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.

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.

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.

scholarly journals VII.—Rupture Stresses in Beams and Crane Hooks.

1914 ◽  
Vol 50 (1) ◽  
pp. 211-223
Author(s):  
Angus R. Fulton
Keyword(s):  
Compressive Stress ◽  
Cross Section ◽  
Bending Moment ◽  
Neutral Axis ◽  
Sectional Area ◽  
Inverse Proportion ◽  
Direct Loading ◽  
The Cross ◽  
External Forces ◽  
Distribution Of Stress

CONCLUSIONS1. It may be taken as conclusive that the final distribution of stress at rupture point in a member subjected to an external bending moment is a rectangular one, unless where the cohesion of adjacent layers is not sufficient to withstand the shear induced by the resisting moment of the section.2. That, provided shear does not take place, the neutral axis moves always to the position which reduces the summation of the tensile and compressive stress areas, across a section, to the equilibrant of the external forces. (In the case of a beam this reduces to zero; in that of a hook, at the principal section to the suspended weight.)3. That the total resisting moment of these stresses must be equal to the external bending moment as measured to the neutral axis at rupture point, but that these balancing moments do not differ materially from those measured to an axis obtained by dividing the sectional area into tensile and compressive stress areas which are in inverse proportion to the magnitude of their respective ultimate direct stresses.The advantage of these formulæ are important. It is possible to indicate with certainty the magnitude of the load which will cause rupture in a beam or a hook provided there is known the point of application or the effective arm of the load, the cross-section of the beam or hook, and the breaking strengths of the material when subjected to the different forms of direct loading.

Analysis of the Arrangement of Prestressed Steel in Web of Continuous Concrete Box-Girder Bridges

2014 ◽  
Vol 587-589 ◽  
pp. 1359-1363
Author(s):  
Lan Qiao ◽  
Shao Wen Zhang
Keyword(s):  
Tensile Stress ◽  
Large Scale ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Long Span Bridges ◽  
Girder Bridges ◽  
Principal Tensile Stress ◽  
Diagonal Section ◽  
Bridge Girder ◽  
Concrete Box Girder Bridges

Concrete continuous box- girder bridges have a large proportion in small span and long span bridges, and it has very broad prospects for development. Along with the large-scale construction of this kind of bridge, various problems have also emerged, especially the damage of RC beam’s diagonal section in bridge girder deflection. It always appears the inclined cracks in webs which cause by principal tensile stress, so it will be the potential damage to the whole bridge. However, the existence of the vertical prestress, will make the principal tensile stress of box girder in greatly reduced. So as to make cracking resistance performance of diagonal section is better than the ordinary reinforced concrete bridge. For an engineering example, this paper puts forward several different vertical prestressed steel arrangements. Based on different decorate a form of vertical pretressd bridge girder under stress numerical simulation, it is concluded that bridge’s web principal tensile stress distribution and its variation law, and then optimize the vertical reinforcing steel arrangement, improve the overall safety of bridge structure. It can provide the reference in the process of construction when we face the similar problems in the future.

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.

Study of Pre-Stress Effect of Ribcage Structure on Chest Response of Crash Dummy Model

2010 ◽  
Author(s):  
Xinghua Lai ◽  
Qing Zhou
Keyword(s):  
Stress State ◽  
Tensile Stress ◽  
Compressive Stress ◽  
Fe Model ◽  
Stress Effect ◽  
Stress Model ◽  
Test Results ◽  
Hybrid Iii ◽  
Structural Responses ◽  
Stress States

Assembling induced pre-stress state commonly exists in the ribcage structure of Hybrid III dummy hardware. In the practice of dummy modeling, however, the pre-stress issue is often neglected. This study is intended to assess the pre-stress effect on chest response of the Hybrid III 50th percentile male dummy model. In this paper, how the pre-stress state is generated in the dummy ribcage assembling process is first elaborated by disassembling and reverse engineering a physical dummy chest structure. A thorax FE model is then built and validated against test results. Using finite element modeling approach, the structural responses with and without the pre-stress state are compared and analyzed at single rib, ribcage and full dummy levels and under a number of loading conditions. The study has found out that, there are two common pre-stress states existing in the rib components of the dummy ribcage, pre-compressive stress and pre-tensile stress. Compared with no pre-stress model, the pre-compressive stress makes a rib stiffer and the pre-tensile stress makes a rib less stiff. It is further concluded that, the pre-stress effect is significant at the single rib level and insignificant at the ribcage level and the full dummy level. This is mainly because the effects of the pre-compressive stress and the pre-tensile stress existing in the six ribs are compensated each other in the assembled ribcage. Therefore, neglecting the pre-stress effect of the ribcage structure in the dummy models is reasonable.

scholarly journals Stress–strain relationship model of glulam bamboo under axial loading

2020 ◽  
Vol 29 ◽  
pp. 2633366X2095872
Author(s):  
Yang Wei ◽  
Mengqian Zhou ◽  
Kunpeng Zhao ◽  
Kang Zhao ◽  
Guofen Li
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Failure Modes ◽  
Axial Loading ◽  
Tensile Failure ◽  
Stress Strain ◽  
Laminated Bamboo ◽  
Bamboo Scrimber ◽  
Strain Relationship ◽  
Strain Model

