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CONCRETE MASONRY

Hollow and solid concrete blocks are used for construction now a day and are common in most of all regions. Hollow block is defined as that the core-void area are greater than 25% of gross area. Now various types of concrete masonry units are manufactured and are having different shape and size. The concrete masonry units are classified under two heads namely Regular concrete blocks and Hollow concrete blocks. The Regular concrete blocks are manufactured from clause aggregate and are used for load bearing walls. Hollow concrete block units are manufactured from light weight aggregate. Hollow blocks are used for load bearing walls and for non-load bearing walls. The Hollow block should have a face thickness of minimum 5cm. Met area of face should be 60% of gross area. Oval shaped core is advisable and the number of core should be minimum two. Recommended size of block is 39x39x20cm, 39x19x15cm and 39x19x10cm. The aggregate used in blocks manufacture consists of 60% fine aggregate and 40% course aggregate. The cement aggregate mix is 1:6. The strength of blocks should be at least 3N/mm2. Various types of concrete masonry blocks are manufactured for easiness in construction of building. They are stretcher blocks, corner blocks, double corner or pillar blocks, jamb blocks, partition blocks, solid block, Beam or Lintel block, Floor block, Forged brick block, solid brick block, Bull nose block and advanced lintel block. Use of various types of blocks in wall masonry can reduce the cost of construction in form of material saving and labor. Surface finish of concrete masonry blocks are considered by builders under the consideration of easiness of plaster and non-plastered architectural finished wall. The available surface finishes are common finished surface, Glazed finish, Slumped finish, specially faced finish and Colored finish. The common finish surface of hollow blocks has fine to course texture which can be obtained by varying the mix proportion using appropriate aggregates. Glazed finish is used for decorative work. This can be done in such way same to glazing of tiles. Glazed finish concrete in water repellent. Slumped finish is the rough finish obtained by using concrete of required slump. When de molding is done, the block settles and which lead to rough surface. In special finished blocks finishing materials as required is in corporate on the facing side of blocks. Pigments are added to concrete mix to obtain colored block. The cement aggregate ratio shall not be leaner than 1:6. The aggregate should have a mixture of 60% fine aggregates and 40% course aggregate of size 6mm to 12mm. The fineness modular of the mixed aggregate should be between 2.90 and 3.60. Blocks should be taken from the mould or molding platform only when the concrete has sufficiently hardened. Concrete should not have very lean constituency. If hand molding is done the holes should be vertical, proper compaction to be given. Machine casting is more preferable than hand molding, to obtain better finish and strength. After taking the mould out of mould or molding platform they should be kept under shade for minimum 24hours. The blocks should be minimum cured well for one week and completed curing for 15 days more continuously by sprinkler or immersed in water tank. The blocks are stacked with cells vertical. Blocks should be used only after 3 to 4 weeks of completion of curing. The compressive strength of blocks should not be less than 3N/mm2 after 28 days curing. The methods of construction of walls with concrete blocks are same as that of brick masonry. First the corner or end of walls is constructed with few courses of blocks. Mortar is applied to the bottom of the block at horizontal face only. For vertical joints mortar is applied to the projections at side of blocks. The wall portions in between the corners are done to a stretched string between the two horizontal end blocks. The closing blocks should be placed carefully. The lines and levels and pump should be checked for each and every layer of blocks. * The concrete masonry blocks should be dry and should not be soaked in water before masonry work. * It should be assumed that the vertical joints are staggered on laying successive of course of blocks. * The joints should be 5 to 10mm thick and should be uniform. * The mortar used for construction of wall should not be stronger than concrete mix used for production of blocks. * Absorption capacity of outer walls should be less than 10% and inner walls less than 15%. * Due to higher thermal expansion of blocks the wall cracks on corners. Long wall should have cracks even its mid span. At junction of walls solid blocks or hollow blocks filled with concrete to be used. 20cm thick minimum wall thickness is essential under structural durability point of view. Hollow concrete block masonry is having a lot of advantages over the brick masonry. 1. Concrete blocks are of regular size and shape. No dressing work required to level the vertical faces. The construction is rapid. 2. Blocks are light and therefore easy to handle. 3. Due to unit characteristic of lightness, the load transferred to foundation is much less than stone or brick masonry. It is advisable to use hollow concrete blocks where the soil has low bearing capacity. 4. Materials saving are higher. 5. Hollow blocks are structurally stronger than bricks. 6. Thinner wall can be constructed. When increases the floor area. 7. Due to higher size the number joints in masonry are getting reduced, resulting is saving in mortar. 8. Because of hollow space, the resulting wall is having better proportions such as against sound, heat and dampness. 9. Blocks can withstand atmospheric actions. Plastering or any other covering work is not essential.

