{{Short description|Structural steel column filled with concrete}} {{more citations needed|date=July 2010}}
A '''Lally column''' is a round or square thin-walled [[structural steel]] [[column]] filled with concrete,<ref>{{cite web |title=Definition of LALLY COLUMN |url=https://www.merriam-webster.com/dictionary/lally%20column |website=www.merriam-webster.com |access-date=17 September 2024 |language=en}}</ref> and oriented vertically to provide support to [[Beam (structure)|beams]] or timbers stretching over long [[Span (architecture)|spans]]. Historically, Lally columns were made of steel up to {{convert|1/4|in|order=flip|sp=us}} in thickness; today, that has been reduced in instances to {{convert|0.06|in|order=flip|sp=us}}.<ref name=fh>{{Cite web |last=Butt |first=Aaron |date=1992-03-01 |title=Boxed Lally |url=https://www.finehomebuilding.com/1992/03/01/boxed-lally |access-date=2025-02-16 |website=Fine Homebuilding |language=en-US}}</ref> As engineered structural load-bearing components, Lally columns must be installed to their specific design specs.
==Fabrication== [[File:Detail, lally columns at northwest end of truss. View to southwest from downstream side. - Red Bank Creek Bridge, Spanning Red Bank Creek at Rawson Road, Red Bluff, Tehama HAER CAL,52-REBLU.V,2-19.tif|thumb|A Lally column at the northwest end of truss of the Red Bank Creek Bridge at Rawson Road, Red Bluff, [[Tehama, California]], United States]]
A Lally column is formed of tubular steel. It is then filled with [[concrete]], which carries a share of the compression load, and helps prevent local buckling of the shell.<ref>{{Cite web |title=Lally handbook of Lally column construction, steel columns concrete filled, 10th ed., Lally Column Companies, Erie and Albany Streets, Cambridge, Mass. |url=https://www.historicnewengland.org/explore/collections-access/gusn/268968 |access-date=2025-02-16 |website=Historic New England |language=en-US}}</ref>
In addition to its low cost, an advantage of a generic Lally column over a custom structural steel column (or conventional [[I-beam]]) is that it may be purchased in its tubular state and cut to length on a construction site with standard jobsite power tools such as an [[angle grinder]] or [[reciprocating saw]] fitted with appropriate metal cutting blades. {{clarification needed span|text=Lally columns are generally not as strong or durable as conventional structural steel columns.|reason=Even when filled with concrete of appropriate compressive strength? These serial claims need to be supported by reliable citations.|date=April 2025}}
The term "Lally column" is sometimes confused with a [[jack post|screw jack]], a temporary rather than permanent steel support.
==Invention== The Lally column is named after a U.S. inventor, John Lally, who owned a construction company that started production of these columns in the late 19th century. He resided in [[Waltham, Massachusetts]], United States, and [[Boston]] during the period 1898–1907. He was issued four U.S. [[patent]]s on composite columns: Nos. 614729, 869869, 901453, and 905888. Patent No. 869869 was assigned to the U.S. Column Company of [[Cambridge, Massachusetts]].
==Design development== Early Lally columns were made with structural steel, "standard" pipes, with wall thicknesses slightly less than {{convert|1/4|in|order=flip|sp=us}}. Modern Lally columns are typically made with 16-[[sheet metal gauge|gauge]] (approximately {{convert|0.06|in|order=flip|sp=us|disp=or}}) shells.<ref name=fh/> Modern Lallies are therefore much lower in strength than the older ones (typically less than half the strength), and are also much more subject to damage by corrosion in moist environments.
Modern Lally columns are primarily intended as somewhat stronger and more durable substitutes for wood posts in light-frame wood construction, although they are sometimes also used with steel beams.
==References== {{Reflist|colwidth=30em}}
== External links == * [http://allthumbsdiy.com/reviews/reviews-lolly-lally-columns-or-jack-post-or-floor-jacks/ Examples of Uses] * [http://www.lally-column.com/history History of inventor John Lally]
[[Category:Structural engineering]] [[Category:Structural steel]]
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