scholarly journals Novel Bending Test Method for Polymer Railway Sleeper Materials

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1359
Author(s):  
Choman Salih ◽  
Allan Manalo ◽  
Wahid Ferdous ◽  
Rajab Abousnina ◽  
Peng Yu ◽  
...  
Keyword(s):  
Prestressed Concrete ◽  
Bending Moment ◽  
Test Method ◽  
Bending Test ◽  
Bending Moments ◽  
Flexural Behaviour ◽  
Wheel Load ◽  
Bending Modulus ◽  
Negative Bending ◽  
Railway Sleeper

Alternative sleeper technologies have been developed to address the significant need for the replacement of deteriorating timber railway sleepers. The review of the literature indicates that the railway sleepers might fail while in service, despite passing the evaluation tests of the current composite sleeper standards which indicated that these tests do not represent in situ sleeper on ballast. In this research, a new five-point bending test is developed to evaluate the flexural behaviour of timber replacement sleeper technologies supported by ballast. Due to the simplicity, acceptance level of evaluation accuracy and the lack of in-service behaviour of alternative sleepers, this new testing method is justified with the bending behaviour according to the Beam on Elastic Foundation theory. Three timber replacement sleeper technologies—plastic, synthetic composites and low-profile prestressed concrete sleepers in addition to timber sleepers—were tested under service loading condition to evaluate the suitability of the new test method. To address the differences in the bending of the sleepers due to their different modulus of elasticities, the most appropriate material for the middle support was also determined. Analytical equations of the bending moments with and without middle support settlement were also developed. The results showed that the five-point static bending test could induce the positive and negative bending moments experienced by railway sleepers under a train wheel load. It was also found that with the proposed testing spans, steel-EPDM rubber is the most suitable configuration for low bending modulus sleepers such as plastic, steel-neoprene for medium modulus polymer sleepers and steel-steel for very high modulus sleepers such as concrete. Finally, the proposed bending moment equations can precisely predict the flexural behaviour of alternative sleepers under the five-point bending test.

Evaluation of the Remaining Prestress Force and Center Negative Bending Moment in Crossties Removed From Track After 25 Years of Service

2019 ◽  
Author(s):  
James D. Scott ◽  
Robert J. Peterman ◽  
Aaron A. Robertson ◽  
B. Terry Beck ◽  
Kyle A. Riding
Keyword(s):  
Bending Moment ◽  
Test Method ◽  
Bending Test ◽  
Direct Tension ◽  
Longitudinal Splitting ◽  
Prestressing Steel ◽  
Prestressing Force ◽  
Four Point Bending ◽  
Negative Bending

Extensive research is currently being conducted by the team to understand the prestressing steel and concrete properties that cause high bonding stresses and lead to longitudinal splitting cracks, and how to mitigate this failure in future designs. One parameter of interest that affects the bonding stress is the amount of prestressing force in a crosstie. To help quantify the amount of prestress force necessary to provide a durable long-term crosstie, a study on existing crossties that have performed well in track for over 25 years was conducted to evaluate the center negative bending moment, and determine the remaining prestress force for each tie. The remaining prestress force in each tie was determined using a new proposed method in which ties are loaded in direct tension. The new test method was also conducted on new ties instrumented with vibrating wire strain gages to verify the method. The testing results reveal that a majority of the existing ties evaluated have a remaining prestress force in the range of 84–95 kips. These forces are significantly lower than the remaining prestress force after losses of newer tie designs. This can be seen when comparing the tension test results of the existing ties with the results of the new ties. Ties were loaded upside-down in four-point bending to determine their center negative cracking moments. The test setup and procedure used closely resembles the center negative bending moment test outlined in AREMA 30, with minor variations. For each different tie design in the study, the center negative design moment was calculated following the AREMA 30 procedure, and compared to the experimental cracking moments. Of the seven different existing tie designs investigated, four would meet the requirements of the current AREMA 30 center negative bending test.

scholarly journals Flexural Behavior of CFRP Laminate at Elevated Temperature

2017 ◽  
Vol 2 (3) ◽  
pp. 330-334
Author(s):  
Rzgar M. Abdalrahman
Keyword(s):  
Elevated Temperatures ◽  
Flexural Modulus ◽  
Peak Load ◽  
Test Method ◽  
Flexural Behavior ◽  
Bending Test ◽  
Effect Of Temperature ◽  
Flexural Properties ◽  
Flexural Behaviour ◽  
Cfrp Laminate

A carbon fibre reinforced polymer (CFRP) laminate forms the surface part of an integrally heated tool. It was made up of carbon non-crimp triaxial fibre and SR8100 epoxy in accordance to the stacking sequence of [(0, ±45)/ (90, ±45)] S, using the resin infusion (RI) method. The laminate is heated up to 90ºC when the tool is operated; therefore under-standing the effect of temperature on the flexural properties is quite significant. This experimental study is carried out to investigate the flexural behaviour of the CFRP laminate and finding its flexural properties under the effect of elevated temperatures. For this purpose, various CFRP specim-ens were prepared and tested, using three point bending test method, at different temperature levels from room temperature to 90ºC. The results show that each of the flexural peak load, modulus and strength of the laminate decreases consistently with the increase of temperature. Also the laminate becomes slightly more flexible and significant loss occurs in its flexural modulus when the temperature elevates from 75ºC to 90ºC. The reduction in the flexural behaviour of CFRP is imputed to thermal softening of the epoxy polymer matrix whenever becomes closer to (HDT).

