STAIRS in BUILDINGS

Post 545  by Gautam Shah

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Stairs and escalators are stepped and inclined-vertical transfer systems. Both provide uninterrupted transfer, unlike the modulated transfer by elevators. Traffic on stairs and escalators is restricted by the width of passage whereas the same on elevators is limited by the module size and its speed. Use of stairs requires some orthopaedic proficiency and cautious posturing, but automated escalators allow freedom to see around during the passage. Some flight of stairs can be used for accent and descent, but escalators require different sets. Though reverse escalator for descent may not be provided, as physically it is not very strenuous to climb down.

Streets of Cusco, Peru Wikipedia image by Author Rod Waddington from Kergunyah, Australia

All movements are essentially directional. A designated unidirectional system like an escalator is more efficient than a mixed movement system like a stair. This factor, however, is relevant for stairs with low to moderate traffic. There are several other transfer systems, such garbage chutes, emergency evacuation tubes, trunks or ramps, and fire-mans’ poles, where movement is unidirectional and generally downwards. The gravity accelerates the down-movement, and inclination retards the rate of passage.

Staircase and escalators at Cabot Circus shopping centre, Bristol, England Wikipedia image by Author Arpingstone

Stairs and escalators are point to point passageways, as there is no mid-way interference, except at landings. Mid-way disturbance occurs in comparatively flatter and very wide stairs over the mountain sides. Here, for ascent or descent, people cross the steps diagonally to increase the ‘tread-depth’ of the steps. Stairs generally have a pitch higher than ramps. Stairs are safer than ramps provided the person is fully mobile and orthopaedically fit, but to ascend or descend stairs are not as easy as the ramps. A ramp can have gradually variable pitch, but a stair has to have a one continuous grade of pitch.

The Grand Staircase of the RMS Olympic Wikipedia image

The inclination of steps is defined by the proportion tread versus riser of the steps. This could vary for stairs used for different purposes, ranging from steep ladders to flatter ramps like foot-ways. The dimensions of tread and riser are proportional and can be plotted on a hyperbola. Certain formulas also provide such proportions: 2T + R = 650 to 680 mm or R x T = 43000 to 45000. For steeper pitch the additional effort required to work against the gravity reduces the efficiency.

High pitch steps of ChetSingh Ghat Benaras India Wikipedia image by Author Patrick Barry from san francisco, ca, USA

Stairs have a pitch of not less than 17.30° (5:16), and of not more than of 48.30° (9:8). Below these limits it becomes a ramp or foot-way, and above it a ladder. A ladder is not a comfortable utility. Step-ladders are lower in pitch, less than 75° and require flat treads. Risers may be open or closed, for toe accommodation and handrails may or may not be provided. In the ladders’ class of stairs, some are easier to climb than others. Ladders are used for fire escapes, boiler rooms, fly galleries, attics, decks, etc. Rung ladders are pitched more steeply, above 75°, and have extremely narrow treads or round rungs to accommodate the foot. In certain cases, the space to accommodate the knee between steps may be necessary. Rung ladders usually do not require additional handrails as the side members of the ladder can be used for holding grips. Rung ladders are often caged for safety, though such cages are more useful for ascent then for descent. It is safer to climb down facing the ladder. Swimming pools, water tanks, and sewers have rung ladders. Manhole steps are very narrow in widths, but the width is otherwise compensated by its staggered placement. The same holds true, for climbers for bunk beds, whether in railways, buses, barracks or homes.

Alternating tread stairs Pinnacles National Park, California, USA Wikipedia image by Author Wing-Chi Poon

Minimum width required for low intensity unidirectional traffic is 600 mm, however most standards specify 900 as minimum width for escape in a hazardous situation. A two-way lane stair should be at least 11200 mm. Sufficient width space for movement is required at torso level, otherwise at feet level a minimum width of 250 mm is required. Where same step is to be used for placing either one of the feet, both, the step and passage widths of minimum width of 500 mm are necessary. Stairs less than 500 mm width are generally emergency stairs rarely to be used, or service stairs to be used by experienced persons. For single lane traffic 750 mm width is an accepted standard. Most of the building bylaws allow minimum 900 mm widths for private buildings. For public buildings a stair width of 1200 mm to 1500 mm is recommended. For pedestrian over bridges and other public thoroughfares, a stair width of 2400 is recommended. On public thoroughfares where traffic is totally segregated or is only one directional, the minimum stair width could be 1800 mm.

