Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Multi-Lat 2003 now available

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Title: Message
I am pleased to announce an update to the Multi-Lat spreadsheet that David Merrick and I wrote upon adoption of the 97 UBC. I have temporarily removed the rigid diaphragm analysis based on a study that I performed which indicated that most engineers were using increased base shears rather than to design residential structures comparing or including rigid and flexible analysis. The outcome was considerably more conservative than using a simplified static principle.
 
I will be adding the rigid analysis back in as soon as I can integrate it better with the flexible analysis. I feel it is more appropriate for commercial and industrial buildings that have large openings which induce greater horizontal shears by rotation that need to be resisted or which can be determined to be included adequately in the capacity of the shearwalls or other shear resisting elements.
 
This new spreadsheet has some improvements for walls that don't stack as well as for cantilevered diaphragms. The spreadsheet performs a flexible diaphragm analysis for up to five blocks and each block up to three stories in height. It compares wind and seismic (based on the type of resisting system's "R" value) and analyzes the block for the worst case scenario.
 
I am also in the process of writing an online tutorial located on the Structuralist.Net that will help you use the spreadsheet. The only changes you need to know how to operate are the printing functions in Excel so that you can adjust the print area for a one, two or three story block.
 
For those familiar with the original spreadsheet, there were problems based on lateral distribution from level to level when walls did not stack. This has been repaired and there are some very creative ways to use the spreadsheet - thus the reason to create an online tutorial.
 
Until the tutorial is complete, I am taking any and all questions on how to use the spreadsheet and creative uses for blocks that are not orthogonal (skewed shear walls).
 
To download the spreadsheet:
1. start at http://www.structuralist.net,
2. Click on the button labeled "Structuralist BBS" on the left side of the screen
3. This will take you to our YABBSE Bulletin Board, scroll down to "User Software Forum" and click on the this title in blue.
4. Click on Multi-Lat 2003 Now Available for Download to open the message posted today.
5. Read the information provided and at the bottom of this message is a bold blue link that says "Click here to download the latest version of Multi-Lat 2003.
6. Either click on this link, or right click on the link and choose "Save Target As...". You may rename the file or simply choose a location such as your desktop to download it.
 
 
The direct link is: http://www.structuralist.net/attachments/Multi-Lat_2003.zip - however, I believe it is important to read the files posted on the software.
 
If and when you need help, please post your questions on the Software discussion forum by clicking on "New Topic" and entering your question or comments. I will be notified when you post. You may need not be registered with the site to post a message, but you will need to leave a valid e-mail address and name to post. It is more convenient to register with the BBS. This prevents any spammers and provides you with a great deal of other useful features. These advantages are covered in the BBS home page (My Community) General Category - Announcements: "Registration Privileges". Please feel to leave your questions or comments here.
 
Some creative uses:
 
1. Diaphragms in each block do not have to be at the same elevation as adjacent blocks.
2. Blocks can be skewed (non-orthogonal) based on the assumption that the direction of the force is normal to the block rather than the entire structure (conservative).
3. Diaphragms can include cantilevers by arbitrarily inputting 2L for the diaphragm span to the first line of resisting shear. The spreadsheet assumes L/2 as the reaction for that level.
4. For multi-story shear distribution ALL LINES OF SHEAR MUST BE DEFINED AS IF THE BLOCK WERE TRANSPARENT. IN OTHER WORDS, EACH GRID LINE MUST BE DEFINED IN EACH LEVEL SO THAT LINES OF RESISTANCE IN EACH LEVEL CAN BE TURNED ON AND OFF AND DISTRIBUTION IS PROPERLY TRANSFERED FROM LEVEL TO LEVEL.
5. The user has the option of changing the method of resistance for each block and in each direction (plywood shear walls, moment frame, proprietary shear elements, cantilevered columns, masonry or concrete walls etc.).
6. Shear is not distributed to flexible walls in the same line of resistance based on wall rigidity. This is not allowed in the 97 UBC and until it is modified, the user can only distribute shear per linear foot of wall.
7. Wind and Seismic forces are compared in each line of resistance and the worst case load is used. Diaphragm deflection is checked, although the aspect ratio of the diaphragm must encroach upon 4:1 before the diaphragm will be considered flexible.
8. The user may input up to five wall segments in each line of shear. Each block allows for 10 lines of resistance with five walls each for three story or a maximum of 150 shearwall sections that may be used in each block.
 
I've used the spreadsheet to design irregular shaped structures and found that it can be a very creative and useful tool. The benefits are not immediately apparent until you learn how to link blocks together to resolve the shears in each line of resistance. You may have a block that does not contain a diaphragm at a level adjacent to one or two other blocks (such as an atrium). You can resolve this in Multi-Lat.
 
I am currently creating a summary shearwall schedule that can be printed and placed on your drawing to identify all shear walls by grid line and wall number.
 
Enjoy the software and please write to let me know of any problems as well as all creative ways you have used the spreadsheet to resolve multi-story lateral distribution in irregular shaped structures.
 
Sincerely,
Dennis S. Wish, PE
California Professional Engineer
Structural Engineering Consultant