Sebastian Montoya-Vargas
University of Maine
Degrees:
Bachelor Civil Engineering – Universidad Nacional de Colombia, Facultad de Minas, Medellin Campus (2018)
M.Sc. Hydraulic Resources – Universidad Nacional de Colombia, Facultad de Minas, Medellin Campus (2019)
Master of Engineering, Civil Engineering – University of Maine (2022)
Ph.D. Civil Engineering – University of Maine (2024)
Preferred Career after Graduation:
Research or Industry
Broad research Area:
Civil Engineering
Specific Research Area:
Solid and fluid mechanics
Other Interests & Activities:
Skateboarding, music, literature, and arts
Top Accomplishment in 2023:
Finished testing program.
Presentation
Poster
Files
Thesis
Title: Flexural Strength of Micropile Threaded Connections
Abstract: Permanent steel casing micropiles are an advantageous foundation system that can provide high geotechnical capacities in tension and compression. However, when lateral and flexural loads are imposed, these micropiles display a limited capacity due to early bending failure of the steel casing threaded connection that couple the casing segments. The proposed research project aims to develop an analytical model capable of predicting the joint bending strength and failure mode of these connections while considering the presence of center reinforcement and combined axial and bending loads. The model will combine displacement fields characteristic of the flexural failure with principles of compatibility and equilibrium to determine the cross-sectional stress distribution at the threaded joint, and thus, allowing to calculate the bending moment corresponding to failure. The project includes four-point bending tests on micropile specimens with different geometric details to characterize the longitudinal (axial) and radial displacements at the box-end of the connection. The specimens were loaded in pure bending or bending combined with axial compression until failure of the threaded joint occurred while the displacements produced by the flexural load were monitored using digital image correlation (DIC). The collected data will be extended using finite element analysis (FEA) to characterize the features that are not observable through DIC, and later used to improve the physical consistency of the analytical model. The outcomes of this project will allow practitioners to reliably determine the flexural strength of the connection and aid decisions regarding the details and milling of threaded connections and selection of appropriate center-bar reinforcement. Also, by providing the industry with a predictive model, financial, physical, and logistical efforts related to structural testing will be saved.
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