Experts speak on strengthening decaying heritage structures

Demolishing and rebuilding heritage structures that develop deep cracks have become common in the city. When maintenance or local repair cannot restore a deficient structure to the required standards, people pitch for a complete or partial demolition and reconstruction. Some may also go in for a total revamp in the name of modernisation. But what people forget is that with each demolition, yet another link to the past is lost. And if this trend continues, Madurai may lose its ‘ancient city' tag one day.

“Heritage structures are the socio-cultural edifices our ancestors have left for us to study and follow. The evolution of technology and how these structures were built to support good ventilation and light are a lesson to the next generation. Some structures are constructed with such superior technology that they are stable even now and stand for ages. People have to be properly educated on this topic to prevent any further damage,” feels art historian K.T. Gandhirajan.

Admitting that lack of awareness is the main reason for such mindless acts, Arvind Kumar Sankar, convenor of Madurai chapter of Indian National Trust for Art and Cultural Heritage (INTACH), says that INTACH has already began documentation of buildings with heritage value in the city but thinks preventing demolition of private heritage buildings is an arduous task. “The Government should motivate owners of heritage structures by announcing sops. Already we are planning to follow what the Puducherry unit has done there. They have signed an MoU with the local body for ‘street scaping', like landscaping. The local body here can contribute by announcing tax concessions for protecting buildings of heritage value. Even if people want to renovate their buildings we have trained professionals to guide them,” he says.

Echoing the same view, G. Vasudevan, past president, Travel Club and Director, Hotel Fortune Pandiyan, says that the State could encourage private building owners by extending soft loans with subsidies and educate them on advantages of preserving the structure. “Private building owners should feel that they are benefited. Their asset should not become a liability. What these people could do is that they can arrange for home stays of visiting foreign tourists to generate some income out of it so that they are enthused to maintain the building.”

But people should also know about the viable alternative of strengthening the building. Demolition and reconstruction as the possible solution for any structural deficiency in buildings have become a thing of the past. With advancing technologies in civil engineering there are economic ways to retain the original strength of the structure.

“The choice between strengthening and demolishing a structure depends on many factors, such as material and labour costs, time during which the structure is out of commission or functioning only partially, and distribution of other facilities. However, the financial benefits of strengthening, as opposed to demolition, can often be considerable, particularly if a simple, quick strengthening technique is available,” says M.C. Sundarraja, Assistant Professor, Department of Civil Engineering, Thiagarajar College.

The structural engineer who has been working in this area for seven years says that the deficient structure could be strengthened through some simple and economic wrapping methods. After trying many wrapping schemes in his research, he has framed design guidelines based on American Codal Provisions for Concrete Structures to predict the most economical wrapping schemes of using glass fibre. He has also reported that about 30 per cent of the original strength can be increased further by the use of fibre-reinforced polymer (FRP) composites externally bonded with the concrete elements.

“Whereas, the conventional technique for strengthening and stiffening metallic structures involves the addition of steel plates to the structure by bolting, riveting, welding, clamping and adhesive bonding. These techniques have been shown to be successful in practice, but there are disadvantages with the utilization of steel plates generally and bonded steel plates in particular,” he says.

According to Mr. Sundarraja, the FRP composites are beneficial in more than one way: it can be tailor made to suit the required shape and specification, the material has high strength and stiffness at a fraction of the weight of steel, transportation and handling becomes easy, less false work is required than for steel plates and the technique can be used in areas where access is difficult.

There are also drawbacks to the use of FRP, its intolerance to the uneven bonding surfaces, possibility of brittle failure modes and material costs. But researchers are working out to set it right.

Experimental and theoretical studies prove that externally bonded FRP composites can be used to improve the desired performance of a structural member such as its load carrying capacity and stiffness, ductility, performance under cyclic and fatigue loading and environmental durability. However, the method is yet to become a mainstream application due to a number of economical and design related issues. In recent years, many researchers have started focussing on this important issue through both experimental and theoretical investigations.

Mr. Sundarraja is working on this emerging research for beams and columns of concrete structures under flexure, compression and shear. He has submitted his findings to many reputed international/national journals and presented papers in conferences.

His research is aimed at predicting proper design guidelines to determine the most economical wrapping scheme of using FRP composites for retrofitting and rehabilitation of concrete and high performance steel structures and implementing the FRP technology to the society.

Once this technique becomes popular, restoration and rehabilitation of buildings of heritage value become easy, he says.

Advantages of strengthening method:

Preserving instead of dismantling

Environmentally free

Protect against failure

Enhance the stability

Economy in strengthening

Advantages of FRP over other materials:

High tensile strength and stiffness

Low weight of the bonded material

Easy installation

Minimum labour cost and site constraints

High strength to weight ratios and durability

Corrosion resistance

Fatigue resistance

Easy applicability and the capacity to cover areas with limited access