Advantages of pre-fabrication over the monolithic methods of construction:-
1. Partial or total saving of material used for scaffolds.
2. Multiple use of structuring
3. Possibility of far more accurate and better work transits.
4. Cross sections more advantages from the new point of stream
5. Working time can be shortened.
6. Fewer expansion joints are required.
7. Interruptions in concreting can be omitted.
8. The work can be carried out with a high degree of mechanization.
9. Requirements in man power decrease.
10. Helps to avoid the seasonal character of the buildings industry.
11. Re use of the members. In pre fabrication scaffolding materials are needed as a temporary support.
The single set of moulds can be used from 10 to times in case of small members. Only the lateral boards are made of timber and the other parts being usually of R.C. In case of plant prefabrication the moulds are made of steel. If they are made of timber. They are covered with steel steels. The same structuring can be used for casting both small and large members.
Since the members are produced in easily accessible places on the ground better. Workmanship can be obtained the moulding assembly of the reinforcement and the concreting can be performed more precisely due to better workmanship and higher strength can be obtained.
Since the permissible and limit stresses can be higher, cross sections can be decreased resulting in the decreases in dead load. The reduced deed load means less concrete and a decrease surface of structuring resulting in the reduction of prime and the use of cross sections which are structurally advantages namely an I profile or tresses does not cause particular difficulties in prefabrication. The application of such a cross section or a tress instead of a girder would be much more difficult in the case of monolithic structure. Even unreasonable because of the complicated shultering, reinforcement and concreting.
In the monolithic construction the separate builds spaces can be performed only in sequence namely the foundation. There the concrete, reinforcements, then the concreting of the structure. In the ease of prefabrication these constructional process namely the generally started,
beginning of the foundation work. The estimation that about 80% of the time is required for prefabrication and 20% for site works.
The greater part of shrinkage of precast concrete members occurs before their placings because of numerous joints the effect of temperature changes is also far less important and hence the spacing of expansion joints can be increased.
In monolithic structures it is the duty of the foreman to select palces where concreting can be interrupted. A matter not usually fore seen by the designers who does not deal with the problem on the other hand for pre-fabricated structures junctions must be carried out according to plans of later place specified and considered by the engineer.
In the fabrication since the work is carry out on mass scale we cane go in for mechanization instead of manual labour and thereby the quality is considerably improved.
In the case of prefabrication the application of industrial methods makes possible the employee me of hands adequately trained within a few weeks. The work is carried out throughout the year it is always easier to give labourers for works to be done in a permanent plant.
Plant prefabrication is absolutely independent the vagaries of the weather. In the case of site prefab the production of smaller members namely roofing members, wall panels, windows, purlins etc can be made in a covered place. In the case of large members the same is not possible but they can produced at an earlier date during favourable weather conditions. In the case of monolithic construction it is difficult to carryout the work during rainy seasons.
The dismantling of building constructed of precast members and the use of certain of these at other places is possible in the case of pre-fabrication such a thing is highly impossible with monolithic structures.
Production techniques in pre-fabrication
In Concreting : 1. Moulding the concrete to the require shape.
2. Hardening of concrete.
In prefabrication : 1. Refined methods of moulding
2. Accelerate the rate of hardening objectives in the manufacture of pre-fab compoenets are
1. Least amount of labour.
2. Specailist possible production.
3. Imporved quality
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