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Winter 2006

Dear Colleague:

For those of you who joined us since our Fall Newsletter, we thank you for choosing Retain Pro 2005 - or for upgrading from an earlier version. Our family of users continues to grow - including many more city, county, and state plan review agencies. We hope we're making your retaining wall designs much easier, and with the reliability you expect. On our side, we'll continue to improve by listening to your suggestions, and fixing any problems called to our attention.

If you're a new user, or missed a previous Newsletter, you can read them on our Home page - in them we discuss important technical issues.

NOTE: If you received this Newsletter and you are not the person in your organization who should receive it, please forward it and ask that person to go to and change to the correct email address.

Coming Soon . . .

Two most requested features you've asked for are for pile foundations, and to design segmental walls. You'll have them in our next upgrade, Retain Pro 2006, planned for a May release. It will include several other unique new features we think you'll like. By the way, we use the term "update" (as in our AutoUpdate system) to mean fixes and enhancements to a current version, whereas an "upgrade" is to a new version with added features, such as our upcoming Retain Pro 2006. Of course our upgrades are always optional, and priced modestly to cover our cost of developing requested features and keeping up with code changes. Watch for an announcement on our website. And if you have suggestions for Version 2006 let us know soon - there's still time to include them.

Technical Issues . . .

Retaining liquids.
We frequently get calls discussing this topic, usually referred to as detention ponds or flood walls. Points to remember are to use an active pressure of 64 pcf (a little more than 62.4 since detention ponds are a little dirty) and the same input for density. Obviously you can't use a Vertical Component of Active Pressure (on the Options screen) since water has zero friction. And remember that water cannot seep under the footing or you will have buoyancy that will counter the overturning resisting weight of water over the heel. In other words, then you can't use the weight of water over the heel to resist overturning or sliding. And since it is a "defined fluid" you may be able to use a load factor of 1.1.

Deep keys to resist sliding.
Don't use them. We recommend limiting their depth to about 18 inches. If greater they could have a "paddle-wheel" effect to actually increase overturning.

Adjacent footings.
If they are farther away from the wall than a 1:1 slope upward from the bottom of the stem to the closest point of the adjacent footing, the effect on the wall will be minimal and therefore this loading entry may not be necessary. But if the adjacent footing is an upper retaining wall, see the following...

Piggyback (cascading) walls.
These conditions occur frequently, when there is a retaining wall above and behind a lower retaining wall. These require special concerns since the higher wall will exert an additional lateral force on the lower wall in addition to the pressure exerted by the vertical load. This is a complex loading condition requiring caution. Two simplified approaches are outlined in Basics of Retaining Wall Design, 6th Edition, pages 45-46. However, an additional word of caution: if the upper wall depends upon passive pressure in front of its footing, this "passive soil wedge" will add a higher lateral force on the lower wall, near the top, which should be considered, in addition to the frictional lateral force from the higher wall/footing interface. We will explore this in more depth in the Spring Newsletter.

Check Load Factors for each design.
You might have changed load factors for a specific design, so it's always wise to check these factors when starting a new design. The defaults for IBC '03 for typical retaining walls are: DL=1.2, LL=1.6, H=1.6, W=1.6, and E=1.0. Other combinations may apply for specific conditions. And remember that for UBC/CBC the load factors are different if seismic is included - see UBC '97, 1612.2.1,

The OPTIONS screen.
Be sure to check this screen with each new design, since your choices may have changed. BTW, we don't recommend using the vertical component of active pressure for sliding or to reduce soil pressure - only use it to resist overturning. Some may disagree, which is why we have it as an option.

IBC '06 and ASCE 7-05.
They're out now, mine just arrived. But it will take time for adoption by the various jurisdictions. Expect many simplifications. Their affect on retaining wall design should be minimal, but we will report on them in our Spring Newsletter, and any necessary changes will be in Retain Pro 2006. Eventually you'll need them both ($207. from Amazon. Ouch!) since IBC '06 heavily references ASCE 7 '05..

Have you read: Six reasons Retaining Walls Fail; And Six Cost Effective Fixes?

This Special Report is available on our Home page. It should be interesting and we will welcome your comments and experiences.

Automatic Update System

This feature, new in Retain Pro 2005, assures that you will never miss any patches or enhancements to the program. When you start Retain Pro 2005 there will be a pop-up asking if you want to check for updates. If you click YES it will either tell you none are available (you are current), or it will search your version install date and automatically enable downloading of any needed files. A description of the changes will be posted on the support page for your reference.

Reminder about your Product Activation Code (PAC)

With our PAC system, you don't need a CD to install Retain Pro 2005 on any computer. Just download a demo version from, and insert your PAC. If you lost your PAC, you can retrieve it from

Geotechnical consultant wanted!

We're looking for a geotechnical consultant to assist us with advanced earth retaining structures design. If you know of one who might be interested, please ask him or her to email me at

Reminder: Before calling or emailing technical support:

Please read the technical FAQs which are accessed from the Support page of our website. The answers to many of your questions will be answered there.

And finally: Our website is being totally redesigned!

Look for it to debut in a few weeks. We hope you will like it!

With best wishes,


Hugh Brooks, SE
Retain Pro Software

PS: If you move or change your email address please let us know!
You can make changes easily at:

And if you have suggestions or comments on these Newsletters? Email me at

© 2006 HBA Publications. All Rights Reserved.