Engineered Semi-Flexible Composite Mixture Design and Its Implementation Method at Railroad Bridge Approach

2021 ◽  
pp. 036119812110049
Author(s):  
Shuai Yu ◽  
Shihui Shen ◽  
Hai Huang ◽  
Cheng Zhang
Keyword(s):  
Transition Zone ◽  
Structural Adjustment ◽  
Asphalt Mixture ◽  
Vertical Displacement ◽  
Smooth Transition ◽  
Railway Track ◽  
Dynamic Force ◽  
Entire Structure ◽  
Bridge Approach ◽  
Composite Mixture

Considerable variation in the vertical displacement can cause railway tracks’ transition problems at the bridge approach. The vertical displacement gaps can result in amplification of the dynamic force and frequency, and gradually degrade the serviceability of the railway track. Many strategies, focusing on either modifying the track component or making changes to the entire structure, were used to mitigate transition problems. In particular, asphalt concrete underlayment as a structural adjustment method provides additional support to the ballast and protects the subgrade. However, its effect of reducing dynamic impact at the bridge approach is limited because asphalt mixture has a limited range of modulus and cannot make enough adjustments to the entire structure. Therefore, this paper aims to develop an engineered semi-flexible composite mixture (SFCM) design to mitigate the transition problem. The experiment showed that SFCM is a viscoelastic material with a wider modulus range, and its modulus can adjust with its air voids and the concrete slurry content. Track analysis using a 2.5D sandwich model was conducted to simulate the effects of the structure and material on the responses of the railway track under the dynamic loads and determine the arrangement of the transition zone. A four-segment transition zone design was eventually proposed for a special case of bridge approach. This method can be used to develop transition zones for achieving a smooth transition at the bridge approaches.

scholarly journals Dynamic Force Identification for Beamlike Structures Using an Improved Dynamic Stiffness Method

1996 ◽  
Vol 3 (3) ◽  
pp. 183-191 ◽  
Author(s):  
S.L. Chen ◽  
M. Géradin
Keyword(s):  
Dynamic Stiffness ◽  
Random Noise ◽  
Parameter Extraction ◽  
Dynamic Force ◽  
Modal Parameter ◽  
Force Identification ◽  
Entire Structure ◽  
Stiffness Method ◽  
Dynamic Stiffness Method ◽  
Measured Response

In this study a procedure of dynamic force identification for beamlike structures is developed based on an improved dynamic stiffness method. In this procedure, the entire structure is first divided into substructures according to the excitation locations and the measured response sites. Each substructure is then represented by an equivalent element. The resulting model only retains the degree of freedom (DOF) associated with the excitations and the measured responses and the DOF corresponding to the boundaries of the structures. Because the technique partly bypasses the processes of modal parameter extraction, global matrix inversion, and model reduction, it can eliminate many of the approximations and errors that may be introduced during these processes. The principle of the method is described in detail and its efficiency is demonstrated via numerical simulations of three different structures. The sensitivity of the estimated force to random noise is discussed and the limitation of the technique is pointed out.

scholarly journals Micro-morphologies of SBS modifier at mortar transition zone in asphalt mixture with thin sections and fluorescence analysis

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Yue Xiao ◽  
Mujaheed Yunusa ◽  
Boxiang Yan ◽  
Xiaoshan Zhang ◽  
Xiwen Chang
Keyword(s):  
Particle Size ◽  
Transition Zone ◽  
Coefficient Of Variation ◽  
Asphalt Mixture ◽  
Area Ratio ◽  
Box Dimension ◽  
Fine Aggregate ◽  
Axis Ratio ◽  
Thin Sections ◽  
Modified Asphalt

AbstractThe microstructure control of modified asphalt, especially the micro-dispersion of the SBS modifier in the mortar transition zone, is a critical technology for the performance design of modified asphalt. To characterize the micro-dispersive morphology of SBS modifiers, thin-section preparation techniques that can be used to analyze the original microstructure of the asphalt mixture were proposed and introduced in this study. Flexible resin is filled into the mixture at vacuum conditions to ensure accepted sample conditions for preparing thin sections of asphalt mixture. The morphology parameters, including SBS area ratio, box dimension, SBS average particle area and its coefficient of variation, area-weighted average axis ratio, and coefficient of variation, were plotted from fluorescence images to characterize the micro-morphological distribution of the SBS modifier in detail. Results have shown that the area ratio increased with the increase in SBS content, while the box dimension was reduced and the distribution uniformity of the particles decreased. The superfluous SBS modifier in the binder at a too high adding ratio will decrease the value of the box dimension. Lower modification temperature worsened the SBS modifier in the mixture, resulting in a wide range of particle size, higher axis ratio, and higher area ratio. The micro-morphologies of SBS in the asphalt mixture phase varied a lot from the asphalt binder phase. The additional materials of mineral filler and fine aggregate, together with the other heating processes, will significantly influence the swelling state and particle size of the SBS modifier.

