Theoretical Analysis of Temperature and Shrinkage Stresses of Box-Girder Section

2011 ◽  
Vol 243-249 ◽  
pp. 1885-1892
Author(s):  
Wei Zhao Li ◽  
Zong Lin Wang ◽  
Fadhil Naser Ali
Keyword(s):  
Tensile Stress ◽  
Cross Section ◽  
Temperature Difference ◽  
Negative Temperature ◽  
Shrinkage Stress ◽  
Box Girder ◽  
Stress Changes ◽  
Longitudinal Cracks ◽  
Bottom Slab ◽  
The Web

The objective of this study is to analyze the temperature and shrinkage stresses of the mid-span cross-section of a 20 meters box girder to find the reasons which cause the longitudinal cracks in the web and bottom of box girder. According to the results of damage inspeation, there are many longitudinal cracks in the web and bottom slab of box girders, especially the web of the edger beam, the crack is very clear. Ansys ver.10 software is used to analyze two dimensional finite element model of a typical cross section of a real bridge to calculate the temperature stresses caused by temperature difference between inside and out side of the box and the shrinkage stresses based on moisture diffusion. The results of analysis show that the outer surface of the web and bottom slab of the fabricated box girder will produce tensile stress at the effect of negative temperature difference. If the concrete reaches a certain age, the tensile stress does not cause creaks in the cross-section. The shrinkage stress changes with the moisture gradient in the box section. It will reach the maximum in 15 days and then decreases with the growth of the age. Shrinkage stress may cause cracking of the concrete surface because of the tensile strength is low in the early age.

Analysis on Stress State of Box-Girder Web under Prestressing

2014 ◽  
Vol 602-605 ◽  
pp. 33-36
Author(s):  
Bao Jun Zhao ◽  
Guo Rui Zhu ◽  
Liang Yin
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Cross Section ◽  
Element Model ◽  
Neutral Axis ◽  
Curved Beam ◽  
Box Girder ◽  
Principal Compressive Stress ◽  
Principal Tensile Stress ◽  
The Web

In order to study the stress of box-girder web under prestressing, and confirming the internal stress distribution of the web, analyzing of vertical prestressed box girder, curved beam prestressed sensitivity under the webs. Establishing finite element model of the box-girder webs vertical prestressing effect is analyzed, results show that the principal tensile stress of the web is sensitive to the vertical prestress, applying the vertical prestress can effectively reduce the principal tensile stress of the web; with the decrease of the effective vertical prestress, the neutral axis above the principal compressive stress decreases rapidly, while below the neutral axis decreases relatively slow; Under the same vertical preloading stress level, the roots of cross section of the compressive stress of web reserves than L/4 section of the web.

scholarly journals Analysis on stress state of box-girder web under prestressing effect

2018 ◽  
Vol 17 ◽  
pp. 03007
Author(s):  
Haijun Yin ◽  
Ziqing Li ◽  
Xianwu Hao ◽  
Baojun Zhao
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Cross Section ◽  
Neutral Axis ◽  
Curved Beam ◽  
Stress Effect ◽  
Box Girder ◽  
Principal Tensile Stress ◽  
Bending Radius ◽  
The Web

In order to study the effect of prestressed box girder webs stresss state, determining the stress distribution within a web, research and analysis of vertical prestressed box girder, curved beam prestressed sensitivity under the web. Establishing the finite element model of the box girder web vertical prestressing effect is analyzed, results show that the principal tensile stress of the web is sensitive to the vertical prestress, applying the vertical prestress can effectively reduce the principal tensile stress of the web; with the decrease of the effective vertical prestress, the neutral axis above the principal compressive stress decreases rapidly, while below the neutral axis decreases relatively slow; Under the same vertical preloading stress level, the roots of cross section of the compressive stress of web reserves than L / 4 section of the web. Calculation and analysis of curved beam under bending point, different bending angles and bending radius of principal stress effect on the web, Results show that the set of curved beam web when the curved beam bending stress concentration easily, appear the main tensile stress; Increase the bending radius can effectively reduce beam cross-section of web principal tensile stress, along with the rising of the next corner, principal tensile stress peak value increases gradually, thus setting bending beam, should try to reduce the bending angle.