Tsarist soldiers march down the “Odessa Steps” from the Goskino film Battleship Potemkin (1925)

Same (filmed as above) Potemkin Stairs giant stairway in Odessa, Ukraine in 1990 Wikipedia image by Author Dezidor

Many stepping arrangements are used for emergency and special purposes. Simplest is a knotted rope or a rope ladder secured to a wall or column. In many countries older buildings were required to confirm to new bylaws, open iron stairways on the building’s exterior were placed. Open iron stairs, though are rendered useless by smoke from windows, so must be placed against a blank wall. One of the best fire escape stairs is a fully enclosed stairway in the building itself or in an adjoining tower. Uncoated or unprotected steel is highly hazardous during a fire as it expands and deforms the stairway. Wood though combustible catches fire slowly, and allows more escape time compared to an unprotected steel stair.

fire exit ladders in Soho. New York City 2005 Wikipedia image by Author Jorge Royan

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COMPONENTS of RAILINGS

Post 412 –by Gautam Shah 

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Railings are barricades against height related hazards, guides for pathways and grabbing elements for support while ascending, descending or any other physically difficult passage (such as slippery floors). Railings have a main holding or grabbing elements in the form of a continuous bar or rail, other in-fill components and support structures. The support structure is often designed as a spanning structural beam to reinforce the bridge, a waist of the stair or escalator. In very steep stairs such as ladders the sides of the stairs allow grabbing, and so are railing by themselves.

Mats Rope Ladders Sailboat

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A railing is nominally a safety barricade used in a standing posture and so needs an optimum height provision. As a result the space between the passage and the railing requires some fill-up panel. This fill-up or in-fill could be of opaque, translucent to transparent material or a lattice. In stiff structures the in-fill could be of stiff construction, but rope bridges (catenary spans) need a flexible in-fill. Railings on roads are designed to take the impact of moving vehicles, and allow it to skid along it, but without an overturning. Railings in public places are designed to resist side thrust in case of pandemonium. Railings are designed with anti-ligature features to prevent suicides or unintentional injuries.

Railings are made of timbers, wood-composites, wrought iron, cast-iron, mild steel structurals or sections, stainless steels, glass, plastics, composites and masonry.

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Pontedellacostituzione

The components of the railing are identifiable in terms of their distinctive form, position and function. In some instances each of these has a perceptible presence, but it may not be a requirement of design. A proximate building element or an architectonic element may serve the functions of a railing. Railings, are bottom supported panel structures, wall supported linear elements, or suspended space entities.

Rope bridge flexible Hand rail

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Rail is the main grabbing and body support element of the railing system. This is a functional element which may not be the top member, but always at the optimum (for adults) height of 900 to 1200 mm. The rail may have an accompanying higher or lower barricading element. A rail could be an independent element of the other components of the railing. Rail can be a bar or an ergonomically conceived section or profiled top (cap-rail) of the in-fill panel or the barricade system. Rails are used with hand and so-called handrails, but a rail could support other parts or limbs of the body such as the buttock (metro trains and stations) or a foot (drink or snack bars). Informal rails are fabric or synthetic stripes that demarcate specific areas. Grab bars are placed in toilets, slippery or wet areas.

Bradbury Building Stairs ironwork

Support for Handrail: A handrail may be supported at end to end of flight of steps (usually negotiating 2 to 2.5 mts height) or may need intermediate supports called banisters.

Vienna state opera stairs Newels

A newel is a large picket or post that supports the handrail at the start and end or landing level. Newels are anchored to the floors or stair waists. Nominally the newel rests one step measure away from the last step. Newels may project upward then the rail level, and may be capped with an urn or finial. Volute is the end of a handrail, shaped like a spiral in a horizontal plane. A rail may not end as a free corner support of a newel, but may terminate into a wall or column as a rosette. A wall return is a bend that turns around a wall, column or a tall newel. Easement is the curved piece in the same plane or rising to form a turning transition of a rail. Similarly a goose-neck is a section between two differently sloped rail systems.

Villa Saint Cyr Staircase Newel Cap

Rail sections carved out of wood are curved against the normal grain of the wood, such as for the volute, rosette, goose-neck or easements. These require additionally under the layer support of wood.