CONCRETE MASONRY

Specification Works-Residences

Well Build Kerala Architects, Engineers & Valuers Pathanamthitta road, Kumbazha- Phone : 0468 2232023 www.wellbuildkerala.com Well build Kerala is an organization of experienced Architects, Engineer , Builders and structural Renovators. We are having a Team of Experts in each discipline and having up to date technical know how in building industry. We offer building construction on turn Key basis satisfying all type of clients from low level to upper class. We undertake turn key constructions structure renovation and remodeling. We undertake site inspection, investigations, planning, structural design, Foundation design, Detailing of structures, Supervision, Renovation of old and weak prestigious buildings, irrespective of its size and shape. Besides architects and engineers we are having a good net work of experienced technicians, masons, carpenters, plumbers and electricians, and laborers. We offer quality construction in a time bound schedule and handing over of key to the owner in the specified time limit with full satisfaction of the client. We undertake interior decorations, room setting including furniture’s and exterior works and garden setting. Well build Kerala offers construction of residential building, Commercial, Flats & Villas at reasonable rates and on time schedule. Well build Kerala undertakes construction of huge Ferro cement water tanks for rain water harvesting up to 500000 liters capacity and Ferro cement houses. We are experienced structural Renovators .Earth Quake Resistant design , construction and Retrofitting are our specialty. TERMS AND CONDITIONS Time of Completion For single storied building - 4 months For Double storied building - 7 months Mode of payment (a) For finalization of plan by us a service charge up to 1% of estimate PAC will be charged (1/2% for residences) (b) For construction we do works on advance payment as four installments. (a) Fist Installment 30 % of cost of construction. (b) 2nd Installment 35 % of cost of construction (c) 3rd Installment 30 % of cost of construction (d) 4th Installment 5 % on completion (a) For completion of works a grace period of one month is allowable for both parties and for which no extra claim is allowable from both sides. (b) If the construction is delayed more than the grace period due to delayed payments the owner has to pay 1% of estimated PAC extra Administrative charges over and above estimate for each month of delayed payment. (c) Any dispute arises in this contract can only be settled in Judicial Court under Pathanamtitta area. (d) If lab our problem arises in the locality the owner has to take up the matter and give a decision within a fort night. (e) The works will be carried out to mutually agreed terms, conditions and only on signed agreement on Turn Key basis. (f) The works can be carried out for detailed measurement for which rates will be quoted separately. (g) For plinth area rate construction, contract agreement will be prepared giving detailed specifications. For extra works payments are to be paid by owner on completion of specified extra item (h) Water for work should be made available at site. The power required is to procured before commencement of work and electrical charges for construction purpose will be paid by company. SPECIFICATIONS Rates starts From 1400/sft onwards Leveling the site should be due by the owner. The rate quoted for the work is from foundation excavation to handing over of the key. If cutting and filling is required at site for leveling site which can be done on a mutually discussed and agreed rate. Which will be over and above the rate quoted. As per specification the excavation of foundation is 70cm wide and 70 cm deep. Foundation Cement concrete 1:5:10 using 40mm metal for leveling course for average thickness of 12.50cm. Foundation Random Rubble Masonry in cement Mortar 1 : 6 (one cement six and) 60 x 60 cm size for single and Double storied buildings. Basement Random Rubble Masonry in cement Mortar 1 : 6, 50 x 45 cm for single and double storied building Plinth belt Reinforced cement concrete 1 : 2 : 4 using 20mm metal of size 30 x 15 cm for single storied and double storied building. Superstructure Brick work in CM 1:6 for ground floor walls using wire cut bricks 3 meter high and 22 cm wide unless otherwise specified. Lintels and Shades RCC 1: 1. 5: 3 using 20 mm metal 22cm wide, lintels 15 cm thick and shades 60 cm wide and 60mm average thickness. Roof slabs RCC 1:1. 5: 3 using 20mm metal 11 cm thick as per structural requirements, doubly reinforced slab to avoid leak age, all slabs are as per detailed designs. Cement used conforms to I S grades. Reinforcement High yield strength tore steel are used for the work obtained from Reputed Manufacturers conforms to TS 40. Wood works Front doors and window frames with Anjili wood frames and shutters with teak wood. Front door with average Architectural designs. For all inner doors and doors on back or sides door frames with Anjili wood. Shutter of all windows in front with teak wood fully glazed with 4 mm plain glass. Inner and other three side door shutters with Jack wood superior to modern designs and painted. Shutter of all windows in other three sides with jack wood fully glazed with 4 mm plain glass. (Detailed on discussion) Furniture Fitting For front door, front windows brass hinges, tower bolts, brass hooks and eyes are fixed. Rear and side windows inner shutters of doors with steel hinges. Aluminums tower bolts and steel hooks eyes. (Detailed on discussion) Front door is fitted with mortise lock, safety catch, door closer bushes etc. Plastering Roof slab top plaster with cement mortar 1 : 3 with Accoproof compound, under side of shades slabs etc. with CM 1:3, walls plaster inside and outside with CM 1:4, 12 mm thick. All cement used conforms to 43 grades. Flooring Sub base course of cement concrete 1: 5: 10 using 40 mm metal for an average thickness of 50 mm (a) Sit out and hall or drawing room with vitrified tiles of size not less than 45 x 45 cm. (b) Bed Rooms, First Floor Hall are of standard ceramic tiles 40 x 40 cm (c) Toilets are floored with ceramic tiles of average co lour and walls of glazed tiles 1.75 m height with glazed tiles 30 x 20 cm Kitchen Working platform - Mirror Polished granite Slab with steel sink single bowl is provided in Kitchen. Above kitchen slab is fixed with