Research on Skew Coefficient for Stresses of Skewly Supported Three-Span Continuous Box Girders

2014 ◽  
Vol 587-589 ◽  
pp. 1483-1487
Author(s):  
Liang Liu
Keyword(s):  
Cross Section ◽  
Shell Element ◽  
Skew Angle ◽  
Box Girders ◽  
Concentrated Load ◽  
Box Girder ◽  
Lag Effect ◽  
The Cross ◽  
Skew Angles ◽  
Bottom Slab

Skewly supported continuous box girders have special mechanical properties compared with common continuous box girders. Skew coefficient for stress of skewly supported three-span continuous box girder is introduced to reflect the decrease degree of the normal stresses at the cross section of the middle span of the box girder. The finite element models of the skewly supported three-span continuous box girders with different skew angles are established by applying the SHELL63 shell element in software ANSYS. The variation of the skew coefficient for stress at different calculation points of middle span cross section under concentrated load is analyzed and the corresponding influence law is revealed. Research results show that the skew coefficient for stress of top slab is different from that of bottom slab at the cross section of the skewly supported three-span continuous box girder. The skew coefficient for stress of top slab is smaller than that of bottom slab. Skew coefficient for stress decreases with the increasing of the skew angle. Because of the shear lag effect, the minimal skew coefficient for stress of flanges occurs at the free tip of cantilever slab while the maximal skew coefficient occurs at the intersection of web and flange slabs.

Long-Term Performance of Concrete Suffered Infant Age Freezing

2012 ◽  
Vol 174-177 ◽  
pp. 524-529 ◽  
Author(s):  
Bao Lin Guo ◽  
Chang He Yu ◽  
Yu Han ◽  
Ju Peng Zhu
Keyword(s):  
Calcium Carbonate ◽  
Cross Section ◽  
Box Girder ◽  
Cover Concrete ◽  
Concrete Quality ◽  
Complicated Process ◽  
Long Term Performance ◽  
Term Performance ◽  
The Web

Interior water migrated towards the surface area when concrete suffered minus temperature during infant ages. Cover concrete became the worst part after the complicated process of water freezing – thawing, intermittent hydration of cementious materials and volatilization. Presentation quality, carbonization depth and rebound value in 120 d ages were observed and tested in situation. There were some calcium carbonate stains spread over the web, many swelling points and radial ice lens spread over the surface of box girder. The carbonization depth was over 10mm, and the rebound value of web concrete lower than 50, some areas’ lower than 35, variance larger than 30. Compared with other parts, the rebound value of web bottom concrete was the lowest and the variance biggest. For the same cross section, there were obviously difference of concrete quality between sunny face and shady ones, which enhanced the un-uniformity of element and made the stress distribution more complicated and uncertainty. Some effective measures must be taken to avoid the infant age frozen in order to assure the concrete quality constructed during the winter.

scholarly journals Cost Aanalysis and Comparison of Rectangular and Trapezoidal Box Girder Section

2021 ◽  
Vol 9 (VI) ◽  
pp. 1325-1333
Author(s):  
Ankur .
Keyword(s):  
Cross Section ◽  
Design Analysis ◽  
Analysis Tool ◽  
Box Girder ◽  
Hand Calculation ◽  
Bottom Slab

The present study aims at design, analysis and parametric comparison of two different cross section of box girder deck system. Objectives of this study are to compare the stresses at important location like top slab and bottom slab using analysis tool MIDAS-2016. And design and estimates different sizes of rectangular and trapezoidal box girder section using hand calculation. Keywords: Box Girder, Rectangular box girder, Trapezoidal box girder and MIDAS-2016

scholarly journals Experimental analysis of gradient of negative temperature for polypropylene fiber concrete U-shaped girder

2020 ◽  
Vol 319 ◽  
pp. 06004
Author(s):  
Xu Dong ◽  
Fengkun Cui ◽  
Xiudong Li ◽  
Songji Xu
Keyword(s):  
Temperature Gradient ◽  
Negative Temperature ◽  
Rail Transit ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Gradient Model ◽  
Transverse Temperature ◽  
Bottom Slab ◽  
Gradient Models ◽  
The Web

