Repair of heavily decayed timber piles using Glass Fiber Reinforced Polymers, GFRP, and cementitious grout

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Hagos, Michael W.
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This experimental study has been conducted to evaluate the effectiveness of using Glass Fiber Reinforced Polymer (GFRP) systems and cementitious grout to restore heavily decayed timber piles to their original load-carrying capacity. The proposed repair scheme involved trimming some of the decayed timber from around the circumference of the pile, followed by encasing the "sound" timber core with a 50 mm thick non-shrink cementitious grou shell. The "sound" timber core and the newly formed grout shell were then confined using external GFRP systems to improve the axial compression capacity of the piles. A total of 43 timber pile specimens were tested to failure in axial compression, while another ten pile specimens were tested in bending. In general, test results demonstrated that a 50 mm thick cementitious grout shell confined by a single layer of GFRP wet-wrap can effectively restore the axial compressive strength of the piles to their original load-carrying capacity or greater. Furthermore, the proposed repair technique serves to reduce the variability in the load-carrying capacity of the repaired piles. The transition zone between the repaired length of pile and the "sound" timber below must be strengthened in order to utilize the full capacity of the unrepaired "sound" timber below. However, the transition zone cannot sustain high moment and should be located at depths with lower levels of applied moment. A conservative design approach has been developed and detailed design recommendations are made. Suggestions for specific areas of further research are also given, and should be undertaken if further refinement of the repair technique and design procedure is required.