GeoTech
Foundations
Area of practice · Donald W. Parnell, PE
Bridge substructures, foundations for heavy substation equipment, transmission and communications tower foundations resisting overturning, and residential and building foundations.
Bridge Substructures
Abutments, bents, and piers
Mr. Parnell was sole designer and design engineer on the bridge projects described under Structural, and that responsibility included the substructures. For the seven-span prestressed concrete ramp over Mallard Creek and the three-span steel overpass in Goldsboro, both at KCI Technologies, he designed the end bents and intermediate bents that carry the superstructure to the ground, sizing footings or pile groups for the girder reactions and carrying scour depths from the hydraulic analysis into the foundation elevations. On the Randleman Lake bridge rebuilds for the Piedmont Triad Regional Water Authority, at Hobbs, Upchurch & Associates, the work included abutment design for the replacement structures, where the abutments retained the approach fill at the new, higher grades and carried the bridge reactions while being placed within or adjacent to the future reservoir pool.
Substation Equipment
Foundations for heavy electrical equipment
Across the substation site-development projects at the City of Austin Electric Utility Department, later Austin Energy, Mr. Parnell designed foundations for the heaviest equipment in the yard: autotransformers, oil circuit breakers, air-break switches, and their supporting structures. The design problems fall into two groups. Autotransformers and large breakers impose extreme gravity loads concentrated on a small footprint, so their pads and mats are governed by bearing pressure, settlement, and the oil-containment detailing that surrounds them. Air switches, bus supports, and dead-end structures weigh comparatively little but stand tall and carry conductor tension and wind at height, so their foundations are governed by overturning moment rather than weight, and are proportioned as drilled piers or spread footings with enough embedment and mass to keep the resultant within the base under the worst load combination.
Transmission Structures
Tower foundations on high-voltage corridors
At Booth & Associates in Raleigh, working in transmission and distribution, Mr. Parnell designed foundations for the tall structures on high-voltage transmission corridors. Transmission towers are dominated by overturning: wind on the structure and conductors, unbalanced conductor tension at angle and dead-end structures, and the vertical and longitudinal components of the catenary under ice and broken-wire cases all act at the top of a tall lever arm. Lattice towers resolve these loads into uplift and compression at each leg, which are carried on individual footings or drilled piers designed for pullout as well as bearing; single-shaft poles carry the full moment into one drilled pier, whose depth and diameter are set by the lateral soil resistance available along the shaft.
Communications Towers
Monopole and self-supporting tower foundations
At KCI Technologies, Mr. Parnell worked on microwave tower design projects whose foundations followed the same overturning-controlled approach. Most were monopoles on a single drilled pier or a large spread footing, with the antenna and dish loads adding wind area near the top of the structure; some were self-supporting steel-framed towers, with a footing or pier under each leg designed for the uplift and compression that the tower’s base reactions produce as the moment reverses with wind direction. Anchor-bolt layouts, pier reinforcement, and the depth needed for lateral capacity in the site soils were carried through the foundation details.
Residential
Single-family home foundations
Mr. Parnell designed foundations for a number of single-family residences for Pulte Homes, mostly crawlspace and slab-on-grade construction. Crawlspace foundations used continuous strip footings under masonry stem walls with interior piers under girders; slab foundations used thickened-edge or turned-down slabs with interior bearing footings where required, with both types sized to the allowable bearing of the site soils and detailed for drainage and moisture control.
Buildings
Medium-rise building foundations
Through the commercial building work at HagerSmith Design in Raleigh, Mr. Parnell had limited exposure to foundations for medium-rise structures, where column loads are carried on spread footings, combined footings, or mat foundations depending on load and soil conditions. This exposure was minor relative to the bridge, substation, and tower work above and is recorded here for completeness.
About this record. This site is a working record of professional experience, maintained to verify subject-matter background. Areas of practice are reached from the menu above. The record is expanded as additional work history is documented.
Donald W. Parnell, PE | North Carolina PE No. 33878