Following the Tiruvottiyur building collapse, activists demanded an overhaul of the Tamil Nadu Urban Habitat Development Board’s (formerly Slum Clearance Board-SCB) ‘building’ quality control mechanism and a review of the quality of older buildings across the state. ”.
The reports also say that the “Tamil Nadu Urban Habitat Development Board (TNUHDB) on Tuesday set up five committees, with the support of Anna University, to assess the quality of its buildings in 62 sites in Chennai that are at least 25 years old. The committees will evaluate and recommend by Friday whether these buildings should be demolished and rebuilt or not.
Also of concern and significance is the statement by the Managing Director of TNUHDB that the buildings of 61 projects out of a total of 123 such projects in Chennai have already been assessed. Out of a total of 22,271 dwellings, 20,453 dwellings were recommended for demolition and reconstruction, or 91% were deemed unusable. It is not clear who carried out this earlier evaluation, or what their terms of reference were. Either way, if the units of the remaining 62 projects also fail to meet standards, then there is a very high chance that another 90% will go under the hammer. Who will bear the cost and what will it mean for other social protection schemes?
Several SCB buildings built 25 years ago are no more than 4 storeys high and are made of a reinforced cement concrete (RCC) frame structure. Basically, if the bearing capacity of the soil has been determined, what is important in such structures is the design of the foundations, the load-bearing elements (columns, beams and slabs) and the quality of the RCC work in the construction. Structural engineers and concrete experts will attest that a good quality RCC frame construction should last 50-60 years with little maintenance. So why are even 25-year-old buildings now seen as a risk?
Here is the loss sequence in poor quality RCC frame structures:
1. It starts with an improper foundation that leads to excessive settlement of the foundation.
2. Such settlements occur within a year of construction and cause cracks in the structure.
3. If cracks occur in the load-bearing members of the RCC (columns, beams and slabs), the steel reinforcement is exposed to external moisture, causing progressive rusting of the reinforcement and loss of strength of the elements. Cracks in non-bearing walls cause no structural problems.
4. Rebar rusting may occur even without settlement cracks if the quality of the concrete is below standard.
5. The failure of the structure occurs over a period of time with the weakening of the members of the RCC gradually reaching the critical slate.
The inspection of the existing structure should therefore focus on the inspection of the members of the RCC.
Make findings public
Accountability and transparency are important to ensure that such incidents do not happen again in the future. It is important to put in the public domain the conclusions and the evaluation of the five committees (as well as the previous evaluation), especially since most of the members are engineers of the TNUHDB itself!
Any recommendation for demolition should clearly detail the distress found, the causes attributed to the distress, and how a final decision was made that the distress was severe enough to recommend demolition. This will help determine what went wrong and can be used as a guideline for the future. The assessment should also consider input from practicing structural engineers, who are likely to have more experience of sites and building repair/rehabilitation, before starting any major work. The residents are the best repositories of what happened in the building that collapsed or are the ones who are destined for demolition. It is important that their story is captured on video and becomes part of the document. Mere technical findings and recommendations alone will not educate the public. Putting the report in the public domain will allow citizens and users to be the watchdogs of future constructions.
The problem with CBS buildings is well known. As the price was affordable and the terms favorable, SCB was able to market the units easily even when they were located in unsuitable sites and the quality of construction was poor and settlement cracks were often found even before construction is completed.
Demolition and reconstruction is big business for funding agencies, developers, owners of high-tech equipment and those in the construction industry. With monetization through densification a priority even for government agencies, reconstruction is likely to be a multi-story, high-rise design.
Safety and quality are important to the buyer and recipient, but high utility costs will negatively impact them. It has often been pointed out that these high-rise constructions are quite unsuitable for the users of these units – especially women, people with disabilities, children and the elderly.
It is therefore necessary to study the real state of the existing buildings and to propose a rational and profitable solution. The rehabilitation of these buildings should be seriously considered. It would be difficult to find land near these locations. The users of these buildings are said to have, over the past twenty-five plus years, taken root in the place closely linked to their lives and livelihoods. Any displacement will have a serious impact on their lives.
The technology of concrete rehabilitation has improved by leaps and bounds and various techniques are available for the repair and rehabilitation of concrete structures in case of concrete failures and defects. The NDT (Non Destructive Testing) of concrete structures will give a clear indication of its rehabilitation capacity.
It can also be kept in mind that construction debris (in the current way of doing things) will end up in landfill and, along with materials for new construction, may not be the best environmental solution.
For the future, some recommendations can be considered — An external quality control mechanism during construction should be in place. Record of visual inspection of each building periodically by the PWD (since it is owned by the government) and interaction with residents should be uploaded to the TNUHDB website.
Finally, the role of a former local councilor was hailed for averting what could have been an even greater tragedy. In our governance scheme, the local elected representative is often the link and interface between citizens and State services. The Tamil Nadu government should immediately hold municipal elections in the state.
(Tara Murali is an architect)