8/20/08 Update – COMMENTS NEEDED

Just a note to keep you posted as to our progress.

For those interested (although irrelevant to Multi-Lat™, the mountain range shown on the top of the Blog is actually the Santa Rosa Mountains located within walking distance of my home in La Quinta where my office is located in a small room off the front of my home. I’ve been a Small Office / Home Office sole-proprietorship for the last 22 years and at this location since 1993. It gets very hot in the summer (I’ve been here when it reached 130-degrees in August). Similar to those in cold climates, we tend to restrict daytime activities in the summer. Winter temperatures are wonderful – typically in the upper 60’s to 80’s during the days and down into the 40’s at night.  But, enought trivia – not to the business at hand.

I have made some changes in the design appearance. I have added an area in the title block for users to add a logo in JPEG and other popular formats. I would suggest that you keep the resolution of the JPEG small enough to appear well in print but not so large as to increase the file size.

Most sheets are now laid out in horizontal or layout format in order to increase the information on the sheet as well as to add graphics such as the roof zones that appear in the code for users to clearly define wind forces. I have also added the tables used in the wind loads with the appropriate footnotes to the resource in ASCE 7-05 that it appears. This does not eliminate your need to purchase a code, but makes look up values for wind speed and zones to be easier to follow. Also, you need not interpolate λ values as I have created tables with intermediate wind loads that will allow you to look up on λ value rather than a range to interpolate. The values are fairly linear and interpolation is easy enough to have put into an automate lookup table based on the basic wind categories B, C, and D.

In the seismic section you need not declare ASD or LFRD – you will be give both and the declaration will occur in the lateral multi-story distribution.

We are still using Excel 2007 until the workbook is completed and time will allow to have the styles stripped out and converted for Excel 97-2007 and the Star Office freeware.

I must remind you that your participation and comments are needed. I will only provide licensing in payment for feedback in the Alpha and Beta versions. I need comments as to the accuracy of the spreadsheet and any recommendations that you may have to improve the input and output – including color schemes. Most important is the output for base shear and wind loads. So far only one or two of the nearly 20 Beta Members have provided me with feedback. If you find the workbook difficult or do not understand something, then feed me your questions and I will help you resolve them. This will assist me in creating a manual and online example or tutorial as it is most likely others will also have the same concerns as you.

To qualify for a licensed version and updates, I require participation in the Beta program. I keep your comments and if you feel uncomfortable writing them to this blog then feel free to send them to me privately and I will reword them and post them anonomosly. You will still be qualified to receive a full licensed version for your participation.

If you disagree with a method or and assumption I’ve used, please let me know. It is a learning process for me as well as for you and I welcome an intelligent debate as to the meaning of the code assumption or compliance. If I am incorrect, I will make the changes necessary and if I am correct, you may also benefit from the knowledge.

Please help me get this program finished by submitting your comments and checking the spreadsheet in each stage against the work you do manually. This is the greatest test to show code compliance and reduce the errors or inaccuracies that Beta testing is to uncover.

Thanks to those who have been supplying me with comments and help – at this point I believe we are looking at completion closer to the end of the year although I am attempting to use as much of Multi-Lat 2008 in the current design of a two story custom home here in the desert.

Best regards,

Dennis S. Wish, PE

Administrator / developer

Simplified Wind Load Assumptions – MWFRS Method 1

MWFRS Method 1 Explanation

Multi-Lat™ 2008 is intended for use on light-framed Bearing Wall or Building Frame Systems that assume the limitations of 3-story wood framed structures with shear transferred though the diaphragms to a lateral load system primarily based on conventional plywood shear walls or proprietary shear wall systems. In most cases buildings under 30-feet in height (40-feet as defined in ASCE 7-05 Section 12.14.1 for certain conditions) and defined as a closed system may fall into the category of ASCE 7-05 Main Wind Force Resisting Systems using Method 1 – the Simplfied design methods.

