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Posts Tagged ‘earthquake proof’

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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Disaster-resistant hemispheric dome made with double ferrocement shells with insulating fill (click to enlarge)

Disaster-resistant hemispheric dome made with double ferrocement shells with insulating fill (click to enlarge)


This 20′ interior diameter, 314 sq. ft. design is my proposed solution to Dustin’s dilemma in Florida for houses that can withstand repeat hurricanes. See How to Build the Strongest Buildings That Can Last Centuries for more details. Features include: lexan windows with removable window and door shutters, monolithic geopolymer slab floor that’s integrated with the walls, build on high ground, plastic mesh that won’t rust, geopolymer plaster both sides, geopolymer pumicecrete or geopolymer perlite fill. Integrating the slab and dome and building on a rubble trench is ideal for seismic zones. In an earthquake, the building would slide back and forth somewhat like an upside down cereal bowl on a kitchen table (meaning the whole house remains intact as one shell).

The design will have to be tweaked for individual homeowner needs, and some details worked out with the engineer. Note how a woodstove is shown to reach a wider audience, even though it’s probably not needed in Florida. The woodstove could be replaced with an emergency water storage and filtration system, etc. A fold-out bed saves space.

Disaster-resistant hemispheric dome made with double ferrocement shells with insulating fill (click to enlarge)

Disaster-resistant hemispheric dome made with double ferrocement shells with insulating fill (click to enlarge)

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World Shelters -- Bags of Shelter

World Shelters -- Bags of Shelter


Today’s post is from the World Shelters website at Appropedia.org.

Bags of Shelter is an earthbag shelter designed for World Shelters to use as transitional shelter for people in Haiti affected by the January 2010 earthquake. World Shelters is a non-profit organization dedicated to producing housing for disaster relief and general humanitarian needs. A four person design team, Humangineers, designed Bags of Shelter as part of Lonny Grafman’s Introduction to Design class at Humboldt State University.

This project was done for our 12-week assignment for Introduction to Design for the Spring 2010 semester. Our client, World Shelters, asked Humangineers to use dirt as a resource in order to provide transitional housing for the people of Haiti. Seven criteria were established by World Shelters and they include: Level of Safety, Use of Local Labor, Durability and Repairability, Ratio of Dirt of the Structure, Cost, Ease of Mass Production and Ecological Impacts.

Humangineers recommends Bags of Shelter because it is a suitable design for World Shelters and meets the client criteria. Bags of Shelter uses dirt as a primary building resource. The design also provides a way for Haitians to stimulate their local economy by making barbed wire and also by building the entire structure itself. Overall, Bags of Shelter is a functional design for transitional housing in Haiti. Humangineers recommends the use of lime plaster as an exterior coating for the structure. The total projected cost for Bags of Shelter is $272.81.

Complete article is at World Shelters Bags of Shelter.

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Reinforced Earthbag Wall Section for Seismic Areas (click to enlarge)

Reinforced Earthbag Wall Section for Seismic Areas (click to enlarge)


I am extremely happy to announce another major first for earthbag building. Precision Engineering has generously provided drawings and specifications for building earthbag structures in seismic areas to meet code. The documents have been combined into one 6-page PDF and are now available online.

Reinforced Earthbag Specifications is a 6-page PDF describing in drawings and text exactly how one might construct a reinforced earthbag wall that would pass most building codes in areas of high seismic risk. This document was prepared specifically at the request of Dr. Owen Geiger and Kelly Hart for use on reconstruction projects in Haiti, but it could be useful wherever reinforced vertical wall structures may be built. We want to acknowledge and thank Nabil Taha of Precision Engineering for his patience and diligence in preparing this document.

This document is now accessible from EarthbagBuilding.com and EarthbagStructures.com with the following disclaimer:

“The information/drawings that follow are just general and preliminary and may not be applicable to your or to any user’s particular project. Users of these opinions/information assume all liability arising from such use. You should retain the service of Precision Structural Engineering, http://www.structure1.com, or a local licensed Professional Engineer for engineering on any specific project. Precision Engineering and http://www.earthbagbuilding.com or earthbagstructures.com make NO warranty, expressed or implied, or assume any legal liability or responsibility for the use and/or application of any material shown here.”

I want to emphasize what an amazing gift this is to the earthbag building community, and to those struggling in stricken areas such as Haiti. As far as I know, this is the first time an engineer has published their drawings and specifications in this manner. It’s truly a pioneering document. There is no big industry driving this movement that can pay for tests that costs hundreds of thousands of dollars, and so we rely on expert advice to take earthbag building into mainstream use.

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Reinforced Mesh Corners (click to enlarge)

Reinforced Mesh Corners (click to enlarge)


The idea presented here is for Haiti and other areas susceptible to earthquakes. It’s a very simple concept, but even small steps like this one can save lives.

