outer "rings" of arches overlaying the one forming the intrados, used in old English bridges since medieval times, are called "counter-arches"[4] following the works of John Smeaton;
an arch that is built adjacent to another arch to oppose its forces or help stabilize it.[5] The counter-arch can be used, for example, when constructing the flying buttress,[6]
buttressing arches built between the opposing building facades over narrow streets of old cities;[7][8]
in fortification, an arch built on the tops of counterforts behind the bastion walls intended to limit the scope of the potential wall breaching;[9]
when a pier of the Old Westminster Bridge started sinking during the construction, Charles Labelye was forced to retrofit the bridge with open spandrels using the counter-arches springing off haunches of the two adjacent arches of the bridge thus relieving the pier.[10]
An old Ouse Bridge, York with middle arch using three rings (two "counter-arches")[11]
The Enneüs Heerma Bridge showing the inverted counter arch in the middle[12]
Murray, J.A.H. (1893). "Counter-arch". A New English Dictionary on Historical Principles: part 1. C-Comm (1893). Clarendon Press. Retrieved 2024-07-05.
Trautwine, J.C. (1874). "The Moseley Bridge". The Civil Engineer's Pocket-book: Of Mensuration, Trigonometry, Surveying, Hydraulics ... Etc. ... Claxton, Remsen & Haffelfinger. Retrieved 2024-07-05.