Construction Technology-1

Construction Technology-1STAIRS & STAIRCASES(SECTION II)

11Text & Ref BookBuilding Construction by A.S. KotadiaBuilding Construction by B.C. Punmia

21. DefinitionA stair is a set (series) of steps, leading from one floor to the other, provided to afford the various floors of a building.

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2. Technical terms1. Tread- Upper horizontal portion of a step upon which the foot is placed, while ascending or descending.

2. Riser- Vertical portion of a step providing a support to the tread.

3. Landing- Level platform at the top or bottom of a flight between the floors.

4. Flight- An unbroken series of steps b/w landings.555. Rise- Vertical distance b/w two successive tread faces.

6. Going- Horizontal distance b/w two successive riser faces.

7. Nosing- Outer projecting part of a tread beyond the face of the riser

8. Scotia- Moulding provided under the nosing to improve the elevation of the step & strength to nosing.6Technical terms (cont.,)9. Pitch/Slope- the angle made by the line of nosing of the stair with the horizontal.

10. Strings/Stringers- Sloping members of wood/metal which support the steps in a stair. They run along the slope of the stair.

11. Newel post- Vertical member of wood/metal, supporting the hand rail.

12. Baluster- Vertical member of wood/metal supporting the handrail.7Technical terms (cont.,)13. Handrail- Rounded/moulded member of wood/metal, generally parallel to the nosing line and fixed on the top of balusters.

14. Head room- Min clear vertical distance b/w the tread of a step and the soffit of the flight immediately above it.

15. Run- Total length of stairs in a horizontal plane.8Technical terms (cont.,)3. Requirements of a GOOD Stair1. Location- Provide easy access to the users of the building.- Well lighted & ventilated.- Approaches convenient & spacious2. Width of Stair- Domestic/ residential building = 900 mm.- Public building = 1500-1800 mm3. Length of flight- No. of steps should not more than 12 nos. should not less than 3 nos. 9

9Requirements of a GOOD Stair (cont.,)4. Pitch/ Slope of Stair - should not more than 40- should not less than 205. Headroom- vertical distance b/w the tread and soffit of the flight immediately above it, should not less than 2100-2300mm6. Balustrade- Open well stair should always provided with this for safety- A wide stair should have a handrail on both the sides10

107. Step Dimensions - Width of landing should not less than width of stairs.8. Materials of Construction- Materials should provide a sufficient strength, fire resistance.

11Requirements of a GOOD Stair (cont.,)1. The design of steps should be carefully worked out, so as not to make either too wide or short.2. Thumb rulesa. (Rise + Going)= 400- 450mmb. (2Rise + Going)= 600mm3. Combinations of Rise x Going140 x 300 mm, 150 x 280mm, 160 x 260mm, 170 x 240mm

4. For Residential building-size of steps= 160 x 260mm

5. For hospital, public buildings- size of steps= 100 x 300mm

124. Fixing of Going and Rise of a Step OrDimensions of a Step1. Flier- ordinary step of uniform width and rectangular shape in plan.

135. Types of STEPSWallUPNewel PostNewel Post2. Bull nose step- Starting step near the newel forms the quadrant of a circle.

14WallUPNewel PostNewel PostQuadrant of a circle3. Round ended step- similar to bull nose except that it has a semi-circular end which projects out from the stringer.

15WallUPNewel PostNewel PostSemi-circle4. Splayed step- beginning of the flight, with its end, near the newel post, splayed like in fig below

16WallUPNewel PostNewel PostSplayed edge5. Commode step- has curved tread and riser

17WallUPNewel PostNewel PostCurved edge6. Dancing step- which do not radiate from a common centre

18UPDancing StepLanding7. Winder- Winders are tapering steps, such as those radiate from a point usually situated at the centre of a newel.

19UPWinders206. Classification of STAIRSStraight flight stairsTurning stairsQuarter turn stairsHalf turn stairsDog-legged stairsOpen-well stairsThree quarter turn stairsBifurcated stairsGeometrical stairs Circular stairsSpiral stairsHelical stairs1. Straight flight stairs- running continuous throughout their entire length in one direction only.Used for small houses where long but narrow space is available.

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2. Turning stairs- a) Quarter turn stairs

The direction of flight changes at right anglesto the left/right.

There are two types1. With quarter spacelanding 2. With winders

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2. Turning stairs- b) Half turn stairs- turned by 180

i. Dog-legged stairs

Used when the length of the staircase is restricted and widthis such that only two flights canbe accommodated.

There is no space b/w the twoflights.

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2. Turning stairs- b) Half turn stairs

ii. Open-well stairs

Open space b/w the outer string of the flights

Needs additional space b/w The flights

Space= 150-1000 mm

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2. Turning stairs- c) Three quarter turn stairs

The direction of the flight is changed 3 times.

Used when the length and breadth of the stair room is limited

Also the vertical distance b/w two floors quite large.

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2. Turning stairs- d) Bifurcated stairs

Used in public buildings at their entrance hall & in palaces.

The stair has a wider flight at the bottom, which bifurcates into two narrow flights, one turning to the left and the other to the right

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3. Geometrical stairs- a) Circular stairsIn this type, stringers as well as handrails are both continuous w/o any newel post and landing.

Commonly provided at the inner & backside of the building for providing entry to its various floors for service purposes.