glazed tiles of suitable co lour for 30 cm. height for easiness of cleaning. Concrete pre cast slabs are provided below and above the working platform as desired. Work Area Work area is floored with ceramic tiles of size 30 x 30 cm with skirting 10 cm above floor. Indian type chimney (smoke less) with three ovens were provided. Steel sink, amithara, and concrete slabs are also provided in work Area as discussed. Bed Rooms In all bed room’s space for cupboard left below loft slab, if necessary wooden built in cupboards are fixed with Anjili wood back and Teak wood front and change will be extra. Bath Rooms Wash basin of average co lour with medium fittings, EWC and standard C.P. fittings of deep or equivalent make. Long body taps and fittings with shower are also provided. Geyser connection is also available. Towel rods, soap dish, mirrors, are also fixed. Wash basin 1 No standard white connections and mirror 1 No. provided in Dining Hall or space provided as per plan.(Detailed on discussion and finalize) Disposal System For Sink and wash Basin, Waste disposal pits are provided with concrete cover slab. For disposal of sewage septic tanks (2.40x1.20x2.10 with solid brick walls plastered with flushing coat) with two compartments and soak pits provided with standard designs. Wiring In every Bed room two Fancy light points. I tube point I Fan point and a plug point. Toilets with one exhaust Fan point one bittern light point. Kitchen and work area with 2 light point each and two power plug point as standard. For all wiring circuits standard Cables and switches, plugs, ceiling rose connections etc. Lights, Fancy fittings, Fans etc. are to be brought and fitted by the owner. Also provision of wiring will be done for Generator supply, Pump etc. (Wiring can be settled on the basis of a detailed discussion ). The additional points required will be extra Offer For inverter separate wiring connecting sit out, hall, Kitchen and Two bed rooms are included and can be discussed and finalized. Telephone Phone points in living room, office room and Master Bed room and living room in First floor. (Can be settled on discussion) Water Supply From tank all necessary tap points, lines and fittings will be given and one tap at Front portion 2 Nos. extra at rear portion of house with standard deep Fittings (Fittings will be specified before commencement**) Painting White cement two coats for outside and inside walls with synthetic enamel paint two coats for wood work. Toilet doors Shutters & door frames with fiber unimoulded for Toilet & bath rooms. For details: - Visit www.wellbuildkerala.com info@wellbuildkerala.com enquiry@wellbuildkerala.com Note: The rate noted can vary either lower or higher depending on the specification of general work and architectural finish of structure. * Electrical drawings prepared before the settlement of work ** The water supply and sanitary fittings will be specified in detail and settled on discussion and can be noted in agreement.

Pathanamthitta Office

wellbuildkerala - starts its consultation office at Kumbazha Pathanamthitta Road, Near Ground Water District Office, Behind Akshaya centre , pathanamthitta ,headed by eminent ARCHITECTS and well experienced ENGINEERS TECHNICAL SERVICES on all civil engineering projects are available. Design and Construction of Buildings, Bridges and Irrigation Structures are Undertaken on time – bound manner. Foundation Designs, Structural Designs. Soil study, Project reports and Valuations. Service of Registered Architect , Approved Valuer and Charted Engineers are available . Expert service for Structural Renovation , Retrofitting , Remodeling old houses with or with out extension and correction to vastu principles Our Specialty is Structural Renovation and Islamic Vastu Consultation And building designs based on Islamic Customs and Sunna Time bound Guaranteed Quality construction of buildings on Turn Key basis. All sorts of Civil Engineering Design, Drawings and Projects under taken Architectural Wing Headed By Ar :Favaz A ,B .Arch.A I I A , F I V Engineering wing headed by Er: T ,S. Biju B E (civil), M I E Under the guidance of seniors in the discipline, Well build Kerala team Shaji.K .A . Builder

Pathanamthitta Office

Cracking of Concrete

Cracks in concrete are inherently develop due to shrinkage and heat of hydration. The settings of cement is an Exothermic reaction. The heat of hydration is proportional to cement content present Richer mixes develop more cracks due to heat of hydration. The structure should be designed with minimum or non cracking conditions Cracks due to Thermal cracking can be avoided by reducing the heat of hydration ? Store aggregate in shade during executions ? Use blended cement ? Replace cement partially by pozzolanas ? Cool the aggregate by water/ ice Carbonation Concrete made by pot land cement is highly alkaline due to presence of calcium hydroxide The effect of reduction of P H factor of concrete in presence of carbon dioxide and sulpher dioxide is called carbonation. Water cement ratio to be controlled to reduce carbonation. Test of carbonation can be done by spraying phenolphthalein on surface. Uncarbonated concrete blushes with bright pink colour. Alkali- Silica reactions causes cracking Alkali in cement and silica in aggregate in the presence of water causes cracking in hardened concrete. To reduce cracks ? Use low alkaline cement ? Limit sources of salt, contaminated aggregate and penetration of sea-water ? Limit maximum cement content in concrete to lower value ? Limit reactive aggregate size, quality and react ability ? Limit the presence of moisture Relative humidity <75% Deep arising of cracks, leaking joints etc. ? Use pozzolanic materials blast furnace slag Silica fume, volcanic ash etc. ? use air entertainment to allow expansion ? Limit access to water avoid de- icing salt ensure adequate compaction good finished surface with proper curing Chemical attacks, chemicals in subsoil and ground water, acids in ground water, Sulphate attacks, Chloride attacks, etc speed up formation of cracks Besides the above corrosion is the main reason for cracks. It is termed as the creeping disaster. Here the volume of corrosion products exerts considerable bursting pressure on the surroundings of concrete, resulting in cracks. Hair line cracks directly above reinforcement and running parallel to it are positive visible indications that the