SPEEDY CONSTRUCTIONSCAST-IN-SITU SERVICES AND STAIR CORES

CROSS WALL AND BOX FRAME CONSTRUCTION

By:

Komal Rastogi

Megha Aggarwal

Jaspreet Singh

CONSTRUCTION & MATERIALS

SPEEDY CONSTRUCTION:In general concrete construction, we have seen that whatever the elements cast (beams, columns, slabs etc.) require time for setting. This is a long drawn process necessary for hardening of concrete. However, nowadays in large scale projects, newer methods of faster construction are being explored.

BOX FRAME CONSTRUCTION:

•In Box Frame construction, the walls and slabs are cast monolithically in the form of boxes with the open ends of the boxes as cladded main external walls.•The lateral front and rear walls do not participate in the load bearing structure. •The load of floors and slabs are carried by internal walls perpendicular to the principal axis of building called as Cross walls and hence also called as Cross Wall Construction.

cross wall

Origin of Cross Wall Construction :

In traditional buildings, the timber joists were arranged in the direction of shorter spans and were often supported on cross walls or partition walls rather than columns or lateral external walls.

LIGHT CLAD, NON-LOAD BEARING WALLS

CROSS WALLS

WOODEN JOIST

RESTING ON PARTITION WALLS

cross wall

Plan- cross wall construction

Merits of Cross Wall Construction…Merits of Cross Wall Construction…

•.. Construction of stairs and lift cores as the erection progresses permitting early

access for subsequent trades.

Structural and non-structural elements can be standardized and can be fabricated, resulting in speeding up of erection.

• The width of windows is not restricted and thus greater freedom is permitted in respect to fenestration.

• The cross-walls result in economy of labor, materials and space.

• The cross wall being internal are not affected by weather provided the designed thickness affords a reasonable standard of sound insulation (namely,230 mm if of brickwork and 175 mm if of concrete), no additional thickness is called for, as the problem of rain penetration does not rise.

`Demerits of Cross Wall Construction…Demerits of Cross Wall Construction…• The limitation of planning which results when the cross walls are maintained at maximum

intervals of about 5.5m.• It is clear that a building would be structurally unsound if it consisted of a number of

detached cross walls extending through several storeys without lateral or longitudinal ties or supports, especially when the cladding is the light weight type.

• Renovation work is most difficult in such construction.• Doors need to come in the middle third of the wall.

cross wall

Economic Achievement in Box Frame Construction :

• As lateral external walls are non-load bearing, so, In contemporary cross wall construction, the external walls are of relatively light cladded construction, which is resistant to rain transmission and is adequately insulated .

• Maximum economy is achieved if cross walls are properly planned to be same distance apart through out the length of the building.

this results in :

Standardization of certain elements. Panels of light weight cladding. R.C.C. concrete floor having same imposed load. Form work can be used again and again. Erection is expedited.

cross wall

Uses…Uses…

TheseThese are used in buildings where floor plans are typical like hospitals, hotels etc. are used in buildings where floor plans are typical like hospitals, hotels etc.

•This type of construction is most suited to building types that are upto 5 storeys high.

•The spacing of cross walls varies from 3-5.5 m

•Used at the site where speedy construction is done.

Points to take care while constructing cross wall :Points to take care while constructing cross wall :

•Care must be taken to ensure that the end of the cross walls are sealed to prevent the admission of rain.

•The facing of external wall can be of terracotta slabs.

•The damp proofing of the cross wall is done with a fibrous asphalt felt or d.p.c.

•To prevent the admission of rain through any defective joints in the terracotta facing, the end of the wall may be given two good coats of bituminous paint or other water repellent emulsion.

cross wall

Construction Details cross wall

cross wall

CAST IN SITU

1. IN SITU CAST FRAME

REINFORCED CONCRETE FRAME

The first reinforced concrete framed building to be built in this country was the general post office building in London which was completed in 1910.

Reinforced concrete was used in this country until the end of the second world war.

Then steel had been traditional material used for structural frames and engineers regarded the new fangled reinforced concrete with some suspicion.

The great shortage of steel that followed the end of the second world war promoted engineers to use reinforced concrete sa a substitute for steel in structural building frame.

At the time the conventional method of providing fire protection to structural steel frames was to encase beams and columns in concrete that was cast in situ in framework around the steel.

•The member of a reinforced concrete frame can be molded to any required shape so that they can be designed to use concrete where compressive strength is required and

steel reinforcement where tensile strength is required. •When concrete is designed cast in situ it will act monolithically as a rigid structure

cast-in-situ

cast-in-situ

Cast in situ construction

Cast in situ piles

Stair Cores :This is the space in the

building where the stairs are constructed. This may require special structural design so that the floors around the stairwell do not require structural walls and the stairs themselves are open to the floors.

stair cores

Terms related to Stairs:

Stairs:

A construction element in a building designed to bridge a large vertical distance by dividing it into smaller vertical distances, called steps. Stairways may be straight,

round, or may consist of two or more straight pieces connected at angles.

Staircore:

This is the space in the building where the stairs are constructed. This may require special structural design so that the floors around the stairwell do not require structural

walls so that the stairs themselves are open to the floors.

Staircase:

Steps, railings and landings are combinedly called as Staircase. Not necessarily enclosed in a staircore.

Stairway:

A series of steps giving floor to floor access including any balustrade or handrail.

terminologies

Other terms:

Landing:

A landing is, structurally, an intermediate floor between flights of stairs. It is typically used to allow stairs to change directions, or to allow the user a rest. As landings consume floor space and are structurally floors, they can be quite expensive to build. However, changing the direction of the stairs allows stairs to fit where they would not otherwise, or provides privacy to the upper level as visitors downstairs cannot simply look up the stairs to the upper level due to the change in

direction.

Spandrel:

If there is not another flight of stairs immediately underneath, the triangular space underneath the stairs is called a "spandrel". It is most often used as a closet.

Flight of Stairs:

A flight is an uninterrupted series of steps.

Nosing:

The front overhanging edge of a stair tread.

terminologies

Newel:

The large, sectioned, vertical member or post at either end of a flight into which the string is jointed.

String:

The inclined board of a stair, also termed as Stringer, into which the treads and risers are cut and housed. Variously named according to their position or type eg. Wall string or outer string etc.

Runner:

Carpetting that runs down the middle of the stairs. Runners may be directly stapled or nailed to the stairs, or may be secured by specialized bar that holds the carpet in place where the tread meets the riser.

Balcony:

For stairs with an open concept upper floor or landing, the upper floor is functionally a balcony. For a straight flight of stairs, the balcony may be long enough to require multiple newels to support the length of railing.

terminologies

precast staircase

Section thru a precast staircase

Plan of a precast staircase

Section thru a staircase, cast in situ

cast-in-situ staircase

Stair cores and Cross wall construction :

The cross-wall system generally utilizes stair cores and lift cores for overall stability, using the floors as stiff diaphragms for the transmittal of horizontal forces into shear walls located at staircase and lift shaft positions. The floors are

made up of either hollow core, solid slab, or composite construction.