Summer 2006

Dear Colleague:

Summer has come and gone. They seem to go by faster every year. You've been busy, and so have we. And this "Summer" newsletter is now four weeks into Fall! One reason for the delay is our push to finish Retain Pro 2007, and we're almost there.

First, we want to welcome those of you who have joined us since our Spring newsletter. We hope you are finding Retain Pro 2005 a valuable and time-saving tool! We also welcome the growing number of cities and counties who have joined us - we now number nearly 200 city, county, and federal agencies that have purchased Retain Pro, and whether it's used to speed plan checking, or for design, we hope you like it! And remember that we always welcome your feedback and suggestions.

If you missed a previous newsletter, they are all posted on our home page. In them you'll find important technical issues and we urge you to read them.

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!

Retain Pro 2007 Update

We base our upgrades mainly on adding features you request. Topping the list -- from our latest user survey - was adding segmental wall design, which we have done. Second was LRFD for masonry, also done. And others we think you'll find useful. We hope to release it within a few more weeks.

Some of the new features will be:

  • Segmental retaining walls, both gravity and with geogrids.
  • LRFD option for masonry walls.
  • Ability to enter differing densities on either side of a wall - especially useful for water retention.
  • A helpful Equation Menu to quick-solve over a dozen often used but complex equations related to retaining structures (such as the Rankine and Coulomb equations for both static and seismic conditions, Coulomb failure plane angle, concrete and masonry design equations, Boussinesq equation, embedded foundations, and moment capacities for cast-in-place vertical elements (pilasters, counterforts, concrete filled cells, and others). Just enter the variables and the filled-in equation appears with the solution. Most of these are built into Retain Pro, but it's often a useful time-saver to access them separately for other applications.
  • Improvements to CalcTrac to see how results were calculated.
  • And others may be added periodically via our AutoUpdate feature.

For a list of ALL features in Retain Pro 2005 and 2007 click on List of Features on our home page.

Pricing information and upgrade discounts are posted on our web site.

See our new web site!

Visit us at www.retainpro.com. On our home page you'll find our new Monthly Design Topic (this month: Design of Segmental Retaining Walls). As these monthly topics continue they will be archived for reference.

Coming soon: Basics of Retaining Wall Design, 7th Edition

The new seventh edition of this popular reference will be available by 11/30. Most topics have been expanded and updated, including extensive coverage of the design of segmental retaining walls, counterfort walls, and drilled-pier and pile foundations. Seismic design is updated. Design examples have been added, including segmental retaining walls.

Technical Issues...

Segmental Retaining Walls (SRWs)
These are becoming very popular and many designers want to acquire the expertise. In our last user survey it was by far the most requested new feature, and their design will be included in Retain Pro 2007. Although most vendors of segmental wall systems offer free software and tech support, we believe there is a need for an easy-to-use program that accesses, through a large database, a wide choice of block vendors and geogrids and have their data directly input into the program. We think you'll like this "one stop" approach for your segmental wall design needs. You won't need to download and learn various vendors' software since nearly all the data you'll need is within this program. The industry standard reference for segmental retaining wall design is Segmental Retaining Walls, 2nd Edition, published by the National Concrete Masonry Association (NCMA). (Caution: it's not an easy read!) To help, the forthcoming 7th edition of Basics of Retaining Wall Design will have an extensive section on design procedures to familiarize more engineers with SRW design.

Footing Dowels
How far should dowels extend above the footing? At least for the development length, whether masonry or concrete, or the required lap length to a continuing bar. If the wall is only five or six feet high it probably isn't economical to splice bars. Typical dowel projections above the footing are two- to three feet. These length requirements are displayed on the Stem Design screen.

Here's a useful tip: For a cantilevered wall with triangular earth pressure loading, the moment at the base decreases to one-half at just 20% of the retained height. This means that at the top of the dowels you can usually drop every other bar or decrease the sizes.

Retain Pro computes and displays required lap lengths, but for your reference, see ACI 318-05 Section 12.2 and 12.15 for laps and splices. For a definition of Class A and B splices see Table R12.15.2. For masonry development lengths and laps see ACI 530-05, Section 2.1.10.3, but note that IBC '06 rescinds equation (2-9) and allows use of the familiar ld = 0.002dbfs (48 bar diameters for Grade 60 reinforcing). Caveat: For masonry walls, if there are changes in block width, be sure to allow sufficient length between step-backs to accommodate bar laps.

