prefabricated construction system

7/27/2019 prefabricated construction system

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BUILDING

CONSTRUCTION

Housing Report

Himani Gaur, 13, V Year, B.Arch



Site

Key Plan

Terrace Gardens

Balcony

Service Core

Detail Area

The construction system used for housing is pre-fabricated systems. The

special feature of design is terrace gardens. The design consists of terracegardens with every unit and with the common spaces connecting thecirculation.



PRECAST CONCRETE

PROPERTIES OF PREFAB STRUCTURES

LIGHT-WEIGHT: Oven dry density of siporex is 400 to 650kg/m ideal for low bearing soils,seismic zones and for adding storey’s to existing buildings.

FIRE RESISTANT AND INCOMBUSTIBLE: Offers twice the fire protection of concrete.Ideal for fire walls and for fire protection of structural steel siporex roof slabs, wall panels,

load bearing blocks.

HIGH STRENGTH TO WEIGHT RATIO: For Siporex 18 to 22 against 16 for concrete of M-150 grade.

WATER PENETRATION: Siporex structure being of closed cells , there is less capillaryaction and high surface activity allows for fast evaporation of moisture .

as its faster and wastage of materials is less

PROBLEMS WITH PREFAB CONSTRUCTION

Panels commonly develop hairline shrinkage cracks, particularly at the perimeter edgesand at corners of punched openings, despite controlled curing procedures. These crackscreate avenues for water to bypass shallow joint sealants, even when they have goodadhesion to the panels.

REMEDIAL OPTIONS

Cracks through the panel can be epoxy-injected to prevent water penetration, providedthe crack arose from overstress during improper handling and overstresses will notreoccur, such as with thermal bowing conditions



SLAB AND BEAM CONNECTION



BEAM CONNECTON



COLUMN CONNECTION



FLOOR DETAIL

ROOF/FLOOR (IS 4326 : 1993)

• The unit is a reinforced concrete component having a nominal width of

300 to 600 mm and thickness of 130 to 150 mm having two circular

hollows 90 mm diameter, throughout the length of the unit

• The minimum flange/web thickness of the unit shall be 20 mm.

• Length of unit varies according to room dimensions, but the maximum

length shall be restricted to 4.2 m from stiffness considerations



WALL SYSTEMS

These wall systems typically contain large prefabricated wall panels that are attached tothe structure at a few discrete points to resist gravity and wind loads. There are horizontaland vertical joints between the panels. Strip windows, i.e., a continuous horizontal band of windows, are common with this system.

Typically, a steel stud wall behind the panel supports the interior finishes, or metal furring,is attached to the interior face of the panel to receive interior finishes.

Precast concrete panel systems can be barrier walls or cavity walls, including pressure-equalized designs. Barrier wall construction results from sequencing the wall erectionsuch that the panels enclose the structural frame quickly and in advance of interior wallconstruction. Consequently, access to the exterior face of the interior walls cannot beachieved for installation of a waterproofing layer or air barrier. Installation of thewaterproofing layer, particularly the seal around panel attachment anchors, and the

continuous through-wall flashings with associated seams and transitions typicallyrequires access from the exterior and coordination with panel erection so that theseoperations can be completed as each panel is erected. Prefabrication and mounting of theflashing before erection can help reduce coordination problems. All of these factors

increase the cost of the project and can reduce overall floor space.

Plan section showing vertical joinery in precastconcrete panels. Note that panel geometryshields vertical joint from weather. Water thatpenetrates outer seal does not have a directpath to the interior.



