| In order to prevent loss and damage to property running into Billions of Dollars and loss of invaluable lives, construction of Ferrocement Structures should be taken up immediately. |
| Reason Mexico experience |
The strong earthquakes that occurred in Mexico in 1999 twice Richer scale 7.2 & 7.4. The Richter scale is logarithmic, and therefore one degree more doubles the intensity of the phenomenon. These earthquakes destroyed or severely damaged thousands of houses,
hundreds of schools and churches and took many lives. The Ferrocement structures such as school, all houses, the class room laboratory, the largest auditorium, all the bridges and small dams that have been designed and constructed were untouched. |
| The above single reason should be sufficient to begin with the Ferrocement constructions in Earthquake Zone. |
| At the same time, research experiments and latest design development can be taken up. |
| Ferrocement is highly ductile and energy absorbing material. |
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| FERROCEMENT- THE LATEST EARTHQUAKE RESISTANT MATERIAL, RETROFITTING &REPAIRS. |
| FERROCEMENT |
is the most efficient material to resist any disaster such as earthquakes, floods, fire, cyclones, enemy, bombardments etc. It has high strength to weight ratio. It is ductile, resilient, energy absorbing better as compared to RCC. When put under load it develops cracks much after crossing elastic limit. Further several cracks develop up to further limits and after this on further loading these cracks widen till the sample will
yield totally. It is because of this property a ferrocement structures frame will not collapse like RCC and therefore there will be least loss of life and property. Ferrocement structures do not collapse but get deformed. A large number of such structures as compared to RCC can be easy to repair. The debris formation will be the least. |
| WORLD TRADE CENTER U.S.A. |
which collapsed on 11th September 2001 due to terrorists
attack,would have collapsed in a different way, if constructed with ferrocement technology.
The impact of aircraft strike would have caused deflection of structures about 10ft. and
restoration after several swings. The aircraft might have been trapped in the wire mesh
network of structures rather not pierced into it. The debris of the structures would have
been trapped in the wire mesh system in the columns, beams, floors, slabs and would not
have fallen down/ with negligible fall. This would cause the least human life loss and
enabled the occupant. Now since the technology is sufficiently developed, it is possible to
construct such structures for earthquake resistance also. |
| We are informing about the performance of Ferrocement structures at different locations as below: |
| INDIA: - |
| Ferrocement structures constructed on small scale in Bhuj, Saurashtra and Ahmedabad have performed very satisfactorily with no crack development at all.
Ferrocement structures constructed in Orissa under direction of HUDCO, have withstood fury of cyclone very satisfactory. |
| CHINA: - |
| A precast ferrocement building (G+4) resisted earthquake better than expected. The building was constructed in 1977, size 19.8 x10 mtrs, total floor area 1000sq. meters. Since last 15years we have no further information about earthquake resistant building in China. |
| MEXICO: - |
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Prof. Alonso Fernandez, Mexico, in his recent e-mail has informed us as below:-
……………Sometimes the earthquakes are stronger, such as two that occurred during 1999 of 7.2 and 7.4 degrees. As you remember, the Richter scale is logarithmic, and therefore one degree more doubles the intensity of the phenomenon. |
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| These earthquakes destroyed or severely damaged thousands of houses, hundreds of schools and churches and took many lives. I am pleased to report that the school, all houses, the class room laboratory, the largest auditorium (My Paper in Ferro-6), all the bridges and small dams that we have designed and constructed were untouched. I am convinced that the geometry of the design helps, but also the elastic nature of ferrocement, that fact that our structures are monolithic and that they are almost completely of ferrocement and do not combine different materials, which necessarily behave differently under this natural phenomenon. These factor are important in preventing damage to our constructions. I should add that several years ago one of my colleagues happened to be walking in front of a 100-m2 auditorium which we had built when an earthquake took place, and he saw that the deformations of the building resembled a jelly when it is carried on a plate, and then recovers its initial form and dimensions when set on the table. ……………. |
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| FERROCEMENT: Material to resist earthquake |
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| 1) |
Ferrocement is thin section high strength structural material highly waterproof, crack formation resistant,energy absorbing material. |
| 2) |
It is manufactured with high cement content, low water cement ratio around 0.4, wire mesh layers, light structural steel, admixtures mainly silica fume super plasticizers, non-metallic fibres, particularly when ferrocement is cast insitu. |
| 3) |
Ferrocement has high strength to weight ratio. Therefore self-weight of ferrocement structure is very less as compared to RCC. The earthquake forces at nodal points of ferrocement structures are less accordingly. Therefore the damage and devastation shall be very less. |
| 4) |
Ferrocement structural members such as beams, floors, columns develop first crack at high value of force reasonably above the elastic point. On further loading more cracks are formed, the same are widened till yield takes place. This point is much larger than the elastic point. At this stage the structure will not collapse but it will deform highly. This development in the structure shall not cause loss of life, heavy damage. The intensity of injury to the people shall be less. The debris formation will be the least. It will be easy to extricate the injured people from the damaged structures. |
| 5) |
In view of wire mesh layers and light structural steel as reinforcement in the skin of beam and column, ferrocement structural frame develops high strength as well as it has high energy absorbing capacity. |
| 6) |
Self-weight of ferrocement water tank on top of the building is less than 50% of similar RCC tank. Therefore damaging force is less. |
| 7) |
Apart from the above earthquake resistant qualities, ferrocement is very much durable since it is crack formation resistant material. It is better waterproof. Crack formation begins to take place after crossing elastic limit reasonably. After this, crack widening takes place at further increase of load. When the load is released the cracks close on their own. |
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| CONSTRUCTION DETAILS : |
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Ferrocement beams, columns are constructed with ferrocement as a skin on the periphery surface. These skins consist of layers of wire mesh, weld wire mesh, HTS wires, MS flats, etc. The core consists of high strength concrete. Some times it is hollow as being done in Mexico. This arrangement increases bending moment, shear, torsion highly. The crack formation can be delayed further by addition of fibres on the surface if feasible. In ferrocement beams and columns MS flats, rings, structural reinforcement in the form of flats angles etc. and round bars, if required after this all, are welded at each and every crossing. Therefore there is induced resistance to deflection during fabrication stage itself. |
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Other features are such that there is high torsion strength and shear strength capacity during fabrication itself. Therefore ferrocement building structures are highly energy absorbing, resilient and ductile. |
Ferrocement slab about 20 to 25mm thick consist of grid of MS flats, wire mesh layers on top and bottom. Weld wire mesh, HTS wires can be used in case thickness is increased. |
Ferrocement structure has properties to face effectively reversal of stresses in the columns and beams of frame. |
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| FERROCEMENT FOR POST EARTHQUAKE REPAIRS AND REHABILITATION: |
| RCC beams and columns loaded upto yield and then strengthened with ferrocement showed strength higher than original strength of beams and columns. Some work in the field has also been done. Many research and experiments to retrofit and strengthening of walls have been carried out since last 15 years. |
