Report by Global Engineers Highlights Main Causes of Building Collapse, Recommends Changes
Kathmandu, Nepal (July 24, 2015) — A team of structural engineers from the US with global expertise in disaster assessment has analyzed the key reasons for building failures in the recent earthquake and provided recommendations in an official report on how to improve the safety of Nepal’s buildings.
“This is the result of very hard work from international experts and will be very valuable, especially for reconstruction of Kathmandu structures. It will also help give a new direction for code development and in developing policies as we go forward for reconstruction,” said Yogeshwar Parajuli, commissioner of Kathmandu Valley Development Authority (KVDA). The report will be available on the KVDA website.
The team of 16 experts from the US, New Zealand and Australia assessed over 3,000 buildings in the aftermath of the earthquake, including homes, schools, colleges, hospitals, heritage sites, high-rise apartments and public buildings.
“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.
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. “The Code can say anything but means nothing if it is not followed or enforced,” the report warned.
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 (NEA), Brick Clean Group Nepal (BCN), Minergy, the Building Back Right campaign and volunteers.
Many recommendations focus on the need for more accountability and oversight to ensure that buildings aren’t only safe on paper but in practice. It calls for accountability for the design team and contractors as well as onsite field investigations during construction to ensure that contractors follow the approved documents while erecting or altering buildings.
“A study of the building codes and standards showed many excellent features. However, 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. “Without effective enforcement, codes and standards cannot be effective at safeguarding against unacceptable losses due to earthquakes. “
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.
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 characterize 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 stories in height resulting in overstressed beams, columns and foundations.”
When those buildings didn’t violate the code, weren’t compromised by shoddy workmanship, and weren’t built on soil that experienced liquefaction, a phenomenon common in former lakebeds such as the Kathmandu Valley in which soil in a quake can behave like jelly, they were able to withstand the 7.8 earthquake with minimal damage.
One major cause of collapse, however, was the prevalence of soft stories, 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 found in the earthquake, such as out-of-plane wall failure caused by lack of anchorage to the roof diaphragm at Durbar High School, along with analysis of the findings, recommendations, and extensive tips on seismic safety and repair after earthquakes.
“This document is created to be useful, so that it contains information that can be used by both engineers and non-engineers, along with lots of tips on what to do to strengthen houses, and information for policy makers with photographic documentation so that non-engineers can also become aware of kinds of common failures were seen and how we can avoid them in the future,” said Homraj Acharya, Nepal Country Director of Global Fairness Initiative (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 labor in the brick industry.
Global Fairness Initiative/Nepal
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