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HERITAGE BUILDINGS PROTECTION

The Heritage Buildings and Monuments (HBM) in any country are mute testimonials of its glorious past.

These could also become a good source of income by way of tourist attraction. A large number of HBM

in India are facing extinction and with them will vanish remainders of civilization, which once upon a

time flourished in India. These HBM are like a chapter of a history book and it must not be allowed to

close. This paper argues that each of these HBM should thoroughly and systematically be examined and

analyzed before arriving at a preservation strategy.

A cosmetic treatment is not enough. To this effect, a general rehabilitation program and modern

rehabilitation and retrofitting techniques are briefly described. Analytical aspects of the problem are

also presented. In particular, simple mathematical models are described, which may help in locating the

exact source of trouble. These models show that the distress in one location may come from a cause,

which is located far away. In actual practice, the load transfer mechanism may be more complicatedthen these simple analytical models. This can be handled by using the advanced analytical technique

such as the Finite Element Method.

It is suggested that the modern repair methods must be perfected in the laboratory before transfer of

this technology for field application. A comprehensive research program must be initiated and a code of

practice should be developed to facilitate proper execution with best results.

India has a huge spectrum of HBM like temples, forts, mosques and other similar structures. Large

number of these were constructed several hundred years ago when the Indian Civilization was at its

peak. Their architecture, design and construction at the time when computers, code of practice, design

guidelines, research institutions and modern construction techniques did not exist makes one to realize

the wisdom and expertise of our forefathers. These structures have survived for hundreds of years while

most of the modern constructions need repair after couple of years of service. In addition, some of HBM

have elaborate arrangement for rain water harvesting, which could be a lesson to all of us in the time of

scarcity. The following reasons may be responsible for deterioration and degradation of HBM.

1. Action of a natural disaster such as cyclone or earthquake

2. Act of sabotage or a casual accident resulting in a fire

3. Corrosive action of the contact materials

4. Uncontrolled vegetation growth

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5. Natural deterioration due to aging and adverse environmental factors

6. Vibrations due to heavier structural and land use

7. Theft and vandalism

8. National priorities

Typical Damage Scenario

Damage in a typical HBM, which has existed for thousands of years, may take any of the following forms.

It must be mentioned that most HBM have been neglected over a period of time so that damage keeps

on accumulating.

* Cracks

* Loose building blocks, particularly in roof

* Seepage and leakage of water

* Tilting

* Corrosion and discoloring

Plant growth and bird menace Management and proper care of HBM requires funds, R & D support,

motivation and trained manpower. Indian HBMs have suffered in the past on account of all these

factors. Most of the monuments suffer on account of bird menace. The birds seek shelter during the

night and their droppings cause a serious threat to the monuments. The cleaning process is very

expensive and a cost effective solution must be found. Recently, live flacons were deployed to scare way

the birds. But it drew objection from bird lovers. A valid solution could be to design battery operated

robotic falcons which could flap its wings for few seconds every one minute. Such robotic falcons may be

placed at several places around the monument to prevent birds from nesting without hurting the birds.

Photo 1 and 2 illustrate damage scenario in HBM.

Sources of Damage

The possible changes in structural system (or load transfer mechanism) of HBM over a period of time

may be one or more of the following:

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* Change in land use

* Change in eccentricity of loading

* Change in cross section of beams and columns on account of corrosion

* Change at interface of the building blocks

cracking and corrosion

* Change in foundation conditions Differential settlement of foundation

* Seepage of water through cracks

* Action of bacteria, insects and rodents

* Plant growth

Effect of Change in Structural Characteristics

The structural characteristics such as joint rigidity and bearing capacity of ground may change with time.

Such changes shall affect the integrity of HBM. Some examples are as follows.

Support Settlement

Consider the structure shown in Figure 4 in which a beam is resting on two columns. The beam is

designed to resist moderate amount of tensile stresses. Let one of the column settle by some amount

due to differential ground settlement. Such ground settlements may occur due to lowering of watertable and are very common. This settlement introduces bending moment (6EId / L), where E is modulus

of elasticity of beam material, I is moment of inertia of the beam Section and L is length.

There will be corresponding increase in bending stresses, which may Introduce distress in the beam. It

should be noted that the cause of distress in the beam is foundation settlement and not the design of

beam. Therefore, no amount of treatment of beam will solve the problem unless the real cause is traced

and addressed as a part of the preservation strategy.

Change in End Stiffness

Another example is given in Figure 5 in which fixed ends of the beam are losing fixity on account ofdeterioration in the material. A comparison of bending moment and deflection of simply supported and

fixed ended beams under a uniform load of w per unit length shows that the deflection becomes five

times while bending moment increases by a factor of 3. The additional deflection may bring the beam in

contact with some other non-load bearing members and damage them by transfer of load. Again it may

be noted that the damage in the beam or any other neighboring member is due to change in the rigidity

of joints. These unrelated events cannot be diagnosed unless analytical models are prepared and

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analyzed. The above simple analytical models serve to illustrate the theme of this paper. However, these

models may become fairly complicated in other real situations and one may have to use more

sophisticated analytical tools like finite element analysis. It is not a bad idea at all to undertake

preparation of finite element models of all HBMs and collect this information in a data base. As soon as

a problem appears in a HBM, it could be immediately sorted out.

Member Size Reduction Due to Corrosion

Table in Figure 5 shows that the deflection of a structural member depends upon modulus of elasticity

(E) and moment of inertia (MI). Reduction in member size reduces MI, which increases deflection.

Similarly, reduction in E also increases deflection. Reduction in EI changes distribution of BM in statically

indeterminate structures. The consequence of change in BM appears in development of tensile stresses.

On the other hand, due to excessive deflection, some load bearing members come in contact with

nonload bearing members and load transfer in unspecified directions takes place. This is clearly a sign

of trouble.

Damage Due to Incoming Ground Vibrations and Control [3]

Vibration of ground due to movement of heavy vehicles and tourists in and around HBM can be a cause

of distress. Trench construction around HBM could help in controlling such vibrations (Figure 6). These

trenches can be scientifically designed and architects may locate these in an Aesthetically pleasing

manner to blend with the surroundings. The length of Raleigh waves, which depends on the frequency

of excitation, is the controlling factor in the design of these trenches. The design parameters in this case

are the depth and distance of trench from the HBM. The presence of water table, if it is shallow, must be

taken into account. These trenches may be filled with any soft material. Fly ash may be used to

advantage.