An overview on the application of FRP composites in piling system

Traditional pile materials such as steel, concrete and timber have limited service life when used in harsh marine environment. Problems coupled with these piles include deterioration of wood, corrosion of steel and degradation of reinforced concrete. To offset this problem, a relatively new trend in deep foundation industry is to use a fibre reinforced polymer (FRP) composite materials as a substitute in piling system. The fundamental advantages of FRP composites compared to other pile materials include lightweight, high strength and possess resistance against corrosion. However, composite materials face hurdle because they do not have a long track record of use in civil engineering application particularly in piling system. To partly address this obstacle, this paper presents an overview in testing, design, and practice of composite piles. Importance is given to history, material types and properties, structural behaviour, geotechnical performance, and durability of composite piles

Numerical Investigation on Hollow Pultruded Fibre Reinforced Polymer Tube Columns

As the axial behaviour of hollow pultruded fibre reinforced polymer (PFRP) profiles is governed by the instability conditions due to the local and global buckling, the determination of the safe load carrying capacity of FRP columns is vital. The compressive performance of PFRP tube depends on many factors such as fibre type, fibre content, and orientation of fibre layers, cross-section, thickness and height of the column member. In this study, concentric compressive testing was conducted using PFRP short columns. Based on the fibre orientation and thickness, the samples were divided into two groups of tubes in a square shape and two groups in a circular shape. The height of columns is designed to keep the slenderness ratio (length/lateral dimension) of 5. The axial behaviour of FRP columns was simulated using STRAND7 finite element software package. The laminate method was followed to define the mechanical properties of the FRP material. Failure was investigated by using the Tsai-Wu failure criterion. The experimental results show that the failure mode of the hollow square tube was either local buckling or corner splitting at the mid-height followed by buckling. Although both types of circular tubes failed in a similar way by crushing one end with high noise, followed by separation of the crushed end into strips, the stiffness and the load capacity of PFRP column was higher for the profiles with fibres oriented close to the axial direction. The numerical results are in close agreement with the peak value of the experimental results. This can be extended to study the effects of all factors that influence the axial behaviour of PFRP columns numerically

Driveability of composite piles

Deep foundation has historically involved the use of traditional materials such as concrete, steel and timber. However, these materials suffered from strength degradation and its repair cost is significant especially if installed in harsh marine environment. A relatively new trend in piling industry is to use composites as substitute material. Composites present a novel solution without most of the traditional materials' shortcomings. The basic advantages of composites among other construction materials include lightweight, high strength-to-weight ratio, corrosion resistance, chemical and environmental resistance, and low maintenance cost. Apart from the mentioned advantages, composite materials face impediments since they do not have a long track record of use in piling system. To partially address the aforementioned barrier, this paper presents information on the driveability of composite piles which is one of the first steps toward understanding its behaviour during driving. Additionally, experimental impact test result conducted by the authors on fibre reinforced polymers (FRP) hollow pile is also discussed in this study. Result from the impact test on laminate confirms that longitudinal specimen exhibited higher energy absorption capacity compared to the transverse specimens. The performed axial impact test on pultruded section revealed that degradation of stiffness increases with increasing incident energies and impact cycles. Generally, literature showed limited information on full-scale driving test and needed field tests to carefully assess and verify the driving performance of the composite piles to be used in developing reliable design procedures

Behaviour of fibre composite pile under axial compression load

Fibre reinforced polymer (FRP) composite piles offer advantages compared to traditional pile materials since the latter materials have limited service life when used in marine environment. As a result, application of composite piles started to gain acceptance in pile rehabilitation and replacement. Apart from composite piles’ advantages, there is a need to assess its structural behaviour under different loading conditions. To perform this, the present paper experimentally and numerically investigates the behaviour of hollow FRP composite pile under axial compression. It was found that fibreglass-reinforced lamina bears 96% of the applied load while 4% was carried by Soric XF-reinforced lamina. Lateral strain of the plies remains the same across the thickness of the tube irrespective of the loading magnitude while axial strain variations on plies were developed at increasing applied load. Furthermore, the load-strain curves of the finite element model are in close agreement with the experimental results

Effects of energy level and impact repetitions on the impact fatigue behaviour and post-impact flexural properties of square FRP pultruded tubes

This paper presents an experimental investigation on the effects of impact energy level and impact repetitions on the impact fatigue behaviour and post-impact flexural properties of square FRP composite tubes. Impact testing was done by axially impacting a 100 mm square pultruded tube with an energy level ranging from 158 to 742 J using a drop-weight impact apparatus. Coupons were then taken from the impacted tubes and tested statically under three-point bending to determine their post-impact flexural properties. The results showed that the effects of energy level and impact repetitions are significant on the rate of energy absorption behaviour of the FRP tubes before its collapse. Their effects, however, are negligible when the tube ruptures. It was also found that the post-impact flexural properties of the impacted tubes are reduced at higher impact energies and more impact repetitions. The maximum reduction of the strength and modulus are 10 and 3.7%, respectively