An excellent resource on this is Donald Breyer’s book published by McGraw Hill “Design of wood Structures ASD/LFRD” for the 2006 IBC and ASCE 7-05 references. However, there are a number of inaccuracies that the user of our software should be aware of:

1. Breyer defines compliance with Method 1 – the Simplified Design Method as limited to 2-story light framed structures not exceeding 30-feet in height. And;
2. A building with virtually no irregularities in the design.

The current code clarifies this definition to a maximum of 60-feet overall height but provides no restriction as to the number of stories. Although a structure that contains irregularities in the design is fairly common in residential structures, the main purpose of the code is to define the entire structure rather than its components. Breyer explains that the main portion of the design used for occupancy (other than covered open patios considers how the main structure can be sealed from debris occurring during a high wind event. In other words, the ability to close windows, doors and in some cases the use of tempered glass panels to defelct debree will qualify most buildings for compliance with the MWFRS Method 1.

Breyer makes some errors in this section ( 2.23-2.28 ) that I have not found an errata which corrects the design assumption, but the ultimate voice on this issue is the code itself. Garages with doors that can be closed to seal the structure against interior wind gust and flying debree may be considered under Method 1. Building normally left open (parking structures, airline hangers etc. ) are the exception to the rule and best left to the use of Method 2 which is included in Multi-Lat™ 2008.

The user is refered to local municpalities for revisions to ASCE 7-05 and the 2006 IBC which have been modified and made into law are an exception to the rule or Breyer’s text. It is, therefore, prudent to check with your local buildng department where the project is to be constructed for the final word.

While Multi-Lat™ 2008 references Breyer’s book on wood design, it does define compliance based on the definition of the entire structure as a preliminary. The software allows the user to break to structure into blocks, irregularities in plan is based not on exterior wall geometry but on the general shape of the entire shear transfer ability of the roof. In other words, if the exterior wall geometry would normally define a “U” shaped building, if the roof spans the courtyard to creating a continuous rectangular plan geometry, then the structure would be defined as a regular plan and the shear would be expected to be dragged across the courtyard.

The discussions that help to understand the discrepancy in the texts and in some cases, the code, are often discussed and archived on the Structural Engineers Association International (SEAINT) List Service in addition to this weblog. The user is recommended to search through the List archives located at http://www.seaint.org . Follow the links to the List archives and use this to search for all discussion threads. It is highly recommended that the user seek the discussions held within the community to become familiar with the code (especially those of us located in the Pacific Ring of Fire that have been using the 1997 Uniform Building Code for the last ten years.

Donald Breyer’s PE book “Design of wood structures – ASD/LFRD” has been the “bible” of the educational institutes and a practical guide – more so than the Seismic Design Manuals – that this author has found in light-framing residential structures.

Multi-Lat™ 2008 Alpha Comments

You can start a comment from anywhere – including a post or creating your own post. To start the ball rolling, feel free to post your comments for the Alpha release issued on May 29, 2008 by clicking on the comment link at the end of this post. You can add any subject you want, but remember, make your comments clear so that others can understand what your post intends to discuss. This way the other members of the beta team can decide to add to your comments or move on to another.

NOTICE: WE HAVE SOME ROOM FOR ABOUT TEN TO FIFTEEN MORE BETA TEAM MEMBERS. IF YOU WANT TO RECOMMEND ANOTHER ENGINEER, PLEASE HAVE THEM WRITE ME AT ADMIN@STRUCTURALIST.NET AND PROVIDE ME WITH THEIR NAME, COMPANY NAME, LICENSE TYPE (CE, PE, SE) AND AREAS OF EXPERTISE. ALL BETA USERS WHO REMAIN ON THE BETA TEAM ARE ASSURED CONTINUED FREE LICENSING OF THE MULTI-LAT™ 2008 AND LATER WORKBOOK. THIS IS IN APPRECIATION FOR YOUR CONTINUED SUPPORT AND ASSISTANCE IN THE CONTINUED EVOLUTION OF THIS SOFTWARE.

