investigations are presented to understand the effect of temperature, boundary conditions, aspect ratio, fiber orientations, laminate stacking and modes of phenomenon on the buckling and vibration behavior of SMPC beam along with the validation and convergence study. Effect of thermal conditions, particularly in the glass transition region of the shape memory polymer, is considerable and presents cohesive relation between dynamic modulus properties with magnitude of critical buckling and vibration. Moreover, it has also been inferred that type of axial loading condition along with the corresponding boundary conditions significantly affect the buckling and vibration load across the glass transition region.

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