embedded reinforcement is corroding. This cracks indicates that the expanding rust has grown enough to split the concrete. Factors influencing corrosion a) PH value b) Carbonation of concrete c) Reaction with chlorides d) Moisture e) Oxygen f) Ambient temperature and relative humidity g) Severity of exposure h) Quality of construction materials i) Quality of concrete j) Cover to the reinforcement k) Initial conditions of curing l) Formations of cracks The above conditions are to be made favorable as per the recommendations of code of practices. Due consideration to be given to the longevity and durability of concrete and the structure under reference . Proper quality control will give positive results. The recommendation for corrosion free rebar’s are explained below. Corrosion Free Rebar’s According to some studies rust formation in first stage increases the bond between concrete and steel. But due to change of Alkaline atmosphere around rebar’s in concrete created by concrete itself as passivating protection and change of P H value from ideal 12.00 to 8.60 due to various chemical actions. Due to the presence of chlorides, sulphates and various ingredients present in atmosphere /environment, water used for mixing, concrete materials, conditions of curing and initial hydration, it is seen that the rusted steel used in concrete in any stage of corrosions including pitting seems unsafe and affect the durability and longevity of structure in its life span. Hence I recommend totally to avoid rusted steel in any manner and in exceptional cases do reinforcement protection / preventing procedure and use for embedment as main reinforcement, stirrups or as tiles Generally the following factors influences the corrosion of reinforcement in concrete such as P H value of concrete, chlorides, sulphates, Moisture, Oxygen ambient temperature, carbonation of concrete and relative humidity. Besides, the conditions of exposure, quality of construction materials, permeability of concrete , cover to reinforcement, initial curing conditions, formation of cracks, high carbon content in reinforcement, high stress levels inadequate grouting of stressed tendons, use of rusted reinforcement prior to embedment, alkali- aggregate reaction, potential difference associated with liquid contact of other materials, stray current and absence of periodic repairs. Corrosion (Rusting of rebar’s) is the destruction of materials due to chemical reaction with the environment, which leads to loss of steel due to formation of rust. Which reduces the alkalinity of concrete through carbonation? Hazards and economic loss occurs due to premature deterioration of steel on buildings and Civil engineering structures. Corrosion deteriorates concrete due to formation of new products - ferric oxide which occupies more volume than steel and exerts and bursting stress on surrounding concrete. Which may (formation of rust) may lead to staining, cracking and spalling of concrete. This process of corrosion is in geometric progression with respect to time. Due to the process of corrosion the cross sectional area of steel reduces. Due to corrosion structural distress occurs due to a) Loss of bond between concrete and steel. b) Cracking and spalling of concrete c) Reduces the cross sections of steel. In pre stressed concrete the loss of minor area may possibly lead to tendon failure. The Process of failure is slow and can be repaired/ strengthened on notice of defects. The increase in volume of oxidized compound in concrete results in tensile force leading to cracks in concrete around steel reinforcement and increases the corrosive environment. (Secondary corrosion which is speedy) The corrosion protections of reinforcement is maintained by the alkalinity of concrete. Which leads to passivation of steel. The reduction of P H value of concrete leads to corrosion of reinforcement. Carbon dioxide and environmental influences reduces the P H value of concrete from 12.6 to 8.00, which removes the protections given by alkalinity around steel by concrete. The Reinforcement in concrete have a gamma ferric oxide passivating layer. It has got its on repair mechanism to protect the passivating layer. For corrosion to occur and to continue oxygen and water are required. The corrosion is higher due to increase in relative humidity. Corroded/ Rusted steel should be avoided fully and use only after taking precaution against corrosions in steel. Damages caused by corrosion are. 1) Formation of white patches Which is due to carbonation and white patches occurs over concrete surface 2) Brown patches along reinforcement This is due to formation of ferric oxide and brown lines are seen on slabs, columns and beams as brown lines 3) Occurrences of Cracks Due to increases in volume of steel area due to corrosion products which exerts bursting pressure on surrounding concrete due to other cracks are developed on concrete along the directions of reinforcement and hair line cracks on surface of concrete indicates rusting process 4) Formation of Multiple Cracks Due to formation of multiple layer of rust on rebar’s, the bond between concrete and steel is considerably reduced and sounds hollow on light hammering. It is seen that cracks in the form of spider net on surface of concrete which is secondary and serious. 5) Spalling of cover of concrete Loss of bond between rebar’s and concrete and reduction of size of rebar’s results in multiple cracks and peeling off of concrete cover. Here the concrete spallen down and corrosions speeds up due entry of air, humidity and full loss of alkaline atmosphere. 6) Snapping of bars Continued reduction of size of bars, results in snapping. This occurs mainly in ties and stirrups first. 7) Buckling of bars & Bulging of concrete Spalling of concrete and snapping of ties cause main bars to buckle which may lead to failure of concrete in the region. Which may lead to structural failure. 8) Preventive Measures in New Concrete – To prevent corrosion, control the water cement ratio, introduction of high - Strength concrete, adoption of higher minimum cement content, strict adherence of thicker concrete cover, proper structural detailing of reinforcement will better up the condition and reduces the corrosion. Reinforcement protections can be done at executions stage itself 1) Cement based coating 2) Galvanizing zinc based paint 3) Epoxy coating 4) Bitumen based paint 5) Phosphatic coating The coating to rebar’s have to satisfy the following a) Ensure uniform coating on the deformed surface configuration of the bars. b) Be flexible enough to allow post- coated bending of the bars. c) Be Mechanically stable to sustain handling, transportation and fabrications of reinforcement. d) Provide the facility of easy application e) Resist corrosion

