How safe is your home?

Detail assessment of each building is compulsory to determine severity of damage to the structure


Sujata Awale

Kathmandu

As many as 72,217 houses in the Kathmandu valley alone were fully damaged by the devastating earthquake that hit Nepal on April 25 and its aftershocks. According to data maintained by Nepal Disaster Risk Reduction Portal, 65,694 houses were also partially damaged by the quake.

The frequent aftershocks have also made unseen cracks in the structure, which could be risky. To mark buildings safe, unsafe and usable after maintenance, the government has initiated the rapid visual damage team for assessment with green, red and yellow stickers. Buildings labelled with red stickers are marked unsafe while ones with green stickers are safe to reside in. Similarly, buildings leveled with yellow stickers need some retrofitting before being occupied again.

Engineers suggest not to hurry back to residing in houses that got a yellow sticker without having a detail assessment done. “There is a wrong concept going around that providing external support to walls makes the building habitable,” said Sanu Babu Dangol, Engineer at MinErgy. Citing that detailed assessment is compulsory to determine the severity of the damage, he said, “Only with the detail assessment, professionals can decide what techniques and methods have to be used for retrofitting. External support and filling cracks are just a temporary solution for preventing further possible damage to the building.”

According to Dangol, looking out for external cracks is not sufficient to term the building safe or unsafe. Structure should be inspected with engineering parametres. Citing that most buildings are found structurally weak, Dangol said, “Seventy per cent of buildings in core city areas like Patan have added floors to weak structures, which make them more vulnerable. In many cases there is no alternative than to dismante upper floors and retrofitting the building.”

Although retrofitting is not new to the world, experts state that it is very new technique to Nepal. “We don’t have sufficient manpower to conduct retrofitting techniques on a huge scale. There are many techniques to use such as grouting, injecting, banding, using carbon fiber et cetera which needs expertise,” he added, suggesting to keep inspecting cracks on regular basis as tremors have been frequent.

Damage varies according to the type of the house and the methods to inspect them also vary. “Houses made of bricks, stones with clay mortar not standing vertical, with horizontal, diagonal and vertical cracks means the house is damaged severely and needs retrofit," said Senior Structural Engineer Dr Rajan Suwal. He further said, “In case of RCC structure buildings, if pillars are damaged and have severe cracks on joints of beam and pillar then it is riskier to live in.” Citing that inspection of RCC frame structure should be done from basement (if there is) or ground floor, he said, “The base of the building should be safe to withstand the whole structure. If there are cracks and the structure of the building is not sound, it can collapse.”

According to Suwal, there is a need to inspect the foundation of the building, structures such as beams and columns, state of the building and wall partition to term the building safe or unsafe. "Retrofitting is viable only if it costs something between 10 to 30 per cent of constructing the new building," he said, adding that otherwise demolishing and constructing anew one would be a wise decision. He suggests using buildings carefully as aftershocks are still frequent and most buildings are not structurally sound, which adds vulnerability to city dwellers.

While engineers stated that retrofitting of buildings take time, Director of National Society for Earthquake Technology (NSET), Bijay Upadhyay said, “Resettlement and retrofitting should be done within mid-June if not it will be too late as the monsoon will start by then.” He said, “There should be proper assessment of the severity of the damage to the property at first. Then, data collection should be done whether to rebuild or retrofit the existing structure.”

Upadhyay further added that government assistance for retrofitting is crucial to encourage the general public. He opined that the government should not delay introducing the required policy and work plans for resettlement programmes and implement them as soon as possible. According to him, there are merely 100 trained experts in the country for retrofitting work and NSET plans to provide trainings on retrofitting.

Published on March 16, The Himalayan Times