Semester

Summer

Date of Graduation

2021

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Hota V.S. GangaRoa

Committee Member

Udaya B. Halabe

Committee Member

Hung-Liang (Roger) Chen

Abstract

Timber pile repair using splicing is widely used but little research has been done to determine their strength capacity after repair using this method. Current timber pile splicing mechanisms utilize various steel or wooden components. Fiber Reinforced Polymer (FRP) wraps can be utilized as replacement to conventional materials in splicing of timber piles. This study evaluated the strength capacities of traditional splicing mechanisms in relation to FRP wrap splice mechanisms. Traditional splicing mechanisms consisted of flat steel plate, C-channel steel plate, and wooden plate splices. The FRP wrap splice consisted of unidirectional glass/epoxy composite with three layers of fabric as well as bidirectional FRP wraps, where the fabrics were reinforcing wooden pieces in both the longitudinal and hoop direction. These four mechanisms were tested and compared under shear, bending, and axial loading scenarios. Of the three traditional splicing methods the C-channel was the strongest for each loading scenario. The FRP warp method was the strongest under axial loading conditions, however it lacked in bending capacity compared to the traditional methods. Bending failure in FRP splicing mechanism occurred due to the lack of fiber reinforcement in the hoop direction of the pile. To account for improving the capacity along the hoop direction, another design was utilized using the same three-layer unidirectional glass/epoxy composite with longitudinal dominant fiber orientation and three additional layers with hoop dominant fiber orientation. This new design was tested under shear and bending loading scenarios. Results of the six-layer wrap design showed significant improvement in bending and shear capacities from the original three-layer FRP composite wrap design. Virgin timber piles were tested under bending to determine the bending strength capacity for each of the splice mechanisms. This comparison provided that splicing a timber pile with splice mechanisms tested in this program decreased the bending capacity of piles (30-60 percent).

A theoretical analysis was performed to determine the shear, axial, and bending capacities of timber piles spliced with FRP wrap using design equations that were developed in this program. Theoretical stress values were compared with experimental stress values gained through laboratory testing to determine the reliability of the design equations. Shear and bending equations had low variability in theoretical versus experimental stress values. For axial analysis, when assuming failure occurs by compression of FRP large variability in theoretical versus experimental data was noted, meaning failure did not occur from compression in FRP. A new design equation was developed using Euler’s Buckling equation for axial failure due to buckling. This equation provided much lower variability in theoretical versus experimental data, meaning failure in axial compression occurred in all three test specimens due to buckling followed by de-bond. The design methodology proposed herein for FRP wrap splices should be adapted as a common practice.

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