A Study of Compressive Stress and Compression of Hard Foam Board for Longitudinally Coupled Slab Track on Bridges

2010 ◽  
Author(s):  
Rui Xiang ◽  
Juanjuan Ren ◽  
Yong Zeng
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Rotation Angle ◽  
Element Model ◽  
Bridge Structure ◽  
Q Value ◽  
Railway Line ◽  
Concrete Base ◽  
Bridge Foundation ◽  
Beam Rotation

Longitudinally Coupled Prefabricated Ballastless Track (LCPBT) system was firstly applied on Suining-Chongqing experimental railway line and Beijing-Tianjin intercity railway line. LCPBT track structure is longitudinally continuous, with fixing a 5-cm-thick hard foam board above every bridge structure joints, between bridge protection layer and the continuous concrete base to reduce detrimental fastening pulling force in case of great rotation angle or displacement. Hard foam board ensures a steady deformation transition, and we calculate its compressive stress, compression and cubical elasticity coefficient Q, for fulfilling force-bearing and deformation requirements. Taking a two-span, simple supported beam, each with 32-m-long bridge for instance, an integral finite element model of continuous welded rail -coupled track slab -coupled concrete base –bridge beam was established, in which a vertical compression amount under 9 different load cases. The maximum bottom tensile stress of concrete base, maximum compressive stress and compression amount of hard foam board are gained from computation results. Besides, Q-value and the control value of rotation angle at bridge structure joints are suggested in this paper. The key findings are: a) under simultaneous actions of train load and beam rotation angle, the maximum bottom tensile stress of concrete base does not exceed its threshold as 250 kPa, given a Q-value of 0.5 N/mm3; b) considering the uniformity of track stiffness and track regularity, a greater Q-value is preferable and we recommend the Q-value as 0.5 N/mm3; c) the beam rotation angle at bridge structure joints should be less than 1.4, including the load cause of uneven settlement of adjacent bridge piers, uneven settlement of adjacent bridge foundation; d) uneven settlement of adjacent bridge foundation on the same bridge pier must be strictly controlled to avoid affecting the service life of hard foam board.

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.

Stress Analysis of a Novel MEMS Microphone Chip Using Finite Element Analysis

2005 ◽  
Author(s):  
Jia Gao ◽  
Ronald N. Miles ◽  
Weili Cui
Keyword(s):  
Finite Element ◽  
Low Temperature ◽  
Tensile Stress ◽  
Finite Element Model ◽  
Oxide Layer ◽  
Compressive Stress ◽  
Failure Modes ◽  
Element Model ◽  
Mems Devices ◽  
Mems Microphone

Residual stress produces major challenges in the fabrication of MEMS devices. This is particularly true in the development of MEMS microphones since the response of the thin sound-sensitive diaphragm is strongly affected by stress. It is important to predict the effects of fabrication stress on the microphone chip and identify the failure modes to ensure a satisfactory fabrication yield. In this study, a finite element model of the microphone chip is developed to analyze the laminated structure under different fabrication stresses. The model of the microphone chip includes the diaphragm, backplate and sacrificial oxide layers on top of the silicon substrate. Fabrication stresses are included through the use of an equivalent thermal stress. The stresses in the different layers have been estimated based on measurements performed on fabricated test structures. The estimated stresses are simulated in the finite element model. An important factor in determining the process reliability is the compressive stress of the low temperature sacrificial oxide layer (LTO). A variety of stress combinations between different layers with the low temperature oxide layer are investigated. It is found that an adequate level of tensile stress in the backplate is crucial to ensure the fabrication yield. In the designs considered here, silicon nitride in combination with a thin conductive layer is identified as a favorable material for the backplate considering its high modulus and tensile stress in ‘as deposited’ film. In addition, the presence of a LTO layer on the backside of the wafer turns out to be very helpful in reducing the deflection of the unreleased chip and the stress in the diaphragm. In the case where there is a net compressive stress in the laminate, the failure mode is identified by nonlinear analysis. This analysis provides a guideline to select robust materials and tune the fabrication process to ensure a satisfactory fabrication yield.

Monolithic Roadbed's Mechanical Behavior Affected by Structural Thickness under Tram

2013 ◽  
Vol 361-363 ◽  
pp. 1664-1670
Author(s):  
Chong Wei Huang ◽  
Er Hao Su ◽  
Xian Zhi Shao ◽  
Yi Zhang ◽  
Lie Ping Wang
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Tensile Stress ◽  
Mechanical Behavior ◽  
Compressive Stress ◽  
Contact Problems ◽  
Element Model ◽  
Nonlinear Contact ◽  
Structure Layer ◽  
Abaqus Software

Based on ABAQUS software, a 3-D finite element model which content the nonlinear contact problems and contact-earth subgrade-monilithic was given to analysis the mechanical behavior of the monolithic roadbed. Mechanics behavior and deflection of the monolithic roadbed, deflection and compressive stress of earth subgrade evaluated in detail with respect to varied structure layer combination and materials parameters. The results indicate that the increase roadbed thickness can significantly reduce the monolithic roadbeds tensile stress, which can reach 1.042MPa. With the increase of the friction coefficient, level of tensile stress σdy, monolithic deflection Dd , the compressive stress σsz and deflection on earth subgrade were slightly reduced.

