This thesis explores the quality of hand-manufactured carbon-epoxy IsoTruss® grid structures for use as reinforcement in concrete piles. Large IsoTruss® grid structures were manufactured and embedded in 14.0" (35.6 cm) diameter concrete to create IsoPiles™. The IsoPiles™ were designed to have flexural characteristics similar to steel reinforced concrete piles of equal diameter. Bending stiffness was matched based on the longitudinal members. A method for comparing transverse steel reinforcement to helical IsoTruss® members was developed, along with equations to facilitate the design of IsoTruss® structures with rounded nodes.

Compression tests were performed on 3.0 ft (0.91 m) long sections taken from the ends of each of the two 30 ft (9.14 m) long IsoTruss® grid structures manufactured. Fiber volume fraction, void fraction, and cross section area inspections were performed on IsoTruss® samples to determine quality. The strength, stiffness, and fiber volume fraction data obtained from these tests are compared to values obtained previously [1] for the same consolidation method. The quality of hand-manufactured large IsoTruss® grid structures was quantified by performing microscopic inspection of the members, by testing the reinforcement cage in compression, and by testing short section of IsoTruss® and steel reinforced concrete piles in compression. Compression tests were performed on short sections taken from the ends of the IsoPile™ specimens. These were compared with compression tests performed on equivalent steel-reinforced piles to evaluate the viability of the IsoTruss® as reinforcement in concrete piles.

Insufficient tension on the fiber during manufacturing and insufficient radial compression during the cure resulted in an average fiber volume fraction 13% lower than previously obtained, causing the ultimate compressive strength and Young's modulus of the IsoTruss® reinforcement cages to be 51% and 22% lower, respectively, than previous data. The IsoTruss®–reinforced piles had an ultimate compressive load that was within 4% of the ultimate compressive load of the steel-reinforced piles.



College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering



Date Submitted


Document Type





IsoTruss, composites, reinforced concrete, piles