WALL SYSTEM

Consequently, the majority of precast panel wall systems are designed as barrier walls.Architectural precast concrete wall panels can develop full-depth cracks, commonly at the re-entrantcorners in the panels. Cracking is more common in sandwich panels—i.e., those with insulation placed within the panel during casting,—than in solid concrete panels, due to greater thermal gradientsacross the panel depth. Proper quality control in manufacturing and handling during erection canreduce full depth cracks in the field of these panels. Using panels with simple geometries, i.e.,

rectangular without “punched” openings, and simple anchorage arrangements that avoid restraint of thermally-induced bowing further reduces the likelihood of cracking. Accordingly, solid precastconcrete panels can provide a fairly effective, but not always perfect, barrier against waterpenetration. Unlike some other wall systems that rely on light-gauge steel framing and gypsumsheathing for attachment, precast concrete panel systems rely on relatively thick steel angles andsimilar substantial materials for structural support and the system can tolerate some water entrywithout rapid structural deterioration.

Exterior building walls generally consist of an exterior veneer or cladding that provides theweathering surface of the building, a backup that provides structural support for the veneer, and aninterior finish applied to the backup.

Vertical section showing horizontal joinery in precast concrete panels. Noteship-lap geometry and recessed sealantto shield the joint from the weather.



BARRIER WALL CONSTRUCTION

Barrier wall construction systems uses the exterior surfacing as the sole waterproofing

system.

A typical masonry veneer wall consists of nominal 4 in. (10 cm) thick brick veneer with a 2in. (5 cm) wide air space (cavity) that separates it from the backup wall. Wire tiesembedded in the veneer bridge the cavity and are attached to a backup wall to stabilizethe veneer against wind loads. A layer of felt waterproofing covers the backup wall, i.e.,

concrete masonry units or gypsum sheathing board/steel stud wall. Mastics have beenused to waterproof concrete masonry unit backup walls, but these mastics can crack asthe backup moves in response to changes in thermal, moisture, and loading condition

Elements within wall openings, such as windows, must be watertight and cannot leakfrom frame corners or face joints. Windows typically contain joints between thehorizontal and vertical framing members that are sealed with gaskets or liquid-appliedsealants. For reasons discussed above, corner seals that are constructed with liquid-a lied sealants are not likel to be waterti ht. In addition, handlin and installation of the window frame can disturb or break these seals. For these and other reasons, it isprudent to install a flashing, such as a sheet metal pan, along the bottom of the windowto collect leakage through the window glazing or frame joints and direct it back to theoutside.

Schematic cross-section of window sill flashing. Theflashing collects water thatpenetrates the window, suchas at corners, and drains itback to the exterior throughweep holes. Window frame

also has drainage ability.



DESIGN CONSIDERATIONS FOR TERRACE GARDENS

Plants should be located to minimize unnecessary physical contact with people,but access to all plants for maintenance purposes should be provided.

5 . Plants should be selected that will survive under the expected levels of light butwill not outgrow their space in a short time . (Note that in most cases, plants in

interior spaces grow very slowly if at all after they are installed .) All constructed elements, such as built-in planters and watering and drainage

systems, should be coordinated with the overall design of the building .

LIGHTING REQUIREMENT STRATEGY

1. Light in typical building interiors is seldom of sufficient intensity to sustain mostplants without skylights or supplemental electrical lighting .

2 . Continuous illumination is not a suitable substitute for low light intensity, asplants require periods of light and dark (photoperiods) . The average photoperiodfor plants is 12-16 hours of light, and 8-12 hours of darkness .

3 . Natural light is ideal for plant growth, however tinted or reflective glass willalter its spectral energy and intensity . Glazing or artificial light sources shouldprovide radiant energy from the blue and red ends of the spectrum.

4 . Windows and clerestories are only about one-third as efficient in admittinglight, as skylights . In the northern hemisphere, the effective area for plant growthin south facing windows is equal in depth to the height of the window

5 . A mix of east and west-facing skylights typically provide the best balance of light for

TREE PITS AND BUILT IN PLANTERS

Tree pits and built-in planters for interior plantings have some Features thatdistinguish them from exterior plantings. The need for a tree pit (with sides and abottom) should be determined after investigation of existing conditions of the soil,Underground springs, and draining ability



TERRACE GARDENS



TERRACE GARDENS

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prefabricated construction system