PART-A
1. Define Define Bea Bearin ring g Capac Capacity ity of of Soil. Soil. It is defined as the maximum load per unit area that the soil n supports without causing undesirable settlements. In other words, it is the inherentCapacity of the soil to bear the load imposed on it.
2. Define Ultimate Bearing Capacity of Soil. Ultimate Bearing Capacity of Soil: The ultimate bearing capacity of a soil is determined by conducting a late !oad Test. in this test, a s"uare rigid steel plate is loaded gradually and the settlement of soil for each load is measured. The graph showing the load#settlement relationship is used to determine the maximum $ad carried, when the soil %ust fails in shear. Ultimate !oad Ultimate Bearing Capacity of Soil & ''''''''''''''''''' (rea of the late
3. Define Safe Bearing Capacity of Soil. ( load much lower than the ultimate bearing capacity iiy should be applied on the soil so that perfect safety of the foundation is ensured. This safe load is called the Safe Bearing Capacity of the Soil. safe Bearing Capacity of Soil is defined as the maximum load per unit area that the soil carry safely without the ris$ of failure )collapse*. Safe bearing capacity is rmined by di+iding the ultimate bearing capacity by a suitable actor of Safely. Ultimate Bearing Capacity Safe Bearing Capacity of Soil &
'''''''''''''''''''' '''''''''''''''''''' actor of Safety
4. Wat are factor! affecting "earing capacity of !oil# (CT-S (/CTI01 B/(I01 C((CIT2 - S-I! Bearing capacity of soil depends upon a number of factors, which are listed below: 3. hysical features of the foundation, namely, Type of foundation, Si4e and shape of foundation, 5epth of foundation below the ground le+el and igidity of the structure. 6. Type of soil and its physical properties such as density, shear strength, crac$s, etc. 7. osition of ground water#table. 8. (llowable total and differential settlements.
$. Wat i! mean "y Bon%! in Bric& 'a!onry# Bond is the method arranging the bric$s in courses so that indi+idual units are tied together and the +ertical %oints of the successi+e courses do not lie in same +ertical line.
(. Di!ting)i! "et*een +ngli! Bon% an% ,lemi! Bon% S.o
3.
6.
+ngli! Bon%
,lemi! Bon%
Stretcher and header courses alternate
/ach course will be a combination of headers and
each other.
stretchers.
or walls thic$er than 3 bric$s /nglish
or thic$er walls it is comparati+ely wea$.
bond is more compact compact and stronger. stronger.
7.
(ppearance is not pleasing.
1i+es a pleasuring appearance for exposed faces.
8.
In this bond, greater s$ill is not re"uired.
This bond re"uires more s$ill and experience.
9.
;ortar re"uirement is less.
;ore mortar is necessary since bric$ bats are used.
/. Define flooring. loor may be defined as a building component that di+ides a building into different le+els, for the purpose of creating accommodation within a restricted space, one abo+e the other.
0. Wat are te Re)irement! of a oo% ,loor# 3.
It shou should ld gi+e gi+e hard hard and smooth smooth surfa surface. ce.
6.
It shoul should d ha+e ade" ade"uat uatee streng strength th and and stabili stability. ty.
7.
It shou should ld be be dam damp p resi resist stan ant. t.
8.
It should should ha+e ha+e good good thermal thermal insul insulati ation on capac capacity ity..
9.
It shou should ld be durabl durablee and easy easy to to maint maintain ain..
<.
It shou should ld be be fir firee resi resist stan ant. t.
=.
It should should ha+e ha+e an an aest aesthet hetin in loo$ loo$..
. Wat are te Component! of a ,loor# Structurally a floor may consist of two main component: 3.
Sub Sub > loo loorr or or Bas Basee Cou Cours rsee
6.
loor loor con con+ +erti erting ng
Subfloor or base course pro+ides paper support to floor co+ering . loor co+ering pro+ides a smooth, clean, imper+ious and durable surface.
1. Define "eam! . Beams are defined as hori4ontal load carrying member in a structure. einforced cement concrete, concrete, pre stressed concrete and steel sections are used as beams to support the slabs. ?ence a beam should be supported by a column
11. Define Span of te Beam : The hori4ontal distance between inner faces of the supporting wall is $nown as clear span of the beam. The hori4ontal distance between the lines of action of the supporting walls is $nown as effecti+e span. or design purpose the effecti+e effecti+e span is considered considered always.
12. Wat are loa%! acting on "eam!# The ma%or loads acting on a structure are 3.
5ead !oad
6.
!i+e !oad
The dead load is the self weight of the +arious components of the building. The li+e load is the super imposed load on a structure. They may be )3* Concentrated load or point load )6* Uniformly distributed !oad )7* Uniformly +arying load.
13. Define col)mn! an% cla!!ification The +ertical load carrying member of a structure is called column. They may be constructed of timber, stone or bric$ masonry, reinforced cement concrete or steel section. einforced cement and steel columns are used +ery commonly. ailure of columns depends on the length of the column compared to its cross > sectional dimensions. It is classified as follows 3.
!ong Column.
6.
Short Co Column.
If
@ 3.6, it is a Short Column
If
, it is a !ong Column.
!eft is the effecti+e length of column. A is the lateral dimension of the column.
14. Define lintel! ( lintel is a hori4ontal member which is placed across the openings. -penings are in+ariably left in the wall for the pro+ision of doors, doors, windows, cupboards cupboards etc. The Bearing of lintel should be the ;inimum of the following 3.
3cm.
6.
?eigh eightt of of !in !inte tel. l.
3. 33th and 36th of the span of the lintel.
1$. Define 5oo&e6! la*. Dithin the elastic limit stress directly proportional to strain.
PART-B 1. Wat are meto%! of impro7ing "earing capacity of !oil# ;/T?-5S - I;-EI01 B/(I01 C((CIT2 - S-I! In early days, areas ha+ing wea$ soils or low bearing capacity soils, were a+oided for construction. But with scarcity of land in urban areas, it is not possible to do so. It is possible to impro+e the bearing capacity of soil at the construction site by adopting any one of the following methods: 3. By increasing the depth of foundation: Soils ha+e got greater bearing capacity at deeper depths. This is especially true for sandy soils. or sandy soils, the bearing capacity increases due to the weight of o+erlying materials. This method cannot be adopted where the ground water le+el is high. (lso, this method is not ad+antageous, since the load of the building foundation also increases with depth. 6. By compacting the soil: Compaction )ramming* of the soil reduces the open )air* spaces between the indi+idual particles in the soil mass. Therefore, they are less liable to displacement, thereby bearing capacity is increased. By pac$ing large si4ed particles li$e boulders, gra+el, etc., to the soil or by dri+ing iles, compaction to a certain extent can be attained particularly in sandy soils of loose nature. 7. By draining the sub#soil water: The bearing capacity of e+ery soil )sandy soil or clayey soil* decreases when its water content increases )i.e., due to a rise in ground water table*. eduction in water content increases the bearing capacity of the soil. Cohesionless soils, i.e., sandy soils and gra+els can be drained easily, either by gra+ity pipe drainage system or installing shallow tube wells. 8. By grouting the soil mass with cement grout so as to fill the crac$s and fissures: Crac$s and fissures in the soil reduce the bearing capacity of soil. Cem ent grout can be in%ected under pressure into the foundation foundation soil to fill any crac$s crac$s or fissures. 9. By confining the soil mass to restrict mo+ement: Sheet iles are dri+en to form an enclosure. Thus, the mo+ement of the soil is restricted. This can help in increasing the bearing capacity. <. In%ecting Chemicals: Chemical solutions li$e silicates are in%ected under pressure into the soil mass. They form a gel and thereby unite to de+elop a compact mass. This method is +ery costly. It is adopted in exceptional cases.
