Buildings Earthquake Engineering Nepal Volunteering

Volunteering with Build Change in Nepal

In March and April, I volunteered full-time with the Nepal office of Build Change, an organization that promotes disaster-resistant design and construction in developing countries. I’ve worked with the organization twice before, first as a summer intern in their Haiti office (2012) and later as part of small group in the Bay Area volunteering remotely for their Nepal office (2016 – 2017). Since I already had some familiarity with the Nepal office, I was especially enthusiastic to have the opportunity to work with them in person.

A learning tool for understanding the components of earthquake-resistant stone masonry walls

About Build Change

Build Change works in areas that have earthquake and/or typhoon risk and a building stock that has not been designed to withstand the natural forces caused by these events. They develop improved building designs, train builders to build them, and provide support in construction.

Currently, they have six offices around the world: Nepal, Haiti, Philippines, Indonesia, Colombia, and Guatemala. Offices have generally opened in direct response to a major event, but in the past few years they have been able to open offices focused on preventive action, rather than post-disaster rebuilding.

Build Change focuses on housing, but they occasionally work on school projects. Programs are a mixture of new construction and retrofits (strengthening of existing structures to be disaster-resistant). Where access to good quality materials (such as masonry) prevents an adequate level of construction, they have implemented programs to improve the access to quality materials. For example, in Haiti, where available masonry units were found to have insufficient strength, they launched a program to train the manufacturers of those blocks to use improved practices.

A stone masonry house in Nepal being retrofit

How Build Change works

Typically, the first step in any new program is to develop the house design. Build Change starts by reviewing existing building practices in the area and identifying the vulnerabilities in their structural systems. Recognizing that communities are more likely to permanently change their construction practices if the new design is similar to what they are already familiar with, Build Change makes great effort to use the same materials and similar means of construction to current practice in the area.

Nepal’s rural houses have a distinctive architectural style. One of the main priorities of Build Change’s design is to respect the architectural tradition and use existing construction methods.
At a hardware store with Mobina, checking what sizes of wire mesh are available in one of the program areas. Only widely available materials are used in the design. In some cases, the lack of a particular material can have a significant impact on the design of an element or connection (i.e. the engineering team has to get really creative).

After becoming familiar with housing types in the area, engineers develop ways to enhance the designs so that they provide an adequate level of disaster resistance. Calculations are usually based on the building code of that country or a country with similar practices.

Engineers work closely with architects to make sure that the designs are acceptable to homeowners. Homes are personal spaces influenced heavily by cultural practices, and it is crucial that the design meets the functional needs and cultural norms of their occupants.

It is common for the attics of rural houses in Nepal to be used for storage. Here, corn is stored in the attic of retrofitted house. Architects at Build Change make sure that the design for new construction or retrofits meet the function needs of the homeowners.

To streamline the design, training, and construction processes, a “typical” building design that meets the engineering, architectural, and financial criteria is developed. The typical design provides general requirements that can be applied to a range of houses, usually in the form of minimum dimensions and maximum spacing for the structural elements. Minor modifications are made only to address an individual homeowners’ functional needs.

Once a general design scheme has been developed, Build Change trains builders and government officials on how to construct it. Even though the designs are based on common building methods, they often have a new type of structural element or important modifications to existing practice. These trainings call attention to those changes and help builders adapt their skills to be more disaster-resistant. Issues of construction quality, such as weak concrete strength, are common in the areas where Build Change works, so the trainings also provide guidance on how to provide adequate quality.

A builder preparing aggregate for use in mortar

During construction, Build Change engineers, or trained partners of Build Change, provide inspection or some degree of construction oversight. This part is especially important, because Build Change often works in places where building codes are not enforced.

Builders removing plaster from the walls prior to the start of retrofit construction

Nepal office

The Nepal office opened in response to the Gorkha earthquake, a 7.8 magnitude event that struck on April 25, 2015 in which at least 9000 people died. Generally, rural areas experienced more damage than the cities. As a result, all of Build Change’s programs are located in rural areas.

Partially collapsed buildings are still visible in many parts of rural Nepal.

Four years after the earthquake, Build Change Nepal has a staff of over 100 people. Engineers are split between the main office in Kathmandu and field offices across the country. In the Kathmandu office, engineers and architects develop the designs and resources, support staff work out the logistics, and program managers coordinate with the government and funding partners. In the field offices, engineers provide trainings to builders and oversee construction. During my time, I worked most closely with the engineering team in the Kathmandu office.

Lunch on my last day with Dev and Liva, the amazing leaders of the Engineering Team.

The Nepal office has developed a strong reputation among the Build Change offices for incorporating new technology into their programs. Their technology team has developed several tools for improving the efficiency of data collection and management related to site investigations and construction monitoring. These tools have helped make the design and construction processes more efficient, thus allowing the office as a whole to scale up their impacts.

Stone masonry buildings

Stones are the most readily available building material in rural areas of Nepal, and as a result stone masonry is the predominant building type in those areas. Mortar made from mud (without any cement) is typical.

Stone masonry buildings with mud mortar have several deficiencies that make their performance in earthquakes notorious. The weaknesses in their structural systems and materials make them incapable of resisting significant earthquakes, and their heavy weight further heightens their risk to the safety of occupants. Many stone masonry buildings collapsed or partially collapsed in the 2015 earthquakes, resulting in death and injuries.