Glulam bamboo has been preliminarily explored for use as a structural building material, and its stress–strain model under axial loading has a fundamental role in the analysis of bamboo components. To study the tension and compression behaviour of glulam bamboo, the bamboo scrimber and laminated bamboo as two kinds of typical glulam bamboo materials were tested under axial loading. Their mechanical behaviour and failure modes were investigated. The results showed that the bamboo scrimber and laminated bamboo have similar failure modes. For tensile failure, bamboo fibres were ruptured with sawtooth failure surfaces shown as brittle failure; for compression failure, the two modes of compression are buckling and compression shear failure. The stress–strain relationship curves of the bamboo scrimber and laminated bamboo are also similar. The tensile stress–strain curves showed a linear relationship, and the compressive stress–strain curves can be divided into three stages: elastic, elastoplastic and post-yield. Based on the test results, the stress–strain model was proposed for glulam bamboo, in which a linear equation was used to describe the tensile stress–strain relationship and the Richard–Abbott model was employed to model the compressive stress–strain relationship. A comparison with the experimental results shows that the predicted results are in good agreement with the experimental curves.

scholarly journals Long-Term Behaviour of Precast Concrete Deck Using Longitudinal Prestressed Tendons in Composite I-Girder Bridges

2018 ◽  
Vol 8 (12) ◽  
pp. 2598 ◽  
Author(s):  
Haiying Ma ◽  
Xuefei Shi ◽  
Yin Zhang
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Precast Concrete ◽  
Concrete Strength ◽  
Steel Girders ◽  
Concrete Creep ◽  
Compressive Stresses ◽  
Girder Bridge ◽  
Concrete Deck

Twin-I girder bridge systems composite with precast concrete deck have advantages including construction simplification and improved concrete strength compared with traditional multi-I girder bridge systems with cast-in-place concrete deck. But the cracking is still a big issue at interior support for continuous span bridges using twin-I girders. To reduce cracks occurrence in the hogging regions subject to negative moments and to guarantee the durability of bridges, the most essential way is to reduce the tensile stress of concrete deck within the hogging regions. In this paper, the prestressed tendons are arranged to prestress the precast concrete deck before it is connected with the steel girders. In this way, the initial compressive stress induced by the prestressed tendons in the concrete deck within the hogging region is much higher than that in regular concrete deck without prestressed tendons. A finite element analysis is developed to study the long-term behaviour of prestressed concrete deck for a twin-I girder bridge. The results show that the prestressed tendons induce large compressive stresses in the concrete deck but the compressive stresses are reduced due to concrete creep. The final compressive stresses in the concrete deck are about half of the initial compressive stresses. Additionally, parametric study is conducted to find the effect to the long-term behaviour of concrete deck including girder depth, deck size, prestressing stress and additional imposed load. The results show that the prestressing compressive stress in precast concrete deck is transferred to steel girders due to concrete creep. The prestressed forces transfer between the concrete deck and steel girder cause the loss of compressive stresses in precast concrete deck. The prestressed tendons can introduce some compressive stress in the concrete deck to overcome the tensile stress induced by the live load but the force transfer due to concrete creep needs be considered. The concrete creep makes the compressive stress loss and the force redistribution in the hogging regions, which should be considered in the design the twin-I girder bridge composite with prestressed precast concrete deck.

An analytical model of a curved beam with a T shaped cross section

2018 ◽  
Vol 416 ◽  
pp. 29-54 ◽  
Author(s):  
Andrew J. Hull ◽  
Daniel Perez ◽  
Donald L. Cox
Keyword(s):  
Analytical Model ◽  
Cross Section ◽  
Curved Beam ◽  
Shaped Cross Section

Stress Analysis and Microstructure Evolution of Titanium Alloy Pipe during Flattening Processing

2019 ◽  
Vol 944 ◽  
pp. 1088-1093
Author(s):  
Jun Chen ◽  
She Wei Xin ◽  
Wei Zhou ◽  
Qian Li ◽  
Si Yuan Zhang ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Tensile Stress ◽  
Compressive Stress ◽  
Outer Layer ◽  
Contact Stage ◽  
Straight Wall ◽  
Vertical Part ◽  
Left And Right ◽  
Titanium Alloy Tube ◽  
Flattening Process

TA24 titanium alloy pipe with 638mm diameter and 19mm wall thickness is carried out continuous load flatten test, and the stress of internal and external pipe wall during flatten process is studied in this paper. The results show that the TA24 titanium alloy tube has good flattening performance, and the flattening process has experienced original stage, flattened oblate stage, flattened straight wall stage, flattened depressed stage, flattened concave contact stage. During the flattening process, the outer layer of the upper and lower wall of the tube is subjected to compressive stress, and the inner layer material is subjected to tensile stress. The tensile and compressive forces cause the vertical part of the upper and lower walls to be concave. The outer layer of the left and right circular arc parts is subjected to tensile stress and the inner layer is subjected to tensile stress. The compressive stress also causes the radius of the arc to decrease due to the combined force of the tensile and compressive forces, that is, the flattening occurs. With the decrease of and pressing distance under continuous loading condition, the metal on the left and right sides of the pipe gathers toward the middle depression, which aggravates the deformation of the upper and lower walls until the upper and lower walls contact, and the arc radius of the left and right walls decreases until the outer surface cracks. The pipe microstructure changes significantly into elongated deformation structure during the flattening process. The most severe part of the deformation is the left and right end arc of the pipe, followed by the upper and lower end depression.

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