Spring 2007
Dear Colleague:

Most of you are now using Retain Pro 2007.
If you haven't upgraded to Retain Pro 2007, here's what we've added...
  • Now design segmental retaining walls, both gravity and with geogrids
  • LRFD option for masonry for more economical designs
  • Option to design pier foundations.
  • A helpful Equation Menu to quick-solve over a dozen often used but complex equations related to retaining structures.
  • Many other improvements throughout, and ongoing enhancements with our AutoUpdate feature.

Upgrade to version 2007 for just $195
(small office license, $295 if upgrading from version 6.1 or earlier).
No waiting! Order, download, and install in 5 minutes!
To order click here, or visit www.retainpro.com.
All orders by 7-31-07 receive a free copy of this new edition...



About these newsletters

These quarterly newsletters update you about happenings with Retain Pro, give you pointers on using Retain Pro, and offer some thoughts on technical issues. We hope you find them useful. If you missed a previous newsletter, they are all posted on our home page. In them you'll find important technical issues we've discussed.

If you downloaded the demo in the last few months and asked to be on our email list you're also be getting this newsletter. If you subsequently bought, excuse the duplicate - or pass it along!

This is our 18th year!

On a historic note, Retain Pro Version 1.0 was introduced in June, 1989! Version 2007 is our ninth upgrade. This averages an upgrade about every two years, which we base upon changes in building codes and your requests for new features.

We've come a long way in these 18 years! Our thanks go to you our users for your suggestions and support!

AutoUpdates

This feature of Retain Pro allows us to alert you to revisions and enhancements to Retain Pro (and yes, we occasionally need to make corrections) which you can download to keep you up to date. The latest AutoUpdate (Version 2007 users) is version 2007-D and includes enhancements and important revisions, particularly to the Pier Foundation option. You can view the changes on our Support page. To access AutoUpdate answer YES when asked to check of updates, or access it from the Settings screen. After this AutoUpdate you should click YES every few weeks to check for any new updates.

Our licensing policy

This is defined on our web site, but we still get questions:
Our "Small office license" is for the 80% of our users who are smaller offices. It allows you to install (using your PAC) on up to four office/home/laptop computers, but only one simultaneous user is allowed. If installed on a server a second simultaneous user will be stopped. The "Site license" is for large offices installing on a network server with unlimited access by any number of engineers, but at one physical site. Branch office discounted licenses are also available. To install on an office computer just follow the download instructions on your order receipt and enter your Product Activation Code (PAC) to activate. If you lose your PAC we can retrieve it for you.

Technical Issues

IBC '03 and '06
There appears to be no significant difference between these two editions regarding retaining wall design, with the exception of the deletion of the onerous masonry lap length equation for ASD design, per IBC '06, 2107.5. This explains why the Retain Pro 2007 printout shows "IBC '03 or '06" when the IBC code is selected.

UBC '97
This code will cease to exist on 12-31-07 and be replaced by the IBC '06 (with California amendments). California engineers are gearing up to make the transition. This ends an 80 year run - the first UBC was published in 1927.

Wind design
Often your design may have an extension of the wall above grade, or be a free-standing wall. In these cases you need to apply wind loads (but not simultaneously with seismic). For wind design IBC '06 refers to ASCE 7-05, which, as many of you have discovered is very complex (it's rumored that it will be vastly simplified in ASCE-7-10, but that's a long wait). ASCE 7-05, Figure 6-20 gives criteria for freestanding walls and signs ("signs" is the same as a fence atop a wall). Note that for freestanding walls and fences atop a wall this requires the resultant wind force to act at a distance above the geometric center equal to 0.05 times the height of the exposed surface. Most designers probably ignore this - in most cases it makes less than 10% difference in results. (An aside: In over 30 years designing walls exposed to wind and using 10-15 psf I've never had one blow down. I wonder what instances prompted this more restrictive code change?). You can model this by putting an equivalent wind point load at 0.05 above the geometric center; this will give you the correct base moment and shear, but not for intermediate heights.

