4 Based on structure, the buildings are divided into three groups : Load-bearing wall structureRCC framed structureComposite structure
5 1. LOAD – BEARING WALL STRUCTURE : In this system of construction, loads from the roof slab or trusses and floors are transmitted through walls to the firm soil below the ground. Therefore, walls of upper storeys will have less thickness than the walls of lower storeys, consequently the carpet area reduces on the ground floor compared to upper floor. This type of construction is adopted at places, where hard strata is available at shallow depths. Generally, this type of system is suited for simple building of 2 storey construction. The materials used are stone, bricks or blocks, bound together with cement or lime mortar. For floors and roof slab, RCC can be used. The structural elements such as beams, trusses, etc. rest directly on the walls. The floor rest on the beams.
7 2. RCC framed structure :An RCC Framed Structure is an assembly of slabs, beams, columns and foundation connected to one another so that it behaves as one unit. It is a methodology, which enables the construction of tall buildings and building with stilts. Majority of urban structures and multistoried buildings are built as RCC framed structures. In an RCC framed structure, the load is transferred from a slab to the beams then to the columns and further to lower columns and finally to the foundation which in turn transfers it to the soil. The walls in such structures are constructed after the frame is ready and are not meant to carry any load. As against this, in a load bearing structure, the loads are directly transferred to the soil through the walls, which are capable of carrying them.
9 3. Composite structure :In many buildings and bridges, it is common to have a concrete slab supported by steel beams. If the steel beams are connected to the concrete slab in such a way that the two act as one unit, the beam is called as composite beam.Composite beams are similar to concrete T-beams where the flange of the T-beam is made of concrete slab and the web of the T-beam is made of the steel section.Composite beam has the advantage that the concrete in the slab takes all or most of the compression (for which it is best suited), while the steel beam takes all the tension in the overall system
11 Dead Load (D.L.) Live load (L.L.) Wind load (W.L.) Design loads :- a structure is designed considering the following loads :Dead Load (D.L.)Live load (L.L.)Wind load (W.L.)Earthquake load (E.L.)
12 1. Dead load (D.L.) :-It consists of self weight of different parts of the building like floor, roof, walls, plaster, doors, windows etc.Dead load of any part of building is calculated by multiplying its volume by unit weight of the material. Unit weights of the common building materials are given below :MaterialUnit Weight kN/m3PCC24RCC25Steel75Bricks22Brick masonry18Stone masonryTimber07Water10Granite27
13 2. Live load (L.L.) :-Live loads consists of moving of variable loads due to people or occupants, their furniture, temporary stores, machinery etc.It is considered to be uniformly distributed static load acting on the area.The minimum live load to be considered for design depends upon the type og building as shown in table :No.DescriptionMinimum live load kN/m31Residential buildings, hospitals2.02Office, small work space2.503Banks, reading rooms3.04Assembly halls, restaurants, classrooms4.05Warehouse, workshop, factory6Stairs, balcony
14 Numbers of floors carried by member (column, wall, foundation) For multistoried buildings, the probability of all the floors to be loaded simultaneously is very low. Hence, a load reduction factor is applied in designing columns, walls and foundations depending upon the number of floors carried by the member.Numbers of floors carried by member (column, wall, foundation)Reduction in live load1No reduction210%320%430%540%6 or more50%
15 3. Wind load (W.L.) :-Wind load is considered in design in case of tall buildings,It is expressed in terms of basic wind pressure which is an equivalent static pressure in the direction of wind.P = K*V*V where, P= wind pressure in kN/m*mK= coefficient depending upon wind velocity, sizeand shape of structure.V= Wind velocity of km/hr
16 4. Earthquake load :-The earthquake load acts in the horizontal direction.Earthquake load is calculated as under :Earthquake force = m.∝ = (w/g)*∝Where, m= mass of the buildingw= total weight of structureg= gravitational acceleration∝= acceleration due to earthquake= (1/20) g to (1/10) g
17 Building Components : Building Components Super structure substructure Plinth foundationWall & columnsBeamsFloorsRoofs & slabsParapetLintel, chajjasDoors, windowsSteps, stairsCupboardscoping
19 Plinth :- the part of the structure lying above the ground and below the ground and below the ground floor level is known as plinth.Substructure :- A Part of the structure lying below the ground surface is known as substructure.Function of building components :1) slab :- it acts as the roof of the building. It protect the building and its occupants from rain, heat etc.2) Walls :- they divide the building space into various rooms. They support slabs and beams. Walls safely transmit the loads coming on them from beams and slabs to the foundation.3)Plinth :- the plinth resists in transmitting the load of the structure to the foundation plinth resists the entry of rain water inside the building.4)Column :- it transmit heavy loads of super structure to the foundation.5)Footing :- it safely transmits the dead loads, live loads, wind loads from a building to the subsoil. It anchor the structure to the ground.
20 “Different types of foundations” Shallow foundation deep foundationsD < B D > BSpread footing pile foundationsCombined footing caissons or well foundationStrap footing coffer damsRaft foundationsGrillage foundations
22 Shallow foundations :when the depth of foundation is less than or equal to the width of foundation, it is called shallow foundation.
23 1) Spread footing :A spread footing is provided to support an individual column. A spread footing is circular, square or rectangular slab of uniform thickness . Sometimes it is stepped or haunched to spread the load over a large area.
24 2) Strip footing : A strip footing is provided for a load bearing wall. A strip footing is also provided for a rowof columns which are so closely spaced thattheir spread footing overlap eachother. A stripfooting is also known as continuous footing.
