Numerical Analysis in Assisting Crane Pad Design and Underground Utilities Evaluation-Paper

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The paper presents a three-dimensional finite element analysis used to design a foundation pad for a 1,500-ton LR11350 crawler crane at an Indiana power plant. The crane’s worst-case track pressure was estimated at 84 psi, and its proposed location overlapped a network of 13 buried utilities, including steel and ductile-iron pipes, corrugated metal drains, and electrical conduits.<br /><br />Geotechnical investigations identified approximately 10 feet of fill over native granular soils, with groundwater about 33.5 feet below grade. The model represented soils using a nonlinear hardening-soil model, the crushed-stone pad with an elastic-plastic model, and crane mats and utilities as elastic elements. Utilities were modeled as embedded beams. The analysis examined three crane positions and assessed soil settlement, utility forces and stresses, pipe ovality, and buckling under the worst loading condition.<br /><br />A one-foot-thick timber mat did not adequately limit ground pressure or settlement. The recommended system—one-foot-thick engineered steel mats over a 1.5-foot-thick crushed-stone pad—reduced maximum ground pressure to approximately 3,500 psf and kept total settlement below two inches, meeting the stated design requirements. Calculated utility stresses and deformations were considered tolerable, and the evaluations indicated that local buckling was unlikely.<br /><br />The case study demonstrates how finite element analysis can support crane-pad design while evaluating both global and local effects on existing buried utilities. The authors note that beam elements can generally represent smaller utilities for calculating internal forces, while local buckling and ovality can be assessed using AASHTO criteria. These conclusions assume the existing utilities are in good condition.

Keywords

finite element analysis

crane pad design

crawler crane

buried utilities

soil settlement

geotechnical investigation

steel mats

crushed-stone pad

pipe buckling

AASHTO criteria