Analysis of a typical railway turnout sleeper system using grillage beam analogy

A simplified grillage beam analogy was performed to investigate the behaviour of railway turnout sleeper system with a low value of elastic modulus on different support moduli. This study aimed at determining an optimum modulus of elasticity for an emerging technology for railway turnout application - fibre composites sleeper. The finite element simulation suggests that the changes in modulus of elasticity of sleeper, Esleeper and the sleeper support modulus, Us have a significant influence on the behaviour of turnout sleepers. The increase in Us from 10 to 40 MPa resulted in a 15% reduction in the bending moment while the increase in Esleeper from 1 GPa to 10 GPa has resulted in almost 75% increase in the bending moment. The shear forces in turnout sleepers is not sensitive to both the changes of the Esleeper and Us while the sleeper with low Esleeper tend to undergo greater settlement into the ballast. An Esleeper of 4 GPa was found optimal for an alternative fibre composite turnout sleeper provided that the Us is at least 20 MPa from the consideration of sleeper ballast pressure and maximum vertical deflection. It was established that the turnout sleeper has a maximum bending moment of 19 kN-m and a shear force of 158 kN under service conditions

Structural behaviour of pultruded fibre composites guardrail system under horizontal loading

Fibre composite guardrails are increasingly being used to ensure safety of workers from fall-from-height incidents due to its high strength, high corrosion resistance and low maintenance. In this study, the structural behaviour of pultruded glass fibre reinforced polymer (GFRP) guardrail was evaluated following AS1657-1992. GFRP guardrail systems mounted on top and side of a steel beam with different joint connectors are loaded horizontally to top of the guardrail post and to the middle of the guardrail member. The results showed that the guardrail system with joints connected with either polypin or rivets combined with epoxy exhibited 20% higher failure load and almost double the stiffness than those connected using polypin or rivets alone. The side-mounted guardrail failed due to failure of the base connector while the guardrail mounted on top of the beam failed at the joints indicating that the structural behaviour of GFRP guardrail system is affected mainly by the type of joints

Performance of an innovative composite railway sleeper

The high maintenance cost and scarcity of the hardwood timber promote alternative technologies for replacing the timber railway sleepers. The advantages of composites in high strength-to-weight ratio, durability, reliability, longer life and less maintenance are of great interest for their application in railway sleepers. This study investigated the performance of an innovative composite railway sleeper manufactured from sandwich panels and bonded with the epoxy polymer matrix. The performance including rail-seat vertical load, centre bending moment, shear strength, screw holding capacity and electrical resistance have been investigated and compared with the timber sleepers. Results showed that the new composite sleeper can maintain the minimum performance requirements and showed a very similar behaviour to the timber ones. This innovative composite technology could be a suitable replacement to the existing timber sleepers

Effect of beam orientation on the static behaviour of phenolic core sandwich composites with different shear span-to-depth ratios

This study thoroughly investigated the flexural behaviour of phenolic cored sandwich beams with glass fibre composite skins in the horizontal and vertical positions. The beams have a shear span-to-depth ratio (a/d) varying between 0.5 and 12, and tested under 4-point static bending. Their failure load are then predicted theoretically. The results showed that changing the beam orientation from horizontal to vertical changes the failure mode from brittle to progressive. The sandwich beam’s high bending stiffness can be efficiently utilised by placing them vertically. The a/d ratio played a major role on the load capacity and failure mode. In both orientations, the load capacity decreased with the increased of a/d. The beam failed in shear, a combined shear and bending, and bending for a/d ≤ 2, 2 < a/d < 6, and a/d ≥ 6, respectively. These failure mechanisms can be correlated to the shear-to-bending stress ratio while the failure load can be reasonably predicted using the available theoretical models. The two-way analysis of variance showed that the beam orientation is a more influential parameter than the a/d ratio. From this study, the horizontal beams are preferable for flexural dominated structures while the vertical beams are desirable for shear dominated structures

Fibre composites for high pressure pipeline repairs, in-air and subsea: an overview

In 2001 it was reported that in North America alone, corrosion to the Oil & Gas pipeline distribution network cost approximately $2-3.3 billion per annum with 10% of that cost being associated with actual failure of the pipeline. In addition pipelines are also susceptible to erosion and mechanical damage producing further losses in pipe structural integrity. This results in high maintenance costs, possibility of adverse environmental consequences and the costly interruption to product transportation and distribution. The cost and technical challenges of adequately addressing repair are significant and greatly increase for underwater applications particularly with increasing water depth. It therefore induces the need of searching for alternative repair techniques involving new advanced materials for ease of installation and application against adverse environmental effects in the long run. Fibre composite materials provide excellent advantages over conventional metals in engineering practices for many decades. These advantages make fibre composite suitable candidate for effective repair technology. This paper provides a comprehensive review on the recent development and future prospect of using these materials for in-air and underwater pipeline external repairs. Various aspects of technical knowhow; benefits and shortcomings of the repair considerations are also presented

The effect of shear span-to-depth ratio on the failure mode and strength of pultruded GFRP beams

