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Engineering Homes on Flat Lots

Engineered Designs for Houses on Flat Lots.

        Retrofit Designs and Foundation Bolts

Engineering and Design for Houses on Flat Lots

 

The Retrofit Engineering is Simpler than you can Imagine.

Understanding retrofit design is by far the most important tool you can have in evaluating contractors’ bids and determining exactly what kind of seismic retrofit your home needs.  A bad design means an expensive ineffective retrofit.  A good design means an affordable effective design.

It works like this:  The building code tells us what the ground acceleration will be in our area in a large earthquake. In the Bay Area it is 0.2gs.  Multiply this by the weight of the house as determined by these exhaustive engineering calculations, and you get a number in pounds that represents the amount of earthquake force that will attack your house.

All hardware is designed to resist a certain force measured in pounds.  A retrofit means you have put in  enough hardware to resist this amount of force and your retrofit is complete.

For example, if a houses weighs 80,000 lbs and we multiply that by 0.186gs (our anticipated ground acceleration) we get 16,000 lbs.  We therefore need to install enough hardware to resist 16,000# of force. That’s it!

If you install too much hardware, or the wrong type of hardware, or not enough, or in the wrong places, or in the wrong way, you can end up with an expensive retrofit that will not withstand a strong earthquake.

This webpage on no cripple wall retrofits describes the mechanics of how this is done

 THIS IS THE FOUNDATION VIEW FROM THE AIR. THE HARDWARE FOR THIS HOUSE MUST RESIT 16,000# OF EARTHQUAKE FORCE. OR 8,000# OF FORCE ON EACH SIDE.

THIS IS THE FOUNDATION VIEWED FROM THE ABOVE. THE HARDWARE FOR THIS HOUSE MUST RESIT 16,000# OF EARTHQUAKE FORCE. OR 8,000# OF FORCE ON EACH SIDE.

 

 

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