Post 176 ⇒ by Gautam Shah →
Very wide doors are required for functional reasons and for splendour. Very wide openings are provided for ceremonies, processions, etc. and in modern times for carriage of wide vehicles like aeroplanes (hangers) and ships (canal gates). Very wide openings are incapable of regulating the multi-element mixed traffic, so need either barricades to channelize the traffic, or use multiple door systems.
Gates have large scale doors for functional reasons and splendour. External gates of forts and estates have been described to have single shutters that dropped down to form a bridge over a moat (fancy, -no real example found), or a shutter that can move up. Wide openings, nominally have double shuttered doors, as they seem symmetrical, and are considered a classic entity.
Size of a shutter, chiefly its width aspect, is very critical. A shutter is ‘hung‘ with hinges from side jambs or over a set of pivots from floor and lintel or door-head. In both the cases, in spite a stiff structure the free end of the shutter settles down, making its opening-closing very difficult. This is the reason very wide gaps have sliding-folding shutters. Hanger doors are designed to be sliding from top, bottom or both. Canal gates (such as on sea routes) and wide estate gates have their width aspect corrected, i.e. ‘reduced’, by a side mast (taller then the shutter) that ‘hangs’ the free end of the shutter.
The shape of the door openings has very strongly affected the view through it. A rectangular door, H:W = 1:2, has been the most common and proportionate shape for a door.
Internal or mid town gates, however, have multiple opening systems to serve traffic of different speed, accessibility, user types (height and physical capacity).
Gothic cathedrals have twin doors with a mid-column support, but where multiple doors are required, the doors’ openings are in odd numbers such as 3 or 5.
Adequate passage width for transit is very important. An insufficient width retards the speed, or even makes it difficult or impossible to transit through. A very generous width fails to enforce the discipline in transit. Doors to safety areas like bombing shelters must be carefully small sized for increasing resistance to blast pressures.
Instead of a wide door, multiple (ganged) doors are used for entry and for an emergency exit in public buildings like railway stations and airports. In verandahs and public places such multiple doors provide the localised choice of controlled opening. Doorways’ gaps are also narrowed by placing side lites or side windows which allow view. Small shutters are inset within large shutters (such as fort doors). A door within a door is also provided for pets, delivery of milk and postal articles.
Stacking of shutters by using multiple channels or guide rails allow larger opening. Where multiple tracks are not, feasible shutters are joined together like the bellows of an accordion to form a sliding and folding stack. Folding or collapsible doors were first used in cabinets and cupboards. For a folding or collapsing shutter stack the first or primary shutter is supported on pivot and other shutters are hinged to them.
Airports and Railway stations, have ganged or multiple doors to serve the demand for a wider but controlled opening. However, air hangers, garages, barns and warehouses require wide doors to meet the functional carriage width, but are inserted with additional small openings for other uses. Openings are spaced out to take advantage of the location and orientation, and diffuse the exchange over a larger zone. Openings are concentrated or grouped together, to few locations to reduce the wastage of distributed operations.
A Small opening makes a barrier system very evident, whereas a large opening or multiple openings make barriers less effective. Significance of a small opening is due to the contrasting scale against the barrier system within which it occurs. The exchange occurring across a small opening is very intense, compared to a large gateway.