ANALYSE BY FEA OF HELICAL PILES AND GRILLAGES - CASE STUDY FROM BRAZILIAN TRANSMISSION LINES-PPT Presentation

PPT Presentation

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The presentation evaluates finite element analysis (FEA) of helical-pile groups connected by steel grillages for a 394 km Brazilian transmission line comprising 788 towers. The project faced remote and difficult-to-access sites, environmental constraints, costly equipment logistics, seasonal rainfall, varied soils, and flooded areas.<br /><br />The proposed system combines helical piles with a fabricated steel cap or grillage to transfer tower loads to the pile group. FEA was used to assess structural behavior, including combined vertical and horizontal loads, load concentration at individual piles, and load distribution from tower legs. The analysis also considered different pile-group arrangements and emphasized refining the mesh to better represent real behavior. Angled pile installation can help accommodate structural loads and challenging site conditions.<br /><br />Compared with conventional concrete-block foundations—which involve excavation, reinforcement, formwork, concrete placement, and curing—the steel grillage and helical-pile approach can reduce construction steps, labor, equipment needs, field documentation, and installation time. The system can also suit sloping ground and help limit environmental disturbance.<br /><br />A cost comparison found steel grillages to be 23% less expensive than concrete blocks. The authors conclude that grillages with helical piles are technically and economically viable alternatives, with potential benefits including lower direct and indirect costs, shorter construction schedules, and improved assessment of foundation safety factors.<br /><br />The presentation recommends using technically qualified companies and maintaining strict quality control for materials and welding. Where piles project above ground at differing elevations, project-specific structural and geotechnical studies are advised. Field welding should follow AWS D1.1 procedures, and welders should be qualified before work begins.

Keywords

finite element analysis

helical piles

steel grillage

transmission line foundations

Brazilian transmission line

pile group

structural behavior

cost comparison

foundation design

environmental constraints