PLEASE KEEP YOUR COMMENTS COMING!

DENNIS S. WISH, PE

CALIFORNIA LICENSED PROFESSIONAL ENGINEER

STRUCTURAL ENGINEERING CONSULTANT

AUTHOR AND DEVELOPER OF MULTI-LAT™ SOFTWARE AND WEBLOG SERVICES AND USERS GUIDE.

ADMIN@STRUCTURALIST.NET

PLEASE FEEL FREE TO VISIT OUR NEW STUCTURALIST.NET WEBSITE NOW UNDER CONSTRUCTION.

Irregularity in Seismic Design Categories; D, E and F

The current code provides an “out” for wood framed buildings with wood diaphragms classified as type I or II structures. These buildings may disregard certain irregularities that would normally trigger the design to require dynamic or rigid analysis. At the very least, it would require the engineer to compare the center of mass to the center of rigidity to ascertain if the building can be designed with a flexible analysis.

I recently picked up a copy of Donald Breyer’s sixth edition of Deisgn of Wood Structures ASD/LRFD co-authored by Kenneth J. Fridley, Kelly E. Cobeen and David G. Pollock (McGraw Hill publications) (see Amazon Book for the best price / delivery times).

While Breyer notes that current code ignores Type I irregularities that may cause torsion in a wood frame structure three stories or less, it points to a number of irregularities (Vertical and Horizontal) that would require additional lengthy analysis and possibly the addition of the Over Strength factor Ω _o to be found in ASCE 7 Table 12.3-1 and in sections 12.3.3.4 for combination with E_m . This appears to include “L” or “U” shaped structures with plan irregularities type 2 at re-entrant corners where the irregularity exceeds 15% of the projection (F1) divided by the corresponding side lengths. In other words if you have an “L” shaped structure 100-feet long with one leg projecting more than 15-feet back from the 100-foot length, then the building will be required to be treated as dynamic or rigid.

However, it appears (and this is where I am presently confused) that if the setback of the projection exceeding 15% of the corresponding length can be penalized by the appropriate Ω _o found in the code. Is this correct, or is there more to it? I’ll be exploring this issue after sending out the Alpha version to see if the Omega penalty will allow light-framed structures three stories or less used in residential construction to be exempt from the rigid analysis or comparison of the center of mass to the center of rigidity.

This article is currently still under construction and will be added to by the author in the near future as confirmation to the issues noted can be verified and documented. Please feel free to add your comments below, or to start a discussion on this topic.

Alpha Version RELEASED today – May 29, 2008

Multi-Lat™ 2008 version 1.040108A

Alpha Version Release Notification

The Alpha version of Multi-Lat™ 2008 was released today. This is not a finished version – far from it. It is a work in progress and not intended to be used as a work product until it has been adequately carried through the entire Beta Program.

The Excel 2007 Workbook was delayed when a discussion was posted on the SEAINT Listservice (http://www.seaint.org click on the listservice choice in the left side of the web page to reach the subscribers page). While working on the spreadsheet software it became apparent that many engineers have been misinterpreting the base method that the seismic shear presents in both the IBC and ASCE 7-05. The default calculations for load cases is in Working Strength Design methods. The user must use the provisions of the ASCE 7-05 to decide to use the Allowable Stress Design (ASD) or Load and Resistance Factor Design (LRFD). This will, in most cases increase the lateral base shear that you evaluate closer to the base shear we used in the 97 UBC.

I have not yet finished this last part of Multi-Lat™ 2008 Alpha pending the next discussion on the need to consider an increased Redundancy Factor – Ρ (rho) and possibly the Over-strength factor – Ω ₀ (Omega). This last factor becomes more important when you consider using the simplified design methods of ASCE 7-05 Section 12.14.1.1.