Iron balusters

Baluster is a moulded shaft, square or circular, traditionally in stone, wood, metal, and now in plastics, supporting the coping of a parapet or the handrail of a staircase. The assembly is called the balustrade. Balusters are vertical mid pickets or members that hold the handrail. Sometimes these are simply called guards or spindles. Treads often require two balusters. The second baluster in such cases is closer to the riser and is taller than the first. A fillet is a decorative filler piece on the floor between balusters.

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ARCHITECTURE of STEPS

Post 204 –by Gautam Shah

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Houses Streets Spain Facade Stairs City Altea

Stairs are stepped and inclined foot-ways. Stairs’ ‘flights’ are point to point passageways, without any side connections (except at landings), so are very efficient transfer systems. Stairs, unlike corridors have no interfering mid-way entrants except at landings. The mid-way disturbance occurs in mountain side and very wide stairs where ‘cross (diagonal) ascent or descent’ occurs to increase the ‘tread depth’ of the steps. Stairs are shortest inclined passages but require some orthopaedic proficiency (capacity of the user to manipulate the legs and bend the body).

rome-601328_640Stairs as stepped ways have a pitch not less than 17.30°(5:16), and not more than of 48.30 °(9:8). Below these limits it becomes a ramp or foot-way, and above it a ladder.

geograph-1483118-by-Evelyn-Simak

  • A ladder is not a comfortable tool though some are easier to climb than others. Step-ladders are lower in pitch, less than 75° and require flat treads. Risers may be either ‘open’ or ‘closed’ for toe accommodation. Handrails may or may not be provided. In this classification are ladders, used for fire escapes, boiler rooms, fly galleries, attics, decks, etc. Rung ladders are pitched more steeply, above 75°, and have extremely narrow treads or round rungs to accommodate the foot. In certain cases, the space to accommodate the knee between steps may be necessary.

gamsangersteig-60051_640Rung ladders usually do not require additional handrails as the side members of the ladder can be used for holding grips. Rung ladders are often caged for safety, though such cages are more useful for ascent then for descent. It is safer to climb down facing the ladder. Swimming pools, water tanks, sewers have rung ladders. Manhole steps are very narrow in widths, but the width is otherwise compensated by its staggered placement. The same holds true, for climbers for bunk beds, whether in railways, buses, barracks or homes.

Maheshwar_Fort_-_Exterior_02

Ziggurats of Urnammu (2125 BC) are one of the oldest examples of ceremonial step ways. Egyptians built ceremonial stairs for a rock-cut temple at Del-el-Bahari (1520 BC). The Cretan palaces (1500 BC) had stairs that moulded the architecture. Greeks and Romans have exploited stepped-architecture for amphi theatres, stadia, thermae (bath houses) where the visual angle, support structure and curvatures in the plan were tackled.

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Italian Steps

In medieval Indian architecture bathing Ghats, Kunds and step wells had a distinctive element of planning. Kutub minar, Azan Minarets of Mosques, entrance steps for Fatehpur Sikri and Jama Mosque Delhi, show functional use of steps. Observatories, Jantar-Mantar, at Jaipur and Delhi have been articulated with steps.

metropolis-498406_1280Romanesque period saw interior stairs and outdoor steps for entrances with converging and diverging flights on a common landing or a foyer. Spiral stair with a column or pier as the central element, often called Newel, were used in Gothic buildings. Later Gothic buildings had large diameter spiral stairs with an open central core. Post Gothic period stairs began to wind in many directions, had variable widths and curved steps. Renaissance stairs were extensively decorative, with balustrades, broad moulded handrails and statuette like newel supports at every start, turn and end. The stairs were not enclosed structures or staircases, but stairways as open structures. Stairs began to visually connect all the floors interim spaces. Stairwells or gaps, created spaces which were multi-layered and yet interconnected. Open or exterior steps became features of landscape design in plazas and gardens, such as in Villa de este at Trivoli, Scala di Spagna at Rome, Capitol at Rome, Kashmir Mughal gardens.

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295px-museum_of_liverpool_spiral_staircase

During 19th C new transportation system required for Ports and stations, and stairways became true transfer system for masses. Like stations, the stairways of large stores, auditoriums, assembly halls, served an identical function, of being visible. Stairs have a problem that one has to be conscious of climbing then enjoy the open space around. This was corrected in automated stairways as escalators, and later in open cage or bubble elevators.

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TRANSFER SYSTEMS

Post 153by Gautam Shah

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A building has many types of systems such as openings systems, services systems, structural and non-structural systems, etc. Transfer Systems denote a very large group of subsystems used for transferring goods and people in various directions, levels and in different modes. These are intentionally facilitated by architectural design or naturally occur irrespective of the adequate provisions in the building fabric.