2. Wat are re)irement! of goo% fo)n%ation!# /FUI/;/0TS - 1--5 -U05(TI-0S 3. !oads on oundations The type of foundation to be used depends upon the loads carried by it. The loads on the foundations are classified into the following three types:
)3* 5ead !oads: 5ead load is the dead weight or self weight of the foundation and the super structure. It includes the weight of all walls, floors, roofs, etc. To determine the dead load, $nowledge of the weight of +arious building materials is necessary. )ii* !i+e !oads: !i+e loads are the mo+able and superimposed loads on the floor. !i+e loads include all the loads that are not permanent. !i+e loads are not constant loads, but +arying loads. These include the weight of persons on the floor, weight of materials such as furniture, etc., stored temporarily on the floor, weight of snow, etc. )iii* Dind !oads: The effect of wind should be considered in case of tall buildings. The exposed sides and roofs of tall buildings are sub%ected to wind pressure. The design wind pressure at a place depends on the wind +elocity, height of the building, etc. The effect of wind pressure is to reduce the pressure on the foundation in the windward side and to increase the pressure in the leeward side. oundation should distribute the abo+e loads to a large area )in Shallow oundation* or through end bearing and s$in friction )in 5eep oundation*. 5istribution of load is done so that the intensity of stress and the settlement are within limits. 6. Safe Bearing Capacity actor The re"uirement of foundation is to transmit the load from the building to the soil such that the supporting soil is not stressed beyond its bearing capacity. 7. 5epth of oundation 5epth of foundation should be sufficient enough to ensure ade"uate bearing capacity of soil. or fine sands and silts, depths should be ta$en below the frost 4one. or compressible soils li$e clay, depth should be ta$en below the 4ones of shrin$age and expansion. 8. !e+el Surface for Super Structure oundation should pro+ide a le+el surface to the super structure. 9. Stability e"uirements oundation should impart lateral stability to the super structure by anchoring it to the ground. <. Safety against 0atural /+ents oundations should sustain hea+y rains, large wind forces and earth"ua$e forces. They should pro+ide safety against scouring or undermining by flood water or burrowing animals. They should also pro+ide safety against sliding and o+erturning due to hori4ontal forces li$e wind, earth"ua$e, etc. =. Control of 5ifferential Settlement Settlement of the foundation should be within reasonable limits. Settlement of foundation is classified as Uniform )or Total*, Tilt and 0on#Uniform )or 5ifferential* settlement.
Structures on rigid foundations should undergo uniform settlement. Dhen the entire structure rotates, the structure is said to be under uniform tilt, If foundations of different elements of a structure undergo +aried settlements, the foundation is said to be under nonuniform or differential settlement. oundations should distribute the load e+enly under non#uniform loading conditions as well as non# uniform soil conditions. Thus, the differential settlement should be pre+ented to a+oid any damage to the structure. This can be achie+ed by adopting suitable types of foundations such as combined footings, mat or raft foundation, etc. G. Safety against Eolume Changes in the Soils 5istress or failure due to seasonal +ariations causing +olume changes in the soils should be minimi4ed by pro+iding special type of foundations. H. Careful 5esign of the In+isible oundation Though the foundation once built is in+isible to the owner and the public, it is a critical part of the total building system. Therefore, it should be gi+en careful attention in design. 3. Safe !ocation The foundation should be so located that it is able to resist any un#expected future influence which may affect the foundation and the superstructure. 33. Sub#surface In+estigation It is necessary to ha+e a proper sub#surface in+estigation at the site to gain information on the strength, compressibility and permeability of the sub#soil. The dimensions of the foundation should be determined to suit the loads from the building and the properties of supporting soil. 36. Selection of oundation System The selection of the foundation system for a structure depends on the si4e, type and importance of the structure, the properties of the subsoil, the design of the structure and the o+erall cost, tempered by engineering %udgment of the designer.
3. +8plain te ca)!e! an% preca)tion! reme%ie! of fo)n%ation! fail)re# -U05(TI-0 (I!U/S # C(US/S (05 /C(UTI-0S I /;/5I/S ailure of foundation results in the utter collapse of the structure resting on it. ( foundation may fail due to +arious causes. The ma%or causes and the precautions remedies are explained below: 3. Une"ual Settlement of Sub#Soil: Soils, in general, are all compressible. Thus.. settlement of soil cannot be pre+ented. Une"ual settlement is due to )i* the une"ia resistance of the soil, )ii* une"ual loading per unit area of the foundation soil t )iii* eccentric loading on the soil. This results in formation of cr#ac#$s in# thestructure. !imited settlement is not a source of danger, pro+ided if it is uniform and ta$es place foa small depth. The small settlement, which may ta$es place, should be such that the relati+e positions of the +arious parts of the structure should remain unaltered.
recautions to be ta$en )i* ressure intensity under the foundation shall not exceed safe bearing capacity of soil. )ii* !ine of action of the resultant load should act on the centroid of the foundation area. )iii* oundation has to be placed on a firm soil or hard roc$. )i+* !oading on foundation should be axial. If loading is eccentric, it should be within the permissible limits. 6. !ateral /scape of Soft Soil from Underneath the oundation: This is liable to occur when the soil is +ery soft and particularly in the ri+er ban$s. recaution: The soil should be confined to the re"uired area by dri+ing Sheet iles. 7. Shrin$age of Sub#Soil: ( structure might ha+e been constructed o+er a soil in which the sub#soil is saturated with water. (fter the construction, if the water is drained away, the sub#soil will shrin$. This results in a considerable settlement. recautions: oundation le+el should extend deeper than any probable cutting nearby. This may become a cause for the draining of sub#soil water. (lso, the soil moisture content is to be maintained constant so that changes due to shrin$age do not occur. 8. Sliding of the Soil: Sliding of the soil occurs, when a building is built on a ground of sloping strata. The weight of the building may cause the sloping strata to become detached and to slide. recaution: Sliding of the soil strata should be pre+ented by pro+iding retaining walls. 9. Compression of ;ortar oints of oundation ;asonry: ;ortar %oints of the foundation masonry may sin$ or compress, leading to une"ual compression of masonry. 5ue to this, the super structure is sub%ected to distress leading to crac$s. recautions: ;ortar should be stiff, consistent with wor$ability. (lso, use of thin mortar %oints, uniform and limited construction height of masonry per day )i.e., not more than 3.9 m* and curing of mortar %oints for at least two wee$s are the other remedies. <. /xcessi+e Settlement of Sub#Soil: oundations placed on slopes and that ar e sub%ected to mo+ement of water may laterally yield, causing excessi+e settlement and reduction of shearing resistance. recautions: (de"uate lateral support by dri+ing iles should be pro+ided. roper drainage arrangements may also be pro+ided. =. !ateral ressure on Super Structure: This may happen due to the thrust of a sloped roof and arch at the end of a wall or wind, tending to cause the wall to o+erturn. Dhen the area of base is too small, the wall tilts causing une"ual settlement in the foundation. recaution: ( sufficient base area should be pro+ided below the walls and columns.
