| Helical screw anchors have been utilized in uplift forces applications for many years. More recently, they have gained popularity for bearing load applications and evolved into Helical Screw Piles (HSPs). The speed and ease of installation, as well as low cost for new construction and repair, make them versatile for many applications. However, their seismic performance has not been investigated.;The research methodology involved conducting more than one hundred full scale field load tests on twenty three helical piles with different configurations installed in cohesive soil. The piles were subjected to axial and lateral monotonic and cyclic loading. The test piles included: seven plain helical screw piles (P-HSP); four grouted helical screw piles (G-HSPs); eight FRP-G-HSPs; and four RG-HSPs. The FRP-G-HSPs were installed two different ways: four piles were grouted inside the tube only and four were grouted both inside and outside the tube.;The cyclic performance of HSPs and G-HSPs was satisfactory and warranted a consideration for seismic applications. They experienced only 5-10% reduction in their capacity after 15 load cycles. However, their lateral capacity was low due to their slender shaft. The lateral capacity and stiffness of internally and externally grouted FRP-G-HSPs were twice the values for FRP-HSP with internal grout only. The RG-HSP piles performed well under axial and lateral. Their axial capacity was more than twice that for P-HSP, with minimal or no reduction due to the cyclic loading, and their lateral capacity was more than 3 times the capacity of P-HSPs. The results of 3-D finite element modeling were used to establish the load transfer mechanism and a design methodology for the considered piles.;Key words. Innovative Instrumented Helical Screw Piles (HSPs), Monotonic and Innovative Cyclic Testing setup, Full Scale Field Testing, Axial and Lateral Loadings, HSPs Stiffness, Load Transfer Mechanisms, Finite element Model (PLAXIS - 3D).;The main objectives of this thesis are to: investigate the monotonic and cyclic axial and lateral behavior of helical pile foundation systems, develop new helical screw pile systems suitable for seismic retrofitting of existing foundations and for implementation in new buildings; and develop a methodology for their design. The new pile configurations proposed in this study include: fiber reinforced polymer grouted helical screw piles (FRP-G-HSP); and reinforced grouted helical screw piles (RG-HSP) in which steel fibers were added to the grout. |
