Strongback (girder)

A strongback is a beam or girder which acts as a secondary support member to an existing structure. A strongback in a staircase is usually ordinary two-by dimensional lumber attached to the staircase stringers to stiffen the assembly. In shipbuilding, a strongback, known as a waler is oriented lengthwise along a ship to brace across several frames to keep the frames square and plumb.{{Cite book |last1=Webster |first1=Fred Bibber |url=https://books.google.com/books?id=fK8fAAAAMAAJ&q=Shipbuilding+Cyclopedia:+A+Reference+Book+Covering+Definitions+of+Shipbuilding+Terms,+Basic+Design,+Hull+Specifications,+Planning+and+Estimating,+Ship's+Rigging+and+Cargo+Handling+Gear,+Tables+of+Displacement+of+Commodities,+Arrangement+and+Working+Drawings+of+Modern+Vessels,+and+a+Composite+Catalog+of+Marine+Equipment |title=Shipbuilding Cyclopedia: A Reference Book Covering Definitions of Shipbuilding Terms, Basic Design, Hull Specifications, Planning and Estimating, Ship's Rigging and Cargo Handling Gear, Tables of Displacement of Commodities, Arrangement and Working Drawings of Modern Vessels, and a Composite Catalog of Marine Equipment |last2=Bates |first2=J. L. |last3=Phillips |first3=Stephen McKay |last4=Haag |first4=Alfred Henry |date=1920 |publisher=Simmons-Boardman Publishing Company |language=en}} In formwork strongbacks (typically vertical) reinforce typically horizontal walers to provide additional support against hydrostatic pressure during concrete pours.{{Cite book |last=Hurd |first=Mary Krumboltz |url=https://books.google.com/books?id=0G9n7dfIvNEC&dq=%22formwork%22+%22strongbacks%22&pg=SA9-PA15 |title=Formwork for Concrete |date=2005 |publisher=American Concrete Institute |isbn=978-0-87031-177-2 |language=en}}

Some rockets like the Antares, the Falcon 9 and the Falcon Heavy use a strongback to restrain the rocket prior to launch.{{Cite web |title=A strongback provides connections to the SpaceX Falcon 9 rocket as final preparations for launch are completed in Florida. |url=https://artsandculture.google.com/asset/a-strongback-provides-connections-to-the-spacex-falcon-9-rocket-as-final-preparations-for-launch-are-completed-in-florida/JwGAf9IAmQVSpA |access-date=2023-09-04 |website=Google Arts & Culture |language=en}} This structure tilts several degrees away from the rocket to clear the launch, either at the moment of launch or a few minutes before.