scholarly journals Analysis of Influence and Formation for Uncoordinated Deformation in Tram Subgrade

2019 ◽  
Vol 136 ◽  
pp. 04037
Author(s):  
Yang Cai ◽  
Chongwei Huang ◽  
Xi Chen ◽  
Yu Sun ◽  
Dandan Guo
Keyword(s):  
Finite Element ◽  
Tensile Stress ◽  
Finite Element Model ◽  
Mechanical Behavior ◽  
Compressive Stress ◽  
Mechanical Response ◽  
Element Model ◽  
The Other ◽  
3D Finite Element ◽  
Remarkable Effect

Aiming at horizontal and vertical uncoordinated deformation formation in Tram Subgrade, a 3D finite element model was established, which was used to analyse the mechanical response of tram monolithic roadbed on multiple depth and width of uncoordinated deformation. The results show that the uncoordinated deformation’s depth has little influence on the mechanical behavior of roadbed, and it indicates that there was remainder disengaging under the monolithic roadbed by the load of tram. On the other side, the width of uncoordinated deformation has a remarkable effect on outstanding to the horizontal tensile stress (σdy) in the slab bottom, deflection (Dd) on the top of slab, compressive stress (σsz) on the top of soil, and deflection (Dss) on the top of soil. The deflection on the top of subgrade surface is about 1.61mm. Therefore, the designer’s attention should be paid to avoid uncoordinated deformation width in the project, and avoid destroy of monolithic slab.

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.

Study on Load Stress of Lean Concrete Base in Asphalt Pavement

2012 ◽  
Vol 178-181 ◽  
pp. 1495-1498
Author(s):  
Li Jun Suo
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Asphalt Pavement ◽  
Element Model ◽  
Pavement Design ◽  
The Other ◽  
Three Dimension ◽  
Traffic Loading ◽  
Concrete Base

Load stress, which is caused by traffic loading, is important parameter used in the analysis of the new pavement design. In order to study the load stress of lean concrete base in the asphalt pavement, first of all, three–dimension finite element model of the asphalt pavement is established. The main objectives of the paper are investigated. One is calculation for load stress of lean concrete base, and the other is analysis for relationship between load stress of lean concrete base and parameters, such as thickness, modulus. The results show that load stress of lean concrete base decreases, decreases and increases with increase of base’s thickness, surface’s thickness and ratio of base’s modulus to foundation’s modulus respectively. So far as the traffic axle loading is concerned, it has a significant impact on load stress of lean concrete base, and it can be seen from results that when load is taken from 100kN to 220kN, load stress increases quickly with the increase of the traffic axle loading.

Numerical analyses on mechanical performance of flat buried approach slab and soil deformation

2021 ◽  
Author(s):  
Junqing Xue ◽  
Dong Xu ◽  
Yufeng Tang ◽  
Bruno Briseghella ◽  
Fuyun Huang ◽  
...  
Keyword(s):  
Finite Element ◽  
Tensile Stress ◽  
Parametric Analysis ◽  
Mechanical Performance ◽  
Element Model ◽  
Soil Deformation ◽  
Longitudinal Deformation ◽  
Expansion Joints ◽  
Approach Slab ◽  
Jointless Bridges

<p><br clear="none"/></p><p>The vulnerability problem of expansion joints could be fundamentally resolved using the concept of jointless bridges. The longitudinal deformation of the superstructure can be transferred to the backfill by using the approach slab. The flat buried approach slab (FBAS) has been used in many jointless bridges in European countries. In order to understand the mechanical performance of FBAS and soil deformation, a finite element model (FEM) was implemented in PLAXIS. Considering the friction between the FBAS and soil, the buried depth, the FBAS length and thickness as parameters, a parametric analysis was carried out. According to the obtained results and in order to reduce the soil deformation above the FBAS, it is suggested to increase the friction between the FBAS and sandy soil, and the buried depth of FBAS. Moreover, it should be paid attention to the vertical soil deformation and the concrete tensile stress of FBAS in pulling condition.</p>

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.

scholarly journals A novel strain sensor using a microchannel embedded in PDMS

2018 ◽  
Vol 4 (2) ◽  
pp. 1 ◽  
Author(s):  
Angelica Campigotto ◽  
Stephane Leahy ◽  
Ayan Choudhury ◽  
Guowei Zhao ◽  
Yongjun Lai
Keyword(s):  
Finite Element ◽  
Rotation Angle ◽  
Strain Sensor ◽  
Element Model ◽  
Strain Sensors ◽  
Gauge Factor ◽  
Sectional Area ◽  
Cross Sectional ◽  
Higher Sensitivity

A novel, inexpensive, and easy-to-use strain sensor using polydimethylsiloxane (PDMS)  was developed. The sensor consists of a microchannel that is partially filled with a coloured liquid and embedded in a piece of PDMS. A finite element model was developed to optimize the geometry of the microchannel to achieve higher sensitivity. The highest gauge factor that was measured experimentally was 41. The gauge factor was affected by the microchannel’s square cross-sectional area, the number of basic units in the microchannel, and the inlet and outlet configuration. As a case study, the developed strain sensors were used to measure the rotation angle of the wrist and finger joints.

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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