This paper presents a design-based real-scale case study of a glass-fiber-reinforced polymer (GFRP) reinforced-concrete raft foundation supporting air-core shunt reactors in a high-voltage electrical installation. The case is characterized by a specific functional constraint: the reinforcement system had to satisfy conventional structural and geotechnical requirements while improving electromagnetic compatibility (EMC) by reducing the risk of interaction with 50 Hz stray magnetic fields generated by the reactors. Because conventional steel reinforcement may form electrically continuous or quasi-continuous conductive paths, the adopted solution used non-metallic, electrically insulating, and non-magnetic GFRP bars. The foundation consists of a 13.0 m × 11.0 m, 0.60 m thick cast-in-place raft reinforced with 12 mm GFRP bars at 150 mm spacing in both orthogonal directions, with local strengthening zones near auxiliary supports. The study presents the design rationale, the main structural and geotechnical verifications, and a simplified order-of-magnitude electromagnetic assessment based on manufacturer clearance requirements and representative conductive-loop calculations. The GFRP solution is then compared with two steel reinforcement alternatives: a like-for-like 12 mm steel mesh at 150 mm spacing and a code-oriented 14 mm steel mesh at 250 mm spacing. The comparison is limited to reinforcement-level indicators, including reinforcement quantity, cradle-to-gate A1–A3 embodied carbon, and material cost. The adopted GFRP layout reduced reinforcement mass by approximately 75% compared with the like-for-like steel solution. Under the adopted emission factors, the reinforcement-related embodied carbon was estimated as 5.77 tCO₂e for GFRP, compared with 14.57 tCO₂e and 13.46 tCO₂e for the two steel alternatives. Conversely, the reinforcement-only material cost was higher for GFRP. The results show that GFRP reinforcement can be a technically suitable option for foundations placed in electromagnetically constrained environments, provided that the conclusions are interpreted within the limits of a project-specific design case study and reinforcement-level environmental and economic assessment.
Design-based case study of a GFRP-reinforced RC raft foundation for air-core shunt reactors: Electromagnetic compatibility and reinforcement-level environmental-cost indicators
Pinna, F.;Mistretta, F.;Puppio, M. L.;Stochino, F.
2026-01-01
Abstract
This paper presents a design-based real-scale case study of a glass-fiber-reinforced polymer (GFRP) reinforced-concrete raft foundation supporting air-core shunt reactors in a high-voltage electrical installation. The case is characterized by a specific functional constraint: the reinforcement system had to satisfy conventional structural and geotechnical requirements while improving electromagnetic compatibility (EMC) by reducing the risk of interaction with 50 Hz stray magnetic fields generated by the reactors. Because conventional steel reinforcement may form electrically continuous or quasi-continuous conductive paths, the adopted solution used non-metallic, electrically insulating, and non-magnetic GFRP bars. The foundation consists of a 13.0 m × 11.0 m, 0.60 m thick cast-in-place raft reinforced with 12 mm GFRP bars at 150 mm spacing in both orthogonal directions, with local strengthening zones near auxiliary supports. The study presents the design rationale, the main structural and geotechnical verifications, and a simplified order-of-magnitude electromagnetic assessment based on manufacturer clearance requirements and representative conductive-loop calculations. The GFRP solution is then compared with two steel reinforcement alternatives: a like-for-like 12 mm steel mesh at 150 mm spacing and a code-oriented 14 mm steel mesh at 250 mm spacing. The comparison is limited to reinforcement-level indicators, including reinforcement quantity, cradle-to-gate A1–A3 embodied carbon, and material cost. The adopted GFRP layout reduced reinforcement mass by approximately 75% compared with the like-for-like steel solution. Under the adopted emission factors, the reinforcement-related embodied carbon was estimated as 5.77 tCO₂e for GFRP, compared with 14.57 tCO₂e and 13.46 tCO₂e for the two steel alternatives. Conversely, the reinforcement-only material cost was higher for GFRP. The results show that GFRP reinforcement can be a technically suitable option for foundations placed in electromagnetically constrained environments, provided that the conclusions are interpreted within the limits of a project-specific design case study and reinforcement-level environmental and economic assessment.
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