scholarly journals A New Extension of the Rank Transform for Stereo Matching

2011 ◽  
Vol 2-3 ◽  
pp. 182-187 ◽  
Author(s):  
Ge Zhao ◽  
Ying Kui Du ◽  
Yan Dong Tang
Keyword(s):  
3D Reconstruction ◽  
Transition Zone ◽  
Stereo Matching ◽  
Color Images ◽  
Smooth Transition ◽  
Discriminative Power ◽  
Rank Transform ◽  
Left And Right ◽  
Disparity Maps ◽  
Image Pixels

Stereo matching methods often use rank transform to deal with image distortions and brightness differences prior to matching but a pixel in the rank transformed image may look more similar to its neighbor, which would cause matching ambiguity. We tackle this problem with two proposals. Firstly, instead of using two values 0 and 1,we increase the discriminative power of the rank transform by using a linear, smooth transition zone between 0 and 1 for intensities that are close together. Secondly, we propose a new Bayesian stereo matching model by not only considering the similarity between left and right image pixels but also considering the ambiguity level of them in their own image independently. We test our algorithm on both intensity and color images with brightnesss differences. Corresponding 2D disparity maps and 3D reconstruction results verify the effectiveness of our method.

scholarly journals Performance Characterization of Semi-Flexible Composite Mixture

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 342 ◽  
Author(s):  
Weiguang Zhang ◽  
Shihui Shen ◽  
Ryan Douglas Goodwin ◽  
Dalin Wang ◽  
Jingtao Zhong
Keyword(s):  
Cement Mortar ◽  
Asphalt Mixture ◽  
Performance Testing ◽  
Field Performance ◽  
Fatigue Cracking ◽  
Thermal Cracking ◽  
Material Design ◽  
Engineering Properties ◽  
Portland Cement Concrete ◽  
Composite Mixture

Semi-flexible composite mixture (SFCM) is developed based on a unique material design concept of pouring cement mortar into the voids formed by open graded asphalt mixture. It combines the flexibility of asphalt concrete and the stiffness of Portland cement concrete and has many advantages comparing to conventional roadway paving materials. The main objective of this paper was to evaluate the engineering properties of SFCM and assess the constructability of the SFCM. A slab SFCM sample was fabricated in the laboratory to simulate the filling of cement mortar in the field. Performance testing was carried out by indirect tensile (IDT) test because it was found to be able to correlate with the field performance of asphalt mixtures at low, intermediate, and high temperatures. They were used in this study to evaluate the thermal cracking, fatigue, rutting, as well as moisture resistance of SFCM. A control hot mix asphalt (HMA) mixture was used to compare with the results of SFCM. Based on the testing results, it was found that the designed SFCM showed good filling capability of cement mortar. SFCM had higher dynamic modulus than the control HMA. It had good resistance to rutting and moisture damage. Based on fracture work, SFCM showed better resistance to thermal cracking while lower resistance to fatigue cracking.

Numerical study of transition zone between ballasted and ballastless railway track

2015 ◽  
Vol 3 ◽  
pp. 58-67 ◽  
Author(s):  
Mojtaba Shahraki ◽  
Chanaka Warnakulasooriya ◽  
Karl Josef Witt
Keyword(s):  
Transition Zone ◽  
Numerical Study ◽  
Railway Track

A study of the phenomenon of wheel climb derailment: Results of basic experiments using model bogies

2002 ◽  
Vol 216 (4) ◽  
pp. 237-247 ◽  
Author(s):  
K Nagase ◽  
Y Wakabayashi ◽  
H Sakahara
Keyword(s):  
Friction Coefficient ◽  
Vertical Displacement ◽  
Railway Track ◽  
Displacement Sensor ◽  
Major Influence ◽  
Laser Displacement Sensor ◽  
Wheel Slip ◽  
Adhesion Coefficient ◽  
The Relationship ◽  
Basic Experiments

Wheel climb derailment sometimes occurs when a train passes through a steep curve on a railway track at low speeds. The authors conducted experiments on the phenomenon of wheel climb derailment using model bogies and a model track. The Nadal formula (Nadal limit) is used to evaluate the risk of derailment. Because the friction coefficient between the rail and the wheel has a considerable influence on the critical values to be calculated using the Nadal formula, it is inappropriate to evaluate the risk of derailment by using the Nadal formula alone. The risk of derailment can be determined in a straightforward way by measuring the wheel vertical displacement. In this study, to measure the wheel vertical displacement accurately, a high-precision laser displacement sensor was used. The experimental results revealed that a wheel both slips downwards and climbs up simultaneously and that vertical displacement of the wheel occurs when the degree of wheel climb-up exceeds the degree of wheel slip-down. Although the friction coefficient between the rail and the wheel is a primary factor responsible for causing wheel climb derailment, measurement of the friction coefficient is difficult to achieve. Therefore, a model slipping adhesion bogie was used to measure the adhesion coefficient instead of the friction coefficient. The data obtained from the experiments were analysed in order to verify the relationship between the adhesion coefficient and the wheel climb-up behaviour. As a result, it was found that the adhesion coefficient has a major influence on the occurrence of wheel climb derailment.

scholarly journals Parameterization of basal hydrology near grounding lines in a one-dimensional ice sheet model