G. Deathering and (tmospheric (ctions: oots of trees and shrubs m ay consume more underground moisture causing settlement and weathering. (tmospheric agents such as sun, wind and rain may cause moisture mo+ements.resulting in foundation settlement. recautions: Trees and shrubs may be grown away from the building. oundation settlement may be a+oided by pro+iding ade"uate drainage arrangements and sun shades in buildings.
4. +8plain te type! of fo)n%ation!. T2/S - -U05(TI-0S
oundations are broadly classified as shown in the Table below:
S5A99:W ,:UDAT;:S )-pen oundations*
( Shallow oundation is a type of foundation in which depth is e"ual to or less than its width. It is built by open exca+ation of the soil. ?ence, it is also $nown as -pen oundation. The base of the structure is enlarged or spread to pro+ide good and indi+idual support to the load. This type of foundation is pro+ided for structures of moderate height, built on sufficiently firm dry ground. This foundation is practicable up to a depth of 7 m to 8 m. It is generally con+enient abo+e the water#table. T2/S - S?(!!-D -U05(TI-0S )i* Spread oundations )ii* aft or ;at oundations
)I* S/(5 -U05(TI-0S Spread foundation is the foundation in which the load of the structure is spread o+er a large area. Intensity of the soil pressure induced should be less than the safe bearing capacity of the soil. Spread foundation is constructed of masonry, plain concrete or reinforced cement concrete. This is the cheapest type of foundation, largely used for ordinary buildings. The different types of spread foundations are explained below: 3. Dall ootings Dall ooting is pro+ided throughout the length of the wall in case of load bearing wall. It is used where soil of good bearing capacity is a+ailable at a depth of e"ual to or less than 7 m from 1round !e+el. The wall footings are of two types: Simple ooting: See ig. 6. It is pro+ided to carry light loads. It has one pro%ection )offset* on either side of the wall. The depth of concrete bed is about twice the offset. In this, lime or plain cement concrete )3:7:< or 3:8:G mix* is used in the foundation bed. The wall may be of bric$ or stone masonry. It is used in small residential buildings such as tiled houses, pump house, watchman cabin, etc.
Stepped ooting: Dhen the foundation width is considerably more than the thic$ness of the wall, then the footings should be stepped for transmission of the load. In such case, the foundation is called Stepped ooting. (lso, stepped footings may be pro+ided when the ground has a slope. The reason is that it may become uneconomical to pro+ide a simple footing at the same le+el on the sloping ground. In each stepping, the pro%ection )offset* of the step should be about one#fourth of the length of the bric$. The footings may be two or more steps of bric$ or stone masonry. (t the bottom of the steps, a concrete bed is pro+ided. Using .C.C.
concrete bed, buildings of maximum number of floors up to three may be built.
6. Isolated or Column or Indi+idual ootings ( footing that supports a single column to transfer the load of the structure safely 3 soil bed is $nown as Isolated or Column or Indi+idual ooting. ooting may be s"uare, rectangular or circular in shape in plan, depending upon shape of the column and constrains of space. S"uare footings are economical hi s"uare and circular columns. Under rectangular column, rectangular footings considered to be more appropriate. Column footings may be Simple, Stepped or Sloped. In the case of hea+y loa columns, steel reinforcement is pro+ided in both the directions in the concrete bed. ;ain einforcement ods: These are placed parallel to the width of foundation be.r. 5istributors: These are placed perpendicular to the main rods.
Simple ooting:. If the load on the column is light, a spread is gi+en under the base of the column. This spread is defined as Simple ooting. Stepped ooting: See ig. 9. or hea+y loaded column, the total width of the footing may be +ery high. This is attained in three or four steps. This arrangement is called Stepped ooting. Sloped ooting: See ig. <. Concrete can be moulded to any shape. Therefore, a concrete footing may be constructed as a sloping one to pro+ide sufficient spread under the column. This arrangement is called Sloped ooting. 7. Combined ootings
( footing which supports two or more columns is termed as Combined ooting. Combined footings are proportioned such that the center of gra+ity of the loads of the structure coincides with the center of gra+ity of the foundation. By this arrangement, the load of the two columns will be e+enly distributed to the soil. Therefore, the combined footings ha+e either a ectangular Shape or Trape4oidal Shape in plan. See ig. =. If the column loads are e"ual carries greater load ) J F*, then ectangular ectangular Combined ooting: ) F*, or the interior column Combined ootings are used.
Trape4oidal Combined ooting: See ig. G. If the column loads are une"ual and the external column near the property )boundary* line is hea+ily loaded, Trape4oidal Combined ootings are used.
Combined footings are used under the following circumstances: K Dhen the space between two columns is so small that separate footings for indi+idual columns will o+erlap. K Eery often, a column is to be pro+ided near the edge )boundary* of some property. It may not be permissible to extend the footing beyond a certain limit. In such a case, the load on the footing will be eccentric. This will result in une+en distribution of load to the sub#soil. (lternati+ely, a common footing to support the edge column and an interior column close to it may be pro+ided. K Dhen the bearing capacity of the soil is so low that indi+idual column footing is of uneconomic si4e.
8. Continuous ooting See ig. H. In continuous footing type, a single continuous .C.C. slab is pro+ided as the foundation of two or three or more columns in a row. This footing pre+ents differential settlement in the structure. (lso, it is suitable at location liable to earth"ua$e.
ii (T or ;(T -U05(TI-0S ;at is li$e a large spread footing, co+ering the entire building area. (ll building loads are supported on a common mat. This is the common foundation pro+ided for all the columns of the building. The mat reduces the possibility of differential )une"ual* settlement and pro+ides a condition of uniform settlement. (lso, it is more economical. aft or ;at foundations are used )i* when the load of the structure is hea+yL )ii* when bearing capacity of the soil is +ery low and the soil ha+ing a tendency to yieldL 5ue to low bearing capacity, large isolated footings are necessary. If the loads transmitted by the columns need large footings, re"uiring aplan area more than half the area co+ered by the building, mat foundation is prd+tded. )iii* when the columns occur closely. See ig. 3. It shows a mat foundation with the ;at )aft*, ;ain Beams, Secondary Beams and Columns. Columns transmit the loads to the ;ain Beams. ;ain Beams transmit the loads to Secondary Beams. Secondary Beams transmit loads to the ;at. The ;at ultimately transmits the load to the sub#soil.