I recently reviewed the information published in Donald Breyer’s book “Design of Wood Structures” sixth edition. I will be posting a discussion once I have some sketches together that we need to throw back and forth that Breyer brings up in Chapter 16 of his book. There are implications that most residential buildings in Seismic Design Category D, E and F will have some form of Vertical or Horizontal Irregularity that must be addressed unless the building is a simple block design where all walls stack (inside and exterior shear resisting elements). Please refer to the on-going discussion in the Weblog regarding Irregular Geometry and the introduction or the Over strength Factor – Ω ₀

_______________________________________________________________________________

In the Code Simple feature published in Structural Engineer Magazine February 2008 edition by S.K. Ghosh and Susan Dowty, the last paragraph emphasizes the ambiguity in the code where it states:

“So what is the code user to do in this quagmire? The good news is that the problem has been solved for the user in the 2007 Supplement to the 2006 IBC. The Supplement has deleted the special seismic load combinations in 2006 IBC Section 1605.1. The section now simply directs the users to use Section 12.4.3 of ASCE 7-05, except that it clarifies: “With the simplified procedure of ASCE 7 Section 12.14, the overstrength factor load combinations of Section 12.14.3.2 of ASCE 7 shall be used.” Although supplements are typically not adopted by local jurisdictions, what the 2007 Supplement has done would be an advisable way to resolve the problem that exists with the 2006 IBC.” ( http://www.gostructural.com/article.asp?id=2605 )

Donald Breyer’s text takes the issue of Plan irregularity (vertical and horizontal) into much greater detail in Chapter 16 of the Sixth Edition. As Professor Ghosh points out, the “quagmire” does not actually disappear from most structures. Unless the home is a one story structures with no horizontal plan irregularity (including reentrant corners) where a prescriptive code such as International Residential Code most of us will find that some Vertical or Horizontal plan irregularity as noted in Table 12.3-1 and 12.3-2 will occur in most of our design. Whether or not the base shear is penalized by use of Ω ₀ depends upon the Seismic Design Category (SDC) and the Occupancy Category the structure conforms to permits (or not) in table 12.6-1. However, remember that the interpretation of Irregularity changed somewhat from what we were using in the 97 UBC on the West Cost until this year. For example, a Vertical Irregularity exists if the second floor shear wall does not align over the first floor shear wall. If there is transverse “jog”, the irregularity exists. If you recall in the 97 code the walls could be within 4′-0″ of the offset to still be in the same line of shear. Of course the engineer had to accommodate the design for potential tension and compression of the upper level walls and their connection to the framing in the diaphragm below. In this version of the code, if both walls are in the same line of shear but the upper level wall is in front of or behind the lower level wall a Vertical Irregularity exists and the base shear formula changes.

Another issue that I have not verified is the limitations on section 12.14.1 and table 12.6-1 to a maximum 2-story building where a setback or vertical irregularity (or horizontal irregularity occurs). To help you, an Irregularity worksheet was added to the workbook so that you can review the tables 12.3-1 and 12.3-2 as well as 12.6-1. Where Multi-Lat™ errs is on the side of conservative results.

Breyer states it very well on page 2.43 of Design of Wood Structures 6th edition where he states:

“ASCE 7 Sec. 12.14 is titled Simplified Alternative Structural Design Criteria for Simple Bearing Wall or Building Frame Systems. This section provides a simplified version of the equivalent lateral force procedure, for use on a limited scope of buildings. Use of the simplified procedure should result in roughly equivalent results. Because the scope of the buildings is limited, there are a number of checks in the general procedure, which do not need to be considered in the simplified procedure. ASCE 7 Sec. 12.14.1.1 provides a list of 12 scoping criteria that the building must meet in order to be designed using the simplified procedure. Among the 12 there is one that will be problematic for a number of wood-frame buildings. Item 11 says the simplified approach is not permitted in structures with system irregularities due to in-plane or out-of-plane offsets of lateral force resisting elements. An exception permits offsets in shearwalls in two story buildings of light-frame construction, provided detailing requirements are met. Because offsets in shearwalls from story to story are so common in wood-frame buildings, there are likely to be a good number that do not qualify for this procedure. For this reason this book addresses the equivalent lateral force procedure instead. “