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3. Geometrical stairs- b) Spiral stairs

Used, where space available is too small and the traffic is less.Used, as a emergency stairs and are provided at the backside of the building.Usually made either of RCC or metal.All the steps are winders, joined centrally with the vertical newel post/ column.

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3. Geometrical stairs- c) Helical stairsThe stair looks fine but its structural design and construction is very complicated.

It is made of RCC/metal in which large quantities of steel is required to resist bending, shear and torsion.

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307. Vertical Transportation SystemsPeoples and various objects must be moved vertically in multi-level buildings, often required the use of special equipments such as

1. Elevators (lifts),

2. Escalators. 317.1. Elevators (Lifts)Used for moving both people and materials in buildings having more than 4 storey's. People movers are described as Passenger lifts. The lifts used for moving materials are called Freight lifts.For powering of the vertical movements-two basic systemsOverhead counter weighted suspension system using steel cables and electrically powered motors and wheels.Large hydraulic piston provided in a chamber beneath the elevator cab.

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347. The elevator shaft must be vertically aligned and the elevator cabs move along vertical guide rails.8. The mechanical operation of the moving cabs, the entry doors and the operating equipment for moving the cab must be properly provided.The dimensional requirements for lifts may depends upon the cab size and the total no. of elevators used in the system.For a small two or three storey building with a single lift, the space required be small vice versa for tall buildings.

35Overhead suspended Lift Vs Hydraulic Lift

Relatively rapid travel and 1. Operate slowlyquicker operation.Suitable for tall buildings2. Used for few stories onlyNeed, considerable height3. Space reqd at bottom levelabove the highest point of entry of the cab. Both the systems require considerable excavation and construction below the level of the lowest entry point of the cab.367.2. EscalatorsAn escalator is a power driven, continuous moving stairway designed to transport passengers up and down short vertical distances (inclined).Escalators are used in shopping centres, hotels and public buildings.Escalators move at approx. 0.3 0.6 m/s.Max angle of inclination of an escalator 30

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397.2. Escalators- ComponentsTop & bottom landing platformsCurved sections of the tracks, as well as gears and motors that drive the stairs.The top platform contains the motor assembly and the main drive gear.Whereas, the bottom holds the step return idler.The platforms contain a floor plate and a comb plate.Floor plate- provides a place for the passengers to stand before they step onto the moving stairs.Comb plate- the piece b/w the stationary floor plate and the moving step.39402. The trussIt is a hollow metal structure that bridges the lower and upper landings.It is composed of two side sections joined together with cross braces across the bottom and just below the top.The ends of the truss are attached to the top and bottom landing platforms via steel/ concrete supports.The truss carries all the straight track sections connecting the upper and lower sections.40413. The tracksThe track system is built into the truss to guide the step chain, which continuously pulls the steps from the bottom platform and back to the top in an endless loop.There are two tracks-one for the front wheels of the steps (called the step wheel track)- another for the back wheels of the steps (the trailer-wheel track)The tracks carry the steps down along the underside of the truss until they reach the bottom landing, where they pass through another curved section track before existing the bottom landing.41424. The stepsThe steps are solid, one-piece, aluminum.Rubber mats affixed to their surface to reduce slippage, and yellow lines added to indicate their edges.The steps are linked by a continuous metal chain so they form a closed loop with each step.The position of the track controls the orientation of the steps.42435. The railingIt provides a convenient handhold for passengers.4-distinct sectionsSlider- allow the railing to move smoothly along its track.Tension member- consists of steel cable, which provides the handrail with the necessary tensile strength and flexibility.4344Treated rubber- on top of tension member are the inner construction components, which are made of chemically treated rubber designed to prevent the layers from separating.

The outer layer- only part actually passengers see, is the rubber cover. This cover designed to resist degradation from environmental conditions, mechanical wear and tear, and human vandalism.

4445Stair- Planning- Numerical Problem1. Plan a staircase for a residential building in which the vertical distance b/w each floor is 3.96 m. The size of stair hall is limited to 4.64 x 3.24 m. (Tread, Rise, Width of stair , Width of Landing, width of passage) Solution:-

4.64 m3.24 m300 mm4546Let us take Width of the stair/flight= 1.20 mSpace b/w two flights= 3.24 2(1.2) = 0.84 mthis suggests can provide Open Well Type StairLet the height of Riser= 180 mm = 0.18 mNo. of risers/flight= (1/2)*(3.96/0.18)= 11 nos.i.e., No. of treads/flight= 11-1= 10 nos.Keeping width of tread= 280 mm and width of landing = width of stair= 1.20 mHorizontal distance reqd to accommodate 10 nos. of treads= (0.28 x 10) + (1.2) = 4 mi.e, Width of passage= 4.64 4 = 0.64 m (Not sufficient)

4647We can accommodate 3 treads, each of 280 mm., which is equal to the width of Well.

So provide 8 treads in each flight.i.e., Total treads= 8+3+8= 19 nos.The stair will be a quarter space landing.

Total no. of risers= 19 + 3 = 22 nos. i.e., ht of rise = 3.96/22 = 180 mmTREAD = 280 mmRISE= 180 mm

4748Horizontal space reqd for 8 treads= 8 x 0.28 = 2.24 mi.e., width of passage hall = 4.64- (2.24 +1.2) = 1.20 m (OK)Final Plan

48Assignment QuestionsSubmit- class notes

Last date of Sub: 07.09.2013 (Saturday) @ 2 p.m.49