To study the negative temperature gradient models of a rail transit U-shaped girder during the winter season, a U-shaped rail transit girder was researched in Qingdao. The temperature field of the midspan section was observed for a 48-h period during the winter. The maximum vertical and horizontal temperature difference distributions were obtained, and the negative temperature gradient models for the winter were established. The results show that the vertical temperature gradient models of the web and bottom slab should be considered. The vertical temperature gradient model of the web is a piecewise function composed of exponential and linear functions. The vertical temperature gradient model of the bottom slab is an exponential function. The transverse temperature gradient of the web is obvious, whereas the transverse temperature gradient of the bottom slab is slight.

Research in Destruction of Concrete Bridge Expanded Joint Influenced by Temperature Difference

2015 ◽  
Vol 744-746 ◽  
pp. 803-806 ◽  
Author(s):  
Xiao Lei ◽  
Yue Yao ◽  
Shi Cao ◽  
Zhi Gang Guo
Keyword(s):  
Temperature Difference ◽  
Curve Fitting ◽  
Effective Temperature ◽  
Joint Damage ◽  
Measured Data ◽  
Concrete Bridge ◽  
Box Girder ◽  
Concrete Box Girder ◽  
Extremum Value ◽  
The Relationship

Destruction of bridge expanded joint is a serious problem for concrete bridge. Based on 5 years measured data, the temperature in the different positions of the concrete box girder was systemically analyzed to illuminate the cause of the bridge expanded joint damage. A method for predicting the extremum value of the temperature difference of concrete girder was proposed by use of the extrema analysis and curve fitting based on the temperature in the different positions of the concrete box girder. The relationship is quite useful in estimating the destruction of bridge expanded joint by effective temperature difference in concrete box-girder.

Internal Stress Change of Phosphorus-Doped Amorphous Silicon Thin Films During Crystallization

1994 ◽  
Vol 343 ◽  
Author(s):  
Hideo Miura ◽  
Asao Nishimura
Keyword(s):  
Thin Films ◽  
Tensile Stress ◽  
Internal Stress ◽  
Crystallization Process ◽  
Chemical Vapor ◽  
Stress Change ◽  
Silicon Thin Films ◽  
Stress Changes ◽  
Phosphorus Doped ◽  
Deposited Films

ABSTRACTInternal stress change of phosphorus-doped silicon thin films during crystallization is measured by detecting substrate curvature change using a scanning laser microscope. The films are deposited in an amorphous phase by chemical vapor deposition using Si2H6 gas. The deposited films have compressive stress of about 200 MPa. The internal stress changes significantly to a tensile stress of about 800 MPa at about 600 °C due to shrinkage of the films during crystallization. The high tensile stress can be relaxed by annealing above 800 °C. The phosphorus doping changes the crystallization process of the films and their final residual stress.

Estimation of Ultimate Longitudinal Bending Moment of Ships and Box Girders

1996 ◽  
Vol 40 (03) ◽  
pp. 244-257 ◽  
Author(s):  
M. K. Rahman ◽  
M. Chowdhury
Keyword(s):  
Cross Section ◽  
Bending Moment ◽  
Fortran Program ◽  
Box Girders ◽  
Limit States ◽  
Box Girder ◽  
Stiffened Panels ◽  
Complete Procedure ◽  
Longitudinal Bending ◽  
Collapse Behavior

The paper describes a methodology of computing the ultimate value of the longitudinal bending moment at any cross section of a ship or box girder. The cross section has been discretized into stiffened panels (one stiffener with its associated effective plating). The limit states for these panels, both tensile and compressive, are modeled in an appropriate manner. Since the ultimate strength of the girder section is largely governed by the behavior of the panels under compression, the authors have paid special attention in modeling the collapse as well as post-collapse behavior of these panels. A new stress-strain relationship is also introduced. The complete procedure has been coded into a FORTRAN program and tested against a number of box girder models and an actual ship for which the true behavior was known. The results obtained from the proposed program appear to be quite satisfactory. Good correlation was also found when compared with the results obtained by more complex and rigorous analytical methods.

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