Cracking of Concrete

Earth Quake Resistant Structures Introduction: Natural calamities are often in the form of flood, cyclones, landslides and earth quakes. Out of which flood and cyclones are predictable on study of sudden temperature changes and variation of atmospheric pressure. But there are no correct way to predict the earth quakes, its intensity and point of occurrence and time of occurrence. In earth quakes, the damages to structure can be reduced by making the structure resistant against damages. Here the joints of building and its openings were maid more durable by providing additional reinforcements giving time to release the load/ forces to escape by making the joints ductile. The ductility of the joints and openings were increased by using good quality steel and by provision of additional reinforcement in order to make the joints hinged. On heavy earth quakes properly designed and construction building gives more time in its life span and there by give proper time to the in makes to gets escape and to save their belongings. a) Occurrence: An earthquake is the result of sudden motion of crustal block on opposite side of fault plane. Here in an earth quake a huge amount of strain energy that have accumulated over a along period of time is suddenly released progressively. A longer period of time in many small shakes, the violence and distresses consequences of major earthquake might be avoided. The radiation pattern of P wave amplitude has four lobes of alternative compression and dilatation. The first motion at the surface of the earth either pushes away from the sources or tags towards it depending on the geometry of focal mechanism. The under ground event causes upwards pressure around the source. The nature of the event can be studied with the focal mechanism, which provides due to its occurrence and nature. Earthquakes are efficient in generating surface waves as that of a powerful under ground explosion. During an earthquake, soft sediments amplify the ground motion enhancing the damages. The damages are more serious when the sediments have high water contents in which causes liquefaction of sediments and so leads to sudden collapse. Earthquake causes random motion of ground. These motions can be resolved in any three mutually perpendicular directions. The random motion vibrates the structure. The intensity of vibration of grounds are governed by magnitude, depth of focus, distance from Epicenter and also the nature of strata on which the structure stands. The structure mainly vibrates in horizontal direction. The in densities of damage/vibrations are a factor of type construction, nature of soil and type of foundation. Besides the above, the main factor is the duration and the intensity of ground motion. The damages can be minimized and can be avoided during an earthquake to a certain extent by introducing proper construction practice. The building should be planned and designed properly giving stress to seismic forces, for which studies should be conducted. The major Earthquake occur rarely any tiny incident on past should never be neglected. Proper planning design and construction can save valuable human life if a major quake occurs too. The property of framed structures should be brought to ductility by reinforcement arrangements where as concrete is brittle in nature. b) Structural Aspects and Considerations: The structure should be as light as possible. The earthquake force is a function of mass. Roof and upper stories of building, in particular as light as possible. As far as possible the building should be monolithic. The part of the building should be tied together on such a manner that the building act as one unit. Floor slab should be continuous through out; they should be connected rigidly or cast with support beams. Alternation and additions to any structure should have a provision of separation from existing structure. If expansion/separation where not possible continuity should be established between new and old structure to get monolith city. As far as possible, projected parts and large cantilever cantle should be avoided. If unavoidable they must be properly reinforced and firmly tied to main structure. The configuration of building is having more importance in case of longevity during an event and after for survival. The buildings should be rectangular in plan to minimize torsion and stress concentrations. The structure should be symmetrical in respect of mass and rigidity. The centers of mass and rigidity of the structure should coincide each other. If not possible in plan, elevation or in mass, sufficient provision should be made for torsion effect due to seismic force in the structural design. Other wise portion containing different rigidities must be separated through crumble sections. When the total length of such portion between separations exceed three times in width. The separation should be preferably about the 1-cm/per store height with a minimum gap of 3 cmts. The foundation of structures should properly found on rocky strata. The grade sub below the entire area of building shall preferably of the same type of the soil. If soil nature differs sand homogeneity is not attained in sub grade soil, to have structural safety and longevity the entire building should be splitter up as different portions by suitably locating separation on crumble sections. No structure should be found on loose soil, which will subside or liquefy during an earthquake. Such liquefaction of sub grade soil may lead to differential settlement and finally structural failure occurs. Building on loose fine sand, soft silt and expansive clays should be avoided as far as possible. If buildings are to be constructed on such soil due to unavoidable conditions, the structure should rest on rigid and properly designed raft foundations or on group of piles driven / castled to firm strata. In case of light construction sub grade below building should be strengthened by sand piling or soil stabilization. As far as possible bearing capacity test