D++P ,:UDAT;:S
The design and construction of 5eep oundations to transfer the load of the super structure through wea$ soils, to deep load bearing strata is a challenging %ob for a ci+il engineer. Dhen the soil a+ailable at a reasonable depth of less than, say, 7 to < meters is not ha+ing the desired bearing capacity, deep foundation is used. ( foundation is said to be a 5eep oundation, when its depth is more than the width of the foundation. 5eep foundations transmit the load of a structure through wea$ soils to strong soil beds or roc$ beds a+ailable at great depth. 1eneral forms of deep foundations are: )i* iles )ii* iers and )iii* Dell. )I* I! -U05(TI-0S ile: In some cases, the soil at a site may ha+e a +ery low bearing capacity for great depths )< m or more*. It may be impracticable to impro+e the strength of such soils by compaction. In such cases, a pile foundation is used to transmit the weight of the structure to a stratum of good strength or to roc$. ile is a .C.C. column member )or a timber column member*, dri+en into the ground to a suitable depth to transfer the load on it to.a deeper and harder layers of the soil or roc$. 1enerally, part of the load on the pile is ta$en by friction offered by the surrounding soil. The remaining part of the load is transmitted to the hard stratum up to which it is sun$.
iles are installed by dri+ing by hammer or by any other suitable means. The piles are usually placed in groups to pro+ide foundations for structures. Te pile groups may be sub%ected to +ertical loads or hori4ontal loads or a combination of +ertical and hori4ontal loads. ( pile occupies less space. It is not liable to big settlements. iles are best used under the following Conditions or Situations: K !oads to be transmitted to the sub#soil are +ery large and concentrated. K ro+iding mat foundation may not be economical. K Dhen foundation soil is loose and hard stratum is a+ailable at about 3 m depth. K Considerable rise or fall of sub#soil water le+el occurs seasonally. K Dhen the structure is tall and hea+y, but deep bed of sandy soil is a+ailable. K Dhen there are possible future constructions of deep sewers canals close to the site. K Dhen the foundation is to be carried below the maximum possible scour depth. K To pre+ent any excessi+e settlement. K The top soil is of expansi+e nature. K Sea#shore or ri+er bed construction or foundations in marshy )moist* areas. C!(SSIIC(TI-0 - I!/S: iles are classified on the basis of 3. Their ;aterial Compositions 6. Installation ;ethods 7. Their unctions 8. 1round /ffects 3. Classification Based on ;aterial Compositions
Under this classification, piles are further classified as Steel, Concrete, Composite or Timber iles.
Steel iles: Steel piles are made in three forms:
olled Steel ?#Section iles, Box iles and Tube iles. There can be no restriction on length due to high strength. ?owe+er, steel piles may be affected by corrosi+e agents li$e salt, moisture, acid or oxygen. To pre+ent the steel pile from corrosion, its thic$ness may be increased or encased in concrete or chemical coating with paint is applied. See ig. ii. In this, ?#Section pile ha+ing wide flanges is used. The pile pro%ects slightly abo+e the ground le+el and functions as a column. 5ue to its small cross section, it can be dri+en into the soil easily. Box pile is rectangular or octagonal. It is filled with concrete. Dhen ?#Section pile is difficult to be dri+en, box file is preferred. Tube pile can be sun$ into the ground easily. It is filled with concrete. Concrete iles Concrete ile is stronger and more durable than steel piles. It is not sub%ected to decay by termite li$e timber piles. Concrete piles may be either Cast#in#situ or re#cast. Cast#in#situ Concrete iles: These piles are cast in the site itself. Standard types of cast#in#situ piles are: Simplex ile, aymond ile, etc. Simplex Cast#in#situ Concrete ile: See ig. 36. ( bore is dug into the ground by inserting a Casing. The reinforcement made of ;ain einforcement ods and !ateral einforcement ods )called Stirrups* are placed into the ground. Then the bore is filled with cement concrete. In the case of aymond ile, the casing is $ept in position inside the ground, after placing the concrete. ?ence, it is called Cased Cast#in#situ ile. In the case of Simplex ile, the casing is withdrawn from the bore after placing the concrete as shown in ig. 36. ?ence, it is called Uncased Cast#in#situ Concrete ile.
re#cast Concrete iles: These piles are cast in a yard and transported to the site, where they ha+e to be dri+en. Concrete pile is pre#cast to specified lengths and shapes with reinforcement. The reinforcement is pro+ided to enable the pile to resist the bending moment de+eloped during lifting and transportation. re#cast piles may be s"uare. circular or octagonal in section. -ften S"uare iles with corners chamfered are used. See ig. 37.
( Solid Cast Iron Shoe is pro+ided at the lower end of the pile to pre+ent the lower end from brea$ing, particularly when it stri$es a boulder under ground. The pile shoe should be coaxial with the pile and firmly fixed to the concrete. The depth to which the pile has to be dri+en should be determined by preliminary borings. This will pre+ent o+er dri+ing of piles. Composite iles: ( composite pile is made up of two different materials dri+en one abo+e the other. Steel and concrete combination or timber and concrete combination of composite piles are in use. Timber pile or steel pile is pro+ided below the ground water le+el. Concrete pile is pro+ided abo+e the timber or steel piles.
Timber iles: Timber iles are the oldest types of piles, made from tree trun$s.
6. Classification Based on Installation ;ethods Based on installation techni"ues, piles are classified as Cast#in#situ piles and 5ri+en piles. Cast#in#situ iles: These piles are explained abo+e in detail.
5ri+en iles: 5ri+en piles may be made of Concrete, Steel or Timber. These are explained abo+e in detail. 7. Classification Based on unctions /nd#bearing iles: See ig. 38. Dhere the top soil is soft or too wea$ to support the super structure, piles are used to transmit the load directly to the underlying bed roc$ or hard stratum. Such piles are called /nd#bearing iles. /nd#bearing piles are resting on a +ery hard stratum. These are also $nown as !oad Bearing iles. The soil through which these piles ha+e passed are not assumed to resist the loads. The soil is only expected to pro+ide lateral support to the piles. Bearing piles act as columns and hence are designed as columns.
Two or more piles support one column. These piles form one group. They are pro+ided with a common thic$ concrete top, called ile Cap. Column of the structure is resting on the pile cap. The pile cap distributes the load e"ually to the piles. The types of end#bearings piles are Concrete iles, Steel Sheet iles and Timber iles.
riction iles: See ig. 39. If the bed roc$ is not existing at a reasonable depth below the ground le+el, the load is transferred through friction along the pile length. Such piles are called riction iles. In these, S$in riction or the frictional resistance is de+eloped between the surface of the piles and the sand particles surrounding them. S$in riction is responsible for transferring the load along the length of the piles. riction piles are used where deep bed of sand is a+ailable. Since friction piles do not rest on hard stratum, they are also $nown as loating iles. The frictional resistance of the surrounding soil against the downward mo+ement of the pile can be increased by pro+iding a longer pile, a greater diameter for the pile, a rough lateral surface to the pile and by pro+iding piles in group. Types of friction piles are: Cement Concrete iles, Steel iles, Timber iles and Composite ;aterial iles. Under#reamed iles In expansi+e soils such as blac$ cotton soil, +ery soft clay, filled up earth, etc., building often crac$s due to relati+e ground mo+ements. This differential settlement is caused by alternate swelling and shrin$ing of the soil due to changes in its moisture content. To a+oid differential settlements, the structure is anchored to a depth where the +olumetric change of soil due to seasonal +ariations is negligible. This can be economically obtained in shallow as well as deep layers of expansi+e soil by using Under#reamed ile. !oad is transferred to a hard strata ha+ing sufficient bearing capacity to ta$e the load. In fact, the building structure is anchored to the ground by using under#reamed piles.
See ig. 3<. Under#reamed ile is a cast#in# situ pile with reinforcement in the form of ;ain Eertical ods and !ateral Stirrups. These piles are pro+ided with Bulb#shaped /nlargement called Under#ream near its bottom end. If the pile is sub%ected to hea+y loads, more than one bulb can be pro+ided. ( pile ha+ing only one bulb near its bottom is $nown as Single Under#reamed ile. Single under#reamed piles can be used successfully for one and two storey buildings. iles ha+ing two bulbs are called 5ouble Under#reamed iles. Dith one additional bulb, bearing capacity is increased by 9M. So, by increasing number of bulbs, +ery high capacity piles )called ;ultiple Under#reamed iles* can be constructed for supporting multi#storey buildings and hea+y structures. (ir 1ap is pro+ided between the ground le+el
and the bottom of the Capping Beam.