Experimental Study on the Size Effect on Flexural Behavior of Larch Glulam Beams

2016 ◽  
Vol 847 ◽  
pp. 3-9 ◽  
Author(s):  
Xian Yan Zhou ◽  
Lei Cao ◽  
Dan Zeng
Keyword(s):  
Size Effect ◽  
Large Scale ◽  
Bending Strength ◽  
Weibull Model ◽  
Test Method ◽  
Flexural Behavior ◽  
Bending Test ◽  
Glulam Beam ◽  
Bending Modulus ◽  
Size Adjustment

At present, design values in codes and regulations are mainly based on test results of small size specimens, which are different from large-scale members used in practical engineering, therefore size adjustment coefficients are needed to be established. The four-point bending test method was adopted to investigate four groups of different sizes of Larch Glulam beams in their flexural behavior. Experiment data such as ultimate bearing capacity, deflection, strains and others are obtained, and the failure pattern and failure mechanism of bending members are analyzed. The research results indicate that the bending modulus of elasticity of Larch Glulam beam is not affected by the size. Bending strength of the Larch Glulam beam show a declining trend as the size of specimens increases, however, the ultimate bending moment increases. In addition, by means of a two-parameter Weibull model, a so-called size effect coefficient has been calculated by the slope method, thus providing a basis for the design and application of Larch Glulam beams.

Backsplinting for Treatment of Thoracic and Lumbar Fracture/Luxation in the Dog: Principles of Application and Case Series

1992 ◽  
Vol 05 (04) ◽  
pp. 179-187 ◽  
Author(s):  
Gail Smith ◽  
R. H. Patterson
Keyword(s):  
Closed Reduction ◽  
Biomechanical Testing ◽  
Case Series ◽  
Bending Moment ◽  
Bending Test ◽  
Bending Moments ◽  
Lumbar Fracture ◽  
Bracing System ◽  
Sufficient Strength

SummarySixteen animals with thoracic and lumbar fracture/luxations were treated with an external bracing system. The splint design and the method of application are described along with the complications seen. All of the animals recovered acceptable function, although six had residual neurologic deficits. Biomechanical testing of the splint revealed sufficient strength to limit angular deformation at a bending moment of 40 Nm. This approximates calculated in vivo bending moments for a large paralysed dog. Principles for closed reduction and external bracing of thoracic and lumbar injuries are presented.External coaptation was used in the reduction and fixation of 16 animals with thoracic and lumbar fracture/luxations. This spinal bracing system is described and principles of its application are presented. An experimental bending test was employed to test the hypothesis that the splint could effectively limit angulation at calculated in vivo bending moments.

scholarly journals Investigation of the Elastic Modulus of Polymer Sleepers Under a Quasistatic and Cyclic Loading

2019 ◽  
Vol 15 (2) ◽  
pp. 125-133
Author(s):  
Vít Lojda ◽  
Aran van Belkom ◽  
Hana Krejčiříková
Keyword(s):  
Elastic Modulus ◽  
Cyclic Loading ◽  
Prestressed Concrete ◽  
Load Level ◽  
Bending Test ◽  
Elastic Behaviour ◽  
Loading Frequency ◽  
Wheel Load ◽  
Four Point Bending ◽  
Four Point Bending Test

AbstractIn ballasted track, the wheel load is transmitted to the subgrade via sleepers commonly made of impregnated wood, prestressed concrete, steel or recently developed polymer sleepers. Mentioned material types of sleepers are characterized by different elastic moduli being a key parameter in any numerical model. Hence, this paper aims to determine the elastic modulus of sleepers subjected to a laboratory four-point bending test. Traffic resembling load level of 60 kN adopted from a typical axle load distributed by the rails to the sleeper was applied in a quasistatic and cyclic loading. The samples included sleepers made of polymers complemented with wood and pre-stressed concrete. The results of this paper are based on the elastic modulus investigation. Main conclusions are focused on the sleeper’s elastic modulus under changing loading frequencies. Wood and prestressed concrete sleepers indicated mainly elastic behaviour resulting in a constant elastic modulus. However, polymer sleepers showed a loading frequency dependent elastic modulus as a result of their viscous elastic behaviour. Moreover, the conclusions of this paper involve E-modulus measurements of impregnated beech sleepers in order to describe their piece by piece elasticity variation due to their natural origin.

Sign in / Sign up

Export Citation Format

Share Document