may be done at site and detailed soil study conducted, considering the fluctuations in water table and nature of soil available. All R.C.C footings, pile caps should properly connected with reinforced concrete beams at least in two directions right angle to each other the concrete used should have a mix of 20 m and steel used should be conformity with I S codes. For better results and longer life span of structure, laboratory test for strength of steel, cube test for compressive strength of concrete and mix design of concrete for workability, durability and for economy are to be carried out. Generally on framed structures / basements are avoided, in such cases i.e.: grade beams should be placed below the ground. In case of buildings with basement, at plinth level, plinth beams must be insisted. Old type of flat roof or floor should not be done in earthquake prone areas. The traditional Indian type joist support brick floors / hour dies floors; generally the supporting joists gets loosen on horizontal vibrations. If this type of constructions is a must using wooden girders, R.C.C per cast beams, or iron joists. The end of joists should be blocked and joists should be bridged at intervals so that their spacing remains same after an earthquake. In case of roofing, loose Mangalore pattern, Allahabad or country tiles should be avoided. For pitched roof, asbestos sheet, corrugated iron or aluminum sheets shall give better results and damages will be low. All roofing materials should be properly tied to the supporting members. The roof trusses of all buildings should on R.C.C roof band with proper bolt length. When trussed roof adjoins on masonry gable the end of purling should carried on to M.S. plate / beaver which must be adequately anchored to reinforced concrete. The trusses should be braced at tie level with diagonal braces in plan. With gabled end this braces transmit the lateral shear due to seismic forces to end gable walls, and the walls act as shear walls. All walls should be designed as shear walls to take up earthquake forces. The basic principle of earthquake resistant construction is to design and construct the structural element and their connections to have a ductile failure. The ductility in structure will enable the structure to absorb energy during earthquake, which avoid sudden collapse of entire structure. If the structure id ductile the failure will be slow as and release of the strain energy will take 3 more time which can save the valuable human life. Generally fire hazards follows after an earthquake. Hence the structure should be designed and constructed in adherence of rules for fire protection. The structural parts and non-structural parts should be connected in such a way that, due to horizontal vibration on earthquakes the structural parts might lead to damages. The after effects of damages structural parts to non-structural parts should be minimized. Considering the height of building and number of stories in adjoin or part of structures the structures should be separated. In case of box system or frames with bear walls, separation will be 15 mm per floor. The buildings constructed on the basis of moment resistant reinforced concrete frame the gap to be provided 20 mm / stored. If the construction is of moment resistant reinforced steel frame the gap required in 30 mm / stored. In any case the minimum should not be less than 30 mm if the structure is single storied too. In case of separation a complete separation should be given above plinth level. The plinth beams, foundation beams, footing ties and footing may be continuous. In case of separation on long buildings temperature changes are also to be considered. In multistoried framed structure the columns, bearing walls should be duplicated to form exact separations. At separation as far as possible cantilever type slabs should be avoided. Generally framed construction are most often practiced and followed in our areas. This type of construction is suitable for multistoried building and industrial structures. In multistoried constructions it is advisable and safer to have up to four floors. With out more modern technique. Steel multistoried buildings; industrial structures and timber construction are generally vertically load-carrying structures. These are having frames with flexible joints and bracing members. These types of building are to be adequately strengthened against lateral force. This can be done with shear walls type bracing on plan and elevation, which shall resist earthquake forces in any direction. Building with rigid or semi rigid joint with either R.C.C or steel frames are coming under the category of moment resistant frames. The wall are rigid capable of acting as shear walls. This can be reinforced concrete, reinforced brickwork or unreinforced brick work with framing members through shear connectors. Here the total lateral force due to earthquake on the building is taken by frames and wall combinations and is designed accordingly. The frame will resist 25% of total lateral force. The shear wall shall be distributed evenly over the whole building. The designs should be checked for tensional effects. Shear connections between the core and floors should be designed to total shear transfer. All traditional masonry constructions are of box type construction. In this type prefabricated or cast in site masonry, concrete or reinforced concrete walls along both the axis of buildings. The wall supports vertical load, which can also act as shear walls for horizontal load acting on any directions. c) Seismic design of building: Our country is classified and de marked on five seismic zone as show in fig. Occurrences of past earthquake were studied and magnitude of such occurrences was know now. Damage surveys were conducted and the intensities of shocks caused were estimated to reasonable degree of accuracy. Based on the known magnitude, known epicenter and past seismic history of the area and on study of terrain the seismic zoning maps were prepared. The basic horizontal seismic coefficient (ao) for different zones is given in the table 1. The vertical seismic coefficient is taken as half the horizontal coefficient. The seismic coefficient in the table 1 is based on design practice followed and performance of structures on past earthquakes. In an actual earthquake the force exerted on structures would be larger. As there is