Strength Design Methodology

California, as most of you know, has adopted the 2006 IBC and ASCE / SEI 7-05 in the form of the 2007 California Building Code. This new code requires the user to obtain a copy of the current ASCE 7-05 to find many of the tables and the revisions of the IBC that are contained in the ASCE document. For example, the redundancy factor (ρ) for seismic design is covered in the 2006 IBC but is not mentioned except in one short reference in the ASCE document. The Design coefficients and factors for seismic force-resisting systems tables are not located in the IBC but are only available in the ASCE 7-05 as Table 12.2-1. Furthermore, it is not always clear that when determining the lateral load distribution V, that the IBC and ASCE default to the basic Strength Design Methods which must be adjusted within the analysis for the design method (Ultimate Strength, LRFD, or Allowable Strength Design (ASD)). The following discussion was held on our local e-mail distribution listservice. Please note that while some of this may seem obvious to you, we are in a first time learning curve on the ICC in California that was previously handled with clear consistency (at least in regard to the design methods) from the UBC.

3/12/08 Update on Multi-Lat™ 2008 Beta

Most will notice a delay in the release of the Beta versions of Multi-Lat™ 2008. The process of creating and testing Beta version Builds will begin as soon as the Alpha version is complete and a basic Quality assurance testing is done by the author. It is not just important to have a workbook template that performs accurately, but to have one that reads well, is intuitive to the user and provides information to those who will be reviewing your work. Until the Beta Members are brought up to speed in testing and evaluating, the work of coding as well as the online User’s Guide (this site) and a forth coming http://www.structuralist.net website is in the works.

I only ask that you be patient and that you check the information on this weblog. There are some issues in the code that are ambiguous and/or difficult to interpret or which many do not agree. I’ve started to post some of these on this Weblog – such as the use of ρ – the redundancy factor and the interpretation of when it is to be applied. Your review of these comments in the Seismic Discussion portion of this Weblog with comments that can be used to help narrow down a profession standard of interpretation by practitioners is extremely important. I hope you will help us.

You can post to this blog, but the access is somewhat limited to reduce the unwanted spam and comments that I must waste time to weed out. The topics are listed, and to comment on a running-thread of discussion, you need only register on the Weblog so that we can control who is allowed to post and stop anything unprofessional before it should occur. I you wish to post a Discussion that is new, please contact me with the questions and issues by writing to me at admin@structuralist.net and I will post the question. Please include your e-mail or user name if you want me to post it under your name or alias.

Please check back soon for more information. I am under pressure to complete and ready the Beta as I am currently motivated by a project that I must use Multi-Lat™ 2008 for. Each day brings me closer, so please bear with me on this and as soon as the Beta Testing is ready, I will post a notice. There will be 25 Beta Tester slots. If interested in becoming part of the team, send a private e-mail to me at admin@structuralist.net with your; Name; State and License Number; Company, address, city and state; Phone contact; e-mail contact; any websites or forums and weblogs that you may wish to link to this site or another structuralist.Net website and weblog. Finally include the version of Excel of a Compatible Spreadsheet that can import Excel files. I recommend Excel 2007 as the software is being prepared in this version because of the difficulties in striping out the style formats embedded in the spreadsheets. However, it is our intent to provide compatibility for

There is a lot of work to complete but with the slow ecconomic picture, the long needed down-time for a learning curve came whether I wanted it or not. So while I have the time, more work can be devoted to the spreadsheet and the online user’s guide.

Multi-Lat™ Supporting Tools

Google Earth (click on the link) is a free download that offers the user the ability to locate a satellite view within a Google browser. The basic version is not intended for vew capturing (a copyrighted protection) but has all of the necessary tools to locate the exact location of your building pad and identify the specific longitude and latitude of the site. The view can be zoomed in to reasonable resolution, but to obtain a clean view at higher resolution , there is a basic $20.00 shareware version.