The main idea involves reinforcing corners of earthbag buildings with plastic mesh or plastic fencing. For background information, see my previous post on Low Cost Reinforcement of Earthbag Houses in Seismic Areas that discussed the research at the Catholic University of Peru. Blondet, one of the lead researchers on the project, said plastic reinforcement mesh was the strongest method they’ve tested in 35 years of seismic research.

The main addition here is ¼” rebar to secure the plastic mesh. Add ¼” rebar and plastic mesh on both sides of the wall and tie together through the wall with baling twine or nylon cord. Bend the rebar and plastic mesh at the top of the wall and embed in the reinforced concrete bond beam. Embed it in the concrete foundation if you have one. Lower cost chicken wire or fishing net may be adequate for the remainder of the walls. There’s also a 1/2″ internal rebar pin pounded through corner bags. Note: earthbag walls in non-seismic areas typically do not use mesh unless required by code.

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There’s obviously a great deal of concern about the recent earthquake in Haiti. Disasters like this are all too common, and so we’re working hard to develop at least two low cost, easy to build earthquake-resistant earthbag house designs.

We hope to be better prepared in the future with plans ‘ready to go.’ But in the meantime, we are making good progress. Kelly Hart and I have roughed out some basic design details. Adobe engineer Bill Druc has offered to help with the calculations and designer Patti Stouter has offered to do some drawings. Also, numerous organizations have expressed interest in raising donations, sending building materials and trainers, and constructing houses in Haiti. For the latest news, see Comments at Responding to Catastrophe.

Earthbag buildings tend to flex and distort during an earthquake rather than suddenly collapse as wood framed, adobe, brick and concrete block structures do. Barbed wire and plaster mesh hold the bags together in case of collapse, thus greatly reducing risk of people getting crushed.

Key building details for earthquake-resistant earthbag houses in Haiti:
– Use compact shapes for greater seismic resistance: round, curved, hexagonal, octagonal shapes or domes when culturally appropriate.
– Avoid long unsupported walls.
– Foundation: gravel-filled earthbag foundation (double-bagged for strength) on rubble trench. Best to have at least two continuous courses of earthbags below door threshold.
– Barbed wire: two strands of 4-point barbed wire between courses
– Limit the size and number of doors and windows: these may be available from collapsed buildings or acquired locally to save shipping space. No glass in windows, only shutters that can be locked. Concrete breeze block or screened openings can reduce number of windows required.
– Steel-reinforced concrete bond beam: 6” high x 16” wide
– Truss anchors in the bond beam: embed L shaped rebar anchors or truss anchors at 24″ on center and weld or bolt to rafters/trusses
– Lightweight roof: about 3:12 pitch, metal roofing for roofwater catchment
– Plaster mesh: poly fishnet is the lowest cost, won’t rust and can easily be stuffed into barrels full of building materials. (Barrels are later used for roofwater collection.) Add fishnet to both sides of earthbag walls and connect with poly twine.
– Plaster: cement or lime plaster on exterior; earth plaster on interior

Virtually no structure can withstand a direct hit from a major earthquake, but by combining the building details listed above there is a very good chance the structure will hold together even if the walls should topple. While not perfect, this strategy could save countless lives over the current building methods used in Haiti.

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It deeply saddens me to see one disaster after another occurring around the world, especially since much of the tragedy could be prevented by building earthquake-resistant earthbag houses.

The recent earthquake in Haiti is but one more example of this. Theo (Father Marc Boisvert) runs a project for the poor in Haiti. Their earthbag Sun House fortunately escaped unscathed even though nearby structures were devastated. According to Theo’s blog “…no one hurt and no structures damaged.”

Earthbag Sun House in Haiti was undamaged by recent earthquake

Earthbag Sun House in Haiti was undamaged by recent earthquake

Nearby structures were severely damaged

Nearby structures were severely damaged

Note: the Sun House example by itself is not conclusive proof of seismic resistance. More testing is called for, but anecdotal evidence and test results keeps growing and so far is extremely compelling.

Bryce Daigle’s testing and thesis, for example, details how earthbag walls obtain maximum compressive strengths almost 10 times as great as those typically achieved by conventional stud-frame housing in terms of load per metre of wall length. Testing Proves Earthbags Very Strong

Nadir Khalili’s tests in Hesperia, California demonstrated how earthbag structures exceeded the strength of the testing equipment with no deflection or failure, and received code approval in the most dangerous level — seismic zone 4.

Properly built reinforced concrete structures, which can be engineered to high earthquake-resistance, are not affordable in Haiti and countless other areas around the world. So even if building codes are in place, builders in these areas will find a way to circumvent them. That, and excessive codes will prevent people from building affordable housing. After years of studying the situation, earthbag and strawbale construction appear to be the most practical solutions.

Additional resources:
Earthbag Testing page
Post-tsunami Affordable Housing Project
Emergency Earthbag Shelter Proposal
Additional testing is underway by Engineers Without Borders at the University of Florida.

Contact the author from our About Us page for more information.

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