25 3) Strap footing :A strap footing consists of two isolated footings connected with a structural strap or a lever. The strap connects the two footing such that they behave as one unit. The strap simply acts as a connecting beam and does not take any soil reaction.A strap footing is also known as cantilever footing.
26 4) Combined footing :A combined footing supports two columns. A combined footing is provided in the following situations :i. when two columns are so close to each other that their individual footings wouldoverlap.ii. When the property line is so close to one column that a spread footing would beeccentrically within the property line.
27 4) Mat or raft foundation : A mat or raft foundation is a large slab supporting a number of columns and walls under the entire structure.A mat is required when the allowable soil pressure is low or where the columns and walls are so close that individual footing would overlap or nearly touch eachother.Mat foundation are useful in reducing the different settlements on nonhomogeneous soil or where there is a large variation in the loads on individual columns.
29 Grillage foundation :This type of foundation is used to transmit heavy loads from steel columns to the soil having low bearing power. This type of arrangement avoids deep excavations and provides necessary area at the base to reduce the intensity of pressure.Grillage foundation is made up of rolled steel joists, known as grillage beams provided in single or double tiers. In double tier arrangement the top tier is laid perpendicular to the bottom tier.
33 Pile foundation are used in the following conditions : When the soil below ground surface is very weak.When load coming from structure is very large and distribution is uneven.When it is required to transmit structural loads through deep water to a firm strata.When structure is to be constructed on sea shore.When deep drainage lines or canals are passing close to the structure.Pile foundation are used to resists horizontal forces in addition to vertical loads in earth retaining structures.Pile foundation are preferred where soil is expansive or collapsible.
34 Open cassion or well foundation : An open cassion is a box of timber,metal, reinforced concrete ormasonry which open at boththe top bottom and is used forbuildings and bridge foundations.
37 Buildings bye-laws :Building bye laws are the restriction laid down by the municipal, town planning or revenue authorities on construction and planning of different types of buildings.Necessity of building bye-laws :to curb the haphazard growth of towns and cities.to ensure proper air, light, ventilation, parking, sanitation, safety etc. to the people.To facilitate future use of land, widening of streets, controlling the ribbon development in the area.To provide safety to human beings who work on or live in the house against fire, noise, structure failure, health hazard etc.To reduce pollution in the area.To ensure that every citizen will receive facilities like water supply, sanitation, ventilation, electric supply etc.
38 Various building bye-laws : Built – up area :Carpet – area :Floor space index (FSI) :Margins :Projection in margins :Minimum room areas :Building height :
39 Plot area size in square meters Max built up area in % of total This is the area useful to the occupant of the house. It includes any area built up on, below or above ground floor. It includes main structure, cellar, out house, attached garage, servants room, bathroom, water closet etc.Plot area size in square metersMax built up area in % of totalFrontRearSide50 to 9060%2.51.5-91 to 20050%3.02.0201 to 50040%4.5501 to 10001001 and above
40 Carpet area : Floor Space index (FSI) : It is the area of a building where usually carpet can be laid if desired. From the plinth area, deductions of wall area, passages, stairs-case lift-shaft, kitchen, store, garage, sanitary,-shaft, bathroom and W.C. are made.Floor Space index (FSI) :It is the ratio of combined gross area of construction on all floors to total plot area.Normally a FSI of 1.0 to 1.2 is very common for small cities.Usually it is taken as 1.2 in residential areas.In big cities this value may be deferred. A FSI up to 1.9 is also allowed in cities where land cost is very high.
41 Margins :These are the open space required to provide sufficient, isolation, protection, ventilation and air circulation in the area. These are space for access and other requirements of free movements around the building even for repair and maintenance.Set back :The land contained in front margins belongs to the owner of the property, but he is prohibited from constructing any thing in set- back portion. The width of set-back varies from 1.5 m for congested street to 6.0 m for new underdeveloped area. The set- back is also referred as a building line.
42 Projection in margins : This is the provision for accommodating cantilever projection from the outer walls of a structure. There are some restrictions like the projected structural part should be provided with no slab or roof. Some of them are :A canopy of 3 m width in margins should always be atleast 2.4 m above the ground level.Maximum allowable length of projection from the wall of the building in the margins are restricted.
43 Minimum Room areas :This provision is to satisfy the functional requirement of important component part of a building.RoomMinimum area in square metersMinimum dimension in of side(short)Meter of heightLiving room18.104.22.168Kitchen5.41.8Bath, puja1.35 to 22.214.171.124W.C. or urinal0.81StoreStair-0.75Garage126.96.36.199Balcony1.2 at minimum height2.4 above ground levelLoft<1/3 of room area
44 Building height : Plot size in m*m Maximum built up area % This restriction is to take care of the space for the comfortable use of the unit. One cannot walk in a room if slab is not located at least at height equivalent to height of a person . To make use of the component part this specifications are adhered. Some of important provisions are listed below :Clear floor height should be minimum 2.7 mClear room height of air conditioned room should be minimum 2.4 mClear height of a roof should be minimum 2.4 mClear floor height of mezzanine floor should be minimum 2.0 mClearance for stair cabin, cellar should be minimum 2.0 mClear floor height for a business building should be minimum 3.0 mPlinth height should be minimum 45 cm for the bath and water closets.Plot size in m*mMaximum built up area %Maximum no. of storeys< 5080G.F. + 250 < 10070100 < 15060150 < 30050More than 30040