Common failure types of stone masonry buildings. Top row: out-of-plane wall failure, gable wall failure. Bottom row: wall cracking due to incomplete floor diaphragm systems, wall delamination

Programs

Up until recently, Build Change Nepal was primarily focused on the new construction of earthquake-resistant stone masonry houses. By the time of my visit, this part of the program had already been well-developed, and the design and construction processes were streamlined to support an ongoing project for thousands of new houses in one of the most affected areas of Nepal.

A new stone masonry house, built with earthquake-resistant elements, in rural Nepal.

With the new construction program already running smoothly, the engineering team has turned their attention toward supporting the retrofit program instead.

Retrofitting is an unfamiliar concept in rural Nepal. The idea of strengthening your existing house to make it earthquake-resistant can be difficult to understand — and easy to misunderstand — when you’re the first person in your village considering the option.

For houses in good condition or easily repairable, retrofitting the existing house is much more cost-effective than building a new one. This means that there is a lot of incentive to promote retrofitting in Nepal. Additionally, houses throughout rural Nepal are surprisingly similar! The similarity of house construction and architectural design made it feasible to develop a retrofit design that could apply over a wide geographical area and to a large number of houses.

Slowly, Build Change is introducing the retrofitting concept in each district of the country, with the hope that the idea will catch on and spread. At the time of my visit, Build Change was retrofitting model houses throughout the country so that people would be more able to understand how their homes would be affected by the retrofit. The design team was also working through solutions to common issues they encountered during construction. Existing buildings always come with a surprise or two (or three), and their efforts to be prepared for these surprises will help streamline the program in the future.

Builders installing rebar for the new concrete ring beam

Retrofit engineering

(Non-engineers may be bored by this section. Feel free to skip to the next one!)

The major elements of a typical stone masonry retrofit design are:

  1. New strongbacks to strengthen the walls “out-of-plane” (i.e. prevents the wall from falling outward or inward)
  2. New reinforced concrete slab strips (and rod bracing) to strengthen the floor diaphragms, so that they are able to safely transfer loads from “out-of-plane” walls to the “in-plane” walls.
  3. New reinforced concrete ring beams at the top of the attic wall to strengthen the attic walls “out-of-plane” (i.e. prevent them from falling outward or inward).
  4. New lightweight gables to reduce the risk of their collapse.
Primary elements of the retrofit design
Top row: (1) strongbacks, (2) slab strips; 
Bottom row: (3) ring beam, (4) lightweight gables

Strongbacks in a retrofitted stone masonry building. The two on the left are reinforced concrete and the one on the right in timber.

Builders digging a new foundation for a strongback
Reinforcement placed for a new ring beam
New slab strips and rod bracing to strengthen the floor diaphragms
Wire mesh for the strengthening of walls in-plane (only required where there are many openings for walls and doors)
Exterior view of a retrofit in progress. Note the concrete poking through the wall, which connects the strongbacks and floor diaphragms to the masonry walls.

What I worked on

I was based in the Kathmandu office, where where I had the opportunity to familiarize myself with the different programs and provide input on engineering designs in development. However, most of my time was spent writing two technical documents:

  • The first document I worked on is an internal reference to guide engineers in the design of shoring. Shoring is a general term for temporary support of a building, and it is installed in a wide range of applications. For example: during installation of freshly poured concrete elements, during building demolition, or post-disaster for support of damaged buildings.
  • The second document I wrote is engineering guidelines for the stone masonry retrofit design. It summarizes the engineering basis of the design and requirements for its implementation. This document will be reviewed by government officials and also be used internally to help new engineers familiarize themselves with the design and its principles.

During my stay, I was also able to visit a few of the retrofit field sites with Mobina, the Quality Assurance Manager. This was one of the highlights of my stay in Nepal. It was a really valuable experience, because I was able to see the retrofits in construction, meet the homeowners, spend time with the field engineers, and see how the engineering teams work through issues in the field.

Out in the field with Mobina and a field engineer from a partner organization

Reflections

My two months were a great balance between learning new things and contributing my own technical skills to interesting and meaningful programs. I enjoyed the opportunity to devote my time to a cause that I believe so strongly in supporting. The engineering team was a joy to work with, and I was consistently impressed with their professionalism and desire to keep improving and expanding their programs to affect more people, more efficiently. I hope to do more of this kind of work in the future.

3 comments

  1. What a well written post – I learned so much! So does Build Change recommend moving away from mud mortar completely? You mentioned Build Change tries to offer designs that work with local building practices/materials to increase adoption, but it sounds like the mud mortar is inherently flawed.

    1. Thanks, Marsha! Really, really good question. In fact, when I was volunteering remotely from the Bay Area in a small group of other engineers (right after the Nepal office opened), we immediately assumed that Build Change would prohibit the use of mud mortar and start requiring builders to add cement to their mortar mixes. As structural engineers trained in California, we couldn’t imagine a solution that involved the continued use of mud mortar, and we made all of our recommendations accordingly. Unfortunately, the office was unable to get builders to adopt cement mortar. Considered in addition to the added cost of other elements needed to make the building earthquake-resistant, the cost of the added cement was not bearable for the homeowners. So, the engineers had to come up with another solution, which was to allow the continued use of mud mortar, but require more reinforced concrete “bands” to make up for the inherent weakness of the mortar. These reinforced concrete bands (which act like belts for the building) are required to make any stone masonry building earthquake-resistant, even if cement mortar is used, so reducing the spacing of the bands was a better solution than changing the mortar mix.

      1. That is so interesting! What a neat example of creatively working around the cultural/local practices.

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