energy-absorbing capacity in inelastic range the ductile structures are able to resist shock with severe damages. It is necessary that ductility must be built into the structure, as brittle structures will be damaged more extensively. The design seismic coefficient (ah) shall be computed on the basis of importance arc factor (I) for structures and soil foundation factor (ß) As per standard formula ah= ßIao Values of important factor (I) and soil foundation factor (ß) for different condition are given in table 2 and 3. For the purpose of specifying the earthquake resisting features, masonry and wooden buildings are divided into five categories. A to E as shown in table 4 based on the value of (ah). Well-burned bricks and solid concrete blocks having crushing strength of 35 m pa and more only are used for masonry units for single storied buildings. If multistoried buildings are constructed on masonry units the bricks should have higher strength and should be given sufficient thickness for walls. Hollow bricks masonry, stone block masonry can also be used. The mixes for mortar are specified in table five. They can be used for masonry construction for variance categories of buildings. Re-in forced brick masonry is preferable as on corners. When steel re-in forcing bars are provided in masonry the bars should be embedded with adequate cover in a cement send mix not leaner than 1:3 and with a minimum cover of 10 mm. Otherwise cement concrete mix of M15 with a minimum clear cover of 15 mm to achieve good bond and for corrosion resistance. Opening in bearing walls are most weak points during an earthquake. Doors and window opening on walls reduce the lateral load resistance; they should be as small as possible and should be centrally located. The guidelines for leaving openings with size and position of opening are explained in table 6 and fig 3. The top of opening should be at the same level so that continuous band of lintel can be coasted over them. The lintel band should be for the full length of buildings. The still and sides of windows, ventilators should also be strengthened with a sill band of R.C.C in MIS or reinforced brick work. If opening left does not comply with above guidelines, they should be strengthened using R.C.C or R.B.W with high yield strength-deformed bars complying with its specification. The reinforcement bar to be used should be got tested and quality assured before use. In case of any projected windows or ventilators for architectural purples it should be with reinforced brickwork or with R.C.C with a minimum grade of M20 and must be properly anchored to basic bearing walls or frames as case may be. Arches over opening are point of weak ness and should be avoided. If not proper steel ties must be provided. All masonry buildings are to strengthened for seismic forces. Strengthening for various type of building is specified in table 7. The over all strengthening arrangements are to be followed for D&E category of building which consist of horizontal bands of reinforcement at critical levels. Vertical reinforcing bars at corners, junction of walls and gap of opening. Lintel band is a R.C.C band provided at lintel level and all load bearing internal, external, longitudinal and cross walls. Lintel band is provided over partition walls too, which will improve their stability during an earthquake. Roof band is provided immediately below the roof or floor. Such band not is provided underneath of reinforced concrete resting on bearing walls. Gable band is a belt provided at the top of gable masonry below the purling. This is to be done continuous with roof band at elves level. The lintel band, roof band, gable band etc., shall be made of R.C.C of grade not less than M 15 or RBW in cement mortar 1:3. This belts should have full width of wall. Longitudinal steel in R.C.C band is given in the table 8. For full integrity of walls at corners and junctions and effective horizontal bending resistance of band / belts with continuity of reinforcement is essential. These are explained in fig. 6 and 7. Plinth band is a band provided at the plinth level of wall on the top of basement. These are provided where strips footing or masonry are used. Where the soil either soft or uneven. Plinth belt / beam increase the soundness of structure by avoiding unequal settlements. Vertical steel at corners and junctions of walls, which are up to 350 mm thick shall be provided as specified in the table 9 and fig: 8. For thicker walls than 350 mm the area of steel bars shall be proportionally increased. In the category of ‘A’ type building no vertical rod need to be provided. Detailing for achieving ductility should be strictly followed in R.C.C structures located in seismic zone IV and V and all industrial structures having five stories and above with importance factor more than I and seismic zone III. (1) All junction of beam and external columns, the top bottom reinforcement shall be provided anchor age beyond the inner face of column equal to the development length in tension plus 10 times bar at a spacing not more than 150 mm or 6 d. (2) For beams up to 5 m span minimum 6 mm stirrups and more than 5 mm span beam 8 mm stirrers detailed separately. (3) Spacing of stirrups over a length of two times depth of a beam at either end of the beam shall not exceed d/4 and 8 times bar diameter of smaller longitudinal bar, but the minimum spacing of strips can be limited to 100 mm. For remaining length of beam stirrups spacing shall not exceed d/2 i.e. half of depth of beam. (4) Vertical reinforcement in column shall be spliced only in the central half of the height. Ties shall be provided for the entire splice length at a spacing not more than150 mm. (5) Details of ties in column are detailed separately and to be followed. (6) Ties shall be provided in the column face for a length of 10 from face of beam at a spacing of not more than ¼ minimum dimension of column and 100 mm, but the spacing need not be less than 75 mm (fig 13) length 10 not less than (a). Larger lateral dimension of the column (b) 1/6th of clear span of member or (c) 450 mm. (7) In the case of R.C.C footing special confounding reinforcement shall be extended to at least 300 mm into footing as detailed in fig 14. There are always possibilities to have a severe earthquake, which can adversely effect a structure designed and constructed with available data. As far as possible