Crowded_Durga_Puja_Pandal_-_Falguni_Sangha_-_Suren_Tagore_Road_-_Kolkata_2013-10-11_3351

Two way system defined by L-R preference for passage But this could be culture and country specific behaviour > Durga Puja festival in Kolkata Wikipedia Image by Biswarup Ganguly

Transfer Systems mark the routes or spaces where concentrated or repeated movement of people and goods occur. Stairs, ramps, elevators, escalators, corridors, passages, bridges, etc. are elements or systems that can be identified as transfer systems. The transfer system denotes an exclusive one or the most efficient node available, leading to concentration of traffic.

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Mixed traffic crates chaos

The efficiency of a transfer system is determined by the fact whether the system is parallel, inclined or perpendicular to the gravity. The additional effort required to work against or towards the gravity, respectively retard or add to the efficiency.

Le Corbusier Ramps -inclined transfer systems

Transfer system denotes movements which start and terminate somewhere. Simple transfer systems have one to one point articulation. Branched transfer systems have one to many points configuration. It may start or end at multiple points. The third option where many to many points transfer start or end, it results in chaos, and there is no system identity.

Transfer systems are parallel -horizontal to the earth, perpendicular -vertical or inclined towards -downwards or against -upwards the gravity. Passages, Roads, Corridors, Automated walkways, are almost parallel to the gravity. Stairs and Escalators are inclined towards or against to the gravity. Elevators are perpendicular to the gravity. All these are designed to allow greater concentration of traffic, compared to many other parallel to gravity areas like Chowks, compounds, plazas, etc.

Walkway or Travelators at Indira Gandhi International Airport, Delhi Wikipedia Image by Vineetmbbsat

All movements are essentially bidirectional, though through design the movements may be bifurcated in time and space. An unidirectional or segregated system is more efficient than any bidirectional or multi-directional (mixed) movement systems. In a built environment too many multi-directional movements confuse clear identity of a transfer system. Within such chaos ultimately all movements cease.

Transfer systems are open-ended or looped. Open-ended systems have finite start and termination points. Start-point is one where the first transferee element gets on the transfer system. The end point is one where the last of the transferee element gets off. It is also a point where another system such as the reverse, or parallel movement system begins. Looped systems are continuous systems and have no start-points or terminal points. Looped systems have a circular formation, or part of the segment is connected by straight (point to point) transfer system.

Circular spiral -but nor a looped transfer system

The intensity of transfer depends on whether the system operates continuously or intermittently. Continuous systems such as the escalators, automated walkways, are governed by the speed of movement, while the intermittent systems such as the elevators, buses, railways are affected by the frequency of movement’s module. Both systems however have a traffic capacity limitation.

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In a transfer system, people move depending on two counts, anthropometric design of the system, and orthopaedic functionality. On other hand vehicles or goods modules are carried by use of external energy through mechanical devices. Variable capacities of the transferee also affect the speed of transfer, and as a result the intensity of traffic.

Escalator as continuous inclined transfer system

Transfer systems are disturbed when elements moving at different pace cause an unwanted change in the speed or direction of the general moving mass. Transfer systems become invalid when all goods and people reach their destinations, or when there is nothing left to transfer.

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Transfer systems necessarily have start-end nodes, but most transfer systems have multiple intermediate exit and entry nodes or points of transfer on the route. Some points of transfer are very clearly defined, like a door in a corridor, railway station, but many others nodes are not clearly delineated such as path or footpath without a barricade.

Multiple transfer systems -too close

Transfer systems that are exclusively directional, with high speed or of mixed traffic, require highly defined points of transfer. At every point of transfer goods and people have to alter the direction and change the speed of movement to embark or disembark the transfer system. Such variations in movements at every entry or exit node reduce the overall efficiency of a transfer system, unless points of transfer provide necessary definitions. Points of transfer provide visual and other information about the available options. A subsidiary system often allows a slow-moving transferee to adjust the speed and direction before moving over to the fast-slow moving system.

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Straight transfer systems have greater efficiency, than any sharp twisting turning system. Transfer systems directed towards gravity or any superior environment such as towards promising – enticing situations tend to have greater efficiency. Point to point systems are superior to continuous systems with many points of transfer on the route. Transfer system with designed points of transfer operate better.

Railway -well defined transfer system

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