8. Classification Based on 1round /ffects in granular soils, there is a tendency for compaction. In clays, hea+ing of ground surface often results. iles used to compact soils are called Compaction or 5isplacement iles. These piles displace substantial +olume of soil during installation. 5ri+en piles installed in pre#driiled holes are called 0on#displacement iles. These piles are used to pre+ent the mo+ement of earth slopes and to safeguard the foundation from damage due to scour. 5-UB!/ U05/#/(;/5 I!/ )ii* I/ -U05(TI-0S iers are large diameter massi+e shafts with or without broad base at the bottom. iers are installed by placing .C.C. concrete#in#situ, after drilling deep hole into the ground. ?ence, piers are also $nown as 5rilled iers. Types of piers: 3. Broad Based ier, 6. Straight Shafted ier and 7. /xtended Straight Shaft ier. 3. Broad Based ier or Belied ier: See ig. 3=. 5rilled piers which are pro+ided with a broad base at the bottom of the straight shaft are $nown as Broad Based ier or Belied ier. The bell may be angled as shown or may ha+e the shape of a dome.
6. Straight Shafted ier: In this, the shaft is ta$en through the upper soil layers. The end of the shaft is placed on a firm ground or roc$. 7. /xtended Straight Shaft ier or Soc$eted ier: In this, the straight shaft is extended into the underlying roc$ layer. (d+antages of drilled piers o+er other types of deep foundations and their uses K Eibration and hea+e of soil are not caused as in dri+en pile installation. K /"uipments used in the construction of drilled piers produce less noise. Therefore, piers are "uite suitable for areas near hospitals and educational institutions. K 5rilled piers are used in the area where it is difficult to install pile foundation. K Inspection and physical test of the soil or roc$ along the sides and at the bottom of the pier shaft is possible. fi%i* D/!! -U05(TI-0 See ig. 3G. Dell foundation is not a solid structure li$e pier. It is hollow inside, resembling a well. It has no top or bottom co+er. ( Dell Curb of steel or .C.C. is constructed in a yard. It is placed where the well has to be sun$. The soil from inside the curb is dug. The well is gradually dri+en down till the re"uired depth of reaching a hard stratum. The soil inside the well is remo+ed and the well is made to sin$. (fter installing the curb in place, a ;asonry Steining is constructed abo+e it. Then, the bottom of the well is plugged with concrete. It is $nown as Bottom lug. The hollow portion abo+e the bottom plug is filled with sand. It is $nown as Top lug. The whole well is then co+ered with a Dell Cap.
Uses K ( well foundation is pro+ided in soils which are sandy and soft for great depths. This foundation is meant for hea+ily loaded structures on low bearing capacity soils. K Dell foundations are used underwater such as bridges, doc$s, etc. Bridgesdoc$s ha+e to resist large lateral forces and are located in shallow running water in ri+ers with hea+y scour. Dell sin$ing is a specialised operation demanding considerable s$ill. It is belie+ed that the famous Ta% ;ahal is founded on bric$ wells. K These are used in the areas, ha+ing large boulders for shore protecting structures, where large lateral stresses are to be encountered.
$. +8plain te Type! of Bon%! ;n Bric& 'a!onry. ollowing are the types of bonds in bric$ wor$s: 3.
Stretcher Bond
6.
?eader Bond
7.
/nglish Bond
8.
lemish Bond
9.
a$ing Bond
<.
Nig#Nag Bond
=.
1arden Dall Bond
1. Stretcer Bon%
In this type of bond, all the bric$s are said with their length parallel to longitudinal direction of the wall. Since Stretchers alone are +isible in ele+ation, it is $nown as stretcher bond
2. 5ea%er Bon%
In this type of bond, all the bric$s are laid with their length perpendicular to the longitudinal direction of the wall. This is suitable for one bric$ wall and also used for the construction of cur+ed walls
3. +ngli! Bon%
This is the most commonly used bond for all wall thic$nesses. This bond is considered to be the strongest. ollowing are the features of an /nglish bond: 3.
This bond consists of alternate courses of headers and stretchers
6.
The "ueen closer is placed next to the "uoin header to brea$ the continuity of the +ertical %oints
7.
/ach alternate header is centrally placed o+er a stretcher
8.
If the thic$ness of the wall is an e+en number of half bric$, the wall presents the same appearance on both the faces
9.
If the thic$ness of the wall is an odd number of half bric$, the same course will present stretchers on one face and header on the other
<.
The hearting of thic$er walls consists of only headers
4. ,lemi! Bon%
In this type of bond, alternately stretchers and headers are laid in each courses. (ppearance of this bond is better that the /nglish bond The special features of this bond: 3.
In each course, stretchers and headers are alternately placed in both the facing and bac$ing.
6.
The "ueen closer in placed next to the "uoin header in alternate courses, to brea$ the continuity of the +ertical %oints.
7.
/+ery header is centrally supported o+er a stretcher below it.
8.
This bond presents the same appearance both in the facing and bac$ing.
9.
Bats are used for walls e"ual to odd.
$. Ra&ing Bon%
In this type of bond, the bonding bric$s are $ept at an inclination to the direction of the wall. The ra$ing course is generally pro+ided between the two courses. This bond used in thic$ walls a$ing bonds are of two types: 3.
5iagonal Bond
6.
?erring > Bone Bond
De can explain these bonds as follows:
1. 5iagonal Bond: In this bond, the bric$s are laid diagonally. The angle of inclination is so selected that there is minimum brea$ing of the bric$s. The triangular pieces of bric$s are re"uired near the sides.
2. ?erring > Bone Bond: In this bond, bric$s are laid at an angle of 89 degrees from the center in both the directions.
(.
This bond is similar to herring#bone bond, except that the bric$s are laid in 4ig#4ag fashion. This band is commonly used for ma$ing ornamental panels in the bric$ flooring.
/. ar%en Wall Bon%
This type of bond is used for the construction of garden walls, boundary walls, compound walls , where the thic$ness of the all is one bric$ and the height does not exceed two meters. 1arden wall bonds are of two types: 3.
1arden Dall /nglish Bond
6.
1arden Dall lemish Bond
These Bonds can be explained as follows:
1. 1arden Dall /nglish Bond: In this bond, the header course is pro+ided only after three to fi+e stretcher courses.
2. 1arden Dall lemish Bond: In this bond, each course contains one header after three to fi+e stretchers continuously placed throughout the length of the course.
(.+8plain te Cla!!ification of Stone 'a!onry# 5epending upon the arrangement of stones in the construction it can be classified as follows: 3.
ubble ;asonry I.
II.
6.
andom rubble masonry a.
Coursed
b.
Un coursed
S"uare ubble masonry a.
Coursed
b.
Un coursed
III.
olygonal ubble ;asonry
IE.
lint ubble ;asonry
E.
5ry ubble ;asonry
(shlar ;asonry I. II.
(shlar ine (shlar rough tooled
III.
(shlar oc$ or Fuarry aced
IE.