structures are able to respond, with out structural damages and without total collapse in shocks of heavy intensities. Seismic design principles are meant for safety of valuable human life not for protecting property. Whenever structure are designed and constructed provisions in 1893-1984 (Criteria for earthquake resistant design of structures) is 4326-1993 (Code of practice for earthquake resistant and construction of buildings) is 13920-1993 (Code of practice for ductile detailing of structure subjected to seismic force) should be followed. VALUE OF BASIC SEISMICCOFFICIENT (HORIZONTAL) ZONE ao V 0.08 IV 0.05 III 0.04 II 0.02 I 0.01 Table: 1 VALUE OF IMPORTANCE FACTOR, I Structure I Dams 3.0 Containers of inflammable poisonousGasses or liquids 2.0 Important service and community structure such as hospital; water tower and tanks school; important bridges; important power house; monumental structures; emergency building like telephone exchange and fire brigade; large assembly structure like cinemas, assembly hall and subway stations. 1.5 All others 1.0 Table: 2 VALUE OF ß FOR DIFFERENT SOIL, FOUNDATION SYSTEM Type soil Piles passingThrough anySoil but rettingOn soil type (A) Piles notCovered under (A) RaftFoundations Combined orIsolated R.C.CFootings with tieBeams Isolated R.C.C footing with out tie beams or un reinforced strip foundations Well Foundations Type I Rock or Hard Soil 1.0 - 1.0 1.0 1.0 1.0 Type II Medium Soil 1.0 1.0 1.0 1.0 1.0 1.0 Type III Soft Soil 1.0 1.2 1.0 1.2 1.5 1.5 Table: 3 BUILDING CATEGORIES Building Categories Range of ah A 0.04 to less than 0.05 B 0.05 to 0.06 (both inclusive) C More than 0.06 and less than 0.08 D 0.08 to less than 0.12 E Equal to more than 0.12 Table: 4 RECOMMENDED MORTAR MIXES Building Category Proportion of Cement – Lime – Sand A M2 (Cement- Sand 1:6) or M3 (lime – Cylinder 1:3) OrRicher B, C M3 (Cement – Lime – Sand 1:2:9) or (Cement – Sand1:6) Or Richer D, E H2 (Cement – Sand 1:4) or M (Cement – Lime- Cylinder1:1:6) Or Richer Table: 5 SIZE AND POSITION OF OPENING IN BEARING WALLS Position of Opening Detail of opening for building category A and B C D and E Distance b5 from the inside corner of outside wall Min 0 mm 230 mm 450 mm For total length of opening ratio (b1+b2+b3)/ L1 or (b6+b7)/ L2 shall not exceed(a) One storied building(b) Two storiedbuilding© Three storied building 0.060.500.42 0.550.460.37 0.500.420.33 Pier width between consecutive opening b4 Min 340 mm 450 mm 560 mm Vertical distance between two opening and one above the other h3, Min 600 mm 600 mm 600 mm Table: 6 STREGTHENING ARRANGEMENTS RECOMMENDED FOR MASONRY BUILDINGS Building Category Number of storages Strengthening to be provided in all storages A 1) 1 to 3 2) 4 aa, b, c B 1) 1 to 3 2) 4 a, b, c, f, ga, b, c, d,f,g C 1) 1 and 22) 3 and 4 a, b,c,f,ga to g D 1) 1 and 22) 3 and 4 a to ga to h E 1 to 3 a to h Table: 7 Where a- Masonry mortar b- Lintel Band c- Roof band gable band where necessary d- Vertical steel at corners and junction of walls e- Vertical steel at jambs of opening f- Bracing in plan at tie level of roofs g- Plinth band where necessary h- Dowel bars RECOMMENDED LOGITUDINAL STEEL IN REINFORCED CONCRETE BANDS SpanM BuildingCategoryBNo of DiaBars mm BuildingCategoryCNo of DiaBars mm BuildingCategoryDNo of DiaBars mm BuildingCategoryFNo of DiaBars mm 5 or Less 2 8 2 8 2 8 2 10 6 2 8 2 8 2 10 2 12 7 2 8 2 10 2 12 4 10 8 2 10 2 12 4 10 4 12 Table: 8 VERTICAL STEEL REINFORCEMENT IN MASONRY WALLS No of Storages Stores Diameter of HSD Single Bar in mm at each Critical SectionCategory B Category C Category D Category E One - Nil Nil 10 12 Two TopBottom NilNil NilNil 1012 1216 Three TopMiddleBottom NilNilNil 101012 101212 121616 Four TopThirdSecondBottom 10101012 10101212 10121620 Four strayedBuildingPermitted Table: 9 Fig: 1 Fig: 2 Fig: 3 Fig: 4 Fig: 5 Fig: 6 Fig: 7 Fig: 6 Fig: 7

Ferro cement was developed during 1940 Main application of Ferro cement is for construction of water tanks, boat body building, light slabs for housing, Pre cast component for various usages such as waste bins, conical shaped vessels, park benches, pre- cast slabs and beams in building industry, etc, Ferro cement is the combination of rich cement mortar And closely spaced reinforcement in the form of weld mesh and chicken mesh. For circular tanks up to 25 000 Liters capacity 100 x100 mm 10 gauge weld mesh as central core and one layer each chicken mesh 25 gauge are fixed on either side for circular walls top and bottom of tank. The top and bottom are made curved shape and top filter tank 60 cm diameter and 60 cm depth .Full reinforcement cage is first formed by tying with winding wire. Ferro cement is too cost effective. No formwork is required, skilled trained workers are essential for better results. Ferro cement tanks are fully watertight and leak proof, they are monolithic in behavior and crack free and are maintenance and repair free is as closely spaced reinforcement and rich cement mortar acts as a single material .The cost of construction as per specifications is only Rs;2.20 per liter up to 25,000 liters And Rs:2.65 per liter up to 2,00,000 liters. Excavation is made to have a minimum depth of 60 cm Below ground level. The bed should be firm ground. A Flooring concrete 75 mm thick with 40 mm metal to be done to shape to place the reinforcement cage .On Bottom of tank spread 1:3 cement mortar to get a clear cover of 6 to 8mm thickness .The work to be started from inside of tank. Plaster the inside bottom first coat covering the weld mesh and chicken mesh on first day. On the second day the first coat to side circular walls can done with stiff cement mortar 1:3 by placing a moving mould at inside of wall .The first coat to top dome portion and filter portion is to be completed as explained .In order to finish the tank walls grout may be applied and then plastered inside with proper floating and trowel ling . Care should be taken to fill all cavities in between first coat done on cage portion and finishing coat inside. Most important precaution is keep up of water cement ratio and proper curing .The out side of tank is finished on the same way. Care should be taken while selecting materials such cement and sand . The cement should be Portland base and sand must be free from mud and dirt. Required outlets for pipes may be fixed at the time of casting it self.

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