The institute’s efforts result in the Indian Standard Code for Post-Earthquake Safety Assessment of Buildings published by the Bureau Of Indian Standards (BIS). The code will be used as part of a post-earthquake survey to determine if affected buildings can be occupied immediately or not.
An earthquake is defined as a sudden violent, shaking of the ground, causing great destruction. But immediate havoc aside, one might experience not only damaged buildings but also damaged power lines, leaking gas and water lines in the aftermath of an earthquake. Plus, there are several aftershocks that can affect the structural integrity of even those buildings that appear unscathed during the actual earthquake itself. To give an idea of how aftershocks can continue for days, months and even years after a large earthquake, Prof. Pradeep Ramancharla, previous head of the Earthquake Engineering Research Centre at IIITH and current Director, CSIR-Central Building Research Institute, mentions the Gorkha district in Nepal recording 480 aftershocks a good two years after its 2015 earthquake. “The affected were waiting out in tents in front of their own homes, uncertain if it was ok to return,” he recalls.
To Occupy Or Not
“In the event of an earthquake, people typically want to know if their homes are occupiable or not,” continues Prof. Pradeep. If buildings are certified as “safe”, then residents can return to their dwellings. But if the structures are unsafe, then structural intervention in the form of retrofitting or strengthening of the structures is recommended by the governmental authorities. In order to have an easy mechanism for quick identification of the occupancy-readiness of such structures, an Indian standard was proposed by the Earthquake Engineering Sectional Committee. The standard uses Level 1 method of assessment which is a ‘simplified qualitative’ one, that is, it assesses damage to buildings through life-threatening factors which are specific to each building typology. “In India, we have around 30 building typologies and each typology has a few sub-typologies”, explains Prof. Pradeep. With the majority of the buildings falling under the category of “masonry”, the standard seeks to provide guidance for two common building typologies – the unreinforced masonry load-bearing buildings and RC framed structures with unreinforced masonry walls.
Simple Visual Survey
What simplifies adherence to the standard is the fact that it involves filling of survey forms based on visual inspection of the buildings and does not rely on any calculations to be performed using geometric dimensions of buildings, or current properties of materials used in the construction of the buildings. Completed survey forms result in colour-coded tagging of buildings. For example, a green tagged building signifies no life-threatening or economic loss-inducing feature present in it and that it can be occupied, while a red tagged building has at least one life-threatening feature and indicates that it cannot be occupied. The standard is applicable to residential buildings, educational institutes – schools, colleges etc, hospitals and healthcare facilities, police headquarters, fire stations, transportation facilities, governance facilities and so on. Cognisant that earthquake safety is a serious matter, it has been proposed that assessment of buildings via surveys shall be done only by a formally trained team of three Safety Assessment Inspectors (SAIs) comprising of at least one architect, and one structural engineer who has a good understanding of the earthquake behaviour of buildings and experience in building construction.
IIITH’s Efforts with AI and Drones
As Convenor of the Working Group that presented the safety standard to the Earthquake Engineering Sectional Committee, Prof. Pradeep mentions that in the past too, efforts led by IIITH resulted in the publication of a primer on rapid visual screening (RVS) consolidating earthquake safety assessment efforts in India, that has since been adopted by the National Disaster Management Authority. In the case of post-earthquake safety assessment, to make the process of assessing building safety post an earthquake even more simple, IIITH has initiated automation of the survey forms required for visual inspection. “The SAIs can directly fill the form using a web-based application on their mobile phones instead of taking printouts of the survey forms,” reveals the professor, adding that the final technical report recommending sealing of the building until further evaluation or marking it as occupiable, will be automatically available. The IIITH multidisciplinary research team has gone a step further than that where safety parameters of buildings can be checked without physical inspection. “Out of 32 parameters listed in the survey form ranging from the kind of soil and foundation conditions to the architectural features and elements, 11 parameters have been successfully captured by drones so far,” says Prof. Pradeep. The remaining parameters can be assessed by inspectors whilst in an office, with the help of images obtained via drone-survey.
Advantages
Physical inspection of structures in the immediate aftermath of an earthquake is risky. That’s where a drone-based inspection comes in handy. “Besides, survey work is labour-intensive too. Using technology speeds up the process manifold, giving us a solution in 7-10 days, which is the need of the hour,” remarks Prof. Pradeep. The survey-based standard has now been officially adopted by the Bureau of Indian Standards (BIS) as a code of practice (IS 18289: 2023). According to Shri Jitendra Kumar Chaudhary, Assistant Director, CED, Bureau of Indian Standards, New Delhi, “The IS 18289:2023 Post-Earthquake Safety Assessment of Buildings Guidelines will guide users to ensure whether a building having suffered an earthquake is safe for occupancy or not through rapid visual survey or detailed assessment. Also, it would help the practising engineers and structural consultants in making the decision for necessary repair or retrofit for strengthening the buildings which are assessed to be critical or unsafe and classified under the “red tagged” category”.
The standard is also now available for the code users and practitioners on the e-sale portal of BIS i.e https://standardsbis.bsbedge.com/