(shlar Chamfered
E.
(shlar Bloc$ in Course
1. R)""le 'a!onry
In this type of masonry, stones of irregular si4es and shapes are used. The stones as obtained from "uarry are ta$en in use in same form or they are bro$en and shaped in suitable si4es by means of hammer as wor$ proceeds.
I.
andom ubble ;asonry: In this type of masonry, the stones used are of widely different si4es. This is the roughest and cheapest form of stone masonry. In coursed random rubble masonry, the masonry wor$ is carried out in courses such that the stones in a particular course are of e"ual heights
In un coursed random rubble masonry courses are not maintained regularly. The larger stones are laid first and the spaces between them are then filled up by means of spalls and snee$s.
II.
S"uare ubble ;asonry: In this type of masonry stones ha+ing straight led and sides are used. The stones are usually s"uared are brought to a hammer dri+en or straight cut finish. In the coursed s"uare rubble masonry, the wor$ is carried out in courses of +arying depth
In the Un coursed s"uare rubble masonry, the different si4es of stones ha+ing straight edges and sides are arranged on face in se+eral irregular pattern
III.
olygonal ubble ;asonry: In this type of rubble masonry, the stones are hammer dressed. The stones used for face wor$ are dressed in an irregular polygonal shape. Thus the face %oints are seen running in a irregular fashion in all directions.
IV.
lint ubble ;asonry: I0 this type of rubble masonry, stones used are flints or cobbles. There are irregularly shaped modules of silica. The stones are extremely hard. But they are brittle and therefore they brea$ easily. The face arrangement may be either warsed or un coursed.
V.
5ry ubble ;asonry: In this type of masonry, mortar is not used in the %oints. This type of construction is the cheapest and re"uires more $ill in construction. This may be used for non#load bearing walls such as compound wall etc.
/. Di!ting)i! "et*een Stone 'a!onry an% Bric& 'a!onry S.o
3.
Stone 'a!onry
Cost of stone masonry wor$ is more,
Bric& 'a!onry
Cost of bric$ masonry is comparati+ely less.
because it re"uires more s$illed labor. 5ue to +arious si4es and shapes stone, 6.
complicated lifting de+ices are re"uired in
Bric$s ha+ing regular shape and uniform si4e, it can
the construction.
be mo+ed easily by manual labor. ?ence no complicated lifting.
7.
In the case of stone masonry mortars
In the case of bric$ masonry any mortar car be used.
other than cement will not be ha+ing any bond with the stone surface. 8.
The dead weight is more because it is
The dead weight is less.
comparati+ely hea+y, for the same reason, it is suitable for under water construction.
9.
Stone ;asonry is stronger than bric$
Bric$ masonry is wea$er than stone masonry.
masonry. <.
Thinner walls are not possible.
Thinner walls are possible.
=.
The ;ortar %oints are thic$, hence
;ortar %oints are thin and uniform due to the uniform
pointing is necessary.
si4e and shape and hence the structure becomes more durable and less consumption of mortar.
G.
Stones are more water tight
Bric$ wor$ is less water tight than stone wor$.
H.
lastering is not necessary.
Bric$s absorb moisture from atmosphere and dampness can enter the building hence plastering is essential, it is an extra expenditure to bric$ wor$.
3.
By stone masonry architectural and
Bric$s are used, due to their light weight, in residential
massi+e effects can be de+eloped. ?ence
and commercial building wor$s.
it is used for constructing temples, monumental wor$s, bridges etc.
0. +8plain te Type! of ,looring 3.
;ud and ;uram looring
6.
Bric$ looring
7.
Stone flooring
8.
Concrete looring
9.
1ranolithic looring
<.
Terra44o looring
=.
;osaic looring
G.
;arble looring
H.
Dood or timber looring
3. (sphalt looring The types of flooring can be explained as follows: 3.
')% an% ')ram ,looring
')% flooring
;ethod of Construction: The floor bed should be well prepared and a 69mm thic$ layer of selected moist earth is e+enly spread out and is rammed well so as to get a consolidated thic$ness of 39mm. 0o water is used during the process of ramming. In order to pre+ent formation of crac$s after drying, chopped straw in small "uantity is mixed with the moist earth before ramming. Upon the bed, a thin coat of cement, cow dung plaster is applied e+enly and wiped clean by hand. ')ram flooring
;ethod of construction: In this type of floor, a hard bed is prepared by laying 69cm thic$ layer of hand pac$ed rubble boulders and then wetted and rammed hard. Upon this hard bed, a 39cm thic$ layer of muram with course pieces at the bottom and finer at the top is laid. -+er this layer of muram another 69mm thic$ layer of powdered muram is spread. Dater should then be sprin$led on the entire surface and rammed well. inally o+er the dry hand surface a thin coat of cement plaster is applied e+enly and wiped cleanly by hand. Suitability: ;ud floors are generally used for unimportant buildings particularly in +illages.
(d+antages: They are cheap, hard, fairly imper+ious and easy in construction and maintenance. 6.
Bric& ,looring
;ethod of construction: In this type of flooring the sub grade is compacted properly to the desired le+el. 3 to 37 cm thic$ layer of lean cement concrete or lime concrete is laid o+er the prepared sub grade. This forms the base course, o+er which bric$s are laid in desired pattern on 36mm thic$ mortar bed in such a way that all the %oints are fill with mortar.
Suitability: Bric$ floors are suitable for warehouses, stones and go downs or in places where bric$s are a+ailable economically. (d+antages: This floor is cheap, non slippery, durable, sufficiently hard and easily repairable. 5isad+antages: It is water absorbent
7.
Stone flooring
;ethod of construction: The sub grade is prepared by laying 3mm to 39 mm thic$ layer of cement or line concrete o+er a bed of well consolidated earth. The stone slabs may be of s"uare or rectangular usually 7 x 7mm, 89 x 89mm, < x <mm or 89 x <mm si4e. The thic$ness of stone +aries from 6mm to 8mm. The selected stone should be hard, durable and of good "uality and of uniform thic$ness and the surface. They should be finely chisel dressed on surface and should ha+e their edges true and parallel from side to side. Dhen the stone slabs are properly ser, mortar in the %oints are ra$ed out to a depth of 6mm and flash pointed with cement mortar 3:7. Suitability: This type of flooring is suitable for go downs, sheds, stores, bus, shelter, schools, hospitals etc. (d+antages: Dhere stones are a+ailable in plenty, this floor is economical. It is hard, durable, easy to construct and ha+ing good resistance to wear and tear.
8.
Cement Concrete flooring
;ethod of construction: This flooring is commonly used for residential, commercial and e+en industrial buildings. The floor consists of two components a*
Base Concrete
b*
Dearing Surface
The abo+e components can be explained as follows:
a) Base Concrete: The base course is laid or a well compacted soil, compac ted properly and le+eled to rough surface. The base course consists of =.9 to 3cm thic$ cement concrete. The top surface of the concrete base is roughly finished to de+elop good bond between the base and topping.
b) Dearing Surface: (fter the base concrete has hardened, its surface is brushed with stiff broom and cleaned thoroughly. The entire surface is di+ided into s"uare of rectangular panels not exceeding 6.9m in length. Cement concrete 3:6:8 of thic$ness 69mm to 8mm is then laid in alternate panels. The top surface is beaten and made in a uniform line and le+el and finally it is smoothened by trowelling. The surgace is $ept under curing for 3 days. Suitability: Suitable for residential, commercial, industrial and public building of all types. (d+antages: It is cheap and durable easy to maintain and it is fire resistant.