The use of structural pultruded fibre reinforced polymers (FRP) sections have gained wide acceptance in civil engineering applications due to their favourable structural characteristics like high strength, light weight and durability in severe environmental conditions. However, due to their relatively low modulus of elasticity and thinned walls, these sections are vulnerable to local buckling which can affect their ultimate strength. This paper investigates experimentally the flexural behaviour of pultruded GFRP beams with shear span-to-depth (a/d) ratios in the range of 1.2 to 6 using full scale pultruded profiles. Failure modes, strength and crack patterns are the main parameters that were examined in this study. The study shows that shear span has a minor effect on the failure modes of the beams while it has a noticeable effect on the ultimate strength. In addition, fibre model analysis was used to validate the experimental results. Comparison between the experimental and the theoretical analysis results shows a good approximation of the moment - deflection behaviour and failure moment of pultruded GFRP beams

Comparison between ASTM D7205 and CSA S806 tensile-testing methods for glass-fiber-reinforced-polymer bars

The American Society of the International Association for Testing and Materials (ASTM) D7205 / D7205M-06 and the Canadian Standards Association (CSA) S806 contain the commonly used test methods for characterizing the tensile properties of glass-fiber-reinforced-polymer (GFRP) bars for use as reinforcement in concrete structures. These two standards, however, use different anchor dimensions and loading rates, thereby possibly yielding different properties for the same type of FRP bars. This paper assessed the results of a four-laboratory testing program comparing the sample preparation methods and test results according to ASTM D7205 and CSA S806. Each laboratory tested at least 10 samples prepared according to the recommendations in Annex A of the ASTM standard, and Annex B of CSA S806. Each type of sample was prepared by a single laboratory in order to minimize variation among the test specimens. The results show a statistically significant difference between the tensile strength measured using the CSA and ASTM provisions. Regardless of specimen preparation, the modulus of elasticity of the GFRP bars was the same with both test standards, but the ASTM standard returned a wider variation than the CSA

Flexural behavior of glued GFRP tubes filled with concrete

The corrosion of steel reinforcement is considered the greatest factor limiting the service life of reinforced concrete structures. Glass fiber reinforced polymers (GFRPs) are known as cost-effective materials offering long-term durability and less maintenance. As a result, these materials show great potential for use in the civil engineering applications. Due to the high cost of the manufacturing die, pultruded GFRP tubes are produced in specific cross-section dimensions only. For high load applications and to comply with the serviceability requirements, a number of these pultruded sections can be assembled together by gluing them appropriately. This study presents an experimental investigation onto the flexural behavior of glued GFRP tube beams with 1, 2, 3 and 4 - cells filled with concrete under four-point loading. The results show that the strength of the 4 cells glued beams increased by 150 % and 88% for hollow and filled beams, respectively, compared with its counterpart single cell beam. The filled beams failed at 42 – 88 % higher load and showed 10 – 22 % higher stiffness compared with their hollow counterparts. The results also show that gluing small section tubes to produce large section beam is a practical solution to enhance the flexural performance of the composite tubes

Testing and characterization of pultruded glass fiber reinforced polymer (GFRP) beams

Elastic properties of the fiber reinforced polymer (FRP) composite represent a significant effect on the structural behaviour of this material. Therefore, it is important to use an accurate method to determine these properties as the behaviour is often governed by deflection rather than strength. In this study, full size pultruded glass FRP (GFRP) beams were used to determine the elastic properties using static four-point bending with different shear span to depth (a/d) ratios. Two different methods -back calculation and simultaneous - were then employed to evaluate the flexural modulus and shear stiffness and were compared with the results of the test using coupon specimens. The results indicate that the elastic properties determined from full scale test using back calculation method can reliably predict the load - deflection behaviour of the pultruded GFRP beams

Behaviour of hollow pultruded GFRP square beams with different shear span-to-depth ratios

It is important to determine accurately the elastic properties of fibre-reinforced polymer composites material, considering that their member design is often governed by deflection rather than strength. In this study, the elastic properties of the pultruded glass fibre-reinforced polymer square sections were evaluated firstly using full-scale with different shear span to depth (a/d) ratios and tested under static four-point bending. Back calculation and simultaneous methods were then employed to evaluate the flexural modulus and shear stiffness and were compared with the results of the coupon tests. Secondly, the full-scale beams were tested up to failure to determine their capacity and failure mechanisms. Finally, prediction equations describing the behaviour of the pultruded glass fibre-reinforced polymer square beams were proposed and compared with the experimental results. The results indicate that the back calculation method gives more reliable values of elastic properties of glass fibre-reinforced polymer profiles. In addition, the behaviour of the beams is strongly affected by the a/d ratios. The shear was found to have a significant contribution on the behaviour of beams with lower a/d ratios while the flexural stress played a major part for higher a/d ratios. The proposed equation, which accounts for the combined effect of the shear and flexural stresses, reasonably predicted the failure load of pultruded glass fibre-reinforced polymer square beams