2014 ◽  
Vol 8 (1) ◽  
pp. 363-419
Author(s):  
G. R. Leguy ◽  
X. S. Asay-Davis ◽  
W. H. Lipscomb
Keyword(s):  
Transition Zone ◽  
Ice Sheet ◽  
Smooth Transition ◽  
Ice Shelf ◽  
Ice Shelves ◽  
One Dimensional ◽  
Basal Friction ◽  
Hydrological System ◽  
Intercomparison Project ◽  
Basal Shear

Abstract. Ice sheets and ice shelves are linked by the transition zone, the region where the grounded ice lifts off the bedrock and begins to float. Adequate resolution of the transition zone is necessary for numerically accurate ice sheet–ice shelf simulations. The required resolution depends on how the basal physics is parameterized. We propose a new, simple parameterization of the basal hydrology in a one-dimensional vertically integrated model. This parameterization accounts for connectivity between the basal hydrological system and the ocean in the transition zone. Our model produces a smooth transition between finite basal friction in the ice sheet and zero basal friction in the ice shelf. Through a set of experiments based on the Marine Ice Sheet Model Intercomparison Project (MISMIP), we show that a smoother basal shear stress, in addition to adding physical realism, significantly improves the numerical accuracy of our fixed-grid model, allowing for reliable grounding-line dynamics at resolutions ~1 km.

scholarly journals Permissible Values of the Dynamic Impact of the Rolling Stock on the Railway Track in the Case of Axle Load Increase

2021 ◽  
pp. 15-23
Author(s):  
О. M Patlasov ◽  
Y. M Fedorenko
Keyword(s):  
Dynamic Effect ◽  
Field Measurements ◽  
Experimental Tests ◽  
Railway Track ◽  
Rolling Stock ◽  
Actual State ◽  
Dynamic Force ◽  
Dynamic Impact ◽  
Railway Line ◽  
The Impact

Purpose. The study is aimed at determining experimentally the values of the parameters characterizing the dynamic effect of rolling stock on the railway track, substantiating the maximum permissible (limiting) values. Methodology. To investigate the interaction between the track and the rolling stock, the devices to record various physical processes were installed on the experimental sections. The devices were installed in 8 sections along the outer railway line. To establish the actual state of the track, field measurements were carried out in accordance with the Program and research methodology. Findings. According to the results of experimental tests of the impact on the track, it was revealed that the average vertical loads, and, accordingly, the average vertical deformations, under the cars with an axle load of up to 25 tf/axle are higher than that under the cars with an axle load of up to 23.5 tf/axle by 8 percent. The maximum vertical loads under the cars with an axle load of 25 tf/axle exceeded the average loads by 10.0 tf, and under the cars with an axle load of up to 23.5 tf/axle exceeded the average values by 12.8 tf. During the tests, no cars were found in which the vertical dynamic force exceeds 20 tf, and the horizontal force exceeds 10 tf. Therefore, the norms of permissible dynamic impact can be taken in accordance with the Regulations on Preventive Maintenance and Repair Track Work on the Railways of Ukraine. Originality. The authors conducted a study to assess the dynamic characteristics of the interaction of track and rolling stock, in particular the stresses in the edges of the rail base, vertical and horizontal forces from the wheels of rolling stock. Practical value. On the basis of the results obtained, it is possible to estimate the permissible values of the dynamic effect of the rolling stock on the railway track to substantiate the need to change the standards for the material consumption of the track superstructure and labor. In turn, this will make it possible to plan the repair and track periods more economically and according to the actual indicators of the state of the track superstructure.

scholarly journals Modeling Dry-Snow Densification without Abrupt Transition

Geosciences ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 464 ◽  
Author(s):  
Elizabeth Morris
Keyword(s):  
Transition Zone ◽  
Transition Density ◽  
Climatic Conditions ◽  
Smooth Transition ◽  
Transition Model ◽  
High Accumulation ◽  
Abrupt Transition ◽  
Best Parameter ◽  
Stage 1 ◽  
Parameter Values

An empirical model for the densification of dry snow has been calibrated using strain-rate data from Pine Island Glacier basin, Antarctica. The model provides for a smooth transition between Stage 1 and Stage 2 densification, and leads to an analytical expression for density as a function of depth. It introduces two new parameters with a simple physical basis: transition density ρ T and a scaling factor, M, which controls the extent of the transition zone. The standard (Herron and Langway) parameterization is used for strain rates away from the transition zone. Calibration, though tentative, produces best parameter values of ρ T = 580 kg m − 3 and M = 7 for the region. Using these values, the transition model produces better simulations of snow profiles from Pine Island Glacier basin than the well-established Herron and Langway and Ligtenberg models, both of which postulate abrupt transition. Simulation of density profiles from other sites using M = 7 produces the best values of ρ T = 550 kg m − 3 for a high accumulation site and 530 kg m − 3 for a low accumulation site, suggesting that transition density may vary with climatic conditions. The variation of bubble close-off depth and depth-integrated porosity with mean annual accumulation predicted by the transition model is similar to that predicted by the Simonsen model tuned for Greenland.

Sign in / Sign up

Export Citation Format

Share Document