The profit is earned on the sale of higher definition map views. For our purpose the basic download will provide more accuate results related to near fault conditions when used with the USGS Acceleration Tools than when inputing the local zip codes.

As an example, my address was input into the software which centered the zoom field over my home. Moving the mouse over the property locates the actual location of 33° 39′ 06.79″N -116° 18′ 25.74″ W. The property is 253-ft above the sea level and the top of the cove in which we live is 299-feet above sea level. The bottom of the cove is at 58-feet. The distance can be determined from a scale on the map and the sum of this information used in both the seismic and wind design sections to determine the building terrain exposure.

Multi-Lat™ Moves to Sun Microsystem’s OpenOffice.org Calc

Multi-Lat™ is pleased to announce the availability of our spreadsheet for the Sun Microsystem’s OpenOffice.org Calc suite of products. Moving to the OpenOffice platform (formerly known as the StarOffice suite) eliminates the compatibility problem with different releases of Excel and maintain compatibility with most Excel spreadsheet functions as well as the industry standard XML based file format.

While this may delay the first beta release, we found it to be a reasonable alternative that can provide a platform that has been available in public domain since 1988. Multi-lat™ was originally written in Excel for Office 2007. Problems occured when saving files in earlier formats. Sun Microsystem’s OpenOffice.org Calc is fuly compatible with all version of Excel up to and including Excel 2003.

Multi-Lat™ will be available in either the native OpenOffice Calc ODS format or in Excel XLS or XLT format for those who wish to remain with Microsoft Excel 97 or later. This move insures compatibility and provides an affordable alternative that is under constant development to keep up with the industry demands.

The following project statement is found on the OpenOffice.org website located at http://about.openoffice.org/index.html. I highly recommend you familiarize yourself with their software as it is an alternative to the commercial Office Suites that are presently available.

Multi-Lat™ Installation

Downloads

NOTE – UPDATED 7/17/08

1. Multi-Lat™ 2008 is NOT YET compatible with Sun Microsystem’s OpenOffice.org Calc and Microsoft Office 97 and later. Excel 2007 is required to evaluate the current Alpha version. Macros are kept to a minimum for printing. Active-X features that are known for potential distribution of viruses have been eliminated from all spreadsheets.
   • Multi-lat™ is a locked spreadsheet template. It is locked to prevent the possibility of changing or overwriting formulas and tables. Unlocking passwords are provided to those who are contributing or helping to maintain the integrity of the spreadsheet and must be obtained by writing to us at admin@structuralist.net.
2. The current Alpha version and future Beta versions will be locked to protect the spreadsheet formulas. You will be able to modify the Dead Load materials and their unit weights. I would be interested in any changes you make that differ or add to what is provided in the present release.
   
3. User header and footers can be changed. Each sheet is embedded with a user intended title block that will print the users company name, information and user’s license number. The purpose of this is to insure that the latest version is used and that the user is authorized to use the software either through licensing or by license offered to all Beta Testers who participate in the Beta program.
   
4. Download Google Earth and install it on your hard drive at the default locations. Click on the link in these instruction (blue underlined text where the cursor turns to a pointed finger) to launch your browser and automatically lauch the Google Earth download page.
   • There are option that you can download, but the basic program will locate your Longitude and Latitude based on the address entered in the address bar once Google earth starts. While it is not specifically noted, the East-West location is at the bottom of the Google Earth page but should be entered as a negative number for those living in Continential United States.
   • For example, if you enter 51000 Arroba, La Quinta CA. 92253 (enter addresses in this format), the map will find the address and present you with an arial view of 51000 Calle Arroba, La Quinta CA. 92253. At the bottom of the screen you will see the actual map coordinates in the form of Latitude (degrees, minutes, seconds) and Longitudes (minus degrees, minutes and seconds). When using the “Seismic Hazard Curves and Uniform Hazard Response Spectra” software from the USGS, you will need to enter the Longitude as negative units.