‘Enforcement more important than improving building code’A team of structural engineers from the United States with global expertise in disaster assessment has analysed the key reasons for building failures in the recent earthquake
While Nepal’s current building codes and standards should be updated, taking steps to improve enforcement and the quality of construction is more important at this point than improving the Code, the report said. Many recommendations focus on the need for more accountability and oversight to ensure that buildings are not only safe on paper but in practice.
The report focuses on the main types of buildings found in Kathmandu and surrounding areas.
The majority of historic and older construction as well as new homes in rural areas are Unreinforced Masonry (URM) structures, comprised of either brick with mud mortar or adobe construction. These types were the worst performers in the earthquake, although URM structures with cement mortar appeared to outperform URM with mud mortar. The report advises banning mud mortar, with exceptions made only for low-rise buildings in rural areas.
It calls for accountability for the design team and contractors as well as on-site field investigations during construction to ensure that contractors follow the approved documents while erecting or altering buildings.
“The Code can say anything but means nothing if it is not followed or enforced,” the report warned.
The team of 16 experts from the US, New Zealand and Australia assessed over 3,000 buildings in the aftermath of the April 25 earthquake, including homes, schools, colleges, hospitals, heritage sites, high-rise apartments and public buildings.
Newer urban buildings tend to be Reinforced Concrete (RC) frame structures, but only a small percentage, such as high-rise apartments and business complexes, are engineered for the site. The vast majority of RC frame structures follow a prescriptive design using “mandatory rules of thumb” laid out in Nepal’s building codes, and are designed by builders without formal training.
“It is not easy to characterise the performance of these buildings because … significant height violations of the [prescriptive rules] were commonplace,” the report noted. “From what was observed, this design was used for buildings, in some cases, exceeding seven storeys in height resulting in overstressed beams, columns and foundations.”
When those buildings did not violate the code, were not compromised by shoddy workmanship, and were not built on soil that experienced liquefaction, a phenomenon common in former lake-beds such as the Kathmandu Valley where soil in a quake can behave like jelly, they were able to withstand the 7.9 earthquake with minimal damage.
One major cause of collapse, however, was the prevalence of soft storeys, meaning the tendency of buildings to include open storefronts or large open spaces on the ground floor. Another common damage was to infill walls, which was non-structural but could still pose a hazard. The report provides photographic documentation of different types of failures.
According to Yogeshwar Parajuli, commissioner at the Kathmandu Valley Development Authority, the report will be available on the KVDA website. “This report will serve as a useful reference to Nepali engineers and will be circulated widely among different departments,” said Minister for Urban Development Narayan Khadka while receiving the report. The structural engineers with expertise in disaster assessment, retrofitting and historic preservation were brought to Nepal by Global Fairness Initiative (GFI) and worked in partnership with the government of Nepal, Nepal Engineering Association, Brick Clean Group Nepal, Minergy, the Building Back Right campaign and volunteers.
“Many buildings were observed that either did not meet the code or were subsequently modified with interior renovations and vertical or horizontal additions, making them non-compliant,” the report said. “This document contains information that can be used by both engineers and non-engineers, along with lots of tips on what to do to strengthen houses,” said Homraj Acharya, Nepal country director of the GFI.
Based in Washington, DC, GFI has been working in Nepal with local partners and funding from Humanity United to promote sustainability and the elimination of child and bonded labour in the brick industry.
Int’l team’s study of 3,000 buildings
n Need for more accountability and oversight to ensure that buildings are not only safe on paper but in practice
n Report advises banning mud mortar, with exceptions made only for low-rise buildings in rural areas
n Accountability urged for the design team and contractors as well as on-site field investigations during construction
n Vast majority of Reinforced Concrete frame structures designed by builders without formal training
n One major cause of collapse was prevalence of soft storeys—tendency of buildings to include open storefronts or large open spaces on the ground floor