Building Classification, Structural Systems and Wall Types Explained
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UNIT-01
3Q.1. Classification of Buildings as per National Building Code (NBC:2005, Part 3).
Ans:-1)Meaning: Classification of buildings means grouping them according to their use or occupancy so that planning, structural, fire-safety and service requirements can be fixed for each group.
2)Basis: NBC 2005 (Part 3 - Development Control Rules and General Building Requirements; Part 4 - Fire and Life Safety) classifies buildings by occupancy into nine groups lettered A to J.
3)Group A - Residential: lodging or rooming houses, one/two-family dwellings, dormitories, apartment houses, hotels. Examples: bungalow, flats, hostel, hotel.
4)Group B - Educational: schools, colleges, universities, training institutes and day-care centres where instruction is imparted.
5)Group C - Institutional: hospitals, nursing homes, sanatoria, orphanages, old-age homes, jails and custodial buildings where occupants cannot easily evacuate.
6) Group D - Assembly: buildings where large groups gather for recreation, worship or travel - theatres, auditoria, temples, stadia, museums, restaurants, railway stations.
7) Group E - Business: offices, banks, professional establishments, post offices, telephone exchanges, laboratories and research institutes.
8) Group F - Mercantile: shops, stores, markets, malls and department stores used for display and sale of goods.
9) Group G and H - Industrial and Storage: factories, mills, workshops, power plants (G); warehouses, godowns, cold storages, garages, hangars (H).
10)Group J - Hazardous: buildings storing or handling explosives, highly inflammable or toxic material. Significance: the group decides
Q.2. Difference between framed structure and composite structure.
Ans:-
| Framed Structure | Composite Structure |
|---|---|
| Slabs load beams, beams load columns, columns load isolated footings; walls only partition | Part of the load goes to walls and part to RCC/steel columns (e.g. wall on one side, column on the other). |
| RCC or structural steel frame with brick/block infill. | Masonry combined with RCC/steel members; also steel-concrete composite beams and decks. |
| Any height - mid-rise to high-rise. | Medium height, about 4 to 6 storeys. |
| Thin (115 mm or 230 mm) as walls carry no load. | Load-bearing walls thick, other walls thin. |
| More - slim columns and thin walls. | It is Moderate. |
| Excellent partitions can be shifted or altered. | Fair - only non-bearing parts are flexible. |
| Isolated, combined or raft footings below columns. | Strip footing for walls plus isolated footings for columns |
| Faster for large projects; economical for tall buildings. | Economical where part of the plan is column-free |
Q.3. Differentiate between load bearing structures and framed structure. Provide advantages and disadvantages of each.
Ans:-
| Load Bearing Structure | Framed Structure |
|---|---|
| Walls carry slab, floor and roof loads directly to continuous footings. | Slabs load beams, beams load columns, columns load isolated footings; walls only partition. |
| Brick, stone or concrete block masonry in cement/lime mortar | RCC or structural steel frame with brick/block infill. |
| Up to about 3 to 4 storeys economically. | Any height - mid-rise to high-rise. |
| Thick (230 mm or more at lower floors). | Thin (115 mm or 230 mm) as walls carry no load. |
| Less - thick walls consume floor area. | More - slim columns and thin walls. |
| Poor walls cannot be removed or openings enlarged freely. | Excellent partitions can be shifted or altered. |
| Continuous strip footing below all walls. | Isolated, combined or raft footings below columns |
Advantages of Load Bearing Structure:- Simple, no skilled design, cheap, good thermal mass.
Disadvantages of Load Bearing Structure:- heavy, slow, low flexibility, poor seismic safety.
Advantages of Framed Structure:- Light, ductile, flexible, fast, high-rise capable.
Disadvantages of Framed Structure:- needs design, formwork, skilled labour, costlier for small works.
Q.4. Explain types of structures.
Ans:- A) Load bearing structures:- 1) Structure Load transfer: The walls carry the load of slabs, beams, roof and other structural elements and transfer it directly to the foundation.
2) Construction: It is generally constructed using brick, stone or concrete masonry walls with suitable foundations.
3) Height limitation: Load-bearing structures are mainly suitable for low-rise buildings, because wall thickness increases as the height increases.
B) Framed Structure:- 1) Structural frame: The main load-carrying system consists of columns, beams and slabs, which form a rigid framework.
2) Load transfer: Loads from slabs are transferred to beams, then to columns and finally to the foundation.
3) Walls: External and internal walls mainly act as partition or enclosure walls and generally do not carry the main structural load.
C) Composite Structure:- 1) Combination: A composite structure uses two or more different materials that work together to resist structural loads.
2) Load sharing: The materials are arranged so that each material performs the function for which it is most suitable.
3) Examples: Common examples include steel-concrete composite beams, slabs and columns.
Q.5. Explain about Partition Wall and Cavity Wall.
Ans:- 1) PARTITION WALL: A non-load-bearing wall that divides interior space of a building into rooms; it carries only its own weight.2) Requirements: Light, thin, rigid, fire resistant, good sound insulation, quickly built, economical and strong enough to carry fixtures. 3) Materials/types: Half-brick (115 mm), clay or concrete hollow blocks (IS 2185), AAC blocks, glass, timber and plywood, metal lath and plaster, gypsum board and drywall.4) Brick partition construction: 115 mm brick wall in 1:3 mortar, reinforced with 6 mm bars or hoop iron every fourth course, tied into adjoining walls and wedged tightly to the slab above.5) Cavity wall: A wall of two separate leaves (outer about 100 mm and inner 100 to 230 mm) with a 50 to 75 mm air gap between them, joined by galvanised metal ties.6) Purpose: Prevents rain penetration and dampness, gives better thermal insulation (cool in summer, warm in winter) and improves sound insulation.7) Wall ties: Butterfly or twisted-wire ties at about 900 mm horizontally and 450 mm vertically in staggered pattern, sloping to the outer leaf so that water does not cross.8) Details: DPC at plinth and over openings (cavity tray), weep holes at base about 1 m apart, cavity bottom filled with lean concrete 150 mm below the lowest DPC, cavity closed at top with coping or roof slab.
Q.6.