Non-Engineered Earthquake Design Principles for Home Construction or Repair : Prepare for what you c

[modern.fakir]

Non-Engineered Earthquake Design Principles

This page describes a number of low-tech and non-engineered principles for earthquake design. Smart Shelter Foundation works in areas where the construction knowledge is low and material options are limited. But as these rules are universal, they can be applied anywhere!We applied these rules on our mountain schools in Nepal, which only have a ground floor. Here we reinforce the walls with horizontal bands. When we use blocks or bricks in the walls, we also incorporate vertical steel bars into the masonry. The 12 rules of thumb are shown below.We have calculated that adding the following steps to the design, makes your buildings roughly 20% more expensive. Meaning that for a reasonable extra investment, you can significantly reduce the risk of collapse during an earthquake.If you need more information, we will gladly provide you with more technical details. On request we can also make a design for you, and we can forward you to our local partner SEED Foundation in Nepal, if you need assistance with the execution of your building. .

12 Rules of Thumb for single-storey buildings


The following rules of thumb apply for buildings that only have a ground floor. All steps as described are shown in the picture gallery below.


Rule 1. Don’t build on slopes.

• Stay at least 3 meters away from edges, or build retaining walls.

Rule 2. Use simple and symmetric shapes.

• Do not make buildings that are shaped like an L, H, U or any irregular shapes. During a seismic event these will be subject to torsion, and the walls will crack.

Rule 3. Separate the building volumes.

• Cut the building configuration into smaller pieces by creating a gap in between of at least 3 inches, or 8 centimetres. Another option is to create a corridor between the volumes.

Rule 4. Maximum dimensions of volumes.

• Maximum ratio of width versus length = 1 : 3.
• Maximum free span of rooms = 6 meters.
• With rubble stone walls, make buttresses to strengthen the walls. The best to do is to make both interior walls and buttresses.
• Example. In Nepal, we make classrooms with a maximum length of 6 meters. That means that the maximum length of any building volume is 18 meters. If we make a school of 5 classrooms, we divide it in 2 volumes with a gap or corridor in between.

Rule 5. Maximum height of walls.

• With bricks, the maximum height = 30 x wall thickness.
• With rubble stone, the maximum height = 2.80 meters.
• In Nepal we prefer a maximum height of 2.40 to 2.60 meters.

Rule 6. Make horizontal reinforcements at all construction types.

Rule 6a. Minimum 2 beams for minor to medium earthquake zones:

• Plinth beam on top of the foundation.
• Lintel beam at the door level.

Rule 6b. Include 5 beams for heavy earthquake zones:

• Plinth beam on top of the foundation.
• Sill beam under the windows.
• In-between stitches at corners and t-sections.
• Lintel beam at the door level.
• Top beam on top of the walls.

Rule 7. Insert vertical steel in thin walled structures.

Rule 7a. YES at all brick and block masonry:

• 3 bars at corners, from foundation to top beam.
• 4 bars at T-sections, from foundation to top beam.
• Next to all doors and windows, from foundation or sill to lintel beam.

Rule 7b. NO vertical reinforcements at thick and massive stone walls:

• The reason is that is it not possible to lay stones around the steel in the corners and in the t-sections, thus making these connections weaker.
• What is needed is good bonding between stones, by inserting ‘through stones’ in the masonry pattern.
• Use cement mortar, do not use earth mortar.

Rule 8. Maximum dimensions of openings.

• Not exceeding 50% of wall surface.
• Minimum 2 feet / 60 centimetres from corners and t-sections, preferably 90 centimetres.
• Doors must open to the outside, so the exits cannot be blocked in any way during an evacuation.

Rule 9. Light and rigid roofing system.

• For ground floor buildings, we usually make a gabled roof. We prefer not to make stone gables on the walls, but place trusses on the end walls. These we fill up with wooden planks, with ventilation openings.
• The trusses are connected with cross-bracing to make sure the roof system acts as one element.
• We make a ceiling in our classrooms. This makes the whole roofing system more strong. Due to the ventilation above the ceiling, the temperature in the rooms is some degrees lower.
• We discourage the use of a concrete slab roof. These are expensive, and the heavy weight is a disadvantage for the seismic resistance of the whole building.

Rule 10. Regular vertical load path, and no soft storey.

• Make sure all load paths are being led evenly to the foundation and that no columns or loadbearing walls are missing. This may result in collapse.
• Do not put a heavy massed volume on top of a floor with only columns (soft storey). During an earthquake this may create torsion at the heavier volume and result in collapse of the building.

Rule 11. No Loose Elements. During a seismic event, many people get hurt by falling debris and flying elements. This can be prevented by the following measurements:

• Reinforce and properly secure overhangs, chimneys and parapets on the roof.
• Avoid, if possible, the use of roofing tiles.
• Avoid stone gable walls on roofs, preferably place wooden trusses on all end walls and fill these up with planks. This also gives the possibility to make a ventilation system under the roof.
• Avoid free standing walls, or make sure they are properly reinforced with columns or buttresses.
• Make sure that water tanks, solar heaters, and such are properly secured..
• Don’t place small loose elements outside, such as flower pots, billboards and such.

Rule 12. Full dedication and presence on-site. To make an earthquake resistant design is one thing. To make sure it is executed properly is something else. If the masons and carpenters do not how to build it, the structure may not be safe. Needed is:

• Extensive training and constant supervision on the building site.
• Include the recipients from day one, make them owners of their project and let them contribute to the realization.
• Find a dedicated and trustworthy local partner, who knows the area, understands the local customs and identifies the real needs.
• Do not reinvent the wheel and certainly do not guess and hope for the best. Find people that have the knowledge and experience with these specific ways of building.

 

[modern.fakir]

Folks ...we know that we cant stop earthquakes but we can PREPARE FOR THEM. Most of the deaths being reported are due to "POOR CONSTRUCTION TECHNIQUES". These deaths can be avoided by following some simple guidelines posted above !

Lets take an educated approach to fixing things !