9.
ranolitic ,looring
;ethod of construction: In this flooring the sub > base preparation and concrete base laying is
done
in a similar manner, as explained for cement concrete flooring. ( finishing layer is gi+en abo+e is made of +ery rich concrete mix with hard stone chips called granolithic finish. To impro+e wearing "ualities, sand may be replaced by crushed granite powder. The surface may be finished smooth with a steel
trowel. The floor area may be di+ided into panels of si4e < x <mm or < x 89mm using threads, if desired. Suitability: This type of flooring is mostly suitable for industrial floors. (d+antages: It is durable, cheap, resistance to abrasion and does not wear easily.
<.
Terra==o ,looring
;ethod of construction: In this flooring the sub > base preparation and concrete base laying is done in a similar manner, as explained for cement concrete flooring. The top layre may ha+e about 8mm thic$ness, consisting of )3* 78mm thic$ clement concrete layer laid o+er the base concrete and )6* about < mm thic$ terra44o is a specially prepared concrete surface consisting of white cement with marble chips of different colors in 3:6 proportion laid in a thin layer o+er a concrete base course. /+en though this flooring is expensi+e, it is decorati+e and has good wearing properties. Suitability: This type of flooring is suitable for hospitals, public buildings, li+ing room and bathroom of residential buildings etc. (d+antages: It pro+ides an attracti+e, clean and durable surface. 5isad+antages: It is more expensi+e.
=.
'o!aic ,looring
;ethod of Construction: ;osaic flooring is made of small pieces of bro$en tile of china gla4ed or of cement, or of marble, arranged in different pattern. These pieces are cut to desired shapes and si4es. This floor is normally laid o+er a hard bed of cement concrete. The top surface of concrete base is cleaned and wetted. -n a small portion of the floor, a layer of rich cement, mortar 3:7 is e+enly spread in a thic$ness
of nearly 3cm and mosaic tiles are laid with hand and set properly in desired pattern. 5ry cement either ordinary or colored is sprin$led and pressed in the %oints. The process is continued for the whole floor. The %oints of the tiles are then rubbed with a carborundum stone. (fter the tiles are set, the surface is completely polished with mosaic polishing machine. G.
'ar"le ,looring
;ethod of Construction: This flooring is laid o+er the prepared sub grade which is cleaned, wetted and mopped properly. ( layer of cement mortar 3:8 is spread in a+erage thic$ness of abour 6mm. ;arble slabs are laid in these bedding mortar, pressed and le+eled. The marble slabs may be rectangular or s"uare in shape and their thic$ness +ary from 6 to 8mm. The %oints between two slabs must be +ery thin. The cement that oo4es out of the %oints is cleaned. The pa+ed area is cured for minimum se+en days Suitability: Suitable for places of worship and for public buildings which re"uire rich appearance, $itchen, bathrooms, operation theatre of hospitals etc. (d+antages: It is attracti+e and easily maintained 5isad+antages: It re"uires high initial cost.
H.
Woo% or Tim"er ,looring
;ethod of construction: Timber flooring is used for dancing halls, auditoriums etc there are two types of timber floors. I. II.
Suspended Type Solid type
The types mentioned abo+e can be explained as follows:
I.
Suspended Type Timber looring: Dhere the problem of dampers is acute, the timber flooring is pro+ided abo+e the ground le+el. In such a case, sleeper walls are constructed at center to center distance of 3.6 to 3.Gm. Dall plates are pro+ided along the sleeper walls. The bridging %oints of timber are nailed to the wall plates at their ends.
II.
Solid Type looring: Dhen the problems of dampers is not acute, timber floors may be supporte d on the ground all along. In this type of flooring, base concrete is first laid in 39 to 6cm thic$ness. -+er it a layer of mastic asphalt is applied. Dooden bloc$ flooring is then laid o+er it.
Suitability: Suitable for dancing halls, auditorium, carpentry halls, in hilly areas, where timber is a+ailable cheaply and in areas where temperature is +ery low. (d+antages: It pro+ides a non > slippery platform and is easy to repair. 5isad+antages: This flooring is not commonly used for residential building due to its cost. 5ampers pre+ention should be carried out before its construction.
3.
A!palt ,looring
;ethod of Construction: ;astic is melted and clean sand is mixed with it and laid in one or two layers on the base of concrete with trowel. ( uniform le+el surface can be obtained by "uic$ trowelling before the mastic losses in plasticity and before it gets hardened. Suitability: It is suitable for use under wide range of ser+ice conditions from light domestic buildings to hea+y duty commercial and industrial buildings, storage houses, foot paths etc. (d+antages: ;astic asphalt flooring is dustless, %oint less and imper+ious. The flooring is easily cleaned and resistant to acids.
. +8plain te Cla!!ification of Roof! The roofs are classified into the following three categories 3.
itched or Sloping oofs.
6.
lat oofs or Terraced oofs.
7.
Cur+ed oofs.
itched roofs ha+e sloping top surface. These are suitable in those areas where rainfallsnowfall is +ery hea+y. lat roofs are considered suitable for building in hot regions, where rainfall is moderate and where snowfall is not there. Cur+ed roofs ha+e their top surface cur+ed. Such roofs are pro+ided to gi+e architectural effects. They are more suitable for public building li$e libraries, theatres, recreation centers etc. Pitce% roof! a7e tree type! namely
3.
Single oofs.
6.
5ouble or urlin oofs.
7.
Trussed oofs.
,lat terrace% roof! a7e t*o type! !)c a!
3.
;adras Terrace roof.
6.
einforced Cement Concrete Slab oof.
Tr)!!e% roof! a7e !i8 type! an% tey are
3.
Oing > ort Truss.
6.
Fueen > ort Truss.
7.
;ansard Truss.
8.
Bel > ast Truss.
9.
Steel Truss.
<.
Composite Truss.
Reinforce% Cement Concrete Sla"!
einforced cement concrete slabs are becoming +ery common in the construction of modern buildings. Cement concrete is wea$ in tension and hence to o+er come this deficiency, steel is pro+ided in the concrete. Thus cement concrete and steel are combined to form reinforced cement concrete construction. There are two types of reinforced cement concrete slabs 3.
Simple .C.C. Slab.
6.
Tee > Beam Slab.
The two types of slabs can be explained as follows:
1. Simple R.C.C. Sla" ( simple slab is suitable for co+ering small spans of room which do not carry hea+y loads. In this roof, the .C.C. slab bends downward causing tension at the bottom fibers. 5ue to this steel bar reinforcements is placed at the bottom of the slab, $eeping a minimum clear co+er of 39mm. ?alf of these bars are bent up near the ends to ta$e up negati+e bending moment. The thic$ness of the slabs depends on the type of concrete used, the span, the floor loads etc. It may +ary from Gmm to 39mm.
2. Tee > Beam Sla" Dhen the width of the room becomes more, the depth of slab increases and hence simple .C.C. slab becomes uneconomical. In Such cases, the floor structure consist of .C.C. beams and slabs cast monolithically. The Tee > Beams act as intermediate supports and the slabs is laid continuously o+er these beams. The beams are supported by columns. Thus the load from the slab is transmitted to the beams and then from beams to columns.