When to use Vertical Component of Active Pressure
We've written on this subject in previous newsletters, but here is a caution:
Although the Options screen gives you the choice of using this vertical force (applicable when sloped backfills) to reduce soil pressure, sliding, and/or overturning, our recommendation is to use it only for overturning resistance. Since this is controversial, we offer the three options. But the mobilization of this force, assumed to act vertically at the rear of the heel, seems more valid at incipient overturning than to reduce soil pressure and sliding. Bowles concurs in his Foundation Analysis and Design, 5th Edition, but there are other opinions, hence the choices. Have an opinion? Post it on the User's Forum.

Watch your vertical axial loads!
Since Retain Pro is not a "footing program" per se, we recommend limiting axial loads to around 3,000 plf, which should handle nearly all load conditions. This magnitude load results in nearly negligible stem axial stress, and slenderness ratios of retaining walls are small, often less than ten. If an extremely high axial load is imposed it could reverse the bending in the heel for which the program is not intended to handle, and this must be avoided (you can detect this if you observe the heel moment decrease to zero with increased axial load). Also remember that if the axial load is a point load on the wall, it will spread over a footing length about equal to the height to the point load, therefore, a point axial load entered should be proportionally reduced when entered.

Seismic kh factor, again
This was discussed in an earlier newsletter, but here is an update: IBC '06 requires retaining walls to be designed for seismic forces if Seismic Design Category D, E, or F applies (see Table 1613.5.6-1), and if SDS accelerations are 0.50g or greater. This is in Section 1802.2.7, which states that unless a site-specific report is provided by a geotechnical engineer, the value of kh (design acceleration) should be a ground acceleration equal to SDS / 2.5. This is further clarified in the NEHRP (FEMA) Handbook, 2003, Part 2, Commentary, Section 7.5.1. Retain Pro uses the Modified Mononobe-Okabe equation (modified Coulomb) to calculate seismic forces for cantilevered retaining walls, wherein the theta (Θ) factor used in the equation is tan-1 kh.. As those of you in high-risk seismic area have discovered, this added seismic force can nearly double the static force and triple the overturning moment, particularly if backfill is sloped. In our opinion this is an overly severe requirement due to the rare instances of seismic problems with retaining walls (waterfront structures subject to liquefaction excepted) and code requirements should be reevaluated. We will report more on this in our Fall newsletter. In the meantime, anyone with an opinion please email us -- we'd like your views and comments on this important issue.

California and the IBC
The latest update is that the California Building Code (CBC) will adopt the IBC '06 (with California amendments) to be effective 1-1-08. A little over a year to wait for us Californians!

Another reminder about your Product Activation Code (PAC)

We get frequent calls from users who have had crashes or bought a new computer, and want to know how to reinstall Retain Pro if they can't find their CD. It's easy, and you don't need a CD (see below). Just download the demo version from www.retainpro.com/downloads, and insert your PAC to activate (version 2005 users only). If you can't find your PAC, you can retrieve it from out support page, but you'll need your password. Still can't find it? Call us.

No more CDs

As our newest users are aware, we no longer provide CDs. They're becoming antiquated with the ease of downloading from the Internet. It's easier for us and easier for you. And it allows activation right after ordering.

Licensing clarification

There is some confusion on this. 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. The "Site license" is for large offices installing on a server with unlimited access by any number of engineers, but at one physical site. We also offer site license discounts for branch offices.

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

PS: Version 2005 users: Although version 2007 isn't available yet, you can pre-order your upgrade for just $95 until 11-30-06, whether from a small office or site license. When it becomes available we'll email you download instructions and your new Product Activation Code (PAC), and mail you the new user's manual. You will also receive a free copy of the 7th edition of Basics of Retaining Wall Design (purchased separately: $65) when it's available. To order, click on Upgrade from 2005 at www.retainpro.com.

© 2006 HBA Publications. All Rights Reserved.