Dowels from footing
For cantilevered walls over five or six feet high it is economical to stop the dowels a height above the footing equal to their development length, then reduce the spacing or size of continuing lapped bars. Usually about a three foot extension above the footing suffices. Here's a useful note: for a triangular soil pressure loading, the moment is reduced to one-half at 0.20 times the retained height. For example, for a wall retaining 10 feet, alternate bars could be dropped above 30" (but not lower than the development length!)

Toe moment factoring
This is an arguable issue: Retain Pro factors the toe moment by a default value of 1.2, which is the IBC dead load factor. This results in a lesser factored toe moment than would result if both the dead load and earth pressure components were factored differently, the latter usually being 1.6. In defense of this position, if the soil pressure is calculated by the Myerhof Method, which assumes a rectangular stress distribution as advocated by some texts (and see Foundation Engineering: Judicious use of LRFD and ASD in foundation design, by Walter P. Hanson, SE, Structural Engineer, May, 2003), the resulting moment if factored by 1.6 for both dead load and soil pressure (conservative!), would be less than using 1.2 for both DL and earth pressure as we now do. This is our justification for using the 1.2 factor for toe soil pressure when a triangular loading is assumed. Hence the 1.2 factor we use is conservative if compared to the Meyerhof Method using a 1.6 factor for both DL and soil pressure. Your comments welcome.

Using a key for sliding resistance
Sliding problems will usually result from property line conditions where there can be little or no footing heel, thus reducing the weight of earth over the heel and therefore reducing sliding resistance due to friction. The usual solution is to use a key under the footing: a deepened trench, such as 12 inches wide, to increase passive pressure resistance. But use caution if the key is deeper than about 20% of the retained height. This could cause what Amrheim (Reinforced Masonry Engineering Handbook) describes as a "paddle-wheel" effect, actually increasing the overturning. The foundation then acts more like an embedded sheet pile. Try other means to increase sliding resistance, such as verifying maximum allowable passive pressure and coefficient of friction, and/or providing some heel extension for additional weight.

Rebar lap lengths in masonry
For ASD, Retain Pro uses IBC 2107.5. However, we missed increasing the lap by 50% if the steel stress exceeds 80% of allowable. We'll fix this in the next AutoUpdate, but in the meantime you will need to increase the lap by 1.5 if the masonry stem stress ratio exceeds 0.80. Seems like overkill, but that's the code. We will also fix our oversight in calculating laps when using LRFD, which should be per IBC 2108.2 and ACI 530-06. Until we correct this you will need to calculate it when using LRFD.

Incognizance award (meaning unaware of what one is doing)

This time it goes to the user who claimed a 12 foot retaining wall worked fine with just an 8" concrete stem! It turned out that on the Stem Design screen he had entered Design Height as the Retained Height, hence zero moments above that level. Remember that on the Stem screen Retain Pro defines the Design Height input as the height above the footing at which level you want to check moments and shears - hence the Design Height of the bottom stem section is always zero.

Remember to check the online User's Tech Forum frequently!

We post announcements there and answer questions posted. To access click on the link on the home page. You will need your email address (the one you used when ordering) and your password.

Changed email address or moved?

To update our records and receive our emails go to the User's Tech Forum and click on Profile.

Suggestions and comments.

If you have suggestions, comments, or corrections on these newsletters, or a technical item to contribute, we want to hear from you. Email me at hbrooks@retainpro.com.

With best wishes,

Hugh

Hugh Brooks, SE
Retain Pro Software

You are receiving this email because you are a Retain Pro user or have downloaded a demo and asked to be on our email list. This email list is for our use only to provide you with information, but if you do not want to receive future copies just email me at hbrooks@retainpro.com and on the subject line type "Cancel", and don't forget to include your company name and email address where you received this.

Retain Pro Software div. HBA Publications, Inc. PO Box 826 Corona del Mar CA 92626 949-721-4099 hbrooks@retainpro.com
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