1. +8plain te Cla!!ification of 9intel! !intels are classified into the following types, according to the materials of their construction. 3.
Timber !intels.
6.
Stone !intels.
7.
Bric$ !intels.
8.
Bric$ !intels.
9.
einforced Cement Concrete !intels.
The !intels mentioned abo+e can be briefly explained as follows
1. Tim"er 9intel! Timber lintels are the oldest type of lintels, though they are not commonly used now#a# days, except in hilly areas. The sound and hard timber li$e tea$ is used to span o+er the opening and masonry is constructed o+er it. (s the timber is easily liable to catch fire, only good "uality timber with a coat of suitable preser+ati+e should be used as lintels. The ends of the lintels rest on a mortar base on the walls for a minimum width of 39cm.
2. Stone 9intel! Stone lintels are used in stone masonry structures. This consists of a simple stone slab of greater thic$ness. Stone lintels can also be pro+ided o+er opening in bric$ walls. 5ressed stone lintels gi+e good architectural appearance. The lease thic$ness of the stone lintel is about =.9cm and as a thumb rule thic$ness is ta$en as at least 33 of the length of the opening.
3. Bric& 9intel! Bric$ lintels are not structurally strong and they are used for small opening, generally not exceeding 3 meter span and light loads. They are built up with hard well burnt, copper # colored, free from crac$s and with sharp and straight edges bric$s. The depth of the lintel +aries from 3cm to 6 cm depending upon the span. ( centering or temporary support is re"uired to construct a bric$ lintel.
4. Steel 9intel! Steel !intels are pro+ided where the opening is large and the super imposed loads are also hea+y. It consists of rolled steel %oints or channels sections.
5. Reinforce% Cement Concrete 9intel! einforced cement concrete lintels ha+e replaced practically all other types of lintels because of their strength, rigidity, fire resistance and ease in construction. These can be used on any span. ?ence we can see about the reinforced cement concrete slabs.
11. +8plain te Type! of Stre!!e! an% Strain! Ten!ile Stre!! Dhen an external force produces elongation of the body in its direction. It is termed as a tensile
force. & /xternal tensile load. & esistance induced in material of the body. ( & Cross sectional area of the body.
Ten!ile Strain !et due to the application of the load the length of the member increases from P3Q to )3Rdi*.
The ratio of the increase in length of the original length is called tensile strain
Compre!!i7e Stre!! Dhen an external force causes shortening of the body in the direction of force. It is termed as
the compressi+e force. & /xternal Compressi+e load. & esistance induced in material of the body. ( & Cross sectional area of the body.
Compre!!i7e Strain !et due to the application of the load, the length of the member decreases from P3Q to )3#di*
the ratio of the decrease in length to the original is called as compressi+e strain
Sear Stre!! Dhen a body is sub%ected to two e"ual and opposite forces acting tangentially across the resisting
section, as a result of which the body tends to shear off across the section, then this tangential force is termed as shear force and the stress induced is called as shear stress.
Sear Strain If the bloc$ does not fail in shear, a shear deformation occurs. !et the hori4ontal displacement of the
upper face of the bloc$ be PdlQ. The ration of the trans+erse displacement to the distance from the lower face is called shear strain.
?ence shear strain is the angle in radian through which a body is distorted by a shear force. ?ol)metric Strain The change in +olume of an elastic body due to external force in unit origingal +olume is called
as the +olumetric strain
9ateral Strain Dhen a ;aterial is sub%ected to Uni > axial stress within the elastic limit, it deforms not only
longitudinally but also laterally. Under tension the lateral dimension diminishes and under compression they increase. The lateral deformation per unit original lateral dimension is call lateral strain.
12.e8plain te cla!!ification of "eam! It is classified as follows: 3.
Simply Supported Beam.
6.
igidly ixed Beam.
7.
Cantile+er Beam.
8.
-+er ?anging Beam.
9.
Continuous Beam.
The types of beams mentioned abo+e can be explained as follows. 3.
Simply Supported Beam: If the ends of a beam are supported freely by columns or walls then it is called simply supported beam. In such cases the moment is not induced at supports because it allows rotation.
6.
igidly ixed beam: If the two ends of a beam are rigidly fixed in walls then it is called fixed beam. In such cases, the moments are induced at supports because it will not allow rotation.
7.
Continuous Beam: If a beam is fixed in one end and the other end is free then it is called cantile+er beam. In such cases, the moment is induced in fixed end only.
8.
-+er ?anging Beam: If a beam ha+ing its end portion extended beyond the support, it is called o+er hanging beam.
9.
Continuous Beam: If a beam is supported on more than two supports, then it is $nown as continuous beam. They may or may not be a o+erhanging beam.
13. +8plain pla!tering an% meto%! of pla!tering# lastering is a process of co+ering rough surfaces of walls and ceilings with a thin plastic material called plaster or mortar to obtain an e+en, smooth, regular, clean and durable surface. 'ortar for Pla!tering
Three types of mortar which can be used for the process of plastering are 3.
!ime ;ortar
6.
Cement ;ortar
7.
Dater > roof ;ortar
'eto%! of Pla!tering
The plaster may be applied either in one, two or three coats. Cement laster is usually applies in a single coat. But in certain cases when thic$ness of plaster is more than 39mm or it is desired to ha+e fines finish, plaster is applied in two coats. The usual proportion is cement and 7 sand. ollowing is the procedure for carrying out the plaster in cement mortar 3.
The bac$ground is prepared. The %oints are rac$ed out to a depth of 6mm. The surface is cleaned, washed with cleaned water and $ept wet for < hours before plastering.
6.
If the surface is une+en a preliminary coat is applies to ma$e it e+en.
7.
To get uniform thic$ness of plaster dots are formed with mortar in +ertical lines at 6m inter+als. To fix a dot, a small "uantity of plaster is laid on the surface ma$ing roughly a s"uare of 39cm x 39cm. another dot is fixed +ertically below at a distance of about 6 meters. The two dots are plumbed by means of a plumb bob. (fter fixing the dots, a +ertical strip of mortar $nown as screed. Sufficient number of screeds should be prepared to obtain the uniform thic$ness of the plaster. The cement mortar is placed between the successi+e screeds and the surface is properly finished.
@)e!tion "an&! PART-A 3.
5efine foundation
6.
5efine wall footing
7.
State the methods to impro+e bearing capacity of soil
8.
5efine stress and strain
9.
State hoo$eQs law
<.
Dhat are the types of modulus
=.
5efine youngQs modulus, modulus of rigidity V bul$ modulus
G.
Illustrate the types of bridges
H.
Dhat are types of dams
10. /xplain the basics of interior design and landscaping 33. Drite down the relation between 2oungQs modulus and shear modulus. 36. Drite down the relation between 2oungQs modulus and bul$ modulus. 37. Drite down the relation between 2oungQs modulus, bul$ modulus and shear modulus.
PART-B 3.
/xplain shallow foundation
2. /xplain deep foundation 7.
/xplain types of dams with neat diagrams
8.
/xplain types of bridges with neat diagrams
9. ( bar of 7mm diameter is sub%ected to pull of < O0 . The extension on a gauge length of 6mm is .Hmm and the change in diameter is .7Hmm .calculate the oissonQs ratio and +alues of the three moduli <. explain the basics of interior design and landscaping