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Posts Tagged ‘seismic resistant’


We’ve had several reports on Project Somos. This video is their May 2011 update. They’re doing outstanding work and I encourage readers to study their website and learn more about how they are building.

Compassion Fruit Society began construction of the eco-sustainable Project Somos Children’s Village near Tecpan, Guatemala. The Village will become the forever home to orphaned and abandoned children. The homes are being constructed using earthbag construction. Each home will have a professionally trained Guatemalan foster mother raising up to seven children.

Previous posts with details about their building system:
Plastering of the First Project Somos Earthbag House
Rate of Earthbag Wall Building
Somos Children’s Village
Interior Bottle Walls
Project Somos in Guatemala

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Keep barbed wire straight and overlap ends in center of wall

Keep barbed wire straight and overlap ends in center of wall


An engineer of note gave us some suggestions on how to improve earthbag corners in seismic areas. The engineer is concerned the barbed wire could shift in a quake. He felt that wire mesh anchors (4- 5 with 1″ long teeth, bent so it stands up nicely) would better secure barbed wire at corners. He preferred the idea of running the barbed wire straight out the end of the wall, around a wire mesh strip at the corner and back into the wall. That way it was nearly tensioned. The barbed wire could also run up and over into the next course.
Wire mesh anchors can better secure barbed wire at corners

Wire mesh anchors can better secure barbed wire at corners


Related:
Reinforced Mesh Corners
Low-Cost Reinforcement of Earthen Houses in Seismic Areas
Source: Special thanks to Patti Stouter of Simple Earth Structures for networking with engineers at a recent earth building conference and coming up with these ideas, the drawing and photo.

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Seismic Resistant Gravel Bag Foundation (click to enlarge)

Seismic Resistant Gravel Bag Foundation (click to enlarge)


Yesterday’s post was about the earthquake resistance of earthbags. Today’s post illustrates what an earthquake resistant gravel bag foundation looks like and explains why this design is so effective. Gravel is an ideal material for this application because it’s durable, reasonably inexpensive, readily available in most areas, has high bearing strength and prevents wicking of moisture up in the wall. Gravel will shift or ‘give’ during seismic activity, thereby relieving stress without causing structural damage.

The gravel is contained in polypropylene bags or tubes, double-bagged for strength. The gravel bags rest directly on a typical rubble trench foundation with a French drain that removes water from under the building. Two courses of 4-point barbed wire between courses reduce slippage and provide tensile strength. Vertical rebar or bamboo pins are placed opposite each other and tied together through the wall with sturdy baling twine. Plaster mesh, fishing net or plastic fencing is tied to both sides for additional seismic resistance. Typical soil-filled earthbags are placed on top of the gravel bags once you’re safely above where moisture can cause problems.

Gravel bag foundations score highly in every category: ease and simplicity of construction, dirt cheap cost, durability (poly bags can last 500 years if protected from sunlight) and earthquake resistance. No concrete forms needed — just a few simple tools such as a shovel. I highly recommend reviewing some previous blog posts on this subject to better understand why earthbag foundations are a favorite among natural builders.
– A similar gravel bag foundation with strawbale walls successfully passed a shake table test in Nevada with forces that surpassed that of the Northridge quake in California.
Earthbag Foundations background info
Scoria or pumice can be used in place of ordinary gravel to create a frost-protected insulated foundation. (Frost-protected foundations save energy and greatly reduce construction costs because you don’t have to dig down to frostline.)
Rubble Trench/Earthbag Foundation
Earthquake-resistant Earthbag Building Details
Low-Cost Reinforcement of Earthen Houses in Seismic Areas
Another Earthbag Foundation Method explains an alternative way of building a foundation with gravel bags.
Rubble Bags
Flood and Earthquake Resistant Earthbag Foundations in Pakistan
Reinforced Mesh Corners
Earthbag/Stone Foundations

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This is another major announcement courtesy of Structure1.com. Instead of building buttresses, which tend to be time consuming and difficult to design correctly for earthquake zones, they recommend using the same specifications we reported earlier for reinforced earthbag walls in seismic regions. The comments below are from the latest email exchange with Structure1.com.

Refer to: ASTM E2392, Standard Guide for Design of Earthen Wall Building system. Please note that this empirical standard is applicable only when engineering design is not available.

Portions of the International Building Code, IBC, and ACI 530. Please note that chapter 5 of ACI allows unreinforced adobe only in Seismic Design Category A. So, it [unreinforced earthen construction] is not allowed in Seismic Design Category B, C, D, E and F. That is to say it is practically not allowed in more than 95% of the world.

If this is the case, reinforcing bars are always required. So, while buttresses add strength to earthbag construction, they are not required as long as we use reinforced steel bars. Buttresses can be eliminated to save money. The project will be more economical and comply with the building code with reinforcing steel bars only.

Once again, we owe a great deal of thanks to Structure1.com for their efforts to move earthbag building to the next level. Note: No one has received any money for any of this work! This is all pro bono work intended to help those most in need.

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Confined Earthbag (click to enlarge)

Confined Earthbag (click to enlarge)


Sometimes incremental changes are the most effective. People are naturally resistant to major changes, but they’ll more readily grasp and utilize small changes. That’s the thinking behind this confined masonry/earthbag system. Confined masonry is one of the most common building systems in the world, with millions of structures built this way.

Confined masonry construction consists of unreinforced masonry walls confined with reinforced concrete (RC) columns and RC bond beams. In Mexico, where confined masonry makes up over 60% of all structures, it is used for lowrise construction and for buildings up to seven stories high. Confined masonry housing construction is practiced in several countries that are located in regions of high seismic risk, including Mexico, Slovenia, Chile, Peru, Argentina, Serbia and Montenegro. A very important feature of confined masonry is that columns are cast-in-place after the masonry wall construction has been completed.

The drawing above shows how to mimic traditional confined masonry using mortared stone or rubble and rebar columns, with earthbags between. Make the columns with steel cages filled with mortared stone or rubble as shown. This is one good way to build long straight walls without buttresses. (Note: mountains of rubble are freely available in Haiti. This system was created to help utilize some of that waste material to rebuild the country sustainably.)

Confined Masonry Construction, by Mario Rodriguez

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[Most text quoted from the referenced article shown below.]
Vernacular earthen houses located in seismic areas are at risk because of their inherent structural vulnerability. Adobe houses, for instance, are strong in compression but weak in tension. Earthquakes pull adobe houses apart, causing great loss of life and property. However, due to economic reasons, earth is the only available building material for many communities in developing countries.

It is possible to provide reinforcement to earthen buildings in order to improve their structural performance and to prevent their collapse during earthquakes. Several low-cost reinforcement techniques developed at the Catholic University of Peru over more than 35 years of research are presented and compared in this paper.

Plastic Mesh Reinforced Adobe

Plastic Mesh Reinforced Adobe


A recent study has been performed at PUCP to evaluate the possibility of using polymer mesh to reinforce earthen buildings (Blondet et al. 2006). The first models were reinforced with different amounts of geomesh and they showed good dynamic response during the earthquake simulation tests: although the adobe walls suffered some damage, collapse was avoided even during very strong shaking. As expected, however, the amount and spread of damage on the adobe walls increased as the quantity of polymer mesh reinforcement decreased. Moderate amounts of strategically placed polymer mesh reinforcement can therefore be used to prevent the collapse of adobe buildings, even during severe earthquakes.

[Note: I read on another website where Blondet, one of the lead researchers on this project, said this method of using plastic reinforcement mesh was the strongest method they’ve discovered in 35 years of seismic research.]

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