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| Summer 2005 |
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In this Newsletter
Dear Colleague: Thank you for choosing Retain Pro 2005 - or for upgrading from an earlier version. We hope it's continuing to make your retaining wall designs much easier, and with the reliability you expect. We hope you like the improvements we've made in Version 2005. First, a few technical issues...The masonry splice length dilemma - an updateThe rebar lap splice requirement in IBC '05, 2107.2.3 has stirred considerable controversy, particularly since it conflicts with the less restrictive requirement in ACI 530-05. And both result in much longer lap lengths. Retain Pro 2005 has the option of applying the former equation for lap lengths (by checking the box on the stem design screen). However, after discussing this issue with both MIA and NCMA, it appears that the complaints have borne fruit and the 2006 IBC code will reportedly rescind these requirements and revert to the familiar 48 bar diameters (with adjustments) per '97 UBC, 2107.2.2.3. Although this reversion is nearly certain, check with your building official for applicability if you're using IBC. Seismic design - selecting the proper kh valueFailures of retaining walls due to seismic events are extremely rare (waterfront structures and liquefaction problems excepted), however, IBC, UBC/CBC, and AASHTO have provisions for seismic design of retaining walls. (see my book Basics of Retaining Wall Design). If seismic design is required by your local jurisdiction, or the foundation investigation, be sure you are inputting a realistic kh value, which Retain Pro uses in the Mononobe-Okabe equations. This value is often misunderstood; it should be an effective design value, reduced from the "peak ground acceleration" value given in foundation investigation reports. A design kh of one-half the peak ground acceleration is considered reasonable. Also see the NEHRP 2000 Part 2 - Commentary, which states a design kh = SDS/2.5, which, for most site conditions is roughly about one-quarter the Ss value for Maximum Considered Ground Motion obtained from the IBC charts. Active earth pressure / sloped backfill clarificationA frequent question we get pertains to active pressure to be used when there is a sloped backfill. And specifically, whether to input the slope value in addition to increasing the active pressure due to the slope. The answer is YES! For a sloped backfill the active pressure increases. These values for varying slopes are usually contained in the foundation investigation (for example, 45 pcf for a 2:1 slope). This value is used for the design of the stem. However, you must ALSO enter the backfill slope since the overturning and sliding forces, and hence the soil pressure, are calculated from the total lateral force applied at an assumed vertical plane at the back of the footing. This vertical plane intercepts the backfill slope at a height greater than the retained height, therefore you must always enter the backfill slope to get the true total lateral forces. Retaining liquidsIf you are designing to retain a liquid you will enter the weight of the liquid as both active pressure and density. Be sure you have not inadvertently entered a surcharge, backfill slope, or activated a vertical component on the Options screen. And remember that the design assumes (for overturning, sliding, and soil pressure) an impervious seal at the heel. Should CalcTrac be re-activated?As you've probably noticed, we took out CalcTrac in version 2005. Our reasoning was that it was somewhat difficult to follow, and to check any calculation it was faster and easier to just do a quick hand calculation. It was not a complete trace of ALL calculations, and some users confused it with the two-page calculation printout which summarizes all the input and results. However, as a few users pointed out, it was a useful supplement to submit for plan review to aid the plan checker. Perhaps we should improve this feature and put it back in? We'll go by the response to this question on the attached survey. Building Department acceptance growingNow over 100 City, County, State, and Federal plan review agencies have purchased Retain Pro, so your design submittals will often be in familiar hands. Retain Pro seems to be widely accepted and we rarely get a question from a plan reviewer. Check the technical FAQs on our Support pageMany of your technical support questions are answered on our Support page. Click on Frequently Asked Technical Questions. We update it as we receive recurring questions. About your Product Activation Code (PAC)You don't need a CD to install Retain Pro 2005 on any computer. Just download a demo version from www.retainpro.com/downloads, and insert your PAC. If you lost your PAC, you can retrieve it from www.retainpro.com/support. Use the online Message Board & Tech ForumIf you have a question or information that would be of interest to others you can post it here. The online Message Board & Tech Forums is accessed from the home page. You'll need your email address and password for access. Every post will be answered. About Enercalc and Retain ProAs many of you know, Enercalc was founded and is run by my son, Michael Brooks, SE. However, we are two separate companies. Although Michael programmed much of Retain Pro. Enercalc's Structural Engineering Library includes a retaining wall program which is roughly equivalent to Retain Pro Version 5. Many Enercalc users have also purchased Retain Pro for additional features such as seismic design, .DXF file creation, gravity walls, load factor editing, and other features not available in the Enercalc version. By the way, Enercalc is one of the most popular integrated structural design programs and you can learn more at www.enercalc.com. Interesting survey highlightsFrom our most recent survey, some interesting results:
Changing your profileAbout 15% of you will not receive this Newsletter since you did not update your profile for our database. Whenever you move or change email address, it's easy to update your profile at www.retainpro.com/support. Watch for our Fall Retain Pro Newsletter coming in November -- we'll have many more topics such as Six Reasons Retaining Walls Fail and Six Cost-effective fixes, survey results, and news of upcoming program enhancements. Best regards, Hugh hbrooks@retainpro.com Hugh Brooks, SE Retain Pro Software PS: A note to Version 6.1 users: We're
including you with this emailing and urging you to upgrade © 2005 HBA Publications. All Rights Reserved.
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